Physiological responses to drought stress and recovery reflect
differences in leaf function and microanatomy among grass lineages
Abstract
Grasses are cosmopolitan, existing in many biome and climate types from
xeric to tropical. Traits that control physiological responses to
drought vary strongly among grass lineages, suggesting that tolerance
strategies may differ with evolutionary history. Here, we withheld water
from 12 species representing 6 tribes of grasses to compare how tolerant
and intolerant species respond to drought in different grass lineages.
We measured physiological, morphological, and microanatomical traits.
Dominant lineages from tropical savannas, like Andropogoneae, tolerated
drought due to above and belowground morphological traits, while
temperate grasses utilized conservative leaf physiology (gas exchange)
and microanatomy. Increased intrinsic water-use efficiency (iWUE)
coincided with a larger number of stomata, resulting in greater water
loss (with inherently greater carbon gain) and increased drought
sensitivity. Inherent leaf and root economic strategies impacting
drought response were observed in all species, resulting in either high
SLA or SRL, but not both. Our results indicate that grasses subjected to
severe drought were influenced by microanatomical traits (e.g., number
of stomata and xylem area) which were shared within lineages. In
addition, grasses recovered at least 50% of physiological functioning
across all lineages and 92% within Andropogoneae species, illustrating
how drought can influence functional responses across diverse grass
lineages.