Growth of Arabidopsis thaliana seedlings under water deficit studied by control of water potential in nutrient‐agar media

Abstract

We have characterized the growth responses of Arabidopsis thaliana seedlings to water deficit. To manipulate the water potential, we developed a method whereby the nutrient-agar medium could be supplemented with polyethylene glycol (PEG 8000); PEG was introduced into gelled media by diffusion, which produced media with water potential as low as -1.6 MPa. For dark-grown plants, hypocotyl growth had a hyperbolic dependence on water potential, and was virtually stopped by -1 MPa. In contrast, primary root elongation was stimulated by moderate deficit and even at -1.6 MPa was not significantly less than the control. That these results did not depend on a direct effect of PEG was attested by obtaining indistinguishable results when a dialysis membrane impermeable to PEG was placed between the medium and the seedlings. For light-grown seedlings, moderate deficit also stimulated primary root elongation and severe deficit reduced elongation only partially. These changes in elongation were paralleled by changes in root system dry weight. At moderate deficit, lateral root elongation and initiation were unaffected and at higher stress levels both were inhibited. Primary root diameter increased steadily with time in well-watered controls and under water deficit increased transiently before stabilizing at a diameter that was inversely proportional to the deficit. Along with stimulated primary root elongation, moderate water deficit also stimulated the rate of cell production. Thus, A. thaliana responds to water deficit vigorously, which enhances its use as a model to uncover mechanisms underlying plant responses to water deficit.

Repression of early lateral root initiation events by transient water deficit in barley and maize

“…However, the effects of WD on LR initiation have been poorly studied in general [13]. A reduction in LR number has been reported for Arabidopsis subjected to osmotic stress (polyethylene glycol), but only emerged and visually detectable LRs were taken into account, which made it unclear at what stage LR formation was (partially) disrupted [26]. Further experiments revealed that osmotic stress blocks LR formation at the emergence stage in Arabidopsis [27].…”

A plant microRNA regulates the adaptation of roots to drought stress

“…Plant roots are responsible for water uptake and are the first plant organ to encounter soil water deficiency. Accordingly, roots exhibit great architectural plasticity to help the plants to better adapt to water availability [1][2][3]. Under normal conditions lateral roots proliferate; under drought stress, both the initiation and the elongation of lateral roots are reduced [1][2][3], presumably facilitating primary root elongation for water uptake from deeper soil.…”

“…Accordingly, roots exhibit great architectural plasticity to help the plants to better adapt to water availability [1][2][3]. Under normal conditions lateral roots proliferate; under drought stress, both the initiation and the elongation of lateral roots are reduced [1][2][3], presumably facilitating primary root elongation for water uptake from deeper soil. Whereas the phytohormone auxin plays an essential role in promoting lateral root initiation and elongation [4,5], the stress hormone abscisic acid (ABA) inhibits lateral root generation [3,6,7].…”

Interaction with ethylene: changing views on the role of abscisic acid in root and shoot growth responses to water stress

“…For example, this occurs in nodal (adventitious) roots of maize, which must penetrate through the often dry surface soil (Westgate & Boyer 1985), and in primary roots of a range of species, which helps seedling establishment under dry conditions by ensuring a supply of water before shoot emergence (Sharp, Silk & Hsiao 1988;Spollen et al . 1993;van der Weele et al . 2000).…”