Shading stress decreases rice seed setting rate by impeding pollination
and fertilisation processes at the heading stage
Abstract
Shading stress has become a worldwide phenomenon and can lead to rice
(Oryza sativa L.) yield loss by decreasing the seed setting rate, which,
in rice, depends primarily on spikelet fertility. However, little is
known about the effect of shading stress on rice pollination and
fertilisation processes. Here, a field experiment, spanning two years,
was conducted using two rice varieties grown under full sunlight and
53% shading stress. Shading stress at the heading stage significantly
decreased the anther dehiscence rate, and a mass of pollen grains
remained in the anthers. Together with a reduction in the in vitro
pollen germination rate and stigma exsertion rate, shading stress
reduced both the number of pollen grains and the number of germinated
pollen grains per stigma by 29.44–71.16% and 9.82–63.16%,
respectively. This ultimately resulted in yield loss due to reduction in
the fertilisation and seed setting rates. We assert that shading stress
decreased the seed setting rate by inhibiting the pollination and
fertilisation processes of rice, particularly anther dehiscence and
pollen grain release. Therefore, future studies should focus on the
mechanisms behind anther dehiscence reduction under shading stress.