Studies on the growth and development of Agropyron repens: interacting effects of humidity, calcium, and nitrogen on growth of the rhizome apex and lateral buds
A previous investigation of apical dominance in the rhizome of Agropyron repens showed that keeping the rhizome in a high humidity promoted the outgrowth of the lateral buds but strongly inhibited the growth of the rhizome apex. A study of these related responses demonstrated that the inhibition of apical growth was not prevented by excision of the lateral buds and was also induced when only the apex of the rhizome received the high humidity treatment. The necrotic lesions that developed in the arrested apices and the reduction of apical inhibition produced by various Ca treatments indicated that the inhibition of apical growth was caused by Ca deficiency. When the rhizome apex was exposed to low humidity, a localized high-humidity treatment of the lateral buds did not release the buds from apical dominance in low-N rhizomes but strongly promoted bud growth at a higher N level. When growth of the buds was induced at low humidity by increasing the N supply, the increase in bud weight was preceded by an increase in the water content of the bud when expressed on a dry weight basis. These results agree with those of previous investigations and suggest that the interacting effects of N and humidity on the water status of the buds may play a significant role in the mechanism of apical dominance.