biologia plantarum

Biologia plantarum 59:198-200, 2015 | DOI: 10.1007/s10535-014-0473-y

The photosynthetic parameters of cucumber as affected by irradiances with different red:far-red ratios

T. Shibuya^1,*, R. Endo¹, T. Yuba², Y. Kitaya¹

¹ Graduate School of Life and Environmental Sciences, Osaka Prefecture University, Sakai, Osaka, Japan

² School of Life and Environmental Sciences, Osaka Prefecture University, Sakai, Osaka, Japan

We compared photosynthetic performance between cucumber (Cucumis sativus L.) leaves acclimated to saturating irradiances with high red: far red (R:FR = 10) and normal R:FR (= 1.4) ratios. The net photosynthetic rate (P_N) and stomatal conductance (g_s) of the leaves acclimated to high R:FR were greater than those of the leaves acclimated to normal R:FR; the greater g_s partly explains the greater P_N. The greater g_s of the high-R:FR-leaves probably resulted from a higher stomatal density and/or a greater size. P_N of the high R:FR leaves was still greater than that of the normal R:FR leaves at the same intercellular CO₂ concentration (c_i). This indicates that non-stomatal factors also increased the photosynthetic capacity of the high R:FR leaves. The maximum Rubisco carboxylase activity estimated from a P_N-c_i curve analysis was also greater in the high R:FR leaves, however, the intrinsic water-use efficiency (WUE_i = P_N/g_s) of the high R:FR leaves was lower than that of the normal R:FR leaves.

Keywords: Cucumis sativus; intrinsic water-use efficiency; Rubisco; stomatal conductance; stomatal density

Subjects: red:far red ratio; net photosynthetic rate; stomatal conductance; water use efficiency; carbon dioxide concentration; stomatal density; stomata size; cucumber

Received: February 7, 2014; Revised: August 21, 2014; Accepted: August 27, 2014; Published: January 1, 2015  Show citation