title: Bottle gourd rootstock-grafting promotes photosynthesis by regulating the stomata and non-stomata performances in leaves of watermelon seedlings under NaCl stress.
abstract: Previously, we found that the amelioration of photosynthetic capacity by bottle gourd (Lagenaria siceraria Standl.) rootstock in watermelon seedlings (Citrullus lanatus [Thunb.] Mansf.) with salt treatment might be closely related to the enzymes in Calvin cycle such as ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) (Yang et al., 2012). We confirmed this and showed more details in this study that improved photosynthesis of watermelon plants by bottle gourd rootstock was associated with the decreased stomata resistance and the increased photochemical activity and photosynthetic metabolism with or without 100mM NaCl stress for 3 days. The analysis of gas exchange parameters showed that self-grafted plants suffered serious non-stomatal limitation to photosynthesis under salt stress while rootstock-grafted plants were mainly affected by stomata limitation in stress conditions. Further, results showed that NaCl stress markedly reduced the chlorophyll content, damaged the structure of photosynthetic apparatus, and inhibited photochemical activity and CO2 assimilation in self-grafted plants. In contrast, rootstock-grafting increased the chlorophyll content, especially chlorophyll b, and minimized the harmful effects on photosystem II (PSII) reaction center and the thylakoids structure induced by NaCl stress. Furthermore, rootstock-grafting enhanced the content and activity of Rubisco and thus elevated carbon fixation in the leaves of watermelon scions under salt stress. The gene expressions of enzymes related to ribulose-1,5-bisphosphate (RuBP) regeneration were also up-regulated by rootstock and this probably guaranteed the sufficient supply of RuBP for the operation of Calvin cycle in watermelon scions under salt stress. Thus, bottle gourd rootstock promoted photosynthesis by the activation of stomatal and non-stomatal abilities, especially the regulation of a variety of photosynthetic enzymes, including Rubisco in grafted watermelon plants under NaCl stress.
authors.affiliation: Key Laboratory of Southern Vegetable Crop Genetic Improvement in Ministry of Agriculture, College of Horticulture, Nanjing Agricultural University, Nanjing 210095, PR China; Department of Horticultural Science, College of Agriculture, Guangxi University, Nanning 530004, PR China. Electronic address: yjyang85@126.com.
authors.forename: Yanjuan
authors.initials: Y
authors.lastname: Yang
authors.affiliation: Key Laboratory of Southern Vegetable Crop Genetic Improvement in Ministry of Agriculture, College of Horticulture, Nanjing Agricultural University, Nanjing 210095, PR China; Horticulture Research Institute, Shanghai Academy Agricultural Sciences, Key Laboratory of Protected Horticulture Technology, Shanghai 201403, PR China. Electronic address: yuliok@qq.com.
authors.forename: Li
authors.initials: L
authors.lastname: Yu
authors.affiliation: Key Laboratory of Southern Vegetable Crop Genetic Improvement in Ministry of Agriculture, College of Horticulture, Nanjing Agricultural University, Nanjing 210095, PR China. Electronic address: wlp29@163.com.
authors.forename: Liping
authors.initials: L
authors.lastname: Wang
authors.affiliation: Key Laboratory of Southern Vegetable Crop Genetic Improvement in Ministry of Agriculture, College of Horticulture, Nanjing Agricultural University, Nanjing 210095, PR China. Electronic address: srguo@njau.edu.cn.
authors.forename: Shirong
authors.initials: S
authors.lastname: Guo
mesh_terms: D029773:Citrullus / Q000502:physiology*; D028464:Cucurbita / Q000502:physiology*; D010788:Photosynthesis / Q000187:drug effects; D018515:Plant Leaves / Q000502:physiology; D018517:Plant Roots / Q000502:physiology; D054046:Plant Stomata / Q000502:physiology; D036226:Seedlings / Q000502:physiology; D012965:Sodium Chloride / Q000494:pharmacology; D013312:Stress, Physiological
chemical_list: D012965:Sodium Chloride
keywords: Citrullus lanatus [Thunb.] Mansf.; Lagenaria siceraria Standl.; Non-stomatal limitations; Rootstock; Salt tolerance; Stomatal limitations