ground meristem mospheric pollution by carbon dioxide, mainly due to the burning of fossil fuels, and many other gases is leading to a rise in global temperatures (global warming), which will eventually affect other aspects of climate and have profoundly damaging effects on natural ecosystems and agriculture, as well as raising sea level.
stops entirely, though it may become extremely slow (indeterminate or indefinite growth). This allows plants to continue growing and many plants grow laterally showing clonal growth. The result is that some can be extremely long-lived, with clones, such as those of the creosote bush (Larrea tridentata) known to have lived for over 10 000 years.
Grew, Nehemiah (1641–1712) British physician and botanist. Grew carried out important work in plant anatomy and was a contemporary of MALPIGHI. His work culminated in his publication of The Anatomy of Plants, in which he was among the first to observe chloroplasts and stomata, describing the latter as ‘breathing pores’.
ground layer The lowermost layer of a plant community, usually comprising mosses, lichens, fungi, and low-growing herbs, especially rosette plants and creeping, prostrate forms. Compare field layer. ground meristem The central region of the apical meristem from which the ground tissues of pith, cortex, medullary rays, and mesophyll differentiate. In root meristem it is also called periblem. ground tissues The unspecialized tissues that are found in any region of the plant not occupied by the specialized tissue of vascular bundles, cambium, epidermis, etc. The pith and cortex of the root and stem are ground tissue, as are the mesophyll layers of the leaf.
growth An irreversible increase in size and/or dry weight. It excludes certain developmental processes that involve no size change, such as cleavage and uptake of water by seeds (IMBIBITION). Growth involves cell division and cell expansion through synthesis of new materials, and is closely related to subsequent developmental processes. If some measure of growth of an organism, such as height or weight, is plotted throughout its life, a characteristic S-shaped (sigmoid) growth curve is obtained for most organisms. In some organisms, including many plants growth never
growth factor Any substance that affects the growth of a plant. This includes SUBSTANCES (HORMONES) and GROWTH INHIBITORS, as well as food reserves and minerals. GROWTH
growth inhibitor A substance that slows the growth of a plant, for example the plant hormones ABSCISIC ACID and ETHYLENE (ethene), which act at very low concentrations. growth ring See annual ring. growth substance See hormone. GSC Gas–solid chromatography. See gas chromatography. guanine A nitrogenous base found in DNA and RNA. Guanine has a purine ring structure. The nucleoside guanosine triphosphate (GTP) is derived from guanine, and supplies energy for certain enzymecatalyzed metabolic reactions. guanosine (guanine nucleoside) A nucleoside present in DNA and RNA and consisting of guanine linked to D-ribose via a b-glycosidic bond.
guard cell A specialized kidney-shaped epidermal cell, located to the side of a STOMA. Two guard cells together encircle each stoma and control the opening and closing of the stomatal aperture. The control is effected through changes in turgidity. The wall of the guard cell bordering the pore is heavily thickened while the opposite wall is comparatively thin. Thus when the guard cell is turgid the thin wall becomes distended, bulging out away from
104