| 2009:
Field 84: 01/2009-12/2009
Field 85: (Progress Report)
There are important engineering and crop production advantages
in growing plants under hypobaric (reduced atmospheric pressure)
conditions for extraterrestrial base or spaceflight environments.
Advantages include reduced pay load, greater safety because
of lower pressure gradients and improved plant growth. The primary
objective of this research was to investigate how low pressure
(hypobaria) and low oxygen (hypoxia) affect functional phytochemicals
and the nutritional quality of 'Red Sails' lettuce (Lactuca
sativa L.). Plants were grown under two levels of total gas
pressure (reduced or ambient (25 or 101 kPa, respectively))
at three levels of O2 partial pressures (low, medium or ambient
(6, 12 or 21 kPa, respectively)). Hypoxia effects on nutritional
and functional phytochemicals were more pronounced than hypobaria
effects. Regardless of the total pressure, hypoxia, in general,
enhanced leaf anthocyanin levels, enhanced total phenolic compounds,
enhanced carbohydrate concentration and enhanced free radical
scavenging capacity of lettuce but reduced leaf mineral concentration.
Hypoxia increased the ethylene production of plants but ethylene
accumulation was not the sole reason for enhanced anthocyanin
production in plants grown under hypoxia. Our results suggest
that low oxygen stress induces the production of protective
phytochemicals and the free radical scavenging potential in
lettuce, which may in turn enhance the functional value (Rajakaske
et al., 2009).
The exploration of space requires the development of Advanced
Life Support Systems (ALS) that have the capacity to recycle
resources and produce food (Wheeler et al., 2001). Such life
support systems will likely combine biotechnology and physicochemical
processes for air and water recycling. The biological component
will include the use of higher plants for air and water purification,
as well as providing food and psychological benefits (NASA,
1988). The National Aeronautics and Space Administration (NASA)
has a research and development effort to build such systems
as part of the Advanced Life Support System Program (Corey et
al., 1997; Goins et al., 2003; Hangartner et al., 2004; Schwartzkopf
and Mancinelli, 1991; Wheeler and Martin-Brennen, 2000), for
lunar (Ming and Henninger, 1989) and Martian (Corey et al.,
2002) agriculture. This is a NASA funded project in collaboration
with the Department of Biological and Agricultural Engineering.
[He, C., F. T. Davies Jr. and R. E. Lacey. 2009. Ethylene reduces
gas exchange and growth of lettuce plants under hypobaric and
normal atmospheric conditions. Physiologia Plantarum
Impact
There will not be a human presence in Lunar or Martian habitation
without Horticulture. Davies, Dr. Chuanjiu He and Dr. Ron Lacey
(Biological and Agricultural Engineering) have been collaborating
on NASA-funded research ($908,102) since 2001. There are engineering,
safety and cost advantages in growing plants under low pressure
conditions. In addition they report that plants do better under
low pressure (25 kPa) than earth ambient pressure (101 kPa),
in part because low pressure depresses the phytohormone ethylene
(which can cause senescence and irregular plant growth), plus
dark respiration (at night) slows down, which leads to greater
biomass production. This research also has application to controlled
crop production systems, sustainable, reduced input production
systems and controlled atmospheric (CA) storage systems of horticultural
crops. Their research was reported in a 2007 British Broadcasting
Corp (BBC)-Science in Action Report and one of their papers
made the Oct 2007 cover of Physiologia Plantarum, one of the
leading plant biology journals. Invited plenary talks on the
NASA supported low pressure research were given at the 50th
Annual Meeting of the Canadian Society of Plant Physiologists,
the University of Arizona, NCERA-101 Committee on Controlled
Environment Technology and Use in Cocoa Beach, Florida, and
International Potato Center (CIP) and Peruvian National Agrarian
University (UNALM). Further information and pdf files of publications
from Davies' research group can be found at http://aggie-horticulture.tamu.edu/faculty/davies/index.html
++++++++++++++++++++++++++++++++++++++++++
Carpio, L.A., F. T. Davies, Jr., T. Fox and C. He. 2009. Arbuscular
Mycorrhizal Fungi and Organic Fertilizer Influence Photosynthesis,
Root Phosphatase Activity, Nutrition and Growth of Ipomoea Carnea
ssp. Fistulosa. Photosynthetica. 47: 1-10. He, C., F. T. Davies
Jr. and R. E. Lacey. 2009. Ethylene reduces gas exchange and
growth of lettuce plants under hypobaric and normal atmospheric
conditions. Physiologia Plantarum. 135: 258-271. He, C., F.
T. Davies Jr. and R. E. Lacey. 2009. Hypobaria, hypoxia and
light affect gas exchange, and the CO2 compensation and saturation
points of lettuce (Lactuca sativa) L. Botany 87(7): 712-721.
