RESPONSE OF PHOTOSYNTHETIC PARAMETERS OF SWEET PEPPER LEAVES TO LIGHT QUALITY MANIPULATION BY PHOTOSELECTIVE SHADE NETS

Abstract

Photoselective nets provide a new tool for light-quality manipulation in protected horticulture. We have studied the photosynthetic activity and leaf characteristics of sweet pepper (Capsicum annuum L. 'Tirza') grown under Pearl, Yellow and Red ChromatiNet® of the same shading factor. Their transmitted light is enriched by diffused light of 390, 520 and 590 nm and up, under the Pearl, Yellow and Red net, respectively, compared to an equivalent black shade net. Leaves of the same age and position were found to respond to this light quality manipulation in the following way: The highest net assimilation (Anet) and stomatal conductance (g(sw)) at midday were obtained under the Pearl net, followed by the Red and Yellow nets; the effective quantum yield (ΔF/F'm) was lowest under the Red net; despite of no significant difference in stomatal density, stomatal width was largest under the Pearl net, and smallest under the Yellow; both leaf thickness and palisade/sponge ratio were lowest under the Yellow net; the specific leaf weight (SLW) was largest under the Pearl net; chlorophyll content was lowest, while chlorophyll/carotenoid ratio was highest under the Red net. Therefore, photoselective shading can differentially affect leaf parameters and activities in sweet pepper. From the aspect of photosynthesis, the Pearl net appears to be more suitable for sweet pepper summer production in Israel, or equivalent areas.