Daytime leaf water use efficiency does not explain the relationship between plant N status and biomass water-use efficiency of tobacco under non-limiting water supply

摘要: The increasing probability of seasonal droughts and freshwater scarcity emphasizes the importance crop traits such as water-use efficiency (WUE) its relation to nutrient management. In an earlier study using soil substrate in a pot experiment, we reported significant positive effects N supply on biomass WUE tobacco. However, there was debate that latter may be due indirect (hidden drought), most likely because plants supplied with adequate generally have greater hence faster depletion water root zone. field situation, therefore, it is difficult relate any variation leaf or direct effect supply. this context, aim current re-examine what extent fertilization directly affects related parameters under non-limiting hydroponics. About 2 weeks after transfer tobacco seedlings into solution containing mM N, were treated high-N low-N form NH4NO3. A marked decrease CO2 assimilation compared measured already 5 d onset treatments (DAO). contrast, three different experiments clearly showed stomatal conductance (gs) remained almost constant until DAO resulting significantly lower high-N. Leaf decreased gradually (up 42% WUE) at later stages. Surprisingly, whole-plant δ13C values not affected by harvest date, which contrast our report where observed same variety experiment substrate. Night-time respiration transpiration rates (measured gas exchange thermal imaging) higher than data show 48.6% 9.8% beneficiary daytime lost when nocturnal night-time leaves taken consideration. Thus, conclude reports showing (e.g., hidden/mild drought).