The coordination of organ growth in developing citrus flowers: A possibility for sink type regulation

The interrelationships between simultaneously developing organs of citrus flowers were investigated. Examination of flower organ growth kinetics shows that petals grow mainly through enhanced water absorption whereas ovaries accumulate a high percentage of dry matter.Using excised flowers implanted in an agar-sucrose medium and supplied with [¹⁴C]-sucrose, [³H]-acetate, and [¹⁴C]-acetate, a characteristic distribution of label among organs could be established for each isotope.Wounding or application of α-naphthaleneacetic acid (NAA) to a single petal completely changed the normal distribution patterns, shifting the bulk of [¹⁴C]-sucrose towards the treated organs.The findings are interpreted in the light of the 'sink' hypothesis. It is proposed that each flower organ meristem creates a sink of its own which acts in a typical manner according to its specific endogenous hormonal balance. The sink activity of all meristems in concert results in a sensitive regulatory mechanism which is responsible for the coordination observed in flower development.