Plant physiology

About: Plant physiology is a research topic. Over the lifetime, 1537 publications have been published within this topic receiving 72038 citations.

Comparative Proteomic Analysis Reveals Elevated Capacity for Photosynthesis in Polyphenol Oxidase Expression-Silenced Clematis terniflora DC. Leaves.

Abstract: Polyphenol oxidase (PPO) catalyzes the o-hydroxylation of monophenols and oxidation of o-diphenols to quinones. Although the effects of PPO on plant physiology were recently proposed, little has been done to explore the inherent molecular mechanisms. To explore the in vivo physiological functions of PPO, a model with decreased PPO expression and enzymatic activity was constructed on Clematis terniflora DC. using virus-induced gene silencing (VIGS) technology. Proteomics was performed to identify the differentially expressed proteins (DEPs) in the model (VC) and empty vector-carrying plants (VV) untreated or exposed to high levels of UV-B and dark (HUV-B+D). Following integration, it was concluded that the DEPs mainly functioned in photosynthesis, glycolysis, and redox in the PPO silence plants. Mapman analysis showed that the DEPs were mainly involved in light reaction and Calvin cycle in photosynthesis. Further analysis illustrated that the expression level of adenosine triphosphate (ATP) synthase, the content of chlorophyll, and the photosynthesis rate were increased in VC plants compared to VV plants pre- and post HUV-B+D. These results indicate that the silence of PPO elevated the plant photosynthesis by activating the glycolysis process, regulating Calvin cycle and providing ATP for energy metabolism. This study provides a prospective approach for increasing crop yield in agricultural production.

Effect of calcium deficiency on the carbon metabolism in photosynthesis and respiration of tomato leaf

Abstract: Changes in carbon metabolism resulting from calcium deprivation of tomato leaf tissue were investigated employing C14O2 in photosynthesis and respiration and by comparing it with the control. By 8 to 10 days of calcium deprivation, the leaf tissue had only half as much chlorophyll, but excess of water soluble metabolites and dry matter. Its rate of apparent photosynthesis was lowered (30%) but not that of respiration. After 15 min photosynthesis in C14O2, the label was considerably low in the lipid fraction, sucrose and malic acid, to a smaller extent in aspartic acid and alanine, but was not altered in serine-glycine, sugar phosphates, and starch. During 6 hours respiration following 15 min photoassimilation of C14O2 the loss of radioactivity from starch, sucrose and sugar phosphates of the deficient leaf tissue was considerably low. Similarly, the gain in radio-activity occurring concurrently in citrate, malate, glutamate and cell wall residue was also low. Although the amount of CO2 given off by the deficient tissue in 6 hours was not significantly lower, the specific activity of the respired carbon dioxide was 10 to 15 times lower than that of the control. The results seem to indicate that in the calcium-deprived leaf tissue the early products of photosynthesis were much less available for the respiratory activities which occur outside the chloroplasts. A restriction in the movement or utilization of early products of photosynthesis outside the chloroplasts is therefore inferred as one of the possible effects of calcium deprivation. re]19740530

Response of transgenic rape plants bearing the Osmyb4 gene from rice encoding a trans-factor to low above-zero temperature

Abstract: Accumulation of soluble sugars (sucrose, fructose, and glucose), proline, phenols (total phenols and flavonoids), and antocyanins during adaptation to low-temperature stress (4°C) of two lines of spring rape (Brassica napus L., cv. Westar) characterized by weak (Bn-1) and strong (Bn-3) expression of the Osmyb4 transgene was studied. Vegetatively propagated transgenic and wild-type plants were grown in the hydroponic culture at 24°C; at the stage of 5–6 leaves, plants were exposed to 4°C for 5 days and then returned to the optimum temperature of 24°C for recovery. Transgenic plants were established to manifest improved cold and frost tolerance, which was evident from more active biomass accumulation at 4°C as compared with wild-type plants and from sustaining their viability after 2-day-long exposure to −6°C. Determination of MDA content showed that one of the reasons of their improved cold tolerance was their capability of maintaining oxidative homeostasis under low-temperature stress. This suggestion is supported by intense accumulation of phenols and antocyanins, manifesting pronounced antioxidant effects, by transgenic plants during their cold adaptation. Thus, during 2–5 days of plant exposure to 4°C, in transgenic plants the total content of phenols increased by 2.6–3.7 times, flavonoids — by 3.7–4.7 times, and antocyanins — by 3.5–5.3 times as compared with control plants growing at 24°C. Transgenic Bn-3 plants with strong expression of the Osmyb4 gene accumulated phenols and antocyanins at 4°C more actively than Bn-1 plants characterized by weak expression of this gene. Transgenic rape plants subjected to cold stress accumulated more proline, manifesting stress-protection effects, and lesser accumulation of soluble sugars. Before the beginning of experiment, the content of soluble sugars was approximately similar in wild-type plants and transgenic lines; at 4°C their level in transgenic plants was substantially lower than in control plants. As distinct from the process of cold adaptation, during recovery, the content of all tested stress-protection compounds dropped sharply. The results obtained indicate that active expression of the Osmyb4 gene from rice in the rape plants was accompanied not only by accumulation of compatible osmolytes but also by biosynthesis of antioxidants of phenolic nature.

Physiological Aspects of Photosynthesis–Respiration Interrelations

Abstract: The review discusses up-to-date concepts of interrelations between photosynthesis and respiration. It considers the quantitative ratio of the processes in the leaf and that in the whole plant reported by Russian and other researches. Special attention is paid to performance of dark respiration in the light and to the methods of its exploration, which employ classical gas exchange, chlorophyll fluorescence, and carbon isotopes. Possible causes of conservatism and variability in the total respiration to gross photosynthesis ratio under stationary and stress conditions are also discussed along with prospects in further investigations.