Effects of leaf aging and light duration on photosynthetic characteristics in a cucumber canopy

Photosynthetic characteristics, chlorophyll index and leaf area were examined in selected leaves of cucumber (Cucumis sativus L cv. Euphorbia). In the first experiment, plants of cucumber were grown horizontally at a lighting period of 20 h day(-1). Photosynthetic measurements in horizontally growing cucumbers showed that there was no decline in photosynthetic capacity when cucumber leaves are developing under good light conditions. In a second experiment, plants were grown in a traditional highwire cultivation system under 20 h day-1 lighting period until they reached final height and then exposed to different lighting periods (20 and 24 h day(-1)) for 3 weeks. In stands of cucumber plants photosynthetic measurements showed that the lower leaves have a significant reduction in photosynthetic capacity due to reduced light conditions. Three weeks exposure to 24 h day(-1) lighting period reduced leaf area by 20%. Plant grown under continuous light had also lower chlorophyll index compared to plants grown under 20 h day(-1) lighting period. (C) 2010 Elsevier B.V. All rights reserved.