Oxygen deprivation stress in a changing environment

Abstract

Past research into flooding tolerance and oxygen shortages in plants has been motivated largely by cultivation problems of arable crops. Unfortunately, such species are unsuitable for investigating the physiological and biochemical basis of anoxia-tolerance as selection has reduced any tolerance of anaerobiosis and anaerobic soil conditions that their wild ancestors might have possessed. Restoration of anoxia-tolerance to species that have lost this property is served better by physiological and molecular studies of the mechanisms that are employed in wild species that still possess long-term anoxia-tolerance. Case studies developing these arguments are presented in relation to a selection of crop and wild species. The flooding sensitivity and metabolism of maize is compared in relation to rice in its capacity for anaerobic germination. The sensitivity of potato to flooding is related to its disturbed energy metabolism and inability to maintain functioning membranes under anoxia and postinoxia. By contrast, long-term anoxia-tolerance in the American cranberry [Vaccinium macrocarpon) and the arctic grass species Deschampsia beringensis can be related to the provision and utilization of carbohydrate reserves. Among temperate species, the sweet flag {Acorus calamus) shows a remarkable tolerance of anoxia in both shoots and roots and is also able to mobilize carbohydrate and maintain ATP levels during anoxia as well as preserving membrane lipids against anoxic and post-anoxic injury. Phragmites australis and Spartina altemiflora, although anoxia-tolerant, are both sulphide-sensitive species which can pre-dispose them to the phenomenon of die-back in stagnant, nutrient-rich water. Glyceria maxima adapts to flooding through phenological adaptations with a seasonal metabolic tolerance of anoxia confined to winter and spring which, combined with a facility for root aeration and early spring growth, allows rapid colonization of sites with only shallow flooding. The diversity of responses to flooding in wild plants suggests that, depending on the life strategy and habitat of the species, many different mechanisms may be involved in adapting plants to survive periods of inundation and no one mechanism on its own is adequate for ensuring survival.

Tolerância à inundação de Cecropia pachystachya Trec. (Cecropiaceae): aspectos ecofisiológicos e morfoanatômicos

“…Assim, a sobrevivência da planta é dependente de um balanço na distribuição de fotoassimilados entre as suas várias partes. A diminuição da TCR da raiz e do caule das plantas de C. pachystachya cultivadas em solo alagado pode ser uma conseqüência da menor quantidade de energia disponível, já que devido à hipoxia ocasionada pelo alagamento as plantas tendem a desviar o metabolismo para vias fermentativas, resultando em uma redução dos níveis energéticos (Crawford & Braendle 1996).…”

Expression of antioxidant defense genes in mung bean (Vigna radiata L.) roots under water-logging is associated with hypoxia tolerance

“…AMP), cytoplasmic acidification, anaerobic fermentation, elevation in cytosolic Ca 2? concentration, changes in the redox state [NAD(P)H/NAD(P)], and a decrease in the membrane barrier function are the main features caused by lack of oxygen (Richard et al 1994;Crawford and Braendle 1996;Drew 1997;Tadege et al 1999;Sairam et al 2008). Regulation of anoxic/hypoxic metabolism is complex and not all the features are well elucidated.…”

Germinação e crescimento de Calophyllum brasiliense (Clusiaceae), uma espécie típica de florestas inundadas

“…Nestas condições, tanto a germinação das sementes quanto o crescimento das plantas podem ser comprometidos, dependendo da espé-cie em questão e da duração da inundação (Kozlowski 1984). Para sobreviver nesta situação as plantas podem apresentar adaptações morfológicas, anatômicas ou metabólicas, de forma a minimizar os efeitos da falta de oxigê-nio (Hook 1984;Joly 1991;Crawford & Brandle 1996).…”