Morphological and physiological differences between dehiscent and indehiscent anthers of Chrysanthemum morifolium.

Spray cut chrysanthemums ornamental value and vase life are rapidly reduced with an increase in the pollen dispersal of the middle tubular bisexual flowers, and excessive pollen grains floating in the air are usually harmful to people. Thus, two cultivars were selected: the dehiscent 'Qx-097' and the indehiscent 'Qx-007', to investigate the morphological, structural and physiological differences in anthers. (1) Prior to the opening of the tubular flower, the anther was completely dehisced, and the pollen grains of 'Qx-097' were then released. 'Qx-007' inflorescences showed no pollen dispersal, and this cultivar was therefore not contaminated by its own pollen grains during flowering. (2) The anther cell structure of 'Qx-007' was abnormal, such that the entire anther wall exhibited hypertrophy due to the non-selective thickening of the endothecium cell size in different areas. Moreover, cracks did not form in the 'Qx-007' anther due to failure of septum degradation and stomium breakage, which resulted in the anther locules being inwardly crushed. Besides, the indehiscent anther accompanies partial pollen abortion due to the impairment of tapetum development, this is not conducive to pollen dispersal. (3) The 'Qx-007' anther contained higher water levels compared with 'Qx-097', and the dehydration of the 'Qx-007' anther was relatively moderate. Furthermore, the 'Qx-007' anther exhibited higher Ca2+ and Mg2+ levels compared with 'Qx-097' during dehiscing periods. (4) The 'Qx-007' anther showed significantly lower jasmonic acid levels and higher indole-3-acetic acid levels compare with the 'Qx-097' anther. These results suggest that the endothecium, septum and stomium constituent of the anther structure exhibit developmental abnormalities, which likely serve as the cellular basis of anther indehiscence. In addition, anther dehydration, the enhancement of anther cell toughness due to a high level of ions, and JA (IAA) dysregulation may be the determining physiological factors of anther indehiscence.