The effect of ultraviolet B radiation (UV-B) on cellular ultrastructure, chlorophyll (Chl), carotenoids, and total phenolics of Acrostichum danaeifolium gametophytes was analyzed. The control group of spores was germinated under standard conditions, while the test group of spores was germinated with additional UV-B for 30 min every day for 34 d. The cell characteristics were preserved in gametophytes irradiated with UV-B, but the number of starch grains increased in the chloroplasts and the more developed grana organization in contrast to the chloroplasts of the control group. Chl a content decreased, while Chl b content increased in the gametophytes cultivated with UV-B for 34 d. Contents of lutein and zeaxanthin decreased and trans-β-carotene concentration was enhanced in the gametophytes irradiated with UV-B. The content of total phenolic compounds increased in the gametophytes cultivated with UV-B. Therefore our data suggest that the gametophytes of A. danaeifolium, a fern endemic to the mangrove biome, were sensitive to enhancement of UV-B radiation at the beginning of their development and they exhibited alterations in their ultrastructure, pigment contents, and protective mechanisms of the photosynthetic apparatus, when exposed to this radiation., A. M. Randi, M. C. A. Freitas, A. C. Rodrigues, M. Maraschin, M. A. Torres., and Obsahuje bibliografii
Anthropogenic activities are changing global precipitation regimes and result in many middle latitude arid and semiarid regions experiencing less precipitation and more extreme weather events. However, little is known about the response of active ingredient accumulation in the medicinal herb Plantago depressa Willd. Therefore, we carried out a greenhouse experiment in order to study effect of control (CK, normal water supply equal to 309 mm per four months), -30 (-WS) and +30% (+WS) of the control water supply on the photosynthesis (PN), C/N ratio, and plantamajoside accumulation in P. depressa. Our results showed that compared with the-WS and CK treatments, the +WS treatment significantly enhanced biomass, the C/N ratio, plantamajoside concentration, yield in shoots and roots, and PN, but declined the N concentration in shoots and roots. The plantamajoside concentration was positively correlated with PN, the soluble sugar content, and the C/N ratio, but negatively correlated with the N concentration. Our results suggested that, under experimental conditions, +WS increased the C/N ratio and promoted the plantamajoside accumulation of P. depressa., Z. Li, W. Bai, L. Zhang, L. Li., and Obsahuje bibliografii
Plant response to the combination of two or more abiotic stresses is different than its response to the same stresses singly. The response of maize (Zea mays L.) photosynthesis, growth, and development processes were examined under sunlit plant growth chambers at three levels of each day/night temperatures (24/16°C, 30/22°C, and 36/28°C) and UV-B radiation levels (0, 5, and 10 kJ m-2 d-1) and their interaction from 4 d after emergence to 43 d. An increase in plant height, leaf area, node number, and dry mass was observed as temperature increased. However, UV-B radiation negatively affected these processes by reducing the rates of stem elongation, leaf area expansion, and biomass accumulation. UV-B radiation affected leaf photosynthesis mostly at early stage of growth and tended to be temperature-dependent. For instance, UV-B radiation caused 3-15% decrease of photosynthetic rate (PN) on the uppermost, fully expanded leaves at 24/16°C and 36/28°C, but stimulated P N about 5-18% at 30/22°C temperature. Moreover, the observed UV-B protection mechanisms, such as accumulation of phenolics and waxes, exhibited a significant interaction among the treatments where these compounds were relatively less responsive (phenolics) or more responsive (waxes) to UV-B radiation at higher temperature treatments or vice versa. Plants exposed to UV-B radiation produced more leaf waxes except at 24/16°C treatment. The detrimental effect of UV-B radiation was greater on plant growth compared to the photosynthetic processes. Results suggest that maize growth and development, especially stem elongation, is highly sensitive to current and projected UV-B radiation levels, and temperature plays an important role in the magnitude and direction of the UV-B mediated responses., S. K. Singh, K. R. Reddy, V. R. Reddy, W. Gao., and Obsahuje bibliografii