Effect Of Water Stress In Soil On Boll Retention In Cotton And Its Relevant Physiological Traits During Flowering And Boll-Setting Period

This experiment was conducted at greenhouse of Nanjing Agricultural University with two Jiangsu-popolarized cultivars Sumian 12 and Nankang 3 from 2002.4 to 2003.11. The pot experiment was carried out during flowering and boll-setting period in 2002 and the pond experiment in 2003. Effect of four soil water treatments on the cotton fruiting and its physiological mechanism was invested. The result were as follows:Cotton yield and its yield components were affected significantly by different soil water content. When relative soil water content was 70%~75% (W2), cotton yield is highest with sound composition and high quality fiber. Over much water (RSWC=100%) in soil led to slightly reduction of seed-cotton yield and soil drought (RSWC 50%~55%) led to the reduction of seed-cotton yield significantly. At the same time Wl treatment led to the slightly increase of boll number but declination of boll weight apparently. Soil drought led to the declination of boll number and slightly boll weight.Mechanism of cotton fruiting was changed by different water treatment. At first, Wl treatment led to the exorbitant growth of cotton. The number of nodes per plant and its growth rate was more than W2. Retained boll percentage was very low. Soil drought restrains the growth of cotton nodes per plant. Ratio of boll retained and intensity of fruit retention was lower than W2 apparently. Overmuch or less water in soil led to deterioration of boll distribution. Fewer bolls retained at lower and middle branches for the higher abscission. The proportion of the bolls on upper branches and outer nodes were very high because later compensation. It was not beneficial to formation of the fiber quality.The soil water changed cotton carbon metabolism, too. Wl treatment led to the declination of SPAD value and the net photosynthesis rate. W3 treatment led to declination of net photosynthesis rate but SPAD value was very high. The nonstructural carbohydrates concentration (NSCC) of vegetative organs including leaf, stem and branch and root declined for the overmuch water in soil. Total soluble carbohydrate (TSC) and starch concentration (SC) declined too. When soil drought, the soluble carbohydrate content of cotton leaf was higher than W2 at the beginning of treatment for its self drought-resisting instinct, but declined quickly later because of senescence. The starch content of leaf waslower than W2 because large proportion of starch was decomposed. The NSCC in leaf and stem was lower than W2 30 days after treatment apparently. But the NSCC in root was very high always. The forming intensity of bolls was positively correlative with the TSC, SC and NSCC in cotton leaf, stem and branch apparently. The carbohydrate content in cotton vegetative organs was the base of boll-setting during flowering and boll-setting period.The water of soil changed nitrogen metabolism. Whether overmuch water or soil drought, the total nitrogen content of cotton was lower than W2. When over much water in soil, the nitrogen content of leaf, stem, branch and root was lower than W2 apparently. It was same to the free amino acid content of vegetative organs. The declination of boll number per plant for soil drought, large part N reserved in the stem, branch and root. But total nitrogen content and free amino acid content in leaf indicated lower than W2 at the beginning of water treatment and higher than W2 later. Soil drought led to the decomposing of soluble protein in leaf. This disturbed the balance of physiological metabolism apparently. The nitrogen and free amino acid content in cotton vegetative organs was positively correlative with the intensity of boll-setting from 10dpt to 30dpt, too. But 30 days after treatment the relativity had been unapparent. At this time,too much nitrogen in vegetative organs was unbeneficial to boll-setting.Whether over much water or drought in soil, it was not benificial for cotton to absorb phosphor and potassium from soil. The phosphor and potassium content of cotton plant was lower than W2, especially in stem and branches of cotton. Thei...