Gibberellic acid induces non-Kranz anatomy with C4-like biochemical traits in the amphibious sedge Eleocharis vivipara

Main conclusion Gibberellic acid induces photosynthetic tissues with non-Kranz anatomy and C 4 -like biochemical traits in terrestrial-form plants of Eleocharis vivipara . This suggests that the structural and biochemical traits are independently regulated. The amphibious leafless sedge, Eleocharis vivipara Link, develops culms (photosynthetic organs) with C 4 -like traits and Kranz anatomy under terrestrial conditions, and C 3 traits and non-Kranz anatomy under submerged conditions. The conversion from C 3 mode to C 4 -like mode in E. vivipara is reportedly mediated by abscisic acid. Here, we investigated the effects of gibberellic acid (GA) on the differentiation of anatomical and photosynthetic traits because GA is involved in heterophylly in aquatic plants. When 100 µM GA was sprayed on terrestrial plants, the newly developed culms had non-Kranz anatomy in the basal part and Kranz-like anatomy in the upper part. In the basal part, the mesophyll cells were well developed, whereas the Kranz (bundle sheath) cells were reduced and contained few chloroplasts and mitochondria. Stomatal frequency was lower in the basal part than in the upper part. Nevertheless, these tissues had abundant accumulation and high activities of C 4 photosynthetic enzymes and had C 4 -like δ 13 C values, as seen in the culms of the terrestrial form. When submerged plants were grown under water containing GA-biosynthesis inhibitors (uniconazole or paclobutrazol), the new culms had Kranz anatomy. The culms developed under paclobutrazol had the C 3 pattern of cellular accumulation of photosynthetic enzymes. These data suggest that GA induces production of photosynthetic tissues with non-Kranz anatomy in terrestrial plants of E. vivipara , without concomitant expression of C 3 biochemical traits. The data also suggest that the differentiation of C 4 structural and biochemical traits is regulated independently.