LIGHT ENVIRONMENT, GROWTH AND MORPHOGENESIS IN A PEACH-TREE CANOPY

Morphogenic and growth processes were studied in relation to photosynt hetically active radiation (PAR), and red, far red and blue spectral b ands monitored at three different heights of a peach canopy during the vegetative season. The PAR intercepted by the bottom of the tree was significantly lower than that at the top, and blue fluence rate change d with height and season in a manner similar to PAR, Phytochrome photo equilibria indicated spatial and temporal differences in the three lay ers of the canopy: significantly lower values were detected at the bot tom in correspondence with the maximum leaf area index. In this layer, a stimulation of internode elongation and a decrease of newer density were detected. Higher shoot growth rates and about double number of l ateral shoots were found at the top of the canopy, where a greater num ber of sun leaves was present. Possible explanations in terms of diffe rent growth strategies induced by shade, depletion of blue, and low ph ytochrome levels at the bottom of the canopy are given.