Soil Temperature Dependent Growth of Cotton Seedlings Before Emergence

Soil temperature is an important variable governing plant growth and development.Studies were conducted under laboratory conditions to determine the effect of soil temperature on root and shoot growth of cotton during emergence. Cotton seedlings were grown for 192 h at 20,32 and 38℃in soil packed in 300 mm long and 50 mm diameter cylinders. The data indicated that the longest roots (173 mm) as well as shoots (152 mm) were recorded at 32℃followed by 20 (130 mm root and 82 mm shoot) and 38℃(86 mm root and 50 mm shoot).Roots grown at 20 and 38℃were 20% and 50% shorter,respectively,than those grown at 32℃after 192 h.Roots and shoots exhibited the lowest length and dry biomass at 38℃.Shoot lengths grown at 20 (74 mm) and 38℃(51 mm) were 44% and 61% shorter than those grown at 32℃(131 mm) after 180 h growth period,respectively.Growth at all three temperatures followed a similar pattern.Initially there was a linear growth phase followed by the reduction or cessation of growth.Time to cessation of growth varied with temperature and decreased faster at higher temperatures.Sowing of cotton should be accomplished before seedbed reaches a soil temperature (≥38℃) detrimental for emergence.Further,the seedbeds should be capable of providing sufficient moisture and essential nutrients for emerging seedling before its seed reserves are exhausted to enhance seedling establishment in soil.

Soil temperature is an important variable governing plant growth and development. Studies were conducted under laboratory conditions to determine the effect of soil temperature on root and shoot growth of cotton during emergence. Cotton seedlings were grown for 192 h at 20, 32 and 38℃ in soil packed in 300 mm long and 50 mm diameter cylinders. The data indicated that the longest roots （173 ram） as well as shoots （152 mm） were recorded at 32℃ followed by 20 （130 mm root and 82 mm shoot） and 38℃ （86 mm root and 50 mm shoot）. Roots grown at 20 and 38 ℃ were 20% and 50% shorter, respectively, than those grown at 32℃ after 192 h. Roots and shoots exhibited the lowest length and dry biomass at 38 ℃. Shoot lengths grown at 20 （74 mm） and 38℃（51 mm） were 44% and 61% shorter than those grown at 32℃（131 mm） after 180 h growth period, respectively. Growth at all three temperatures followed a similar pattern. Initially there was a linear growth phase followed by the reduction or cessation of growth. Time to cessation of growth varied with temperature and decreased faster at higher temperatures. Sowing of cotton should be accomplished before seedbed reaches a soil temperature （≥ 38 ℃） detrimental for emergence. Further, the seedbeds should be capable of providing sufficient moisture and essential nutrients for emerging seedling before its seed reserves are exhausted to enhance seedling establishment in soil.