CHANGES IN WATER AND NUTRIENT USE EFFICIENCY DURING WHEAT GROWTH AND DEVELOPMENT.

Abstract

Wheat (cv. Yecora Rojo) plants were grown in a closed chamber as part of NASA's Controlled Ecological Life Support System (CELSS) program. Plants were grown using a recirculating hydroponics with EC controlled at 0.12 S m-1 by automatic additions of a nutrient concentrate, and pH was controlled at 5.8 units with automatic additions of nitric acid. Daily CO2 exchange, water uptake, and nutrient uptake were monitored for the entire 20 m2 canopy throughout growth. Nutrient use efficiency (NUE) relative to water and CO2 uptake were determined, where NUE-W was defined as the amount of water taken up per unit of nutrient and NUE-C as the amount of carbon fixed per unit of nutrient. Water uptake remained relatively constant after canopy closure (25 DAP), where CO2 uptake peaked during rapid vegetative growth and then declined gradually with age and gain fill. Nutrient uptake also peaked during vegetative growth but declined sharply after anthesis. Water use efficiency (WUE) was high early in growth and then declined with age due to the decrease in CO2 exchange over time. In contrast NUE-C and NUE-W were low during vegetative growth and the increased nearly 10-fold during grain fill.