Abstract
It is fundamental for gene transformation and ecosystem hazard evaluation to study the pollen characteristics of
transgenic plants. In this research, the characteristics of pollen from 7- or 8-year-old transgenic apple plants carrying an
exogenous CpTI gene were analyzed. The results showed that there was no significant difference in terms of size,
morphology, or exine ornamentation between the pollen of the transgenic plants and the non-transgenic control. However,
the transgenic plants had more abnormal pollen grains. Of the 13 transgenic lines tested, 12 had a significantly lower
amount of pollen and six exhibited a significantly lower germination rate when cultured in vitro. The pollen viability of
three transgenic lines was determined, with two showing significantly lower viability than the control. The transgenic
Gala apple pollen grains germinated normally via controlled pollination on Fuji apple stigmas. However, the pollen tubes
extended relatively slowly during the middle and late development stages, and another 8 h were needed to reach the
ovules compared with the control. The gibberellic acid concentration in transgenic Gala apple flowers was lower than in
the non-transgenic control during all development stages tested. The abscisic acid concentration in the transgenic flowers
was lower during the pink stage, and higher during the ball and fully open stages. Microscopic observation of the anther
structure showed no difference. The tapetum of the pollen sac wall in transgenic plants decomposed late and affected
pollen grain development, which could be one of the reasons for the lower number of pollen grains and poor viability in
the transgenic plants.