Effects Of Water And Fertilizer Coupling On Growth And Development Of Fruit Cucumber And Its Physiological Mechanism Under Soilless Culture In Greenhouse

Fruit Cucumber var. Zhongnong 19 was used to investigate the effects of water and fertilizer coupling on growth and development of fruit cucumber and its physiological mechanism under soilless culture in greenhouse. Three irrigation levels : 87 L·plant^-1 (W1), 125 L·plant^-1 (W2), 162 L·plant^-1 (W3), and three fertilization levels : 64 g·plant^-1 (F1), 92 g·plant^-1 (F2), 119 g·plant^-1 (F3).1. Effects of water and fertilizer coupling on growth and development of fruit cucumber;(1) Effects of water and fertilizer coupling on morphological indexes of fruit cucumber were significant. Under the low irrigation level (W1), several indexes(leaf area?leaf number?plant height) of the cucumber were lower than that under the other levels. Stem diameter of high irrigation level (W3) was lower than other treatments. Middle irrigation level (W2) was the best irrigation level for morphological indexes. Leaf area and plant height of cucumber were enhanced with increasing fertilizing amounts in whole growing stage. Middle fertilization level (F2), high fertilization level (F3) were significantly larger than low fertilization level (F1) for leaf numbers and stem diameter. Fruit cucumber root activity increases markedly with increasing fertilizing amounts.(2) Effects of water and fertilizer coupling on fresh weight and dry weight of fruit cucumber leaf?stem?fruit and root were significant. W2 was the best irrigation level; F3 was the best fertilization level.(3) Effects of water and fertilizer coupling on yield of fruit cucumber were significant. W2 was remarkably higher than other levels for yield in fruiting early stage and fruiting middle stage, except W3 was the highest level in fruiting later stage under F3 level. Yield was remarkably influenced by different fertilization levels in whole fruiting stages, F3 was the highest level for yield. there were significantly positive correlation among plant height?stem diameter?leaf number?leaf area and yield in whole growth stage.(4) Effects of water and fertilizer coupling on quality of fruit cucumber were significant. Content of free amino acid?soluble protein?organic acid and soluble sugar of W3 were lower than other levels, and vitamin C of W1 was lower than other levels. Nitrate and nitrite contents of fruits had no significant effects on irrigation treatment. W2 was the best level for quality indexes of the cucumber. Contents of free amino acid?soluble protein and vitamin C of F3 superior to those of other levels, but nitrate and nitrite contents of F3 level exceed standard. Content of free amino acid?soluble protein?organic acid and vitamin C of F1 level were lower other levels and organic acid content higher other levels. For the upward factor F2 was the best fertilization level.2. Physiological mechanism of effects of growth and development of fruit cucumber under water and fertilizer coupling;(1) Effects of water and fertilizer coupling on photosynthetic characteristics of fruit cucumber were significant. Under the middle irrigation level, net photosynthetic rate(Pn)?transpiration rate(Tr)?stomata conductance(Gs)?chlorophyll contents?ribulose diphosphate carboxylase activity(RuBP)and Hill reaction of the cucumber were higher than that under the other levels. F2 was the highest level in seedling stage and fruiting early stage, and F3 was the highest level in fruiting middle stage and fruiting later stage, in effects of fertilization on several photosynthetic characteristic indexes. There was an obvious interaction between irrigation and fertilization.Correlation analysis indicated that there existed positive correlations among Pn?Tr?Gs?chlorophyll contents?RuBP activity and Hill reaction in whole growth stage. The correlation analysis showed that photosynthetic characteristic indexes was positively correlated with morphological indexes?yield?nitrate contents of fruits?nitrite content of fruit?free amino acid of fruit?soluble protein of fruit?soluble sugar of fruit and vitamin C of fruit,but not with organic acid of fruit in fruiting early stage.(2) Effects of irrigation treatment on sucrose synthase(SS)?sucrose-phosphate synthase (SPS)?acid invertase (AI)?neutral invertase (NI) activities and soluble sugar content were significant difference. SS?SPS?AI?NI activities and soluble sugar content in high irrigation(W3)level was the lowest. Effects of fertilization amount on soluble sugar content and SPS activity were significant difference, the order was high fertilization level (F3), followed by middle fertilization level (F2) and low fertilization level (F1), except fruiting later stage (F2>F3>F1). Effects of fertilization on SS?AI and NI activities were significant difference, F2 was the best fertilization level for SS?AI and NI activities. There was an obvious interaction between irrigation and fertilization. Correlation analysis indicated that there were positive correlations among SS?SPS activities and soluble sugar content in fruit cucumber. There were significantly negative correlation among AI?NI activities and plant height?leaf area. SS?SPS activities and soluble sugar content was positively correlated with yield?nitrate contents of fruits?nitrite content of fruit?free amino acid of fruit?soluble protein of fruit?soluble sugar of fruit and vitamin C of fruit,but AI?NI activities with these kinds of quality indexes was negatively correlated .(3) Effects of water and fertilizer coupling on the nitrogen metabolism of fruit cucumber were significant. Nitrate reductase (NR), glutamine synthetase (GS), glutamate synthase (GOGAT), glutamate dehydrogenase (GDH), nitrate nitrogen and soluble protein contents were remarkably influenced by different irrigation levels. Under the F1 level, several metabolism indexes of the W1 level were higher than other levels. Under the F2 level and F3 level, the W2 level was the best level. Activities of NR, GS, GOGAT, GDH, nitrate nitrogen and soluble protein contents were remarkably affected by the fertilization levels, the order was F3 level, followed by F2 level and F1 level under the same irrigation levels. There was an obvious interaction between irrigation treatment and fertilization treatment. Correlation analysis indicated that there were positive correlations among NR?GS?GOGAT?GDH?nitrate nitrogen and soluble protein contents in whole growth stage. Nitrogen metabolism indexes was positively correlated with morphological indexes?yield?nitrate contents of fruits?nitrite content of fruit?free amino acid of fruit?soluble protein of fruit?soluble sugar of fruit and vitamin C of fruit,but not with organic acid of fruit in fruiting early stage.(4) Effects of water and fertilizer coupling on the oxygen metabolism of fruit cucumber were significant. Superoxide dismutase (SOD)?catalase (CAT)?peroxidase (POD) and malondialdehyde(MDA) contents were remarkably influenced by different irrigation levels, W2 was the best irrigation level. F2 was the best fertilization level in the early growth stages;F3 was the best fertilization level in the later growth stages. There was obvious interaction between irrigation treatment and fertilization treatment. Correlation analysis indicated that there were positive correlations among SOD?CAT?POD activities in fruit cucumber. MDA content with SOD, CAT, POD three enzymes were negatively correlation. SOD, CAT and POD activities positively correlated among morphological indexes. SOD and CAT with yield has significant positive correlation, MDA has significantly negative correlation with yield in fruiting middle stage and fruiting later stage. SOD and CAT were positively correlated with nitrate contents of fruits?nitrite content of fruit?free amino acid of fruit?soluble protein of fruit and soluble sugar of fruit,but not with organic acid of fruit in fruiting early stage, MDA with these kinds of quality indexes is negatively correlated or no significant correlation.3. Comprehensive indexes, F3W2 was the best model in this experiment referred as the water- fertilizer coupling management model.