Defense strategy of old and modern spring wheat varieties during soil drying

Abstract

Different defense mechanisms of three spring wheat (Triticum aestivum L.) varieties were studied by withholding watering in well-watered pots to gradually increase water deficit of plants grown in containers. The strategies of plant adaptation were divided into three phases according to the severity of drought: first, a positive defense phase that started from commencement of non-hydraulic root-sourced signals (nHRS) and ended at onset of hydraulic root-sourced signals (HRS)--the plant responded to imminent drought by decreasing stomatal aperture to lessen water loss and no membrane injury occurred. The second defense phase occurred between the onset of HRS and temporary wilting (TW), characterized by enhancement of reactive oxygen species (ROS), marked enzyme activity and increased MDA content. Mild lipid membrane peroxidation came mainly from a dynamic imbalance between free radical production and enzymatic defense reaction, which indicated that injury by ROS had not been completely repaired by increasing enzymatic activity. The third defense phase was from TW to permanent wilting (PW), the synthesis of SOD and CAT during TW could not deal with the collapse of antioxidant enzymes, and SOD and CAT activities began to decrease, which caused the excessive ROS production and thus serious membrane lipid peroxidation. The defense strategies to drought are similar among the varieties, but modern varieties LC8275 and GY602 bred after 1975 had relatively higher defense levels at all three defense phases, which suggest that modern varieties are more resistant than old ones, and artificial selection would lead to a different direction in evolution from natural selection.

-Aminobutyric acid increases abscisic acid accumulation and desiccation tolerance and decreases water use but fails to improve grain yield in two spring wheat cultivars under soil drying

“…The early response of nHRS will facilitate the reduced water loss from stomata and serve as the first defence against possible drought (Henson et al , 1989 a , b ; Davies et al , 1994; Fan et al , 2009). With prolonged soil water depletion, the leaf water status triggers changes in the leaf, hydraulic signals (HS), leading to physiological changes such as osmotic adjustment (Jones and Turner, 1980) and evoking antioxidant defence mechanisms (Wang et al , 2008; Fan et al , 2009). With soil drying, temporary wilting (TW), evident as the drooping of leaves during the day followed by rehydration and recovery during the night, is first observed followed by permanent wilting (PW) when the leaves fail to regain turgor overnight.…”

“…The activity of antioxidant enzymes and the level of non-enzymatic compounds generally increase during abiotic stress and are correlated with enhanced cellular protection, thereby preventing oxidative damage (Khanna-Chopra and Selote, 2007). During soil drying, endogenous ABA and the water relations of the plant play crucial roles in modulating the equilibrium between ROS and antioxidant defence systems (Jiang and Zhang, 2002 a , b ; Srivalli et al , 2003; Fan et al , 2009) and this equilibrium between ROS and the antioxidant defence system is also associated with the induction of non-hydraulic and hydraulic signals (Wang et al , 2008; Fan et al , 2009). However, at higher stress levels, the antioxidant defence system collapses and oxidative damage to lipids, proteins, and DNA occurs (Sgherri and Navari-Izzo, 1995; Apel and Hirt, 2004).…”

Expressão gênica diferencial em genótipos de mamona (Ricinus communis L.) submetidos a déficit hídrico induzido por PEG

“…Alguns trabalhos têm mostrado que o déficit hídrico ativa o sistema de defesa enzimático das plantas para eliminação das espécies reativas de oxigênio ou ERO (Fan et al, 2009;Jaleel et al, 2007;Jambunathan, 2010;Jebara et al, 2005 (Alscher et al, 2002). A produção das enzimas como: Catalase (CAT), Ascorbato Peroxidase (APX), Guaiacol Peroxidase (GPOX) e Superoxide Dismutase (SOD) é essencial para a eliminação das ERO presentes nas células.…”

Different oxidative burst patterns occur during host and nonhost resistance responses triggered by Xanthomonas campestris in pepper

“…Many reports suggest that NO radical induces phytoalexins, phenylalanine ammonia-lyase (PAL) and pathogenesis-related (PR) proteins (Durner et al, 1998;Delledonne et al, 1998;Wendehenne et al, 2004). Many studies have proposed a role for lipid peroxidation in plant defense (reviewed by Feussner and Wasternack, 2002;Fan et al, 2009, Cacas et al, 2009. Lipoxygenase (LOX) has been shown to contribute to defense reactions in plants by synthesizing antimicrobial and signal molecules.…”