Low temperature enhances photosynthetic down-regulation in French bean (Phaseolus vulgaris L.) plants

The mechanisms of photosynthetic adaptation to different combinations of temperature and irradiance during growth, and especially the consequences of exposure to high light (2000 µmol m(–2) s(–1) PPFD) for 5 min, simulating natural sunflecks, was studied in bean plants (Phaseolus vulgaris L.). A protocol using only short (3 min) dark pre‐treatment was introduced to maximize the amount of replication possible in studies of chlorophyll fluorescence. High light at low temperature (10 °C) significantly down‐regulated photosynthetic electron transport capacity [as measured by the efficiency of photosystem II (PSII)], with the protective acclimation allowing the simulated sunflecks to be used more effectively for photosynthesis by plants grown in low light. The greater energy dissipation by thermal processes (lower F(v)′/F(m)′ ratio) at low temperature was related to increased xanthophyll de‐epoxidation and to the fact that photosynthetic carbon fixation was more limiting at low than at high temperatures. A key objective was to investigate the role of photorespiration in acclimation to irradiance and temperature by comparing the effect of normal (21 kPa) and low (1·5 kPa) O(2) concentrations. Low [O(2)] decreased F(v)/F(m) and the efficiency of PSII (Φ(PSII)), related to greater PSII down‐regulation in cold pre‐treated plants, but minimized further inhibition by the mild ‘sunfleck’ treatment used. Results support the hypothesis that photorespiration provides a ‘safety‐valve’ for excess energy

Relations between photosynthetic performance and polyphenolics productivity of Artemisia alba Turra in in vitro tissue cultures

Establishing optimal growth conditions for secondary metabolites production in vitro is vital for the biotechnological development of medicinal plants. In the present work we investigate the relations between the supplementation of plant growth regulators (benzyl adenine and indole-3-butyric acid) to in vitro shoot cultures of the medicinal plant Artemisia alba Turra, the productivity of antioxidant polyphenolic compounds and the structural and functional characteristics of the photosynthetic apparatus. We assayed the structural characteristics of isolated thylakoid membranes from the aerial parts by means of circular dichroism spectroscopy and atomic force microscopy, and the photosynthetic performance by pulse amplitude fluorescence modulated imaging. Although a complex relationship between benzyl adenine and indole-3-butyric acid supplementation, the polyphenolic levels and the architecture and functionality of the photosynthetic thylakoid membranes was revealed, a clear correlation was established between the concentration of the produced polyphenolic compounds and the quantum yield of photosystem II. Our data demonstrate that there is an optimal combination of the applied plant growth regulators that triggers efficient photosynthesis and high phenolics production

Plant-soil Water Status-induced Changes in Physiological and Biochemical Properties of Yarrow

WOS: 000392637400021As medicinal plants are generally collected from the wild flora, it is of fundamental importance to identify the optimum growth conditions for increasing the yield and quality potential of ex-situ cultivated plants. Effects of different soil water content [20, 40, 60 and 80 % of water holding capacity (WHC)] on growth, physiology and biochemical profile of Achillea millefolium group-related cv. Proa were investigated in the present study. Alterations in drug herbage, chlorophyll content, quantum efficiency of photosystem II, essential oil rate and composition, proline content and lipid peroxidation, antioxidant activity and flavonoid content of the plants under different plant and soil water status were determined. Decrease in soil water status under 40 % of WHC resulted in degradation of chlorophyll pigments, reduction in photochemical efficiency and lower dry matter production. The essential oil (EO) rate of cv. Proa was higher under limited and excessive water content of soil whereas the main component of EO, chamazulene, was negatively correlated with WHC of soil. Our results suggest a general trend of inverse correlation of antioxidant capacity and flavonoid content with essential oil rate in contrast to the positive correlation of these parameters with chamazulene content. The data obtained may serve as a basis of programming the optimum soil moisture conditions for successful cultivation of cv.Proa.Research Fund of TUBITAK (The Scientific and Technological Research Council of Turkey)Turkiye Bilimsel ve Teknolojik Arastirma Kurumu (TUBITAK); BAS (Bulgarian Academy of Science) [180O290]The authors thank Research Fund of TUBITAK (The Scientific and Technological Research Council of Turkey) and BAS (Bulgarian Academy of Science) for their financial support (Bilateral project No. 180O290)