Kandelia (Rhizophoraceae) has long been regarded as a monotypic mangrove genus. Recent studies in chromosome number, molecular phylogeography, physiological adaptation, and leaf anatomy, however, reveal that there are two well differentiated sets of geographical populations separated by the South China Sea. These are recognized as two distinct species, Kandelia candel (L.) Druce and Kandelia obovata Sheue, Liu & Yong sp. nov.
H. 1994. Gibberellin and temperature influence carbohydrate content and flowering in Phalaenopsis -Physiol Plant. 90; 391-395.When Phalaenopsis atnabilis is grown under high temperature {3O/25°C, day/night), flowering is blocked, and this can be reversed by gibbereliin A, (GA,) treatment. Associated with GAi treatment under high temperature are increases in sucrose. glucose and fructose as compared with warm-treated plants. Spraying with sucrose solution alone caused ieaf epinasty in plants grown under high temperature. Epinasty was released by ahout 9 days of GA, treatment. In GA,-treated plants under high temperatures, sucrose application to the source leaves led to an increase in sugar contenl in both leaves and inflorescence. In contrast, although in warm-treated plants sucrose application to the source leaves increased sugar content in the leaves, it did not increase sucrose content in the inflorescence. These results corroborate our hypothesis that in Phalaenopsis GA, stimulates sink activity in the apical meristem and promotes the translocation of sucrose from source leaves to the apex of the inflorescence, where ii accumulates. GA, treatment led to an increase in sucrose synthase activity and had no effect on invenase activity.
Study of the unique leaf anatomy and chloroplast structure in shade-adapted plants will aid our understanding of how plants use light efficiently in low light environments. Unusual chloroplasts in terms of size and thylakoid membrane stacking have been described previously in several deep-shade plants. In this study, a single giant cup-shaped chloroplast, termed a bizonoplast, was found in the abaxial epidermal cells of the dorsal microphylls and the adaxial epidermal cells of the ventral microphylls in the deep-shade spike moss Selaginella erythropus. Bizonoplasts are dimorphic in ultrastructure: the upper zone is occupied by numerous layers of 2-4 stacked thylakoid membranes while the lower zone contains both unstacked stromal thylakoids and thylakoid lamellae stacked in normal grana structure oriented in different directions. In contrast, other cell types in the microphylls contain chloroplasts with typical structure. This unique chloroplast has not been reported from any other species. The enlargement of epidermal cells into funnel-shaped, photosynthetic cells coupled with specific localization of a large bizonoplast in the lower part of the cells and differential modification in ultrastructure within the chloroplast may allow the plant to better adapt to low light. Further experiments are required to determine whether this shade-adapted organism derives any evolutionary or ecophysiological fitness from these unique chloroplasts.
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