NDS Water Pressures Affect Growth Rate By Changing Leaf Area, Not Single Leaf Photosynthesis 2001-01-2277
Plant growth conditions must be optimized for use in advanced life support systems during space flight. Wheat cv. Apogee was grown in a nutrient delivery system (NDS) using porous tubes held at three levels of applied water pressure (Pw), or suction: −0.5 kPa, −0.3 kPa, and −0.1 kPa for 24 days. Measurements of leaf area and dry mass were made at 5, 9, 14, 18 and 24 DAP and used to determine the leaf area index (LAI), net assimilation rate (NAR), and crop growth rate (CGR). Pw did not have a significant effect on plant development until after 9 DAP, at which time growth at different treatments began to diverge. Plants grown at −0.1 kPa exhibited the largest CGR and LAI and had the greatest biomass, suggesting that −0.1 kPa was the optimal Pw. Growth analysis indicated that changes in CGR were due to changes in leaf area, rather than changes in photosynthesis. There were no significant differences between measures of chlorophyll fluorescence: Fv/Fm, qN and qP of plants grown at different Pw, which further indicated that Pw had little effect on leaf photosynthesis. Slight differences in starch content of plants grown at different Pw were observed. This study served as a ground control to determine baseline data characterizing the effect of P w on wheat growth.