The agony of choice: how plants balance growth and survival under water-limiting conditions

Abstract

When confronted with water limitation, plants actively reprogram their metabolism and growth. Recently, it has become clear that growing tissues show specific and highly dynamic responses to drought, which differ from the well-studied responses in mature tissues. Here, we provide an overview of recent advances in understanding shoot growth regulation in water-limiting conditions. Of special interest is the balance between maintained growth and competitiveness on the one hand and ensured survival on the other hand. A number of master regulators controlling this balance have been identified, such as DELLAs and APETALA2/ETHYLENE RESPONSE FACTOR-type transcription factors. The possibilities of engineering or breeding crops that maintain growth in periods of mild drought, while still being able to activate protective tolerance mechanisms, are discussed.

Figure 1.

The balance between stress tolerance and maintained growth. In response to water limitation, stress avoidance and tolerance mechanisms are activated to ensure survival in case the stress is prolonged or becomes more severe, resulting in growth limitation and a potential competitive disadvantage. However, several adaptations allow plants to balance survival and continued growth depending on the stress level.

Figure 2.

Mechanisms regulating growth and stress tolerance in developing leaves, and their interactions. In the top and middle panels, mechanisms regulating cell proliferation and expansion in short-term growth inhibition and more long-term acclimation to stress, respectively, are depicted. In the bottom panel, stress tolerance mechanisms that interact with growth-regulating mechanisms are shown. Font color indicates the direction of change by stress: red for up-regulation, green for down-regulation, and black for no change.