Hormonal regulation of the growth of leaves and inflorescence stalk in Muscari armeniacum Leichtl.

It is known that chilling of Muscari bulbs is necessary for the growth of the inflorescence stalk and flowering, but not for the growth of leaves. Gibberellic acid (GA) accelerated stem growth and flowering in chilled Muscari bulbs. In the present experiment it was shown that in unchilled derooted Muscari bulbs the growth of leaves, but not the growth of the inflorescence stalk, was observed when bulbs were stored in water, GA at a concentration of 50 and 100 mg/L, benzyladenine (BA) at a concentration of 25 and 50 mg/L, or a mixture of GA+BA (50+25 mg/L), but abscisic acid (ABA) at a concentration of 10 mg/L greatly inhibited the growth of leaves. In chilled derooted Muscari bulbs the growth of leaves and inflorescence stalk was observed when bulbs were stored in water or GA, but BA and GA+BA treatments totally inhibited the growth of the inflorescence stalk without an effect on the growth of leaves. These results clearly showed that the growth of leaves and inflorescence stalk in Muscari bulbs are controlled by plant growth regulators in different ways. ABA totally inhibited the growth of leaves and inflorescence stalk in chilled derooted Muscari bulbs. It was shown that after the excision of the inflorescence bud in cultivated chilled Muscari bulbs, the inflorescence stalk died, but application of indole-3-acetic acid (IAA) 0.5% in the place of the removed inflorescence bud induced the growth of the inflorescence stalk. IAA applied under the inflorescence bud inhibited the development of flowers (flower-bud blasting) and induced the growth of the inflorescence stalk below the treatment site. These results are discussed with reference to hormonal regulation of stem (stalk) growth in tulip, narcissus, hyacinth, and Hippeastrum