Light transmission into apple fruit and leaves

Abstract

Light transmission into tissue of fruit or leaves of apple ( Malus pumila Mill.) cultivars ‘Golden Delicious’, ‘Gloster’ and ‘Cox's Orange Pippin’ was studied both quantitatively and qualitatively. For comparative purposes, fruit or leaf was exposed to a constant photosynthetically active radiation (PAR) of 1750 μmol m −2 s −1. Under these conditions, transmission of PAR into the inner tissues of apple fruit ranged between 0.04 and 8.4 μmol m −2 s −1, dependent on development stage, cultivar and position of the apple tissue relative to the light source. Parenchyma of apple fruit transmitted 1.5–2% of the incident PAR 1.5 mm −1 fruit tissue. Peel of apple fruit transmitted 1–3% of incident PAR at 400 nm, increasing to 10–12% at 850 nm. Whole apple leaves transmitted up to 2%, whereas an upper epidermis and mesophyll layer transmitted up to 7% of incident PAR. With green fruit, transmission and action spectra were dominated by chlorophyll absorption at 678 nm, whereas apple fruit with red or yellow peel additionally absorbed at 480 nm.