Enhanced antioxidant protection at the early stages of leaf expansion in ginkgo under natural environmental conditions

Abstract

Photosynthetic pigments, gas exchange, chlorophyll (Chl) a fluorescence kinetics, antioxidant enzymes and chloroplast ultrastructure were investigated in ginkgo (Ginkgo biloba L.) leaves from emergence to full size. Under natural conditions, the net photosynthetic rate (P N ), contents of Chl a, Chl b and total soluble proteins and fresh and dry leaf mass gradually increased during leaf expansion. The maximum photochemical efficiency of photosystem (PS) 2 (variable to maximum fluorescence ratio, F v /F m ) was considerably higher at the early stages of leaf development than in fully expanded leaves. During daily course, only reversible decrease in F v /F m was distinguished at various stages, implying that no photo-damage occurred. Absorption flux per cross section (CS) and trapped energy flux per CS were significantly lower in newly expanding leaves compared with fully expanded ones, however, dissipated energy flux per CS was only slightly lower in expanding leaves. The ratio of carotenoids (Car)/Chl decreased gradually during leaf expansion due to increasing Chl content. Moreover, activities of the antioxidant enzymes, such as superoxide dismutase, ascorbate peroxidase, catalase and peroxidase, increased at the early stages of leaf expansion. The appearance of osmiophilic granules in fully expanded leaves further proves that photo-protection is significantly strengthened at the early stages of leaf expansion.Additional key words: ascorbate peroxidase, carotenoids, catalase, chlorophyll fluorescence, chloroplast ultrastructure, Ginkgo biloba, net photosynthetic rate, peroxidase, superoxide dismutase. ⎯⎯⎯⎯

Effects of Exogenous Melatonin on the Growth and Physiological Characteristics of Ginkgo biloba L. under Salinity Stress Conditions

“…Consequently, there is a growing interest in understanding Ginkgo's salinity tolerance mechanisms, especially regarding salinity stress. Current research, primarily on young Ginkgo trees, has explored aspects such as chlorophyll and chloroplast protein changes [11], osmoregulation [31], and alterations in antioxidant enzyme systems [32]. While some studies delve into Ginkgo's molecular-level salinity resistance mechanisms, there is a notable scarcity of research into the potential of exogenous hormones like melatonin in alleviating salinity stress in Ginkgo.…”

Effects of Different Substrates on the Growth and Rhizosphere Microorganisms of Vallisneria natans

“…SOD and CAT activities were determined using the guaiacol method. Root activity was determined using the triphenyltetrazolium chloride method [24].…”

Ascorbic Acid—The Little-Known Antioxidant in Woody Plants

“…Studies of Robinia pseudoacacia revealed that ROS removal by antioxidants such as APX is additionally enhanced by the presence of arbuscular mycorrhizal fungi symbiosis [74]. Increased APX activity was also observed in tobacco seedlings inoculated with arbuscular mycorrhizal fungi [196] and tomato seedlings under salt stress [197].…”

“…Interestingly, in the fruit peel of tangerine x sweet orange, the level of APX decreased during the postharvest aging process and increased during drought [73]. The early stages of Ginkgo biloba L. leaf expansion were accompanied by increased activity of APX [74], emphasizing the involvement of Asc in the maximization of leaf-space to increase both the interception of light and photosynthesis. Studies on photosynthetic activity in nonwoody plants frequently focus on stress conditions such as water deficits [75] or mineral element imbalances [76].…”