| This paper comparatively studied the photosynthetic characteristics of Katy apricot grown in greenhouse and in open field, while determined the various environmental factors in greenhouse to morphological characteristics and physiological characteristics during the fruit development period. The results showed that:1)Under greenhouse cultivated conditions, the initional bloom stage of Katy apricot was advanced by 40 days compared with that in the open field, blooming period was prolonged for 4 days to that in the open field. The blooming period was 9 days in greenhouse, which was 5 days in open field. The fruit maturation period was advanced by 30 days compared to the open field.2)Under greenhouse cultivated conditions, Katy apricot the ratio of fresh and dry leaf weight and specific leaf weight were decreased, while the relative water content increased, new shoots lengthen significantly, leaf area expanded obviously. The thickness of leaves, the palisade tissue and the radio of palisade to spongy tissue were all reduced, the stomata density were decreased, stomata length and stomata width were all less than those in open field, the stomata length had no significant difference.3) The light saturated poin(tLSP)and light compensate poin(tLCP) of leaves grown in greenhouse Katy apricot were about 1233.3μmol·m-2·s-1 and 45.5μmol·m-2·s-1 respectively, and the apparent quantum yield(AQY)was 0.0282 at Shoot-speed long period of Hard-core stage, while the LSP and LCP of leaves grown in open field Katy apricot 1387.5μmol·m-2·s-1 and 87.5μmol·m-2·s-1 respectively, and the AQY 0.0317 in the same time. Compared with the open field cultivation, the light saturated point and light compensate point of leaves grown in greenhouse Katy apricot were lower than those in open field, the light saturated point decreased by 11.1%, the compensate points down 48%, the AQY decreased by 11%.4) The CO2 saturated poin(tCSP)and CO2 compensate poin(tCCP) of leaves grown in greenhouse Katy apricot were about 1090.8μmol·m-2·s-1 and 80μmol·m-2·s-1 respectively at Shoot-speed long period of Hard-core stage, while the CSP and CCP of leaves grown in open field Apricot cultivar'Katy'1522.5μmol·m-2·s-1 and 87.5μmol·m-2·s-1 respectively in the same time. Compared with the open field cultivation, the CO2 saturated point and CO2 compensate point of leaves grown in greenhouse apricot'Katy'were lower than those in open field, the light saturated point decreased by 28.4%, the compensate points down 8.6%.5) Diurnal variation of net photosynthetic rate (Pn)in leaves grown in greenhouse and open field Katy apricot appeared single-peak curve in Shoot-speed long of Hard-core and Fruit enlargement stages, which occurring at about 10:00 and 15:00, and decreased 32.5﹪and 35.9﹪compared with that in open field. However, there are varying degrees of chlorophyll content increased in greenhouse cultivation, which was more than that in open field cultivation, the total amount of chlorophyll increased by 50%, chlorophyll a, b contents were increased by 44% and 69.8%, but the chlorophyll a / b decreased.6) The results show that, diurnal variation of PAR and Pn had a significantly positive relation, and diurnal variation of Pn was affected by regulating the stomatal conductance (Gs) and transpiration rate (Tr) to change air CO2 concentration and temperature. It was showed that Pn was positively to correlated to Gs and Tr. It can be effectively reduced the inhibition effect of environmental factors on the Pn by noon let in fresh air to avoid midday depression.7) Seasonal variation of Pn demonstrated that both greenhouse and field Katy apricot had the highest Pn in April and May which were 10.02μmol·m-2·s-1 and 13.36μmol·m-2·s-1 respectively in fruit development period. The Pn of greenhouse apricot was decreased that of field apricot obviously during the whole experiment and Pn decreased the overall level, affected by the light intensity.8) The experiment results of transpiration rate(Tr)and water use efficiency(WUE)showed that apricot grown in greenhouse had higger transpiration rate and lower water use efficiency, which indicated that apricot grown in greenhouse needed more water and the ability of adapting to high temperature and dry environment stress is worse, So strengthen the watering management of greenhouse apricot in production.9) Malondialdehyde (MDA) content in leaves showed that the trend of the decreased next to rise in both the greenhouse and open field, the highest in maturity period. MDA content in leaves of greenhouse was higher than those in open field, the MDA content increased perhaps because of the low temperature in early spring and the less soil water, and other reasons. In order to avoid the greenhouse apricot under the adverse circumstances of the low temperature and drought stress, the greenhouse heat preservation and irrigation work should be in a timely manner to enhance.10)The content of soluble sugar of greenhouse Katy apricot leaf was lower than that in the field, which reached the highest in Hard-core and reduced slightly in Fruit maturity period. The same with soluble protein content, the soluble protein content of greenhouse Katy apricot leaf also was lower than that in the field, but it showed the trend of increasing. Both the content of greenhouse were all higher lower than that of the field, which be related with the intensity of photosynthesis, however, the reason of the content of soluble sugar decreased in Fruit maturity period might be that this period is the chief period of reproductive growth in Katy apricot, the photosynthetic production is used mainly for fruit development while the accumulation is little.11)Studied on the dynamic changes of antioxidant enzyme activities such as superoxide dismutase(SOD), peroxidase(POD), catalase(CAT), the results showed that the POD, SOD activity in greenhouse Katy apricot was lower than that in the field, the southern of greenhouse was higher than that in northern and central of greenhouse. However, CAT activity was the opposite, CAT activity in greenhouse was higher than that in the field, the southern of greenhouse was lower than that in northern and central of greenhouse, the reason is to be further studied. |
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