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1

The acceptor side of photosystem II is damaged more severely than the donor side of photosystem II in ‘Honeycrisp’ apple leaves with zonal chlorosis

100%
Chen L.-S., Cheng L.
Acta Physiologiae Plantarum
|
2010
|
tom 32
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nr 2
To investigate the photoinhibition of photosynthesis in ‘Honeycrisp’ apple (Malus domestica Borkh. cv. Gala) leaves with zonal chlorosis, we compared pigments, CO₂ assimilation and chlorophyll (Chl) a fluorescence (OJIP) transient between chlorotic leaves and normal ones. Chl and carotenoids (Car) contents, Chl a/b ratio, and absorptance were lower in chlorotic leaves than in normal ones, whereas Car/Chl ratio was higher in the former. Although CO₂ assimilation and stomatal conductance were lower in chlorotic leaves, intercellular CO₂ concentration did not differ significantly between the two leaf types. Compared with normal leaves, chlorotic ones had increased deactivation of oxygen-evolving complexes (OEC), minimum fluorescence (Fₒ), dissipated energy, relative variable fluorescence at L-, W-, J- and I-steps, and decreased maximum fluorescence (Fm), maximum quantum yield for primary photochemistry (Fv/Fm or φRₒ/ABS), quantum yield for electron transport (ETₒ/ABS), quantum yield for the reduction of end acceptors of photosystem I (PSI) (uRo and REₒ/ABS), maximum amplitude of IP phase, amount of active photosystem II (PSII) reaction centers (RCs) per cross section (CS) and total performance index (PItot,abs). In conclusion, photoinhibition occurs at both the donor (i.e., the OEC) and the acceptor sides of PSII in chlorotic leaves. The acceptor side is damaged more severely than the donor side, which possibly is the consequence of over-reduction of PSII due to the slowdown of Calvin cycle. In addition to decreasing light absorptance by lowering Chl level, energy dissipation is enhanced to protect chlorotic leaves from photo-oxidative damage.
2

Antioxidant system of tea (Camellia sinensis) leaves in response to phosphorus supply

80%
Lin Z.-H., Chen L.-S., Zhang F.-Z.
Acta Physiologiae Plantarum
|
2012
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tom 34
|
nr 6
Self-rooted, 10-month-old, uniform tea [Camellia sinensis (L.) O. Kuntze cv. Huangguanyin] trees were supplied for 17 weeks with 0, 40, 80, 160, 400 or 1,000 µM phosphorus (P). Thereafter, plant growth, leaf malondialdehyde (MDA), antioxidant enzymes and metabolites were measured to determine how antioxidant system functions to protect P-deficient leaves from photo-oxidative damage. Whole plant dry weight increased as P supply increased from 0 to 160 µM, and then kept unchanged with further increasing P supply. Phosphorus-deficient leaves displayed lower or similar activities of superoxide dismutase, ascorbate peroxidase, monodehydroascorbate reductase, dehydroascorbate reductase, glutathione reductase and catalase and contents of ascorbate and reduced glutathione depending on the degree of P-deficiency and enzyme species, but P supply did not significantly affect leaf MDA content. In conclusion, the antioxidant system in P-deficient leaves provides considerable protection to them against photooxidative damage.
3

Roles of rootstocks and scions in aluminum-tolerance of Citrus

71%
Liao X.-Y., Yang L.-T., Lu Y.-B., Ye X., Chen L.-S.
Acta Physiologiae Plantarum
|
2015
|
tom 37
|
nr 01
Four scion-rootstock combination [i.e., X/X and X/SP, ‘Xuegan’ (Citrus sinensis) grafted on ‘Xugan’ and ‘Sour pummelo’ (Citrus grandis), respectively, and SP/X and SP/SP, ‘Sour pummelo’ grafted on ‘Xuegan’ and ‘Sour pummelo’, respectively] plants were treated for 18 weeks with 0 (-Al) or 1.2 mM AlCl36H2O (?Al). Thereafter, leaf, stem and root concentrations of phosphorus and aluminum (Al), leaf and root levels of organic acids (OAs), Al-induced release of OA anions (i.e., malate and citrate), photosynthesis and chlorophyll a fluorescence (OJIP) transients were measured. Al-induced decrease of photosynthesis and damage of photosynthetic electron transport chain were less pronounced in X/X and X/SP leaves than in SP/SP and SP/X leaves, which might be related with the higher Al-induced root efflux of OA anions and leaf P concentration. C. sinensis rootstock alleviated the influences of Al-toxicity on leaf photosynthetic electron transport chain by enhancing Al-induced release of root OA anions, hence lessening Al-induced photosynthesis inhibition in SP/X plants, while the reverse was the case for C. grandis rootstock in X/SP plants. In conclusion, the tolerance of grafted Citrus plants to Al depends on the scion as well as rootstock genotype, and the scion-rootstock interaction.
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