Summer Drought Survival Strategies and Sustainability of Perennial Temperate Forage Grasses in Mediterranean Areas

Abstract

Perennial grasslands provide numerous agroenvironmental benefits due to continuous soil cover. In Mediterranean areas, chronic summer drought is expected to increase as a result of climate changes. Plant adaptations that protect meristematic tissues include dehydration delay, dehydration tolerance, and summer dormancy. Summer dormancy can only be reliably tested in plants not subjected to water deficit. Under summer irrigation, complete dormancy is manifested by cessation of growth in association with full senescence of foliage and induced dehydration of leaf bases. Incomplete dormancy occurs when leaf growth is partially constrained and associated with moderate levels of foliage senescence. Summer dormancy is under hormonal control and is induced under increasing photoperiod and temperature. Recent results show that drought cannot induce summer dormancy under early‐spring short days, although a water deficit under late‐spring long days reinforces it and could enhance drought survival. Dehydration tolerance and dormancy are independent phenomena. Summer dormancy has been correlated with superior survival after severe summer droughts in many perennial grass species. This trait has potential for improving cultivars able to meet agronomic and environmental goals.

Implications of plant functional traits and drought survival strategies for ecological restoration

“…Our study supports the anticipated trade‐off between dehydration tolerance/summer dormancy and rapid resource acquisition, and thus, the association between dehydration tolerance/summer dormancy and more conservative resource acquisition (Reich, ; Volaire et al., ; Zwicke et al., ), notably in the context of intraspecific variability. The more conservative strategy was characterized by lower potential productivity and higher LDMC (lower SLA).…”

How can forage production in Nordic and Mediterranean Europe adapt to the challenges and opportunities arising from climate change?

“…In the past, breeding efforts in tall fescue and cocksfoot have mainly been directed towards use in temperate areas with summer active material that are short lived under drought, and there are therefore very few cultivars adapted to severe drought currently available in southern Europe . Persistence during severe drought is governed by mechanisms different from those conferring resistance to moderate droughts (Milbau et al, 2005;Volaire et al, 2009). Plants with responses resulting in resistance under moderate drought and maintenance of shoot growth have to either avoid or tolerate leaf dehydration.…”

Senescence, dormancy and tillering in perennial C4 grasses

“…Depending on the environmental stress that is placed on these plants, responses can be neutral, positive or negative. However, the basal mechanisms affecting these changes appear to come from specific genes (DAM genes in peach; [64]) which are of importance to dormancy in other dicot species or from a suite of traits that primarily affect the onset leaf senescence in grasses experiencing summer dormancy [4,6,81]. These studies point to potential mechanisms that tie into the overall integration of timely aerial senescence to the onset of dormancy in the perenniating structures, and provide targets for study in the temperate C 4 perennial grasses.…”

“…This allows the plant to resume growth with prior stored reserves once conditions are favorable. Seasonal dormancy can occur in the summer months (generally induced by lack of water and/or high temperature) [4][5][6] or in the winter months (generally induced by low light and low temperature limitation; see below). It is possible that summer dormancy in grasses might share some similar molecular pathways to winter dormancy in temperate C 4 grasses (for example signaling responses to senescence, desiccation, and meristem metabolism).…”