Seedlings of Chrysanthemum, cultivar 'Puma Sunny', were grown under a range of shading regimes (natural full sunlight, 55, 25, and 15% of full sunlight) for 18 days. Here, we characterized effects of varying light regimes on plant morphology, photosynthesis, chlorophyll fluorescence, anatomical traits, and chloroplast ultrastructure. We showed that leaf color was yellowish-green under full sunlight. Leaf area, internode length, and petiole length of plants were the largest under 15% irradiance. Net photosynthetic rate, water-use efficiency, PSII quantum efficiency, and starch grain were reduced with decreasing irradiance from 100 to 15%. Heavy shading resulted in the partial closure of PSII reaction centers and the CO₂ assimilation was restricted. The results showed the leaves of plants were thinner under 25 and 15% irradiance with loose palisade tissue and irregularly arranged spongy mesophyll cells, while the plants grown under full sunlight showed the most compact leaf palisade parenchyma. Irradiance lesser than 25% of full sunlight reduced carbon assimilation and led to limited plant growth. Approximately 55% irradiance was suggested to be the optimal for Chrysanthemum morifolium., S. Han, S. M. Chen, A. P. Song, R. X. Liu, H. Y. Li, J. F. Jiang, F. D. Chen., and Obsahuje bibliografii
Water stress is a major abiotic constraint leading to serious crop losses. Recently, in the Mediterranean region, water stress has become markedly sensed, especially in Citrus orchards. This study investigated the physiological responses of local sour orange (Citrus aurantium L.) clones to severe water stress. Water stress was applied by withholding irrigation during weeks, followed by a rewatering phase during three months. Under water stress, sour orange clones decreased their stomatal conductance, net photosynthetic rate, and transpiration rate. On the contrary, biomass was stable, especially in the Kliaa clone. In addition, reduced leaf water potentials (-3 MPa) and water contents were measured in most of the clones, except Kliaa which kept the highest water potential (-2.5 MPa). After rewatering, all clones recovered except of the Ghars Mrad (GM) clone. Ultrastructural observations of leaf sections by transmission electron microscopy did not reveal marked alterations in the mesophyll cells and chloroplast structure of Kliaa in comparison to the sensitive clone GM, in which palisade parenchyma cells and chloroplasts were disorganized. This contrasting behavior was mainly attributed to genetic differences as attested by molecular analysis. This study highlighted GM as the drought-sensitive clone and Kliaa as the tolerant clone able to develop an avoidance strategy based on an efficient stomatal regulation. Although a high percentage of polyembryony characterizes C. aurantium and justifies its multiplication by seeds, heterogeneous water-stress responses could be observed within sour orange plants in young orchards., A. Ben Salem-Fnayou, I. Belghith, M. Lamine, A. Mliki, A. Ghorbel., and Obsahuje bibliografii