[Effects of shading on chlorophyll content and photosynthetic characteristics in leaves of Phoebe bournei.] / é®é˜´å¯¹é—½æ¥ å¶ç»¿ç´ å«é‡å’Œå ‰åˆç‰¹æ€§çš„å½±å“.

To explore the photosynthetic adaptation of Phoebe bournei to different light conditions, two-year-old P. bournei seedlings were grown under three light regimes (full light, shading rate 50% and 78% of full light). The chlorophyll contents, leaf gas exchange and chlorophyll fluorescence of P. bournei were measured after six-month treatment. The results showed that the contents of chlorophyll a, chlorophyll b, chlorophyll (a+b) and carotenoids in leaves were in a descending order of shading rate 78% > shading rate 50% > full light. There was no significant difference of chlorophyll a/b between natural and shade treatments. The shading treatment reduced light compensation point (LCP), but increased light saturation point (LSP) and apparent quantum yield (AQY), suggesting that plants could utilize both the weak light and the high light. Maximum net photosynthetic rate (Pn max), dark respiration rate (Rd), and maximum electron transfer rate (Jmax) increased under the shading treatment. There was significant difference between natural and shade treatment in net photosynthetic rate (Pn), stomatal conductance to CO2(gsc), intercellular CO2 concentration (Ci), and mesophyll conductance (gm). Pn and gm of different light regimes were sorted from the highest to the lowest as shading rate 78% > shading rate 50% > full light. gsc under shading rate 78% was higher than that under full light. Ci under shading rate 50% and 78% were lower than that under full light. Actual photochemical efficiency of PS2 (Fv'/Fm'), quantum yields of PS2 (ΦPS2), and electron transport rate (J) of P. bournei leaves were significantly higher under shading rate 78% than those under shading rate 50% and full light. In conclusion, P. bournei could increase Pn by increasing chlorophyll content, AQY, J, gsc, and gm under shade condition.

Modified nucleoside triphosphates exist in mammals.

DNA and RNA contain diverse chemical modifications that exert important influences in a variety of cellular processes. In addition to enzyme-mediated modifications of DNA and RNA, previous in vitro studies showed that pre-modified nucleoside triphosphates (NTPs) can be incorporated into DNA and RNA during replication and transcription. Herein, we established a chemical labeling method in combination with liquid chromatography-electrospray ionization-mass spectrometry (LC-ESI-MS) analysis for the determination of endogenous NTPs in the mammalian cells and tissues. We synthesized 8-(diazomethyl)quinoline (8-DMQ) that could efficiently react with the phosphate group under mild condition to label NTPs. The developed method allowed sensitive detection of NTPs, with the detection limits improved by 56-137 folds. The results showed that 12 types of endogenous modified NTPs were distinctly determined in the mammalian cells and tissues. In addition, the majority of these modified NTPs exhibited significantly decreased contents in human hepatocellular carcinoma (HCC) tissues compared to tumor-adjacent normal tissues. Taken together, our study revealed the widespread existence of various modified NTPs in eukaryotes.

[Effects of flash scheme on maximum chlorophyll fluorescence under illumination and its derived parameters]. / ä¸åŒå ‰è„‰å†²æ–¹æ¡ˆå¯¹å ‰ä¸‹æœ€å¤§è§å ‰å‚æ•°åŠå ¶è®¡ç®—å‚æ•°çš„å½±å“.