Rajapakse, N.C., C. He, L. Cisneros-Zevallos, and F. T. Davies
Jr. 2009. Hypobaria and hypoxia affects growth and phytochemical
contents of lettuce. Scientia Horticulturae 122: 171-178. He,
Chuanjiu, F.T. Davies, Jr. and R.E. Lacey. 2009. "Hypobaria,
Hypoxia and Light Affect Gas Exchange, and the CO2 Compensation
and Saturation Points of Lettuce Plants". NCERA-101 Committee
on Controlled Environment Technology and Use Annual Meeting.
April 4 - 8, 2009 Park City, Utah. Chow, A. and A. Chau, P.
Krauter, C. Bográn, F. Davies and K. M. Heinz. 2009. Manipulating
fertilizer input for container production of woody and herbaceous
ornamentals: a viable approach to pest management? Greenhouse
Grower. Aug. 2009. http://www.greenhousegrower.com/production/?storyid=2419#
He, C., F. T. Davies Jr. and R. E. Lacey. 2009. Hypobaria, hypoxia
and light affect gas exchange, and the CO2 compensation and
saturation points of lettuce (Lactuca sativa). HortScience.
2008:
Field 84: 01/2008-12/2008
Field 85: (Progress Report)
There are important engineering and crop production advantages
in growing plants under hypobaric (reduced atmospheric pressure)
conditions for extraterrestrial base or spaceflight environments.
Advantages include reduced pay load, greater safety because
of lower pressure gradients and improved plant growth.
Elevated levels of ethylene occur in controlled environment
agriculture and in spaceflight environments, leading to adverse
plant growth and sterility. The objectives of this research
were to characterize the influence of ethylene on carbon dioxide
(CO2) assimilation (CA), dark-period respiration (DPR) and growth
of lettuce (Lactuca sativa L. cv. Buttercrunch) under
ambient and low total pressure conditions. Lettuce plants were
grown under variable total gas pressures of 25 kPa (hypobaric)
and 101 kPa (ambient) pressure. Endogenously produced ethylene
accumulated and reduced CA, DPR and plant growth of ambient
and hypobaric plants. There was a negative linear correlation
between increasing ethylene concentrations [from 0 to around
1000 nmol mol-1 (ppb)] on CA, DPR and growth of ambient and
hypobaric plants. Declines in CA and DPR occurred with both
exogenous and endogenous ethylene treatments. CA was more sensitive
to increasing ethylene concentration than DPR. There was a direct,
negative effect of increasing ethylene concentration reducing
gas exchange, as well as an indirect ethylene effect on leaf
epinasty, which reduced light capture and CA. While the CA was
comparable, there was a lower DPR in hypobaric than ambient
pressure plants -- independent of ethylene and under non-limiting
CO2 levels (100 Pa pCO2, nearly 3-fold that in normal air).
This research shows that lettuce can be grown under hypobaria
(@ 25% of normal earth ambient total pressure), however, hypobaria
caused no significant reduction of endogenous ethylene production.
The exploration of space requires the
development of Advanced Life Support Systems (ALS) that have the
capacity to recycle resources and produce food (Wheeler et al.,
2001). Such life support systems will likely combine biotechnology
and physicochemical processes for air and water recycling.
The biological component will include the use of higher plants
for air and water purification, as well as providing food and
psychological benefits (NASA, 1988). The National Aeronautics
and Space Administration (NASA) has a research and development
effort to build such systems as part of the Advanced Life Support
System Program (Corey et al., 1997; Goins et al., 2003; Hangartner
et al., 2004; Schwartzkopf and Mancinelli, 1991; Wheeler and Martin-Brennen,
2000), for lunar (Ming and Henninger, 1989) and Martian (Corey
et al., 2002) agriculture. This is a NASA funded project in collaboration
with the Department of Biological and Agricultural Engineering.
[He, C., F. T. Davies Jr. and R. E. Lacey. 2009. Ethylene
reduces gas exchange and growth of lettuce plants under hypobaric
and normal atmospheric conditions. Physiologia Plantarum.
In press.]
Impact
There will not be a human presence in Lunar or Martian habitation
without Horticulture. Davies, Dr. Chuanjiu He and Dr. Ron Lacey
(Biological and Agricultural Engineering) have been collaborating
on NASA-funded research ($908,102) since 2001. There are engineering,
safety and cost advantages in growing plants under low pressure
conditions. In addition they report that plants do better under
low pressure (25 kPa) than earth ambient pressure (101 kPa),
in part because low pressure depresses the phytohormone ethylene
(which can cause senescence and irregular plant growth), plus
dark respiration (at night) slows down, which leads to greater
biomass production. This research also has application to controlled
crop production systems, sustainable, reduced input production
systems and controlled atmospheric (CA) storage systems of horticultural
crops. Their research was reported in a 2007 British Broadcasting
Corp (BBC)-Science in Action Report and one of their papers
made the Oct 2007 cover of Physiologia Plantarum, one
of the leading plant biology journals. Invited plenary talks
on the NASA supported low pressure research were given at the
50th Annual Meeting of the Canadian Society of Plant Physiologists,
the University of Arizona, NCERA-101 Committee on Controlled
Environment Technology and Use in Cocoa Beach, Florida, and
International Potato Center (CIP) and Peruvian National Agrarian
University (UNALM). Further information and pdf files of publications
from Davies’ research group can be found at http://aggie-horticulture.tamu.edu/faculty/davies/index.html
++++++++++++++++++++++++++++++++++++++++++
Alarcon, A., F. T. Davies Jr., R. L. Autenrieth and D. A. Zuberer.
