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

Abstract

1. Xanthium pennsylvanicum plants low in phosphorus, potassium, and nitrogen had the same critical day length as plants supplied with a nutrient solution containing all these elements. 2. Rate of development of terminal inflorescences of -N, -K, and -P plants was considerably affected at photoperiods near the critical. Lack of phosphorus decreased the rate of development more than lack of either nitrogen or potassium; and lack of nitrogen resulted in slower development than lack of potassium. 3. With each half-hour increase in length of the dark period from 81/2 to 101/2 hours there was an increasing tendency for the plants low in phosphorus, nitrogen, or potassium to develop at the same rate as the plants grown with a non-deficient solution. Thus it appears that by increasing the length of the dark period the detrimental effect of mineral deficiency on rate of development of floral primordia may be overcome. 4. Age of leaf tissue definitely affects the critical day length. The first fully expanded leaf h...