Abstract
A better understanding of physiological responses of crops to drought stress is important for ensuring sustained crop productivity under climate change. Here, we studied the effect on 15-day-old maize (Zea mays L.) plants of a 6 d non-lethal period of soil drying [soil water potential (SWP) decreased from -0.20 MPa to -0.81 MPa]. Root growth was initially stimulated during drying (when SWP decreased from -0.31 MPa to -0.38 MPa, compared with -0.29 MPa in well-watered pots), followed by inhibition during Days 5-6 (SWP from -0.63 MPa to -0.81 MPa). Abscisic acid (ABA) in the root began to accumulate as the root water potential declined during Days 2-3. Leaf elongation was inhibited from Day 4 (SWP less than -0.51 MPa), just after leaf ABA content began to increase, but coinciding with a decline in leaf water potential. The stomatal conductance was restricted earlier in the younger leaf (fourth) (on Day 3) than in the older leaf (third). The ethylene content of leaves and roots decreased during drying, but after the respective increase in ABA contents. This work identified critical timing of hydraulic and chemical changes at the onset of soil drying, which can be important in initiating early stomatal and growth responses to drought.
Highlights
Drought is a major factor restricting crop production in many regions of the world (Boyer, 1982; Boyer et al, 2013)
To establish a non-lethal progressive soil drying episode and to investigate maize root and shoot physiological responses during this process, several preliminary experiments were conducted and this 6 d drying treatment was chosen for this study
Previous studies have reported that shoot and root growth in maize respond differently during soil drying (Sharp and Davies, 1979; Watts et al, 1981)
Summary
Drought is a major factor restricting crop production in many regions of the world (Boyer, 1982; Boyer et al, 2013). Whilst maize (Zea mays L.) is among the top three staple crops worldwide (Varshney et al, 2012), its production is likely to suffer more from drought stress in the future under a changing climate with increased risk of high temperatures and more variable precipitation (Battisti and Naylor, 2009; Challinor et al, 2014; Tardieu, 2012). It is important to breed plants that are more drought resistant and to improve current irrigation management for agricultural systems. Both of these requirements can depend upon a better understanding of the physiological responses to drought stress of shoots and roots (Tuberosa et al, 2007). A non-lethal drought stress is common in the field and is considered to be an important target for the improvement of plant performance in droughted environments (Tuberosa et al, 2007; Skirycz et al, 2011)
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