Does cross‐acclimation between drought and freezing stress persist over ecologically relevant time spans? A test using the grass Poa pratensis

Abstract

Despite evidence that prior exposure to drought can increase subsequent plant freezing tolerance, few studies have explored such interactions over ecologically relevant time spans. We examined the combined effects of drought and subsequent freezing on tiller growth and leaf sugar concentrations in the grass, Poa pratensis. We exposed tillers to no drought (-0.04 MPa), moderate drought (-0.19 MPa) or severe drought (-0.42 MPa) for 3 weeks in summer. Tillers were then frozen in autumn or spring at -5 °C (frost damage) or at 0 °C (control) for 3 days and harvested after a re-growth period. For shoot growth, there was a significant interaction between drought and autumn freezing, whereby the relative effect of freezing on growth was least for the plants previously exposed to severe drought; however, there was no significant interaction between drought and spring freezing. For root growth, there were no significant interactions between drought and freezing in either season. Leaf sugar concentrations increased significantly with drought intensity, but these effects dissipated within a month, prior to the onset of the autumn freezing treatment. Overall, our results suggest that interactions between prior drought and subsequent freezing in P. pratensis may be most relevant in the context of autumn freezing, and despite the important role of soluble sugars in increasing both drought and freezing tolerance in this species, the retention of these compounds after drought stress does not appear to explain the occurrence of drought-frost interactions at ecologically relevant time scales.

Drought survival and recovery in grasses: Stress intensity and plant–plant interactions impact plant dehydration tolerance

“…This ultimately led to higher dehydration tolerance. Although they were not tested here, carbohydrate and nutrient concentration changes depending on the relative rates of leaf growth versus LS of each population in monocultures, 2‐ and 4‐component mixtures can also be explicative (Keep et al, 2021). Plastic adjustments in response to changes in plant–plant interactions are potentially important mechanisms underlying the variation of plant dehydration tolerance in plant communities, impacting drought survival.…”

“…Hence, the usual focus on leaves underscores the importance of surviving organs which are usually not the lamina blade but the meristematic tissues in grasses (Volaire et al, 1998) and, equivalently, the vascular cambium in trees (Hammond et al, 2021; Mantova et al, 2021). In perennial grasses, the ability of plants to ‘stay green’ and remain photosynthetically active under moderate drought (i.e., dehydration avoidance) trades off with the ability to survive under severe drought (i.e., dehydration tolerance, Bristiel et al, 2017; Keep et al, 2021). Hence, dehydration avoidance in leaves is often inversely correlated with dehydration tolerance in meristems that enhance survival under severe drought when most leaves have senesced (Volaire, 2018).…”

“…Plant–plant interactions are a crucial issue in understanding the resilience of grasslands since diverse grass communities may become more resilient through the local expansion of drought‐tolerant species in the face of climate change (Craine et al, 2013). Moreover, migrations of grass species are expected, for example, the predicted biogeographical areas of Mediterranean populations of perennial grasses will extend towards the current temperate areas under a future climate scenario in Europe (Keep et al, 2021; Shihan et al, 2022). Grasslands may then increasingly contain populations of various origins and levels of adaptation to drought in the future, and for instance, the association of Mediterranean and temperate populations of grass species is advocated to enhance forage crop resilience (Norton et al, 2016).…”

To grow or survive: Which are the strategies of a perennial grass to face severe seasonal stress?

“…The optimization of the costs–benefits balance between fast growth and plant survival has been demonstrated in species with seasonal endo‐dormancy enhancing survival under harsh winters or summers (Gillespie & Volaire, 2017; Lang, 1987). Interestingly, frost and drought stresses may lead to similar plant adaptive responses as both cause cellular dehydration (Kong & Henry, 2018). For instance, under both kinds of stress, a high investment in protective compounds, such as water‐soluble carbohydrates in reserve organs (Sanada et al., 2007; Volaire, 1995), enhances stress tolerance but reduces resource allocation to growth in grasses.…”

Interactions of plant growth responses to spring freezing and summer drought: a multispecies comparison

“…When the order of the stressors is switched, and plants are exposed to drought immediately after freezing, there also are higher concentrations of antioxidants when compared to drought‐only plants (Horváth et al., ; Grudkowska and Zagdanska, ; Hossain et al., ). However, prolonged elevation of soluble sugars concentrations after drought was not responsible for increased freezing tolerance in Poa pratensis L. (Kong and Henry, ), nor did the retention of soluble sugars after freezing stress influence drought tolerance in this species (Kong and Henry, ).…”