Effects Of Temperature-Light Factors On Cotton Yield And Fiber Qualities At Different Spatial Positions

Flowering and boll-forming stage (FBS) is an important stage to cotton production and quality formation. The influence of temperature and solar radiation (more rainy days in the early stage of FBS and low temperature in the late stage of FBS) during cotton growing season in Yangtze River significantly decreased cotton yield and fiber quality. Cotton plant has an indeterminate growth characteristic, and bolls on different fruiting positions developed under different meteorological conditions. Study on the effect of temperature-light factors on cotton yield component and fiber quality at different fruiting positions may be helpful in improving yield and fiber quality and providing reasonable cultivation measure theory. In 2009-2010, field experiments were carried out in the Lower Reaches of Yangtze River (Nanjing, Jiangsu province). By setting different sowing dates and different relative light rate, different meteorological conditions during flowering and boll-forming stage were formed. Two cotton cultivars (Kemian 1 is a high quality cotton cultivar and Sumian 15 is a regular quality cotton cultivar) were employed. The study focused on:(1) Effects of temperature-light factors on cotton yield component at different spatial positions. (2) Effects of temperature-light factors on cotton fiber qualities at different spatial positions. (3) Effects of temperature-light factors on cotton biomass accumulation and distribution. The main results were as follows:1 Effects of temperature-light factors on cotton agronomic characters and biomass accumulation and distribution(1) Under cool temperature due to late planting (from 25-Apr to 25-May and/or 10-Jun), the fruiting sites and boll number decreased and abscission rate declined, but buds increased; Shading decreased fruiting sites and boll number; There was significant influence on plant height of the interactive effects (P<0.05). (2) The eigenvalues of the dynamic accumulation model of dry matter accumulation was affected significantly by the temperature-light factors. Theoretical maximum for biomass decreased under cool temperature and shading. The starting day of rapid cummulation came earlier under cool temperature. The duration of rapid cummulation got shorter under cool temperature. Effective accumulated temperature and daily solar radiation not only play separate utility, but significant positive interaction effect. In the test condition, the temperature and light level in 25-Apr and CRLR100% approximate the best level but were not sufficient. Both cool temperature due to late planting and shading lead to the increase of vegetative organs biomass distributive indexes, and the decrease of reproductive organs biomass distributive indexes, shading effect is more significant with delayed planting date.2 Effects of temperature-light factors on cotton yield and yield component at different spatial positions(1) Under cool temperature, boll number on fruiting branch at the lth to 5th node and the 1st and 2nd fruiting position decreased, and boll number on fruiting branch at the 1th to 5th node and the 3rd or greater fruiting position and on fruiting branch at the 10th to 15th node and the 1st and 2nd fruiting position increased, which changed the distribution of bolls on the cotton; Shading decreased boll number on the fruiting branch at the 6th to 9th node and the 1st and 2nd fruiting position sharply. (2) Under cool temperature, boll weight on fruiting branch at the lth to 5th node and 10th to 15th node declined. Temperature due to 25-May was bad to boll weight on fruiting branch at the 6th to 9th node and the 1st and 2nd fruiting position, which, however was in favor of boll weight on its 3rd or greater fruiting position; Shading decreased boll weight on fruiting branch at the 1th to 5th node and the 1st and 2nd fruiting position and fruiting branch at the 6th to 9th node and the 1st and 2nd fruiting position. Boll weight on fruiting branch at the lth to 5th node and the 3rd or greater fruiting position varied due to different planting dates. (3) Cool temperature and shading decreased lint percentage. (4) Cool temperature and shading decreased the contribution share of bolls to yield, relatively increased the contribution share of boll weight and lint percentage.3 Effects of temperature-light factors on cotton fiber qualities at different spatial positions(1) Differences of mean daily temperature, mean daily maximum temperature, mean daily minimum temperature and daily solar radiation during flowering and boll-forming stage were observed between different spatial positions. The value of these meteorological conditions reduced with the increase of fruiting branch and fruiting position. They were the reasons for the difference on fiber qualities. (2) Among cotton fiber quality indexes, micronaire, followed by fiber strength and fiber length was more sensitive to the changes in meteorological conditions. (3) With PTP increasing, the changing trends of pivotal quality indexes (length, strength and micronaire) of cotton fiber accord with the curve of parabola with peak value. The theoretical maximum for each pivotal quality index ranked first on fruiting branch at the 6th to 8th node, followed by the 2nd to 4th node and the 10th to 12th node; The theoretical maximum at the 1st and 2nd fruiting node position were higher than those at the 3rd or greater fruiting node position. The pivotal quality indexes on fruiting branch at the 6th to 8th node and the 1st and 2nd fruiting position had broader PTP range when reaching quality cotton in accordance with A grade and AA grade. (4) Fiber strength got a smaller range of PTP, being the main restrictive factor to achieving quality cotton in accordance with A grade; the suitable PTP range of fiber strength and micronaire matched poorly, making them both the restrictive factors to achieving quality cotton in accordance with AA grade.