[Effects of sunlight and temperature on ultrastructure and functions of chloroplast of cucumber in solar greenhouse].
ABSTRACT Studies on the effects of sunlight and temperature on the ultrastructure and functions of leaf chloroplasts of cucumber (Cucumis sativus L.) in solar greenhouse showed that the size of cells, chloroplasts, and starch grains and the number of chloroplast, grana, grana lamella and grana thickness of leaf chloroplast of cucumber increased with lowering leaf position. The microstructure of leaves and the ultrastructure of chloroplast of cucumber leaves were different because of the difference of temperature and sunlight among different months. In January, the light intensity was lower, and the cell size of cucumber leaves was larger than that in May, but the number of chloroplasts was less than that in May. The relationships between photosynthetic rate (Pn) and ultrastructure of chloroplast of cucumber leaves were not direct and very close. The Pn of the fourth leaf of cucumber was the highest, that of the first spreading out leaf was the second, and the near ground leaves had the lowest Pn. The primary reasons of the difference of Pn among different position leaves were that the leaf age and accepted light intensity were different. If different position leaves of cucumber accepted the same sunlight intensity, the difference of Pn among leaves of different positions would be smaller. Less efficient light hours and lower light intensity were the main factors influencing cucumber growth and yield in solar greenhouse. Comparatively, under sunny circumstance, the restriction of temperature on cucumber growth was very small, but in cloudy days, lower temperature induced by low light intensity became a key factor that restricted cucumber growth.
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ABSTRACT: A shed-microspore culture protocol was developed in Wageningen for producing doubled haploid plants in several genotypes of Indonesian hot pepper (Capsicum annuum L.). For transfer of technology to Indonesia, three factors were studied that appeared crucial for successful implementation in practice. First, application in the culture medium of a combination of the antibiotics timentin and rifampicin at the concentrations of 200 and 10 mg/l, respectively, prevented bacterial contamination from the donor explants. Second, in vitro application of colchicine (100 μM) during the first week of culture was highly effective in increasing the percentage of doubled haploid plants. Third, a comparative analysis of the ploidy level of plants regenerated from shed-microspore-derived embryos using chloroplast counts in guard cells of leaf stomata and flow cytometric measurement of leaf nuclear DNA content, revealed that the first procedure is a reliable and an easy to use method for ploidy determination with hot pepper.Scientia Horticulturae. 01/2006;
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ABSTRACT: With water culture, this paper studied the effects of exogenous spermidine (Spd) on the net photosynthetic rate (P n), intercellular CO2 concentrations (C i), stomatal conductance (G s), transpiration rate (T r), apparent quantum yield (Φ c), and carboxylation efficiency (CE) of cucumber seedlings under hypoxia stress. The results showed that P n decreased gradually under the hypoxia stress, and reached the minimum 10 days later, which was 63.33% of the control. Compared with that of the hypoxia-stressed plants, the P n 10 days after the application of exogenous Spd increased by 1.25 times. A negative correlation (R 2=0.473−0.7118) was found between P n and C i, and G s and T r changed in wider ranges, which decreased under the hypoxia-stress, but increased under the hypoxia-stress plus exogenous Spd application. There was a significant positive correlation between G s and T r (R 2=0.7821−0.9458), but these two parameters had no significant correlation with P n. The hypoxia stress induced a decrease of Φ c and CE by 63.01% and 72.33%, respectively, while the hypoxia stress plus exogenous Spd application made Φ c and CE increase by 23% and 14%, respectively. The photo-inhibition of cucumber seedlings under hypoxia stress was mainly caused by non-stomatal inhibition, while the exogenous Spd alleviating the hypoxia stress by repairing photosynthesis systems.Frontiers of Agriculture in China 2(1):55-60.