PHOTOSYNTHETICA

Photosynthetica 2020, 58(3):732-739 | DOI: 10.32615/ps.2020.029

Light reacclimatization of lower leaves in C₄ maize canopies grown at two planting densities

T. YABIKU^1,2, S. AKAMATSU³, O. UENO⁵

¹ Graduate School of Bioresources and Bioenvironmental Sciences, Kyushu University, Motooka, Nishi-ku, 819-0395 Fukuoka, Japan

² NARO Tohoku Agricultural Research Center, Akahira 4, Shimokuriyagawa, Morioka, 020-0198 Iwate, Japan

³ School of Agriculture, Kyushu University, Motooka, Nishi-ku, 819-0395 Fukuoka, Japan

⁵ Faculty of Agriculture, Kyushu University, Motooka, Nishi-ku, 819-0395 Fukuoka, Japan

C₄ plants have high photosynthetic capacity but are inefficient under low light. In a canopy, lower leaves developed under high light are progressively shaded. To elucidate how lower leaves in a C₄ canopy reacclimatize to low light, we investigated maize canopies differing in light environment grown at standard and low planting densities (SPD, LPD). Although upper leaves at SPD and both upper and lower leaves at LPD had light-response curves of photosynthesis of sun leaves, lower leaves at SPD had that of shade leaves. All leaves at both densities had anatomical framework of sun leaves, but the chloroplast content in mesophyll and bundle-sheath cells of lower leaves at SPD was greatly reduced to reacclimatize to low light. This study demonstrates that lower leaves at SPD reacclimatize to low light by adjusting their physiological and chloroplast traits while maintaining anatomical framework, whereas those at LPD behave as sun leaves.

Additional key words: chlorophyll content; chlorophyll fluorescence; leaf anatomy; leaf mass per area; leaf nitrogen content.

Received: June 16, 2019; Revised: February 9, 2020; Accepted: March 23, 2020; Prepublished online: April 18, 2020; Published: June 11, 2020  Show citation