Regulation Of Soil Moisture Content In Sink-Source Relationships Of Cotton Under Mulch Drip Irrigation In Xinjiang

【Objective】In striving to increase the yield level of cotton in Xinjing and exert the high yield potential of under-mulch-drip irrigation technology it is of great importance to study the regulating effects of different soil moisture on source-sink relationship and the coordination between endogenous hormone and source-sink relationship for making sure the limiting factors to increasing cotton yield.【Methods】Three cotton cultivars of different leaf type were used: Xinluzao13(big-normal leaf),Xinluzao10(semi-normal leaf),BiaozaA1(okra-leaf hybrid cotton). In the experiments we designed three soil moisture content treatments, controlled the lower limited of soil water content in 0~60 cm soil layer at 85%~90%( high moisture), 70%~75% (moderate moisture) and 55%~60% (low moisture) of the field water capacity and upper limit of soil water content at field capacity by applying drip irrigation from full bud stage. The source-sink treatments were as follows: half leaf from one side of the leaf removed except the main nerve; quarter leaf from one side of the leaf removed excep the main nerve; various numbers of buds or flowers were removed from the even number sympodia branch; various numbers of buds or flowers were removed from the second or the second, the sixth sympodia branch; the intact plants were control.【Results】The effect of source-sink regulator on the quantity, quality, yield and fiber quality of cotton and the response to soil moisture were researched. The results were as follows:1. Effect of source removeal and sink removal on source: sink ratio. Source removal could enhance sink: source ratio (boll number per unit leaf area) and sink removal could decline it significantly. With the soil moisture content increasing, the sink: source ratio reduced. It could due to cotton yield declined with sink: source ratio much more bigly or small. To the small leaf type variety, the deficiency of leaf could be compensated by increased soil moisture properly. Big leaf type variety could be planted in water deficiency area. The variety which sink was big, source was small, could satisfy the nourishment supply to sink by removing sink aptly.2. Effect of alteration of source: sink ratio on cotton yield and quality. (1) Abating source seriously affected the yield, for insufficient source evidently reduced the yield, the number and the weight of boll per plant. In some degree yield reduction caused by insufficient source can be compensated by increasing moisture, which realized by increasing the number of boll per plant, so excessively abating source and sink was impossibly compensated by that. The yield was not evidently affected by abating sink, for the weight of boll was not greatly changed based on the stabilized number of boll per plant. But the yield was greatly reduced by excessively abating sink; for the number of boll per plant was greatly reduced despite the weight of boll was not greatly changed. (2)In this investigation, the degree of variety hereditary characters and the condition of soil moisture, which affected fiber length,strength and Macron were much serious than that of source-sink ratio. The fiber length increased along with the augment of soil moisture was not evidently affected by source and treatment. In some degree, fiber strength increased along with the reduction of soil moisture was affected by reducing source-sink ratio by removing half leaf. Macron of plants dealt with removing leaves, reduced along with the augment of soil moisture, was lower than that of CK and the one dealt with removing buds.3. Effect of alteration of source: sink ratio on source in some degree. (1) With the degree of abating source increasing and the degree of soil moisture reducing, the senescence of cotton was getting more seriously. With the soil moisture increasing, the damage of dry matter accumulation, which caused by abating leaf, was compensated, but which couldn't be realized when abating leaf seriously. Abating sink also affected the photosynthetic production transportation to boll, which aroused more photosynthetic production rested on the vegetative organ. With the degree of abating sink increasing, this effect was more serious. Under the condition of high moisture, the leaf area of abating sink augmented persistently and appeared the phenomenon of excessive vegetative. (2) The photosynthetic rate(Pn) of leaf appeared declined than that of CK after abating source, in some degree, while the abating sink made the transportation of photosynthetic production baffled, which caused the Pn decline, the inhibit function of abating quarter sink was smaller compared with CK. With the increasing and droping of soil moisture, the Pn of leaf declined significantly, but the Pn r of leaf was higher than that of CK after removing source and sink under the condition of low soil moisture. Leaf removal brought forward the accumulation of indole-3-acetic acid (IAA) and enhanced the contents of abscisic acid (ABA) of sympodial leaf, which accelerated the plant senescence. Square removal delayed the accumulation of IAA and the contents of ABA remained steadily; High soil moisture made the source activity stronger of different cotton varieties, what's more the activity of Biaoza A1 were the strongest those of Xinluzao 13 and Xinluzao 10. Low soil moisture induced the content of ABA increasing rapidly, which promoted the senescence of cotton leaf.4. Effect of alteration of source: sink ratio affected sink in some degree. (1) Leaf removal put forward the optimum period of reproduction organ dry matter accumulation, and declined the capacity of cotton bolls; Square removal delayed the accumulation time of photosynthetic product in reproduction organs. With the increase and decrease of soil moisture, the capacity of cotton bolls and reproduction organ dry matter accumulation were all declined, but tBiaoza A1 appeared much advantage of sink strength than other varieties. (2) In the earlier stage of boll development, higher contents of IAA were detected in the boll wall and seed cotton, which can induce the development of boll. Furthermore, square removal was of great benefit to the boll development than leaf removal; low soil water was of great benefit to the boll development than high soil water. In the term of boll development, BiaozaA1 were better than two other cotton varieties under the condition of high soil water. What's more, the ABA content of square removal adds gradually after 25 days anthesis, which conduced to the boll weight.【Conclusions】The change of source: sink ratio have affected yield formation of cotton significantly. Soil moisture could regulator sink: source ratio evident. Source removal affected sink: source ratio and Pn slightly, but which made the reproduction organ dry matter accumulation reduce, and seed cotton yield decline, while quarter sink removal affected yield no significantly. So at blossoming and boll-forming stages,under the condition of mulch drip irrigation in Xinjiang, the activity of source was regulated by sink, however, the development of sink was affected source size. In the actual produce high cotton yield can be gained in the condition of high-level dynamic balance of source and sink relationship, namely cultivating stronger source and sufficient sink population, while the balance can be get by regulating the soil moisture or the other cultivable measures.