| Plant density is one of the important factors influencing lint yield and quality. Field trials were arranged in a split plot design that 2 transgenic insect resistant Bt(Bacillus thuringiensis) cotton hybrid cultivar CRI75 and conventional cultivar SCRC28 were placed as the main plots and plant densities(15,000, 51,000 and 87,000 plant·hm-2) were placed as the sub-plots with 3 replications in 2012 and 2013 at Anyang, Henan, China, to analyze effect of plant density on light distribution, LAI and accumulate of biomass and economic yield, and especially on yield components that are seed cotton and lint yield per seed, seed number per boll and seed mass and quality parameters across locule seed positions(SP). The methods are as follows.Experiment 1:Seed cotton was calculated, so did boll weight and boll number and lint percent. Two plants of per plot were sampled every 15 days since the middle of May, which was disassembled to determine the fresh weight of leaf, stem and boll. Then dry matter was determined by putting the fresh samples into a dryer when the weight was constant. The PARi and PARr were measured using a 100 cm line light quantum sensor Lincoln and datalogger. Finally, fibers were tested at the Testing Center of Cotton Quality, Ministry of Agriculture, Anyang, Henan, for high volume instrument fiber analysis(HVI).Experiment 2:20 plants from 2 center rows of each plot were hand harvested by nodes and fruiting positions. Then the first fruiting position bolls from nodes 6-10 had their seeds separated by locule positions from the base to apex. Individual projected seed area(SA) was determined by Phantom 9800 X and IPWIN60. After seed scanning, one step further cool-warm vigor index was used to determine seed vigor. Fiber quality parameters, namely fiber length(FL), fiber uniformity(FU), micronaire value(FM) and fiber strength(FS), were analyzed. The following results were observed:Experiment 1:In the group level, significant difference of lint yield was found at 15000 plant·hm-2(1034.3 kg/hm2) and 51000 plant·hm-2(1581.3 kg/hm2), while not at 51000 plant·hm-2 and 87000 plant·hm-2(1590.7 kg/hm2). Boll number per area was significantly increased as plant density increased. However, boll weight was decreased with increasing plant density. Additionally, light transmitted was decreased as plant density increased, but LAI was increased. As plant density increased, the maximal accumulated biomass was lower.Experiment 2:In the plant level, in current study, boll numbers(upper nodes, distal fruiting positions) were increased with decreased plant density. Boll weight was decreased at higher plant density on the same fruiting node and position. Moreover, greater boll weight was occurred at inner fruiting positions and lower nodes. In this study, ratio of total number of fruiting positions to fruiting nodes was reduced as plant density increase, for which boll number per plant was reduced too.In the boll level, boll weight was decreased as plant density increase for seed numbers per boll, seed mass and lint yield per seed decreasing with plant density increase. Effect of plant density on seed cotton per seed(SY) and lint yield per seed(SL) was bigger at the apex of the boll than the base and middle; and SA was the highest at the base to middle of the boll and the lowest at the apex of the locule; frequency of motes(PM) was the lowest at the middle of the boll and increased from middle to the both ends of the boll, which might be for the reason of insufficient fertilization of the ovule. And PM increased with plant density increased; fiber length was the greatest at 51000 plant·hm-2, but micronaire value was decreased with plant density increase. And fiber strength was the greatest at 15000 plant·hm-2 in 2012 while 87000 plant·hm-2 in 2013. Favorable fiber parameters and seed vigor occurred at the base to middle of the boll. These findings were important to adjust cotton planting density and breeding. |
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