Chlororespiration is involved in the adaptation of Brassica plants to heat and high light intensity

Abstract

Two species of Brassica were used to study their acclimation to heat and high illumination during the first stages of development. One, Brassica fruticulosa, is a wild species from south-east Spain and is adapted to both heat and high light intensity in its natural habitat, while the other, Brassica oleracea, is an agricultural species that is widely cultivated throughout the world. Growing Brassica plants under high irradiance and moderate heat was seen to affect the growth parameters and the functioning of the photosynthetic apparatus. The photosystem II (PSII) quantum yields and the capacity of photosynthetic electron transport, which were lower in B. fruticulosa than in B. oleracea, decreased in B. oleracea plants when grown under stress conditions, indicating inhibition of PSII. However, in B. fruticulosa, the values of these parameters were similar to the values of control plants. Photosystem I (PSI) activity was higher in B. fruticulosa than in B. oleracea, and in both species this activity increased in plants exposed to heat and high illumination. Immunoblot analysis of thylakoid membranes using specific antibodies raised against the NDH-K subunit of the thylakoidal NADH dehydrogenase complex (NADH DH) and against plastid terminal oxidase (PTOX) revealed a higher amount of both proteins in B. fruticulosa than in B. oleracea. In addition, PTOX activity in plastoquinone oxidation, and NADH DH activity in thylakoid membranes were higher in the wild species (B. fruticulosa) than in the agricultural species (B. oleracea). The results indicate that tolerance to high illumination and heat of the photosynthetic activity was higher in the wild species than in the agricultural species, suggesting that plant adaptation to these stresses in natural conditions favours subsequent acclimation, and that the chlororespiration process is involved in adaptation to heat and high illumination in Brassica.

Plastid Alternative Oxidase (PTOX) Promotes Oxidative Stress When Overexpressed in Tobacco

“…This was the case in Ranunculus glacialis, an alpine plant, when it was acclimated to high light and low temperature (17); in the halophyte Thellungiella halophila when it was exposed to salt stress (18); and in Brassica fruticulosa when it was exposed to elevated temperature and high light (19). Although these findings support the hypothesis that PTOX may serve as a safety valve under stress conditions, they are in direct conflict with the data of Rosso et al (20).…”

Effects of n-propyl gallate on photosynthesis and physiological parameters in Dunaliella salina are affected by stressful conditions

“…Plants have developed individual tolerance mechanisms to cope with the environmental stress during evolutional processes, as the mechanisms are much varied between species and different groups (Quiles, 2006;Diaz et al, 2007). Under environmental stress conditions, such as salinity and high irradiance, plants show the ingenious adaptations at all levels of organization, from morphological to biochemical, molecular, and physiological levels (Diaz et al, 2007).…”

“…Stress usually refers to an unfavorable condition in which an external factor exerts undesirable influence on plants, and it can cause the happening of special responses in all physiological levels of an organism (Quiles, 2006;Diaz et al, 2007;Ibanez et al, 2010). Plants have developed individual tolerance mechanisms to cope with the environmental stress during evolutional processes, as the mechanisms are much varied between species and different groups (Quiles, 2006;Diaz et al, 2007).…”

“…Plants have developed individual tolerance mechanisms to cope with the environmental stress during evolutional processes, as the mechanisms are much varied between species and different groups (Quiles, 2006;Diaz et al, 2007). Under environmental stress conditions, such as salinity and high irradiance, plants show the ingenious adaptations at all levels of organization, from morphological to biochemical, molecular, and physiological levels (Diaz et al, 2007). At the biochemical and physiological levels, plants can alter their flow of photosynthetic electron transfer in several ways in order to cope with the stress (Dijkman and Kroon, 2002;Quiles, 2006;Diaz et al, 2007;Gamboa et al, 2009;Ibanez et al, 2010).…”

Using Chlorophyll Fluorescence Imaging for Early Assessment of Photosynthesis Tolerance to Drought, Heat and High Illumination

“…Neither did the concentration of photosynthetic pigments or the F v /F m values show any significant decrease after the stress photoperiods, suggesting that chloroplasts are protected by mechanisms that dissipate excess excitation energy to prevent damage to the photosynthetic apparatus under adverse conditions. In this respect, we have reported that chlororespiration and cyclic electron flow pathways are involved in the tolerance to adverse factors in both sun and shade species (Díaz et al, 2007;Gamboa et al, 2009;Ibañez et al, 2010;Quiles, 2006;Tallón & Quiles, 2007). However, when the light response curves for the relative electron transport rate were depicted, differences were observed between control plants and those exposed to stress photoperiods, the capacity of photosynthetic electron transport being lower in plants exposed to stress photoperiods in both species.…”