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  • Author or Editor: Gang Wang x
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The floral homeotic C-function gene AGAMOUS (AG) has been shown to be critical in the determination of stamen and carpel identity in Arabidopsis. In the present study, a new homologue of AGAMOUS gene from pecan [Carya illinoinensis (Wangenh.) K. Koch], denoted by CiAG, was isolated and its function was characterized. The complementary DNA (cDNA) of CiAG contains an open reading frame of 687 base pairs (bp) encoding 227 amino acids. Multiple sequence comparisons revealed that CiAG had the typical MIKC structure. Phylogenetic analysis indicated that CiAG is closely related to C-lineage AG. The expression of CiAG was highly accumulated in the reproductive tissues (staminate flowers, pistillate flowers, and fruitlets) than in vegetative tissues (leaves and current-growth branches). Arabidopsis overexpressing CiAG exhibited earlier flowering. The homeotic transformations of petals into stamen organs were observed in 35S::CiAG transgenic plants. All these results indicated that CiAG plays a key role in the process of flower development of pecan.

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Photosynthetic physiology of Dendrobium nobile, Dendrobium pendulum, Dendrobium chrysotoxum, and Dendrobium densiflorum was studied. A bimodal diurnal variation of the net photosynthetic rate (Pn) was observed in the four Dendrobium species with the first peak [5.09 to 6.06 μmol (CO2) per m−2·s−1] ≈1100 hr and the second peak [3.83 to 4.58 μmol (CO2) per m−2·s−1] at 1500 hr. No CO2 fixation was observed at night. For all four Dendrobium species, the light compensation point (LCP) was 5 to 10 μmol·m−2·s−1, light saturation point (LSP) ranged from 800 to 1000 μmol·m−2·s−1, apparent quantum yield (AQY) was 0.02, and CO2 compensation points (CCP) and saturation point (CSP) were 60 to 85 μmol·mol−1 and 800 to 1000 μmol·mol−1, respectively. Carboxylation efficiency (CE) values ranged from 0.011 to 0.020. The optimum temperature for photosynthesis was between 26 and 30 °C. The measurement of Pn seasonal variation indicated that July to August had the higher Pn for Dendrobium species. Additionally, the chlorophyll a/b (Chl a/b) ratios of the leaves were 2.77 to 2.89. Measurement of key enzymes in the photosynthetic pathway indicated relatively high Ribulose-1,5-bisphosphate carboxylase (RuBPCase) and glycolate oxidase (GO) activities but very low phosphoenolpyruvate carboxylase (PEPCase) activities. It suggested that these four Dendrobium species are typical semishade C3 plants.

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