Interactions of auxin and cytokinins in regulating axillary bud formation in sunflower (Helianthus annuus L.)

Abstract

Sunflower is an important oilseed crop, known to grow a strong dominating single flower head. In recent times, axillary buds initiation and formation of multi flower heads is a common feature in many sunflower hybrids. To find out the reason for multi headedness an experiment was carried out in the hybrid KBSH-41. It was found that this trait is regulated by the interaction of environmental signals and plant growth regulators such as auxin and cytokinin. Any kind of stress induces the bud growth which affects the translocation of hormones in the transpiration system, especially auxin. When the translocation of basipetally moving auxin reduces, concentration of acropetally moving cytokinin increases leading to the development of axillary buds. When, under normal conditions,auxin to cytokinin ratio is not altered the plants develop single flower heads. The results of this study suggest that auxin has an inhibitory effect on the growth of axillary buds, while cytokinin promotes their growth. The mechanism of axillary bud growth depends on the ratio of these two hormones.