2008. Arbuscular
Mycorrhiza and Petroleum-Degrading Microorganisms Enhance Phytoremediation
of Petroleum-Contaminated Soil. International Journal of
Phytoremediation. 10(4): 251-263.
Davies, F.T. Jr. and A. Alarcon. 2008. Enhancing Phytoremediation
of Heavy Metals with Arbuscular Mycorrhizal Fungi. In:
A. Alarcón and R. Ferrera-Cerrato (Eds.), Bioremediation
of Soils and Water Contaminated by Organic and Inorganic Compounds.
Mexico City: Mundi-Prensa S.A. de C.V. (Book Chapter).
Estrada-Luna, A. A. and F. T. Davies Jr. 2008. Nutrient status
and growth of micropropagated prickly-pear cactus (Opuntia
albicarpa Scheinvar cv. “Reyna”) plantlets
colonized with three-selected endomycorrhiza isolates. In: Arbuscular
Mycorrhizae in Arid and Semi-Arid Ecosystems. N. Manuel Montaño
Arias, S. Lucía Camargo Ricalde, R. García Sánchez
and A. Monroy Ata (Eds.) Mundi-Prensa México, S. A. de
C. V. pp. 33-44. (Book Chapter)
He, Chuanjiu, F.T. Davies, Jr. and R.E. Lacey. Hypobaria, Hypoxia
and Ethylene Influence Gas Exchange and Growth of Lettuce Plants.
2008 International Meeting on Controlled Environment Agriculture.
Mar 8-12, 2008, Cocoa Beach, Florida. p. 28. (Symposium
Proceedings)
Davies, F.T., Jr. 2008. Invited & sponsored presentation:
“Challenges in NASA Low-Pressure Crop Production Systems
-- Separating the Effects of Hypobaria and Hypoxia on Lettuce.”
Canadian Society of Plant Physiology – 50th Anniversary
Meeting. Ottawa, Ontario, Canada. June 2008. (Symposium
Proceedings)
Spiers, J.D., F.T. Davies, Jr., C. He, K. M. Heinz, C.
E. Bográn, and Terri W. Starman. 2008.
Do Insecticides Affect Plant Growth and Development? –
(Research tests foliar insecticides to determine whether applications
affect development in gerbera daisies). Greenhouse Grower.
Feb. Vol 2. http://www.greenhousegrower.com/grower_tools/200802_insecticides.html
Amaya-Carpio, L., F. T. Davies, Jr., T. Fox, and C. He. 2008.
Arbuscular Mycorrhizal Fungi and
Organic Fertilizer Influence Photosynthesis, Growth, Nutrient
Uptake and Root Phosphatase Activity of Ipomoea Carnea
subsp. Fistulosa. SNA Research Conference Proceedings.
53: In press.
He, C., F. T. Davies Jr. and R. E. Lacey. 2008. Ethylene Reduces
Gas Exchange and Growth
of Lettuce Plants Under Hypobaric and Normal Atmospheric Conditions
HortScience.
43(4): 124.
Davies, F.T., M. Lamberts, T. Ferriss, G. Fitzpatrick, S. L.
Steinberg, K. Panter, J. Cole, M. Neff and R.Talke. 2008. Opportunities
for Industry, the Public, and the Profession of Horticulture
with the ASHS-Certified Horticulturist (ASHS-CH) Program. HortScience
43(4):
Davies, Jr., F.T. 2008. Opportunities Down Under – How
Mycorrhizal Fungi Can Benefit Nursery Propagation and Production
Systems Combined Proceedings of International Plant Propagators’
Society. 58: in press
2007:
Field 84: 01/2007-12/2007
Field 85: (Progress Report)
There are important engineering and crop production advantages
in growing plants under hypobaric (reduced atmospheric pressure)
conditions for extraterrestrial base or spaceflight environments.
Advantages include reduced pay load, greater safety because
of lower pressure gradients and improved plant growth.
Objectives of this research were to determine the influence
of hypobaria and the partial pressure of oxygen (pO2) on carbon
dioxide (CO2) assimilation, dark respiration and growth of lettuce
(Lactuca sativa L. cv. Buttercrunch). Lettuce plants
were grown under variable total gas pressures [25 and 101 kPa
(ambient)] at 6, 12 or 21 kPa pO2. While plant growth was comparable
between ambient and low pressure lettuce during the 10-day study,
growth was lower at 6 kPa pO2 than 12 or 21 kPa pO2. The specific
leaf area (SLA) of 6 kPa pO2 plants was lower than 12 or 21
kPa pO2 lettuce, indicating thicker leaves associated with plant
stress. Greater carbon partitioning into above ground dry mass
(higher leaf/root ratio) occurred with 6 kPa pO2 plants. Leaf
chlorophyll levels were greater at low than ambient pressure.
