Studies on the Cultivation of Upland Cotton, Especially in Regard to Its Blooming and Ripening : 4. Effects of different sowing times on wall thickening and tensile strength of cotton fibre.

Abstract

The results of the experiment with upland cotton plant (variety Kanno 1) were as follows; 1) The wall thickness and tensile strength of fibre both tend to decrease as the sowing time becornes later, fruiting positions are higher (Fig. 1, 3), and the period from blooming to ripening becomes longer respectively (Fig. 2, 4). 2) The tensile strength (Fig. 5), average lint weight, and number of convolutions tend to increase as the wall thickens. 3) If we assume that the wall thickening occuring after fibre elongation has been completed is responsible to the changes of average temperature in field condition (X) (Tab. 1, 2), the amount of wall thickening of cotton fibre (Y) can be estimated by the following equation: Y^^^= -0.00805X₁+0.04080X₂-0.05251X₃-0.00651X₄+3.61242 It may be supposed that the rate of wall thickening obtain for the average temperature interval of 20 to 25°C is more larger than that of above 25°C, while it considerably decrease under 15 to 20°C and cease under below 15°C. 4) If we assume that the critical temperature for elongation and wall thickening of fibre is 15°C, the effective longest period from, blooming to ripening could be estimated at about 93 days (Tab. 5), the result being coincident with that already known for the effective ripening period. 5) The relative decrease in wall thickening with the increase of days from blooming to ripening under natural condition suggests that the limitation of physiological processes as photosynthesis rather than translcotion by low temperature, acts to retard the wall thickening by limiting the supply of raw materials into the cotton fibre.