| The process of cotton fiber development determines the final cotton fiber quality, the study on the physiological mechanism of cotton fiber development is an important foundation on regulation of cotton fiber development, the formation of high-quality cotton fiber. Temperature is a key factor affects cotton fiber development. Thus, study on effect of temperature on the physiological basis of cotton fiber development would provide the theoretical basis on the regulation of cotton fiber development and exploration of improving fiber quality. In this study, high strength fiber (Kemianl, average fiber strength35cN·tex-1)and low strength fiber(NuCOTN33B, average fiber strength32cN-tex-1)cotton cultivars was used as test materials in the field experiment, two planting dates (25April and25May) was applied. And the experiments were conducted in Jiangsu Nanjing (118°50’E,32°02’N, lower reaches of Yangtze River Valley) and Jiangsu Xuzhou (117°11’E,34°15’N, Yellow River Valley) in2005-2006. The main study topic are as follows:(1) Effect of boll period temperature on cotton boll development and main fiber qualities development during the cotton boll forming stage;(2)Effect of temperature on saccharide metabolism of cotton fiber and its relationship with cotton fiber quality formation during cotton boll development;(3) Effect of temperature on endogenous protective enzymes of cotton fiber and its relationships with fiber cellulose accumulation and cotton fiber quality;(4) Effect of temperature on C, N metabolism in the leaves subtending boll and its relationships with cotton boll development and fiber quality;(5) Effect of the temperature on endogenous protection enzymes in the leaves subtending boll and its relationship with cotton boll development.The main results are as follows: 1. Effect of boll period temperature on cotton boll development and main fiber qualitiesThere were positive relationship between cotton fiber length, strength, mic value and boll weight, the average boll weight increase rate, fiber weight, percentage of cellulose, seed weight, the transportation of dry matter from shell. As the boll period temperature decreased, the starting and ending time of boll, fibe rapid increasing stag would be delayed, the rapid increasing duration of fiber weigh would be prolonged, the average boll weight increase rate would be decreased. Under low temperature (≤20.1℃), the starting and ending time of boll weight and fiber rapid increasing stage would be advanced, the rapid increasing duration would be shortened. There had an allometry relationship between cottonseed and cotton fiber development, that was the starting and ending time of fiber fast elongation was delayed, duration was shortened with boll period temperature decreasing. There was difference in the fiber strength forming ratio during the daily mean temperature of different cotton boll development, the fiber strength increased faster before24days under high temperature (≥25.3℃), and after45days the fiber strength increasing almost stopped; the rate of fiber strength increasing was slower before24days under low temperature (≤20.5℃), and after45days, the fiber strength growth still kept faster speed. Under the suitable temperature condition (23.1℃～23.2℃) fiber strength increased faster before24days, the fiber strength growth still kept a certain speed after45days. Mic value in the lower boll period temperature of cotton boll development decreased.2. Effect of temperature on saccharide metabolism of cotton fiber and its relationship with cotton fiber quality formation23.1℃～23.2℃was the optimal temperature for high strength fiber formation,23.1℃～25.3℃was the optimal temperature for long length fiber formation. Under the suitable boll period temperature, there had close relationships between sucrase,β-1,3-glucanase and fiber elongation in the major fiber elongation period (5～17d), in this period, higher activities of sucrase and β-1,3-glucanase activities could increase hydrolysis of sucrose, stablize the accumulation velocity of cellulose, improve the extensibility of the fiber cell wall, and these would be benefit for fiber elongation. During the period of fiber thickening stage (17d～Boll opening), there had close relationships between activities of sucrose synthase and sucrose phosphate synthase with fiber strength, mic value. In this period, sucrose synthase activities, sucrose phosphate synthase activities increased rapidly and were very high, sucrase and β-1,3-glucanase activities decreased rapidly, these would be helpful to improve sucrose conversion and to inmprove the accumulation of cellulose and the fiber quality. In Kemianl, the sucrase and P-1,3-glucanase activities in its early development stage and the sucrose synthase and sucrose phosphate synthase activities in its middle and later development periods were all higher than those in NuCOTN33B.3. Effect of temperature on endogenous protective enzyme of cotton fiber and its relationship with fiber cellulose accumulation and cotton fiber qualityDaily mean temperature of cotton fiber