The neotropical genus Clusia comprises arborescent species exhibiting Crassulacean Acid Metabolism (CAM) as was first reported for a Mexican species, Clusia lundellii. Here, the occurrence of CAM photosynthesis was studied in 20 species of Clusia, 18 from Mexico, and 2 from Guatemala, using leaf carbon isotopic composition. In most species, samples from individuals collected in different locations were analyzed. CAM was present in at least 11 species, eight of which contained specimens with δ13C values less negative than -20.0 ‰, indicating strong CAM (C. chanekiana, C. flava, C. lundellii, C. mexicana, C. quadrangula, C. rosea, C. suborbicularis, and C. tetra-trianthera). δ13C was highly variable in some species, but CAM expression was not correlated to life form (epiphytic, hemiepiphytic, terrestrial) or habitat. CAM specimens were not collected at altitudes above 1 700 m a.s.l. and J. G. Vargas-Soto, J. L. Andrade, K. Winter.
Morphological functional types and photosynthetic pathway types were identified for the forage species from steppe communities in Inner Mongolia, China, using the data of both field survey and published papers. Seven typical steppe communities were selected to investigate the morphological functional type and photosynthetic pathway type compositions and plant functional type (PFT) diversity in steppe communities at regional scale. Morphological functional types, based on plant height and leaf type combined with life span, were optimal for comparing the community differences in the region, while photosynthetic pathway types were fairly coarse for such studies. Of the seven morphological functional types in the steppe communities, perennial forbs (PEF) were the dominant type, and 60 % of species belonged to this type. Each of the high perennial grass (HPG), short perennial grass (SPG), and annual grass (ANG) types represented less than 10 % of the total, even though the grass species were dominant in the seven steppe communities. The differences of PFTs between the steppe communities were remarkable, and the PFT richness and diversity increased from the communities with moist conditions to the ones with dry environments.
Productivity of most improved major food crops showed stagnation in the past decades. As human population is projected to reach 9-10 billion by the end of the 21st century, agricultural productivity must be increased to ensure their demands. Photosynthetic capacity is the basic process underlying primary biological productivity in green plants and enhancing it might lead to increasing potential of the crop yields. Several approaches may improve the photosynthetic capacity, including integrated systems management, in order to close wide gaps between actual farmer’s and the optimum obtainable yield. Conventional and molecular genetic improvement to increase leaf net photosynthesis (P N) are viable approaches, which have been recently shown in few crops. Bioengineering the more efficient CC4 into C3 system is another ambitious approach that is currently being applied to the C3 rice crop. Two under-researched, yet old important crops native to the tropic Americas (i.e., the CC4 amaranths and the C3-CC4 intermediate cassava), have shown high potential P N, high productivity, high water use efficiency, and tolerance to heat and drought stresses. These physiological traits make them suitable for future agricultural systems, particularly in a globally warming climate. Work on crop canopy photosynthesis included that on flowering genes, which control formation and decline of the canopy photosynthetic activity, have contributed to the climate change research effort. The plant breeders need to select for higher P N to enhance the yield and crop tolerance to environmental stresses. The plant science instructors, and researchers, for various reasons, need to focus more on tropical species and to use the research, highlighted here, as an example of how to increase their yields., M. A. El-Sharkawy., and Obsahuje seznam literatury
Among various epiphytic ferns found in the Brazilian Atlantic Forest, we studied Vittaria lineata (L.) Smith (Polypodiopsida, Pteridaceae). Anatomical characterization of the leaf was carried out by light microscopy, fluorescence microscopy, and scanning electron microscopy. V. lineata possesses succulent leaves with two longitudinal furrows on the abaxial surface. We observed abundant stomata inside the furrows, glandular trichomes, paraphises, and sporangia. We examined malate concentrations in leaves, relative water content (RWC), photosynthetic pigments, and chlorophyll (Chl) a fluorescence in control, water-deficient, and abscisic acid (ABA)-treated plants. Plants subjected to drought stress (DS) and treated by exogenous ABA showed significant increase in the malate concentration, demonstrating nocturnal acidification. These findings suggest that V. lineata could change its mode of carbon fixation from C3 to the CAM pathway in response to drought. No significant changes in RWC were observed among treatments. Moreover, although plants subjected to stress treatments showed a significant decline in the contents of Chl a and b, the concentrations of carotenoids were stable. Photosynthetic parameters obtained from rapid light curves showed a significant decrease after DS and ABA treatments., B. D. Minardi, A. P. L. Voytena, M. Santos, Á. M. Randi., and Obsahuje bibliografii