Temperature effects on cotton seedling emergence, growth, and development

Establishing vigorous cotton (Gossypium hirsutum L.) seedling stand for an early planted crop will help to develop healthy root and canopy development. Cotton planted early in the season will be subjected to low, but variable temperatures and soil moisture conditions. There has been little exploration of temperature effects on the cotton root system architecture. The objective of this study was to study the effects of a wide range of temperatures during seed germination and early seedling growth stages on above- and belowground growth and developmental parameters of four cotton cultivars. 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 planting (DAP). The small differences observed between the obsolete molecular standard, TM-1, and the three modern cultivars in response to temperature indicate that successive breeding efforts did not change the rate or behavior of these traits to temperature. 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 functional relationships between temperature and cotton seed emergence and pre-squaring above- and belowground growth and developmental responses will be useful in assisting management and in improving functionality of many cotton models for on-farm and research and policy decisions.