Effect of Nutrition and Age upon Rate of Development of Terminal Staminate Inflorescences of Xanthium pennsylvanicum

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Abstract
Plants low in P, K, and N were found to have the same critical daylength as plants receiving all these elements. Rate of development of terminal inflorescences of[long dash]N,[long dash]K, and[long dash]P plants was considerably affected at photoperiods near the critical. Lack of P resulted in the slowest development; lack of N resulted in slower development than lack of K. However, with each half-hr. increase in length of the dark period from 81/2 to 101/2 hrs. there was an increasing tendency for the plants low in P, N, or K to develop at the same rate as the plants grown with a non-deficient soln. Apparently the detrimental effect of mineral deficiency on rate of development of floral primordia may be overcome by increasing the length of the dark period. Age of leaf tissue affects the critical day length: the first fully expanded leaf had a critical dark period of 9 hrs.; in the older leaves it was between 101/2 and 15 hrs. Rate of development subsequent to initiation was dependent on the length of the dark period and age of the leaf tissue.