Relative water content (RWC) was the same among treatments,
indicating that hypobaria and pO2 did not adversely affect plant
water relations. There was about a 10% lower CO2 assimilation
(net photosynthesis) and 25% lower dark respiration rate in
low (25/12 kPa pO2) than ambient (101/21 kPa pO2) pressure plants.
The ratio of CO2 assimilation/dark respiration was higher at
low than ambient total pressure, particularly at 6 kPa pO2 ¾
indicating a greater efficiency of CO2 assimilation/dark respiration
with low pressure plants. Hypobaric plants were more resistant
to hypoxic conditions (6 kPa pO2) that reduced gas exchange
and plant growth. The considerably lower dark respiration
rates (reduced consumption of metabolites) could lead to greater
plant growth (biomass production) under low pressure than under
ambient conditions during longer crop production cycles.
The exploration of space requires the development
of Advanced Life Support Systems (ALS) that have the capacity
to recycle resources and produce food (Wheeler et al., 2001).
Such life support systems will likely combine biotechnology and
physicochemical processes for air and water recycling. The
biological component will include the use of higher plants for
air and water purification, as well as providing food and psychological
benefits (NASA, 1988). The National Aeronautics and Space Administration
(NASA) has a research and development effort to build such systems
as part of the Advanced Life Support System Program (Corey et
al., 1997; Goins et al., 2003; Hangartner et al., 2004; Schwartzkopf
and Mancinelli, 1991; Wheeler and Martin-Brennen, 2000), for lunar
(Ming and Henninger, 1989) and Martian (Corey et al., 2002) agriculture.
This is a NASA funded project in collaboration with the Department
of Biological and Agricultural Engineering. [He, C., F.
T. Davies Jr. and R. E. Lacey. 2007. Separating the effects of
hypobaria and hypoxia on lettuce: growth and gas exchange. Physiologia
Plantarum 131: 226–240.]
Impact
There will not be a human presence in Lunar or Martian habitation
without Horticulture. Davies, Dr. Chuanjiu He and Dr. Ron Lacey
(Biological and Agricultural Engineering) have been collaborating
on NASA-funded research ($808,102) since 2001. There are engineering,
safety and cost advantages in growing plants under low pressure
conditions. In addition they report that plants do better under
low pressure (25 kPa) than earth ambient pressure (101 kPa), in
part because low pressure depresses the phytohormone ethylene
(which can cause senescence and irregular plant growth), plus
dark respiration (at night) slows down, which leads to greater
biomass production. This research also has application to controlled
crop production systems, sustainable, reduced input production
systems and controlled atmospheric (CA) storage systems of horticultural
crops. Their research was reported in a 2007 British Broadcasting
Corp (BBC)-Science in Action Report and one of their papers made
the Oct 2007 cover of Physiologia Plantarum, one of the
leading plant biology journals. A Visiting Professor, Dr.
Nihal Rajapaske, on sabbatical leave from Clemson University conducted
research in 2007 in Davies’ Lab on “Effect of oxygen
concentration in the growing environment on phytochemical composition
and functional quality of lettuce plants”, in collaboration
with Drs. Luis Cisneros, Ron Lacey and Chuanjiu He. Further information
and pdf files of publications from Davies’ research group
can be found at http://aggie-horticulture.tamu.edu/faculty/davies/index.html
2006: Field
84: 01/2006-12/2006
Field 85: (Progress Report)
The exploration of space requires the development of Advanced
Life Support Systems (ALS) that have the capacity to recycle
resources and produce food. Such life support systems will likely
combine biotechnology and physicochemical processes for air
and water recycling. The biological component will include
the use of higher plants for air and water purification, as
well as providing food and psychological benefits. The National
Aeronautics and Space Administration (NASA) has a research and
development effort to build such systems as part of the Advanced
Life Support System Program for lunar and Martian agriculture.
Plants can respond adversely even to very low ethylene levels.
Elevated levels of ethylene have been reported in enclosed environments
and implicated in microgravity — spaceflight experiments.
Wheat grew poorly in an ambient (101 kPa) chamber with ethylene
at 100–200 nmol mol-1 (ppb). Wheat plants grew normally
when the ethylene was removed by an activated alumina column.
Chronic exposure to ethylene levels of 50 to 100 nmol mol-1
reduced growth of lettuce and Easter lilies. On the Russian
space station, Mir, ethylene ranged from 1000 to 1700 nmol mol-1,
about 1000x to 1700x greater than ethylene in terrestrial, open
field agricultural conditions, leading to abnormal growth and
sterility. Ethylene levels are maintained around 50 nmol mol-1
on the international space station (ISS), but even these levels
can have adverse effects on plant growth and sterility. Under
hypoxia (low oxygen) one would expect that higher (rather than
lower) levels of ethylene occur, as is common during anaerobic
conditions when plants experience flooding. It would be profoundly
interesting to characterize ethylene levels and other volatile
organic compounds, particularly with the expected differences
in gas diffusion rates at low pressure. Hence, the objectives
of this research were to characterize the influence of hypobaria
on optimal growth, plant gas exchange and ethylene evolution
of lettuce (Lactuca sativa cv. Buttercrunch).
