Temperature Effects on Cotton Seedling Emergence, Growth, and Development.

One of the major problems facing cotton producers in the US is the establishment of a vigorous seedling stand early in the season. However, there has been little work to investigate cotton responses particularly on temperature effects on seed germination and seedling growth including roots. The objective of this study was to test the hypothesis that cotton cultivars differ in their response to different temperatures. A molecular standard Texas Marker (TM)-1 and three modern cotton cultivars (DP1522B2XF, PHY496W3R, and ST4747GLB2) were sown at five day/night temperature regimes of 20/12, 25/17, 30/22, 35/27, and 40/32 °C (day/night).  Shoot and root growth parameters were measured 20 days after sowing. The small differences were observed between the older molecular standard, TM-1 and the three modern cultivars in response to temperatures indicating that successive breeding efforts did change the rate or behavior of those traits. Seedling emergence was best described by both linear (TM-1 and PHY496W3R) and quadratic (DP1522 B2XF and ST4747 GLB2) functions. Node numbers and root tips increased linearly with increase in temperature, and no cultivar differences were observed for this trait. The temperature and cotton seed emergence and pre-squaring above- and below-ground growth and developmental responses will be useful in assisting management and in improving functionality of many cotton models.