THE IMPACT OF LIGHT PENETRATION INTO CANOPY AND SEASONALITY ON PHOTOSYNTHETIC INDICES IN APPLE TREE LEAVES
The aim of this study was to analyse the impact of light penetration into canopy and the effect of distances between technological tools and seasonality on photosynthetic behaviour. Apple tree cultivar ‘Auksis’ was grafted onto superdwarfing rootstock P22 and planted at different distances (from 0,25 m to 1 m in rows, while space between rows was 3 m). Photochemical reflectance and plant senescence reflectance indices were measured at two heights: 1.0 – 1.2 m above ground and 1.8 – 2.0 m above ground; specific leaf area, fresh and dry weight were evaluated from all the canopy. Strong positive correlations were determined between photochemical reflectance index and plant senescence reflectance index in higher and lower levels of the canopy. Strong negative correlations were determined between photochemical reflectance index and plant senescence reflectance index and between specific leaf area and dry and fresh mass ratio. Increasing density between apple trees from 1 m to 0.5 m led to increase in photochemical reflectance index and specific leaf area, but plant senescence reflectance index decreased. Meanwhile, seasonality had significant impact on specific leaf area formation and dry to fresh weight ratio. Dry and fresh weight ratio increased by 5% in autumn compared to summer. Our results indicated that with decreased light penetration into canopy photochemical reflectance index decreased, but plant senescence reflectance index increased. Moreover, in autumn, trees prepare for winter by storing more nutrients and leaves accumulate more dry mass.