This research shows that lettuce can be successfully grown
in a hypobaric environment. Lettuce has high potential of being
included in NASA’s Advanced Life Support System. Lettuce
plants grown under low total pressure (50 kPa) had comparable
growth to plants grown under ambient pressure conditions in
a series of short-term experiments lasting up to six days. There
was also a tendency for tip burn under ambient pressure, possibly
due to higher levels of ethylene and potential differences in
calcium mobility. Tip burn also increased under high light (600
vs. 300 mmol m-2s-1) and high CO2 (600 Pa vs. 100 Pa). Tip burn
of ambient pressure plants was observed two days earlier (day
4) under high light than low light (day 6). Under ambient pressure
there were higher CO2 assimilation rates and dark respiration
rates (higher night consumption of metabolites) compared to
low pressure.
Impact
There are important engineering and crop production advantages
in growing plants under hypobaric (reduced atmospheric pressure)
conditions for extraterrestrial base or spaceflight environments.
Advantages include reduced pay load, greater safety because of
lower pressure gradients and improved plant growth. Elevated
levels of the plant hormone, ethylene, can occur in enclosed crop
production systems and in space-flight environments¾leading
to adverse plant growth and sterility. Objectives of this research
were to characterize the influence of hypobaria on growth and
ethylene evolution of lettuce (Lactuca sativa L. cv.
Buttercrunch). Growth was comparable in lettuce grown under 50
and 101 kPa (ambient) total gas pressures in a series of short-term
experiments lasting up to six days. However, tip burn occurred
under ambient, but not low pressure. Tip burn also increased under
high light (600 compared to 300 mmol m-2s-1) and high pCO2 (600
Pa compared to 100 Pa). Under ambient pressure, there were higher
CO2 assimilation rates and considerably greater dark respiration
rates (higher night consumption of metabolites) compared to low
pressure. This could lead to greater biomass production of plants
grown in low pressure plants over longer crop production cycles.
Ethylene evolution was lower under low than ambient pressure.
2005:
Field 84: 01/2005-12/2005
Field 85: (Progress Report)
Gerbera (Gerbera jamesonii) is an economically important
greenhouse crop produced and sold for cut flowers, potted plants,
and bedding plants. A wide variety of insecticides from different
insecticide classes with diverse modes of action are frequently
used on gerbera to reduce the occurrence of insecticide resistance.
Often there is near zero tolerance for insect pests on ornamental
crops, hence, insecticides are applied at frequent intervals to
prevent insect infestation. Due to increasing concern over the
use of toxic chemicals in greenhouse production, reduced-risk
insecticides are used because they are less toxic to workers,
have short residual properties, and have minimal adverse environmental
impact. These insecticides also may have a narrower spectrum of
pest activity and require frequent applications for sufficient
pest control. Insecticides are evaluated for visible phytotoxicity
and their impact on non-target organisms during their registration,
but impacts on plant physiology and plant growth and development
are not often tested.
Studies on the effects of insecticides on gas exchange have been
conducted primarily on agronomic crops with varying results. Many
of these studies were conducted with insecticides that are no
longer commercially applied or that are not applicable to ornamental
greenhouse crops. While it is generally thought that insecticides
can adversely affect plants, few studies have looked at insecticidal
effects on host plant physiology, in addition to plant growth
and development.
The most obvious effects were observed with the 4X Triact 70 (neem
oil) and Orthene TT&O (acephate) treatments. The 4X neem oil plants
had significantly reduced photosynthesis and stomatal conductance
- which resulted in reduced shoot and total aboveground DM, reduced
flower production, later flower development, thicker leaves (lower
SLA), reduced leaf area, and a reduction in plant quality. The
4X acephate plants had poorest marketablity due to severe phytotoxicity,
i.e. leaf burn, which contributed to lower shoot DM and total
aboveground DM. The highest quality were the plants treated with
1X or 4X Conserve SC (spinosad) or Avid 0.15 EC (abamectin). These
plants experienced no negative effects from insecticidal applications
and were not infested with the natural infestation of thrips that
damaged control and Talstar Flowable (bifenthrin) treated plants.
Neem oil, which is commonly used as both a fungicide as well as
an insecticide in potted gerbera production, also acted as a growth
retardant in this study. It is common practice to apply growth
retardants in the production of many ornamental crops to reduce
internode elongation and induce compact growth. Plants treated
with neem oil at the recommended concentration had reduced plant
growth and development due to reduced net photosynthesis and stomatal
conductance. Neem oil plants, particularly at the 4x concentration,
were not rated as marketable - due to excessively stunted growth,
unwanted residue, and reduced flower quality. However, when used
sparingly, neem oil may also be useful for reducing elongation
in gerbera, in addition to its insect and pathogen control.