The maximum chlorophyll fluorescence yield under illumination (Fm') is one of the most important parameters in plant eco-physiological research, and usually was estimated with rectangular flush scheme (RF). However, the estimation accuracy of RF for Fm' was affected by the rapid turnover of photosystem 2 (PS2). In order to eliminate the effect of the rapid turnover of photosystem 2 (PS2), the multiphase flush scheme (MPF) based on the linear relationship between the flush (Q') and chlorophyll fluorescence (F') is proposed to estimate Fm' at infinite irradiance. Leaf gas exchange and chlorophyll fluorescence of three woody species (Castanopsis sclerophylla, Cyclobalanopsis glauca, and Sapium sebiferum) were respectively measured with RF and MPF, Fm' and the derived parameters [the quantum efficiency of PS2 (ΦPSII), the electron flux through PS2 (J), the maximum electron transfer rate (Jmax), mesophyll conductance (gm) and chloroplast CO2 concentration (Cc)] were compared between the two different schemes, and the effects of RF and MPF on these parameters were analyzed. The results showed that no significant difference was found in the parameters for the three species between RF and MPF at the light intensity lower than 200 µmol·m-2·s-1. Fm' estimated with MPF for the three species were 3.5%-5.2%, 11.7%-18.0%, and 3.2%-7.1% higher than those with RF, respectively, at the light intensity higher than 200 µmol·m-2·s-1. The derived parameters (ΦPSII, J and Jmax) estimated with MPF for the three species were higher than those with RF, while the derived parameters(gm and Cc) estimated with MPF were lower at the light intensity higher than 200 µmol·m-2·s-1. In conclusion, estimates of parameters (Fm', ΦPSII, and J) were not significantly affected by the two different schemes at the light intensity lower than 200 µmol·m-2·s-1. The estimates of parameters (Fm', ΦPSII, J, Jmax, gm, and Cc) were significantly affected by the two different schemes at the light intensity higher than 200 µmol·m-2·s-1. Compared with MPF, parameters of Fm', ΦPSII, J and Jmax estimated with RF were underestimated, while parameters of gm and Cc were overestimated.

[Photo-physiological and photo-biochemical characteristics of several herbaceous and woody species based on FvCB model]. / 基于FvCBæ¨¡åž‹çš„å‡ ç§è‰æœ¬å’Œæœ¨æœ¬æ¤ç‰©å ‰åˆç”Ÿç†ç”ŸåŒ–ç‰¹æ€§.

To explore the photosynthetic capacity and the leaf photosynthetic apparatus for plants with different life forms, CO2 response curves of 7 woody species and 4 herbaceous species were fitted by the modified rectangular hyperbolic model and the FvCB model, and the photosynthetic parameters, including maximum net photosynthetic rate (Pn max), maximal Rubisco carboxylation rate (Vc max), maximal electron transport rate (Jmax), day respiration (Rd), and mesophyll resistance to CO2 transport (rm), were compared among different woody species, among different herbaceous species, and between woody and herbaceous life-forms, respectively. The results showed Pn max of seven woody species descended in the order of Sapium sebiferum and Boehmeria nivea ＞ Machilus pingii and Pittosporum tobira ＞ Cyclobalanopsis glauca, Castanopsis sclerophylla, and Quercus nuttallii. Vc max of S. sebiferum, B. nivea, M. pingii, and P. tobira was significantly higher than that of C. glauca and C. sclerophylla. Jmax of woody species was in descending order as S. sebiferum ＞ B. nivea and P. tobira ＞ Q. nuttallii, C. sclerophylla, and C. glauca. rm of M. pingii and C. sclerophylla was higher than that of S. sebiferum, P. tobira and B. nivea. Pn max of Phytolacca acinosa was significantly higher than that of Ageratum conyzoides and Achyranthes aspera. There was no significant difference in Vc max among 4 herbaceous species. Jmax of P. acinosa was higher than that of A. conyzoides. rm of S. nigrum and A. aspera was higher than that of A. conyzoides. Rd of P. acinosa was higher than that of A. conyzoides and A. aspera. The photosynthetic parameters (Pn max, Vc max, Jmax and rm) of woody species were significantly higher than those of herbaceous species, but no significant difference was found in Rd between woody and herbaceous species. In conclusion, the difference in photosynthetic capacity among different species and between the two plant life-forms resulted from the difference in Rubisco carboxylation capacity, electron transport capacity, and mesophyll resistance among these species.