Hormone action and plant adaptations to poor aeration

Abstract

SynopsisThe actions of endogenous plant hormones are invoked to explain several morphological adaptations to poor aeration. These include changes to the growth and internal morphology of inundated roots, the promotion of extension growth by stems or leaves of aquatic and semi-aquatic species by submergence, and morphological changes in shoots where only the roots and lower shoot are inundated. This article considers ethylene-promoted aerenchyma formation in maize (Zea mays) and compares the promoting action of ethylene, low oxygen partial pressures and carbon dioxide on shoot extension in rice (Oryza sativa), a rice mimic Echinochloa oryzoides and a submersed aquatic monocot Potamogeton pecrinatus. Different kinds of hormonal messages (positive, negative, accumulative and debit) passing between roots and shoots co-ordinate shoot development with the roots and their environment. Recent progress in quantifying the delivery of abscisic acid (ABA) or the ethylene precursor 1-aminocyclopropane-1-car-boxylic acid (ACC) from roots to shoots in the transpiration stream is summarised in relation to control of stomatal closure and leaf epinastic curvature in flooded plants.

Aerated subsurface irrigation water gives growth and yield benefits to zucchini, vegetable soybean and cotton in heavy clay soils

“…Since flowering and fruiting in zucchini were improved by HP application, and flowering and fruiting in many cucurbits is regulated by cytokinin production (Wien, 1997), it may be that HP application promoted cytokinin production and transport. Both are known to be sensitive to oxygen deficiency in the root zone (Jackson, 1992).…”

Does flooding favour galling insects?

“…In a flood‐prone forest, flooded plants may be a safer site for oviposition, if gall‐induction success is related to plant stress. In addition, some plants grow rapidly when flooded to avoid complete submersion (Jackson 1994), possibly favouring flush feeders such as gallers (White 1993). On the other hand, the premature abscission of leaves of flooded plants, due to ethylene accumulation (Jackson 1994), may enhance mortality of endophytic insects (Kahn & Cornell 1989).…”

“…High leaf abscission and production rates and development of large leaves seem to be part of the physiological responses of C. brasiliense to superficial flooding. Premature leaf abscission is common among plants subjected to flooding (Stolzy & Sojka 1984; Jackson 1994), and many species are capable of rapid elongation of stems and leaves to escape from complete submersion and prolonged asphyxiation, resulting in large leaves and internodes (Jackson 1994). The premature abscission of leaves may inflict large mortality on endophytic insects (Kahn & Cornell 1989).…”

“…The development of a general theory on the effects of flooding and hypoxia on arboreal species, and thus on their herbivore communities, seems to be a long task. Plant responses to flooding are frequently idiosyncratic and related to phenology and flooding regime (Scarano & Crawford 1992), and the effects of flooding on arboreal dicotyledons have received little attention until recently (Stolzy & Sojka 1984; Jackson 1994, and references therein). It thus remains an open and fertile field of study.…”

Oxygation Enhances Growth, Gas Exchange and Salt Tolerance of Vegetable Soybean and Cotton in a Saline Vertisol

“…Whatever the cause, the development of hypoxia in the soil also favors an accumulation of ethylene and products of root and bacterial anaerobic processes and presents a range of challenges for plants, especially for metabolism associated with root membrane structure and function (Visser et al 2003). Paradoxically, initial symptoms of excessive soil water are similar to those of drought stress; leaves wilt and growth ceases (Jackson et al 1992). At the plant level, salinity and poor oxygen supply to the roots result in shorter plant stature and smaller and sometimes fewer leaves and reduced plant growth (Meek et al 1983).…”