Impact
The commonly used insecticides Avid 0.15 EC, Talstar Nursery Flowable,
and Conserve SC did not alter plant gas exchange, and were not
detrimental to plant growth and development of gerberas—even when
applied at 4X the recommended rate. Orthene Turf, Tree & Ornamental
Spray 97, when applied at recommended rates, did not adversely
affect plant growth and development or plant gas exchange of gerbera.
However, Orthene was phytotoxic to gerbera when applied at rates
above label recommendations. Triact 70 (neem oil) significantly
reduced plant gas exchange, plant growth and development, and
flower production, with greatest reductions occurring at the highest
concentration. Insect infestations on some of the control plants
and Talstar - treated plants negatively impacted their commercially
acceptable value, demonstrating the importance of insect pest
control. However, when using insecticides, caution and judicious
use should be exercised in order to prevent plant damage, minimize
development of pest resistance, and reduce production costs.
2004:
Current dogma has been that arbuscular mycorrhizal fungi (AMF)
are more beneficial for organic slow release fertilizer (OSRF)
than inorganic controlled-release fertilizer (ICRF). To the contrary,
our research shows that AMF enhancement is better with ICRF than
OSRF under stressful, high temperature production conditions.
This research determined the effects of two commercial AMF inocula,
OSRF and ICRF on plant growth, marketability and leachate of container-grown
Ipomoea carnea N. von Jacquin subsp. fistulosa (K.
Von Martinus ex J. Choisy) D. Austin (bush morning glory) grown
outdoors under high temperature summer conditions (maximum container
media temperature averaged 44.8 °C). Uniform rooted liners were
planted into 7.6 liter pots containing a pasteurized substrate
[pine bark and sand (3:1, by volume)]. The AMF treatment consisted
of BioterraPLUS and MycorisePro and a noninoculated control (NonAMF).
Fertilizer treatments included OSRF [Nitrell: 5-3-4 (5N-1.3P-3.3K)]
and ICRF [Osmocote: 18-7-10 (18N-3.0P-8.3K)]. OSRF was tested
at three rates: 8.3, 11.9 and 16.6 kg.m-3, which were respectively,
70%, 100% and 140% of manufacturer’s recommended rate, while ICRF
was tested at two rates: 3.6 and 7.1 kg?m-3 which were, respectively,
50% and 100% of manufacturer’s recommended rate. The P levels
were equivalent between 70% and 140% OSRF and, respectively, 50%
and 100% ICRF. Greatest growth [leaf, shoot, flower bud and flower
number, root, leaf, shoot and total plant dry mass (DM), growth
index, leaf area], N, P and K uptake, leaf chlorophyll, and plant
marketability occurred with BioterraPLUS plants at 50% and 100%
ICRF rate and MycorisePro at the 100% ICRF rate. Greater plant
growth occurred with increasing fertility levels; however, plants
at the 140% OSRF (same P level as 100% inorganic SRF) had poorest
growth, in part due to high temperature. While AMF enhanced growth
of plants with OSRF at all concentrations, better growth and marketability
occurred with ICRF than OSRF plants inoculated with AMF. AMF plants
at the 50% ICRF had comparable or better growth, higher N, P and
K and marketability than NonAMF plants at either 100% OSRF or
ICRF. AMF were able to survive under high temperature and colonize
plants grown from low to high fertility conditions. AMF inoculation
had minimal effect on container leachate [pH and electrical conductivity
(EC)]. However, the larger-sized AMF plants at 100% ICRF rate
had greater total leaf tissue N, P and K, suggesting greater nutrient
utilization ? thus reduced potential risk for leachate runoff.
Impact
To comply with these environmental regulations the nursery and
greenhouse industries have developed best management practices
(BMPs), such as more efficient fertilization systems, including
inorganic controlled-release (ICRF) and organic slow-release fertilizer
(OSRF) usage, reducing irrigation water volume and subsequent
nutrient leaching, and capturing and treating water runoff. One
of the most important challenges facing the nursery and greenhouse
industries is the incorporation of practices into production systems
that reduce pesticide and fertilizer usage, without reducing plant
quality and marketability. Beneficial microorganisms include arbuscular
mycorrhizal fungi (AMF), which establish symbiotic associations
with roots of most nursery crops. High container temperature is
a frequent summer problem in Southern U.S. nursery production
systems, directly affecting release of nutrients from ICRF, and
indirectly from OSRF, which are influenced by fungal and bacterial
microbial activity.
Plants inoculated with AMF at the recommended rate (100%) of inorganic
SRF had the best growth response. This work is of particular importance
to commercial nurseries and greenhouse production since ICRF are
much more commonly used than OSRF. Hence, lower fertilization
for AMF plants could minimize leaching and runoff of fertilizer
leachate. While AMF had little effect on pH or EC leachates, AMF
plants were larger than NonAMF plants and subsequently absorbed
a greater total amount of ions, which could potentially minimize
leaching and runoff of fertilizer nutrients.
