Variations in the Leaf Angles of Different Rice Cultivars in Response to Nutrient Deficiencies

Leaf angle is an important agricultural trait of cereal crops because leaf inclination influences light interception, photosynthetic availability, cultivation density, and grain yield. Leaf angle enlargement in seedlings of a rice cultivar Shiokari is inhibited by increased strigolactone (SL) levels, which are produced by seedlings in response to nitrogen (N), phosphorus (P), and sulfur (S) deficiencies. In this study, we evaluated variations in the leaf angles of 12 rice cultivars in response to N-, P-, and S-limitation and analyzed the effects of SLs on leaf angle. The leaf angles of Shiokari, Koshihikari, and Hitomebore did not increase under N-, P-, and S-limitation when compared with each control. Under P- and S-deficient conditions, the leaf angles of Hinohikari, Kinumusume, Akitakomachi, Taichu 65, Kasalath, and Sasanishiki increased. However, under only N-deficient conditions, the leaves remained erect. The leaf angles of Hinohikari, Kinumusume, Akitakomachi, Taichu 65, Kasalath, and Sasanishiki increased under P- and S-deficient conditions, but the leaves were erect under only N-deficient condition. Expression levels of DWARF27 (D27), D17, and D10 increased and a natural SL 4-deoxyorobanchol was accumulated in Shiokari seedlings grown under N-deficient condition. Here, we showed that the leaf angles of all rice seedlings cannot increase under N-deficient condition and the influence of P- and S-deficiencies on the leaf angle depends on the rice cultivar. Moreover, we found that ammonium, but not nitrate, mainly affects the leaf angle in rice.