Dead or Alive? Using Membrane Failure and Chlorophyll a Fluorescence to Predict Plant Mortality from Drought

Abstract

Climate models predict widespread increases in both drought intensity and duration in the next decades. Although water deficiency is a significant determinant of plant survival, limited understanding of plant responses to extreme drought impedes forecasts of both forest and crop productivity under increasing aridity. Drought induces a suite of physiological responses; however, we lack an accurate mechanistic description of plant response to lethal drought that would improve predictive understanding of mortality under altered climate conditions. Here, proxies for leaf cellular damage, chlorophyll a fluorescence, and electrolyte leakage were directly associated with failure to recover from drought upon rewatering in Brassica rapa (genotype R500) and thus define the exact timing of drought-induced death. We validated our results using a second genotype (imb211) that differs substantially in life history traits. Our study demonstrates that whereas changes in carbon dynamics and water transport are critical indicators of drought stress, they can be unrelated to visible metrics of mortality, i.e. lack of meristematic activity and regrowth. In contrast, membrane failure at the cellular scale is the most proximate cause of death. This hypothesis was corroborated in two gymnosperms (Picea engelmannii and Pinus contorta) that experienced lethal water stress in the field and in laboratory conditions. We suggest that measurement of chlorophyll a fluorescence can be used to operationally define plant death arising from drought, and improved plant characterization can enhance surface model predictions of drought mortality and its consequences to ecosystem services at a global scale.

Influence of drought and heat stress, applied independently or in combination during seed development, on qualitative and quantitative aspects of seeds of lentil (Lens culinarisMedikus) genotypes, differing in drought sensitivity

“…Moreover, upon exposure to both stresses at the same time, the lentil leaves showed extensive damage to their membranes (as indicated by high EL), chlorophyll content, and photosynthetic efficiency, which might be attributed to a significant reduction in leaf water status and stomatal conductance (Awasthi et al, 2014). Damage to membranes may occur due to the direct impacts of these stresses (Guadagno et al, 2017;Horváth et al, 2012) or intense oxidative stress generated by two stresses (Johnson et al, 2014) and has been reported in chickpea (Awasthi et al, 2017).…”

“…Moreover, upon exposure to both stresses at the same time, the lentil leaves showed extensive damage to their membranes (as indicated by high EL), chlorophyll content, and photosynthetic efficiency, which might be attributed to a significant reduction in leaf water status and stomatal conductance (Awasthi et al, ). Damage to membranes may occur due to the direct impacts of these stresses (Guadagno et al, ; Horváth et al, ) or intense oxidative stress generated by two stresses (Johnson et al, ) and has been reported in chickpea (Awasthi et al, ). Chlorophyll loss is attributed to increased photo‐oxidation (Guo, Zhou, & Zhang, ), dehydration, inhibited synthesis, or increased degradation (Tewari & Tripathy, ), which matches the observations in chickpea (Awasthi et al, ), tomato (Nankishore & Farrell, ), and rice (Kumar, Vijayalakshmi, & Vijayalakshmi, ) exposed to both stresses.…”

Coordinated plasticity maintains hydraulic safety in sunflower leaves

“…and finally, Ψ min calculated as Ψ min = E max /K plant . The maximum quantum efficiency of photosystem II ( F v / F m ) is a well-known parameter typically used as an index of photosynthetic potential and injury in leaves (Guadagno et al, 2017). Here, we assessed F v / F m in the same plants used for the OV method over the desiccation course as a proxy for leaf damage.…”

Drought-induced mortality: stem diameter variation reveals a point of no return in lavender species

“…Consequently, the growth cannot resume since there is no more meristematic cells or any parenchyma cells that can dedifferentiate. On the contrary, when PLD max was not reached, the growth resumed despite a dead volume in the branches, involving an active cambium that generates new xylem vessels to recover from an episode of drought (Brodribb et al, 2010; Guadagno et al, 2017)…”

“…According to Li et al, (2015) and Guadagno et al, (2017), a threshold in the cell death (membrane injury or mortality of cambial cells) can be a point of no return associated with plant death. Maintaining the stability of cell membranes is an integral part of drought tolerance (Bajji et al, 2002).…”