Drought stress imposes reversible photosynthetic damage under
fluctuating light conditions in crops
Drought stress is a major limiting factor for crop growth and yield.
Water availability in the field can cyclically change between drought
and rewatering conditions, depending on precipitation patterns.
Concurrently, light intensity under field conditions can fluctuate,
inducing dynamic photosynthesis and transpiration during crop growth
period. The present study aimed to characterize carbon gain and water
use in fluctuating light under drought and rewatering conditions by
conducting gas exchange measurements in two major crops, namely rice and
soybean. In both crops, drought stress reduced steady-state
photosynthesis and/or photosynthetic capacity, and delayed
photosynthetic induction even when it had relatively small impact on
photosynthetic capacity, suggesting that the drought effects on
photosynthesis should be evaluated based on induction, maximum, and
steady states. This delayed photosynthetic induction resulted in a
substantial loss of carbon gain under fluctuating light conditions,
which can be a limiting factor for crop growth and yield in the field.
Meanwhile, rewatering after drought conditions completely recovered
photosynthetic capacity and induction in both crops, whereas drought
experience would be memorized to slow down the stomatal opening.
Therefore, the stability of photosynthetic induction can be a promising
target to improve drought tolerance during crop breeding in the future.