thickening development had significant effect on physiological activities of cotton fiber, its physiological activities had effect on cotton fiber sucrose transformation, cellulose accumulation and final fiber quality. Under normal daily temperature, the soluble protein content of cotton fiber was lower, SOD, POD, CAT activities rose slower with boll age increasing, the peak keeping time was longer, and still maintained higher level after28day of fiber thickening development, MDA content was lower and increased slowly. Sometimes the pervious acumulative rate of cellulose steady rose, the peak keeping time was longer, and late steady declined, and subsequently the fiber length and fiber strength were the highest, micro value more appropriate; while daily average temperature was below19.5℃, in which it was in lower temperature condition, SOD, POD and CAT activities rose more slowly and then decreased faster, then MDA content increased significantly, the cellulose synthesis speed and the fiber quality reduced; When the boll period temperature was above24.9℃, in which it was in higher temperature condition, the soluble protein of cotton fiber was lower, SOD, POD, CAT activities rose quickly with boll age increasing and then felled speedily, the MDA content increased obviously, the cellulose maximum accumulation rate was higher, but the duration of cellulose synthesis was shorter, then final fiber quality reduced ly. The physiological activity and sucrose conversion rate in high fiber strength cultivar Kemianl were higher than that in NuCOTN33B during cotton fiber thickening development, and had a longer duration of cellulose rapid accumulation, so the final fiber quality was superior to NuCOTN33B. 4. Effect of temperature on C, N metabolism of leaf subtending boll and its relationship with cotton boll development and fiber qualityC/N was closely related to cotton fiber length, strength and Mic value formation. Within different boll perild temperature condition, there were significant differences on soluble sugar, free amino acid content and C/N in leaf subtending boll (P<0.05). While the boll period temperature was at23.1℃～26.1℃, C/N metabolic in the subtending leaf, cotton boll was coordinated, cotton boll weight increase quickly, the rapid weight increasing period was longer, cotton fiber length and strength were higher, Mic value was more appropriate. While in the lower boll period temperature, the soluble sugar content in the leaf subtending boll presented lower (the early cotton boll development), increasing (the middle cotton boll development), decreasing (the later cotton boll development) and amino acid content had maintained a relatively higher level, C/N decreased, the start time of rapid boll weight increase period delayed, the rate of boll weight increasing, the boll weight, fiber length, strength and micr value all decreased. Therefore, the daily mean temperature at23.1℃～26.1℃is beneficial to increasing cotton boll weight and high fiber quality formation, the temperature at25.3℃～26.1℃is suitable for big boll forming, the temperature at23.1℃～25.3℃is helpful to increasing fiber length, the temperature at23.1℃～23.2℃is adapted to optimize fiber strength and Mic value. There have regional differences on average C/N in the subtending leaf, Nanjing and Xuzhou were respectively5.6,9.4.5. Effect of the temperature on endogenous protection enzymes in leaf subtending boll (LSB) and its relationship with cotton boll development.When the daily mean temperature (DMT) during boll maturation period was in the range of23.1℃to25.3℃, the LSB had higher soluble protein content, higher physiological activities and longer functional time. That mainly present as higher activities of endogenous protective enzymes, lower MDA content, and more ideal C/N ratio, and these characters were helpful to increase the average velocity and prolong the time for rapid increasing in boll developing, and to form higher boll weight. When the DMT during boll maturation period was above27.2℃, the physiological activities in LSB decreased, but C/N ratios increased, which resulted in the increase of average velocity, the shorter duration time for rapid increasing in boll developing, and the lower boll weight in some extent. When the DMT during boll maturation period was below20.5℃, the LSB had higher physiological activities at the prophase, but it had faster velocity of physiological activities decreasing during middle and later of boll development and lower C/N ratios, these led to longer duration time for rapid increasing and lower average velocity in boll developing, resulting in lower boll weight. Under the low temperature conditions in this study, the physiological activities and the boll weight in LSB of Kemian1were higher than that in NuCOTN33B. The way to increase boll weight is to improve the physiological activities and to abtain ideal C/N ratio, the suitable daily mean temperature (DMT) during boll maturation period can improve the physiological activities in LSB. |
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