Developmental and Environmental Effects on the Expression of the C3-C4 Intermediate Phenotype in Moricandia arvensis1

Cellular anatomy and expression of glycine decarboxylase (GDC) protein were studied during leaf development of the C3-C4 intermediate species Moricandia arvensis. Leaf anatomy was initially C3-like and the number and profile area of mitochondria in the bundle-sheath cells were the same as those in adjacent mesophyll cells. Between a leaf length of 6 and 12 mm there was a bundle-sheath-specific, 4-fold increase in the number of mitochondrial profiles, followed by a doubling of their individual profile areas as the leaves expanded further. Subunits of GDC were present in whole-leaf extracts before the anatomical development of bundle-sheath cells. Whereas the GDC H-protein content of leaves increased steadily throughout development, the increase in GDC P-protein was synchronous with the development of mitochondria in the bundle sheath. The P-protein was confined to bundle-sheath mitochondria throughout leaf development, and its content in individual mitochondria increased before the anatomical development of the bundle sheath. Anatomical and biochemical attributes of the C3-C4 character were present in the cotyledons and sepals but not in other photosynthetic organs/tissues. In leaves and cotyledons that developed in the dark, the expression of the P-protein and the organellar development were reduced but the bundle-sheath cell specificity was retained.

Environmental services of biodiversity.

Humans derive many utilitarian benefits from the environmental services of biotas and ecosystems. This is often advanced as a prime argument to support conservation of biodiversity. There is much to be said for this viewpoint, as is documented in this paper through a summary assessment of several categories of environmental services, including regulation of climate and biogeochemical cycles, hydrological functions, soil protection, crop pollination, pest control, recreation and ecotourism, and a number of miscellaneous services. It is shown that the services are indeed significant, whether in ecological or economic senses. Particularly important is the factor of ecosystem resilience, which appears to underpin many of the services. It should not be supposed, however, that environmental services stem necessarily and exclusively from biodiversity. While biodiversity often plays a key role, the services can also derive from biomass and other attributes of biotas. The paper concludes with a brief overview assessment of economic values at issue and an appraisal of the implications for conservation planning.