A kinetic analysis of hyponastic growth and petiole elongation upon ethylene exposure in Rumex palustris.

Background And Aims: Complete submergence is an important stress factor for many terrestrial plants, and a limited number of species have evolved mechanisms to deal with these conditions. Rumex palustris is one such species and manages to outgrow the water, and thus restore contact with the atmosphere, through upward leaf growth (hyponasty) followed by strongly enhanced petiole elongation. These responses are initiated by the gaseous plant hormone ethylene, which accumulates inside plants due to physical entrapment.

Auxin perception and polar auxin transport are not always a prerequisite for differential growth.

Using time-lapse photography, we studied the response kinetics of low light intensity-induced upward leaf-movement, called hyponastic growth, in Arabidopsis thaliana. This response is one of the traits of shade avoidance and directs plant organs to more favorable light conditions. Based on mutant- and pharmacological data we demonstrated that among other factors, functional auxin perception and polar auxin transport (PAT) are required for the amplitude of hyponastic growth and for maintenance of the high leaf angle, upon low light treatment.

Differential petiole growth in Arabidopsis thaliana: photocontrol and hormonal regulation.

Environmental challenges such as low light intensity induce differential growth-driven upward leaf movement (hyponastic growth) in Arabidopsis thaliana. However, little is known about the physiological regulation of this response. Here, we studied how low light intensity is perceived and translated into a differential growth response in Arabidopsis.

The stimulating effects of ethylene and auxin on petiole elongation and on hyponastic curvature are independent processes in submerged Rumex palustris.

The flooding-tolerant plant species Rumex palustris (Sm.) responds to complete submergence with stimulation of petiole elongation mediated by the gaseous hormone ethylene. We examined the involvement of auxin in petiole elongation.

Auxin dynamics after decapitation are not correlated with the initial growth of axillary buds.

One of the first and most enduring roles identified for the plant hormone auxin is the mediation of apical dominance. Many reports have claimed that reduced stem indole-3-acetic acid (IAA) levels and/or reduced basipetal IAA transport directly or indirectly initiate bud growth in decapitated plants. We have tested whether auxin inhibits the initial stage of bud release, or subsequent stages, in garden pea (Pisum sativum) by providing a rigorous examination of the dynamics of auxin level, auxin transport, and axillary bud growth.

Ethylene-induced differential growth of petioles in Arabidopsis. Analyzing natural variation, response kinetics, and regulation.

Plants can reorient their organs in response to changes in environmental conditions. In some species, ethylene can induce resource-directed growth by stimulating a more vertical orientation of the petioles (hyponasty) and enhanced elongation. In this study on Arabidopsis (Arabidopsis thaliana), we show significant natural variation in ethylene-induced petiole elongation and hyponastic growth.

The roles of ethylene, auxin, abscisic acid, and gibberellin in the hyponastic growth of submerged Rumex palustris petioles.

Rumex palustris responds to complete submergence with upward movement of the younger petioles. This so-called hyponastic response, in combination with stimulated petiole elongation, brings the leaf blade above the water surface and restores contact with the atmosphere. We made a detailed study of this differential growth process, encompassing the complete range of the known signal transduction pathway: from the cellular localization of differential growth, to the hormonal regulation, and the possible involvement of a cell wall loosening protein (expansin) as a downstream target.

Plant movement. Submergence-induced petiole elongation in Rumex palustris depends on hyponastic growth.

The submergence-tolerant species Rumex palustris (Sm.) responds to complete submergence by an increase in petiole angle with the horizontal. This hyponastic growth, in combination with stimulated elongation of the petiole, can bring the leaf tips above the water surface, thus restoring gas exchange and enabling survival.

Submergence research using Rumex palustris as a model; looking back and going forward.

Flooding is a phenomenon that destroys many crops worldwide. During evolution several plant species evolved specialized mechanisms to survive short- or long-term waterlogging and even complete submergence. One of the plant species that evolved such a mechanism is Rumex palustris.