Abstract:

To elucidate the pollen morphological characteristics of six Aquilegia species and to examine the impact of various sample preparation methods on alterations in pollen morphology, we prepared pollen samples using cryo-scanning electron microscopy, fresh pollen drying, and glutaraldehyde fixation techniques. The results revealed that under the same sample preparation method, different species of Aquilegia pollen exhibited certain commonness and specificity. All six species of Aquilegia pollen grains were characterized by isopolarity and radiate symmetry, with 3 germination furrow, covering layer surface ornamented with spinesis, indicating a high degree of conservatism among different species. Meanwhile, significant differences were observed in terms of polar axis length, equatorial axis length, polar axis/equatorial axis ratio, and other parameters, which could serve as palynological evidence for the classification and identification of Aquilegia species. Regardless of the sample preparation method, the size ranking of pollen grains among the six species of Aquilegia remained basically consistent. A. viridiflora var. Atropurpurear had the largest pollen grains, followed by A. ecalcarata, while the remaining four species showed no significant differences in pollen grain size. Cryo-scanning electron microscopy emerges was the preferred method for studying Aquilegia palynology due to its ability to preserve the ultrastructural characteristics of pollen grains. Compared with cryo-scanning electron microscopy, the data obtained through fresh pollen drying and glutaraldehyde fixation methods revealed varying degrees of reduction in polar axis length, P/E value, and P×E value. This research successfully established a cryo-scanning technique for ultrastructural observation of pollen grains and provided a theoretical foundation for the classification and identification of Aquilegia species in the field of palynology.

Key words: Aquilegia, pollen, morphology, scanning electron microscopy, ultrastructure