Generally speaking, cereal crops prefer sunny weather during their floral induction, even though there are three essentials for reproductive growth including obligate vegetative growth, specific photoperiodism, and thermoperiodism i.e. vernalization (Gardener et al., 1985). There is a yield loss if there are not enough sunshine hours during floral induction and initiation. For example, winter wheat lost 37%, 60%, and 99% grain yield for 30%, 60%, and
90% shadow during floral development, respectively (Liu, 2000). Lang (1965) reported that floral induction had as many as eight processes including: 1) the high-intensive-light process, 2)pigment conversion, 3) the time-measuring process, 4) florigen synthesis, 5) florigen stabilization, a post-inductive process preparatory to florigen translocation, 7) florigen translocation and 8) floral differentiation. Fewer sunshine hours result in lower grain yield because four of the eight processes of floral induction require intensive sunshine (Lang, 1965). Actually, the first phase for floral induction can NOT start without intensive sunshine. Phases 5, 7, and 8 also require light for proper grain production. These processes need at least three consecutive sunny days. Otherwise, the plant reverts to the previous physiological status. This reversion if light requirements are not met is one of the main reasons why grain yield of winter wheat is only 1500 kg per hectare in Guizhou, Hunan, and other southern provinces in China. Availability of sunlight hours from October to April in the provinces is inadequate for proper grain production.
Was this article helpful?