Lower photosynthetic capacity under higher spectral reflectance? The case of Actinidia polygama

Abstract

The variegated leaves of Actinidia polygama exhibit a striking colour change during development. However, little is known whether the photosynthetic capacity of white leaves can be maintained. Therefore, spectrum properties, leaf structure, net photosynthetic rate (PN), and chlorophyll fluorescence in the green and white leaves were investigated. Although reflectance at 400 - 700 nm in white leaves was higher than that in green leaves, total chlorophyll content of white leaves was similar to that in green leaves. Palisade tissue cells of white leaves contained functional chloroplasts. Large intercellular spaces were observed between the epidermal and mesophyll cells and within the palisade tissue cell layer in white leaves. Both PN and the actual quantum yield of photosystem II in white leaves were similar to green leaves. At different leaf growth stages, PN of white leaves was about 88 - 100 % of the PN of green leaves. The efficiency of electron move beyond QA- (ET/TR) and the quantum yield of electron transport (ET/ABS) in white leaves was higher than in green leaves. In conclusion, photosynthetic capacity in white leaves of A. polygama showed two favorable characteristics during the whole sampling period: 1) despite a higher spectral reflectance in white leaves, PN of white leaves remained relatively high compared with green leaves; 2) the higher activity of photosystem II of white leaves enabled photosynthetic capacity maintenance.