The effect of light penetration on the changes of photosynthesis indices in apple tree leaves

Abstract

The impact of light penetration into crown and the effect of seasonality and growth technology on photosynthetic behavior were analyzed. Apple cultivar ‘Rubin’ was grafted onto dwarfing rootstock P60 and different growth regulating methods were used (pruning, trunk incision, plant growth regulator). Nitrogen balance index and photochemical reflectance index were measured in 1.5 m above ground outside the canopy and 0,8 m above the ground deep in the canopy; specific leaf area, fresh and dry weight were evaluated from all canopy. The significantly effect of seasonality on all tested indices was observed. Dry and fresh mass ratio was significantly lower during harvest time compared to results obtained in summer, but specific leaf area was significantly lower in summer time compared to harvest time. Photochemical reflectance index was significantly negatively affected by trunk incision. This index was significantly lower during harvest time compared to summer time, but nitrogen balance index during harvest time was significantly bigger during harvest time. Both indexes, photochemical reflectance and nitrogen balance index, were significantly bigger outside canopy compared to measurements deep in the canopy. Summarizing, it can be stated, that decreasing light penetration into the crown results in the decrease in NBI and PRI. Moreover, seasonality has significant effect on apple tree photosynthetic behaviour.