Effect of hypobaric conditions on ethylene evolution and growth of lettuce and wheat

by He, Davies, and Lacey

Elevated levels of ethylene occur in enclosed crop production systems and in spaceflight environments, leading to advers 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 lettuce (Lectuca sativa) and wheat (Triticum aestivum). Plants were grown under variable total gas pressures [from 30 to 101kPa (ambient)]. In one study, lettuce and wheat were direct seeded, germinated and grown in the same chambers for 28 d at 50 or 101kPa. Hypobaria increased plant growth and did not alter germination rate. During a 10-day study, 28-day-old lettuce and 40-day-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 30kPa compared with ambient pressure (101kPa). Low O2 concentrations [partial pressure of O2 (pO2)=6.2kPa] inhibited ethylene production by lettuce under both low (30kPa) 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 senstivity to ethylene than 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).

J. Plant Physiol. 160. 1341-1350 (2003).