2003:
Elevated levels of ethylene occur in enclosed crop production
systems and in spaceflight environments?leading to adverse plant
growth and sterility. There are engineering advantages in growing
plants at hypobaric (reduced atmospheric pressure) conditions
in biomass production for extraterrestrial base or spaceflight
environments. Objectives of this research were to characterize
the influence of hypobaria on growth and ethylene evolution of
lettuce (Lactuca sativa) and wheat (Triticum aestivum).
Plants were grown under variable total gas pressures [from 30
to 101 kPa (ambient)]. In one study, lettuce and wheat were direct
seeded, germinated and grown in the same chambers for 28 d at
50 or 101 kPa. Hypobaria increased plant growth and did not alter
germination rate. During a 10-day study, 28 d-old lettuce and
40 d-old wheat seedlings were transplanted together in the same
low and ambient pressure chambers; ethylene accumulated in the
chambers, but the rate of production by both lettuce and wheat
was reduced more than 65 % under 30 kPa compared with ambient
pressure (101 kPa). Low O2 concentrations [partial pressure of
O2 (pO2) = 6.2 kPa] inhibited ethylene production by lettuce under
both low (30 kPa) and ambient pressure, whereas ethylene production
by wheat was inhibited at low pressure but not low O2 concentration.
There was a negative linear correlation between increasing ethylene
concentration and decreasing chlorophyll content of lettuce and
wheat. Lettuce had higher production of ethylene and showed greater
sensitivity to ethylene than wheat. The hypobaric effect on reduced
ethylene production was greater than that of just hypoxia (low
oxygen).
Impact
The exploration of space will require the development of Advanced
Life Support Systems (ALS) that will have the capacity to recycle
resources and produce food. The biological component will include
the use of higher plants for air and water purification, as well
as providing food and psychological benefits.
Important environmental variables that have received little research
effort in relation to an Advanced Life Support System are: (i)
total atmospheric gas pressure, (ii) high CO2 partial pressure,
up to 70 Pa or higher, greatly in excess of the range currently
studied by researchers interested in global change, (iii) wide
differences in humidity and (iv) effects of trace gases - including
ethylene under low pressure conditions. Hence, the objectives
of this research were to characterize the influence of hypobaric
conditions on growth and ethylene evolution of lettuce (Lactuca
sativa) and wheat (Triticum aestivum).
To our knowledge, this is the first report that hypobaric environments
per se reduce ethylene evolution of lettuce and wheat, and that
lettuce is more sensitive to ethylene than wheat in sealed microenvironments.
Hypobaria increased plant growth and did not alter germination
rate. This research shows that plants can be successfully grown
at hypobaric (as low as 30 kPa total gas pressure) and hypoxic
(pO2 = 6.2 kPa O2) environments. Hypobaric conditions subsequently
reduced the adverse effect of ethylene on plant growth. We found
that the hypobaric (low pressure) effect on ethylene production
was greater than that of just hypoxia (low oxygen).
2002:
Little is known about the role of arbuscular mycorrhiza
fungi (AM) on physiological changes of micropropagated plantlets
during acclimatization and post-acclimatization. Using chile ancho
pepper (Capsicum annuum L. cv. San Luis), measurements
were made of water relations, gas exchange, abscisic acid (ABA),
plantlet growth and AM development. Plantlets had low photosynthetic
rates (A) and poor initial growth during acclimatization. Relative
water content (RWC) decreased during the first days after transfer
from tissue culture containers to ex vitro conditions. Consequently,
transpiration rates (E) and stomatal conductance (gs) declined,
confirming that in vitro formed stomata were functional and able
to respond ex vitro to partial desiccation — thus avoiding excessive
leaf dehydration and plant death. Colonized plantlets had lower
leaf ABA and higher RWC than NonAM plantlets during peak plant
dehydration — and a higher A and gs as early as days 5 and 7.
During post-acclimatization, A increased in all plantlets; however,
more dramatic changes occurred with AM plantlets. Within 48 days,
AM plantlets had greater E, A, leaf chlorophyll, N, P and K, leaf
dry biomass and leaf area, fruit production and carbon allocation
compared with NonAM plantlets. Rapid AM colonization enhanced
physiological adjustments, which helped plantlets recover rapidly
during acclimatization and obtain greater growth during post-acclimatization.
Impact
With many species, use of micropropagation is limited because
of poor plantlet survival rates during acclimatization, which
is the transition from in vitro to ex vitro conditions. In commercial
micropropagation systems, plant losses of 10 to 40% and higher
can occur. Some micropropagated plantlets may lack functional
roots, are photomixotrophic and typically have leaves with low
photosynthetic rates that impede growth. Transpiration rates are
considerably higher in micropropagated plantlets than in vivo
grown plants because of the poor stomatal control and the abnormally
high cuticular water loss, which cause senescence and death of
leaves and plantlets.
Acclimatization is critical because these abnormalities must
be corrected to ensure survival and continued normal plant growth.
