The response of rbcL, rbcS and rca genes in cucumber (Cucumis sativus L.) to growth and induction light intensity

Abstract

Low light is one of the most important factors affecting cucumber growth in winter solar greenhouses in northern China. Whether induction light intensity has an effect on expressions of rbcL, rbcS and rca genes in cucumber leaves grown under low light for long periods of time remains unclear. Here, two genotypes of cucumber were used to determine the effects of growth and induction light levels on photosynthetic induction. It was found that regardless of growth and induction light intensity, the transcript levels of rbcL, rbcS and rca increased quickly once the plant was exposed to light. The variations of the photosynthesis (P N), stomatal conductance (g s), actual photosystem II efficiency (ΦPS II) and Rubisco activity were similar to transcript levels. Plants grown at a photon flux density (PFD) of 100 μmol m−2 s−1 had lower P N, and initial and total Rubisco activity than those grown at 600 μmol m−2 s−1, regardless of induction PFD; for plants grown at the same PFD, P N, g s and Rubisco activation rate induced under PFD of 100 μmol m−2 s−1 were lower than those under 600 μmol m−2 s−1. Rubisco, especially RCA, played a great role on photosynthesis during photosynthetic induction. Compared with Jinyan No. 2, Deltastar may possess potential low-light tolerance with a lower decrease of P N, and initial and total Rubisco activities when grown and induced at 100 μmol m−2 s−1 than 600 μmol m−2 s−1. Moreover, the mechanism of Rubisco activase in regulating Rubisco during photosynthetic induction is also discussed.