Abstract:

Objective: To explore the mechanism of leaf color variation of six bamboo species, we investigated the relationship among leaf color, chlorophyll and carotenoids, and cell ultrastructure in different color stripe of six colorful bamboo species. Method: We collected leaves from six bamboo species. In this study, 6 colorful bamboo species were targeted, and they are Indosasa hispida 'Rainbow' (IH), Pleioblastus fortunei (PF), Sasaella glabra f. albostriata (SG), S. kogasenis 'Aureostriatus' (SK), Hibanobambusa tranquillans f. shiroshima (HT) and Sinobambusa tootsik var. luteoloalbostriata (ST). The leaves were separated into albino stripe and green stripe regions according to leaf color. The pixel value of leaf color and the contents of chlorophyll a, chlorophyll b and carotenoids in different zones of leaves were tested. Meanwhile, the microstructure of leaves in different development stages and the ultrastructure of different color zones of mature leaves were observed and analyzed. Result: There were significant differences in photosynthetic pigment content, microstructure and ultrastructure among different leaf color zones of six bamboo species. The photosynthetic pigment content in green stripe was significantly higher than that in albino stripe. The content of chlorophyll a was the highest in green stripe, and that of carotenoid was the highest in albino stripe. Microstructure of leaves at different developmental stages showed that albino stripe appeared in mature leaves for SK, while albino stripe appeared in the leaves at middle developmental stage for IH, PF, SG, HT, ST. The albino stripe of mature leaves in IH and SK showed the serious deficiency of cytoplasmic substances, while albino stripe in the other four bamboo species showed partial deficiency. The ultrastructure of the leaves of six bamboo species showed that chloroplast distributed in two types of mesophyll cells which are arm cells and rosette cell cells in green stripe. While there were a few organelles and abnormal chloroplasts in albino stripe. And the plastid morphology of six bamboo species were different. Conclusion: The appearance of white (yellow) stripes in leaves of six colorful bamboo species is not related the arrangement of cells. The appearance of yellow stripes in SK is caused by the degradation of photosynthetic pigment and the destruction of chloroplast structure after leaves matured. While the different leaves color in IH, PF, SG, HT and ST are related to the chloroplast dysplasia and low content of photosynthetic pigment in some cells. The proportion of carotenoids in albino stripe affects the yellow degree of leaves.

Key words: bamboo leaves, leaf color variation, photosynthetic pigment, chloroplast, microstructure, ultrastructure