| To study the effects of temperature（accumulated effective temperature,AET）and solar radiation（SR）on cotton organs development,field experiments were conducted during two growing seasons（2015–2016）using two cultivars ‘Huamian 3109（V1,a conventional cultivar）and Huazamian H318（V2,a hybrid cultivar）’ in 2015 and one cultivar ‘V1’ in 2016 with three sowing dates: 25 April（S1）,16 May（S2）and 6 June（S3）on the experimental farm of Huazhong Agricultural University,Wuhan,China（30°28’13.45 " N and 114°20’ 44.69" E,altitude 22 m）.On the first sowing（S1）,in rows 4 data loggers for air temperature and relative humidity recording every 30-minute were fixed with a bamboo stick 3 m above the field ground.Plant mapping was carried out every 3-5 days by recording the status of each node and position and plant height from the fixed 10 plants continuously in each plot’s middle row.The results showed:1 Temperature and solar radiation strongly influenced the growth periods.During 2015 growing season,S1 spent the emergence（from sowing to emergence）for 8 days,while S2 and S3 took 5 days,and had the lowest AET（66.6 DD）and SR(150.9 MJ m-2)for V1.In seedling period（from emergence to squaring）,the highest AET and SR was observed around 40 DAS（days after sowing）(463 DD and 710.3 MJ m-2 in S1,however the highest AET during squaring was found in S3（426.0 DD in 25 days）as compared to S1（340 DD in 22 days）.During flowering and boll setting（from blooming to boll opening）,S3 accounted 44 days with AET 698 DD and SR 782 MJ m-2,respectively.During the growing period,V1 and V2 had no significant difference in 2015,but V1 had the difference between two years.2 In 2015,three sowing dates had the following plant heights of 23.7,27.5 and 25.9 cm for V1 in squaring stage（S1 in 48 DAS,S2 in 40 DAS and S3 in 31 DAS）with respective AET of S1,S2 and S3（529.6,533.8 and 469.0 DD）and SR(710.3,562.9 and 458.1 MJ m-2).V2 was relatively higher than V1 for both S1（26.3 cm）and S2（29.6 cm）and also showed the same trend for flowering stage.On the contrary,S3 was shorter than S1 or S2 for V1 and V2 in the first growing season.V1 had significant difference between two years（p-value<0.05）for both squaring and flowering period.3 Newly expanded leaf occurred every 2 – 5 days with AET of 21 – 73 DD and SR of 20 – 76 MJ m-2.V1 had longer lifetime（41-51 days）than V2（39-46 days）for all the sowing dates（S1,S2 and S3）with the corresponding AET of 537 – 808 DD for S1V1,384 – 756 DD for S1V2 and SR of 547 – 862 MJ m-2 for S1V1,393 – 811 MJ m-2 for S1V2,S3 was shorter than S1 or S2 that was 22 – 54 days with AET of 241 – 775 DD and SR of 265 –786 MJ m-2 for V1 and 16 – 40 days with AET of 152 – 686 DD and SR of 180 – 696 MJ m-2 for V2.4 AET in the days from planting to squaring stage in 2015 remained no difference between S1（529.6 DD）and S2（533.8）for V1 and non-significant among all sowing dates with AET of 519.1 DD,533.4 DD and 516.6 DD for S1,S2 and S3,respectively in V2.But was different among the sowing dates for SR of 710.3 MJ m-2,562.9 MJ m-2 and 458.1 MJ m-2,for S1,S2 and S3,respectively.5 In first flower stage,SR were significantly different among the sowing dates（S1,S2 and S3）for V1 in 2015.In addition to that DAS remained significant for three sowing times（S1 = 70,S2 = 64,S3 = 57）and was observed non-significant for AET（S1 = 869.6 DD,S2 = 905.2 DD and S3 = 895 DD）;and there is no big different was found among S1,S2 and S3(1023.4,899.7 and 879 MJ m-2,respectively)for SR.Contrary to this,V2 remained shorter in S3（60 DAS）but found to have highest AET（962.7 DD）and SR(1015.7 MJ m-2)in S1.6 During the days from planting to first boll open,V1 and V2 were significantly different for S1 and S3（112 DAS and 101 DAS,respectively for V1）;and V2 was 111 DAS and 105 DAS（S1 and S3,respectively）in 2015 growing season but SR remained non-significant across three sowing dates.Between 2015 and 2016,DAS and SR were significant in all parameters accept AET was no significant different which p-Value greater than 0.05. |
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