Chile pepper is an important vegetable crop that is cultivated
worldwide. Chile Ancho 'San Luis' is highly mycorrhiza dependent
and thus a good potential model system for studying AM induced
physiological effects during acclimatization. This research
was conducted with a mixed isolate of Glomus spp. from
Mexico (ZAC-19) that enhances drought resistance and nutrient
uptake of chile ancho seedling peppers (Davies et al. 2000,
2001). Our research shows that mycorrhizal can benefit Chile
Ancho water relations, gas exchange, reduce ABA, and increase
growth of the micropropagated plantlets during acclimatization
and post-acclimatization.
2001:
Chromium (Cr) is a heavy metal risk to human health,
and a contaminant found in agricultural soils and industrial sites.
Phytoremediation, which relies on phytoextraction of Cr with biological
organisms, is an important alternative to costly physical and
chemical methods of treating contaminated sites. The ability of
the arbuscular mycorrhizal fungus (AM), Glomus intraradices,
to enhance Cr uptake and plant tolerance was tested on the growth
and gas exchange of sunflower (Helianthus annuus L.). Mycorrhizal-colonized
(AM) and non-inoculated (Non-AM) sunflower plants were subjected
to two Cr species [trivalent cation (Cr3+) {Cr(III)}, and divalent
dichromate anion (Cr2O7--) {Cr(VI)}]. Both Cr species depressed
plant growth, decreased net photosynthesis (A) and increased the
vapor pressure difference; however, Cr(VI) was more toxic. Chromium
accumulation was greatest in roots, intermediate in stems and
leaves, and lowest in flowers. Greater Cr accumulation occurred
with Cr(VI) than Cr(III). AMF enhanced the ability of sunflower
plants to tolerate and hyperaccumulate Cr. At higher Cr levels
greater mycorrhizal dependency occurred, as indicated by proportionally
greater growth, higher A and reduced visual symptoms of stress,
compared to Non-AM plants. AM plants had greater Cr-accumulating
ability than Non-AM plants at the highest concentrations of Cr(III)
and Cr(VI). Arbuscules, which play an important role in mineral
ion exchange in root cortical cells, had the greatest sensitivity
to Cr toxicity.
Impact
Heavy metals are one of the main sources of environmental pollution.
Pytoremediation utilizes biological organisms for phytoextraction
or removal of plant biomass containing more concentrated levels
of heavy metals from polluted soils. Pytoremediation is an alternative
to conventional physical and chemical methods of treating contaminated
soils. Chromium (Cr) is a heavy metal risk to human health, and
a contaminant found in agricultural soils and industrial sites.
Phytoremediation is an important alternative to costly physical
and chemical methods of treating contaminated sites. The ability
of the arbuscular mycorrhizal fungus (AM), Glomus intraradices,
to enhance Cr uptake and plant tolerance was tested on the growth
and gas exchange of sunflower (Helianthus annuus L.). AM
enhanced plant accumulation and tolerance to Cr. Under lower phosphorus
conditions [to aid Cr phytoextraction] AM plants had greater vigor,
greater photosynthesis and less visible Cr stress). This led to
higher biomass and subsequent greater phytoextraction of Cr. Since
most metal-accumulating wild plants are relatively small in size
and have slow growth rates, their potential for phytoextraction
is limited. Optimum plant-mycorrhizal systems for phytoextraction
of Cr should not only be able to tolerate and accumulate high
levels of Cr in harvestable parts, but also have a rapid growth
and potential to produce high biomass in the field. Hence, the
high biomass, rapid-growing sunflower-Glomus association might
be an excellent candidate for phytoextraction when transplanted
to the field.
2000:
New nursery production systems are being developed
that emphasize the use of slow-release fertilizers, minimize the
use of pesticides and soluble herbicides, and more efficiently
utilize water. Research was conducted to demonstrate that mycorrhiza
can survive in a commercial nursery container production system,
and enhance plant productivity. Four species were used as host
plants [Nandina domestica ‘Moon Bay’, Loropetalum chinense
variety Rubrum ‘Hinepurpleleaf’ Plumb delight®, Salvia
gregii, and Photinia fraseri]. Plants were inoculated
with arbuscular mycorrhizal fungi, Glomus intraradices,
and grown in a commercial nursery in Texas. For the first 5.5
months, plants were grown in #1 cans containing either 3 kg cu
m or 4.2 kg cu m 24N-4P205-8K20. For the final 6.5 months of the
study, plants were in larger containers, all of which contained
4.2 kg cu m 24N-4P2O5-8K2O. The commercial inoculum of Glomus
intraradices only enhanced growth of N. domestica. The shoot
dry mass of mycorrhizal N. domestica plants at 3 kg cu m was the
same as non-colonized plants at the higher fertility level of
4.2 cu m. Intraradical hyphae development and colonization (total
arbuscules, vesicles/endospores, hyphae) of L. chinense, N.
domestica, and S. gregii increased at the higher fertility
levels. S. gregii had the greatest mycorrhizal development and
a 216% increase in hyphae development and colonization at the
higher fertility level.
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