Effects of irradiance and water supply on grain development in wheat

Abstract

SUMMARYThe effects of two levels of irradiance and of water supply on grain development in two cultivars of winter wheat were studied by imposing treatments during the phases of cell production and cell expansion in the endosperm. The storage capacity of the grain was determined by cell number in the endosperm, which was reduced by both treatments during the cell production phase. Changes in cell number caused by the treatments were due to changes in the rate of production of cells; the duration of the cell production phase was constant. Weight per grain at maturity was proportional, both within and between cultivars, to the number of endosperm cells, except when treatments altered the supply of assimilate to the grain during the cell expansion phase.Reducing irradiance and water during the cell expansion phase decreased the rate of accumulation of dry matter in the grain and reduced weight per grain at maturity, with no effect on the duration of grain filling. Shrivelled grain resulted from a failure of the endosperm cells to fill completely, and was characterised by a reduction in the number of ‘B’‐type starch granules.

Abscisic Acid Inhibition of Endosperm Cell Division in Cultured Maize Kernels

“…Starch granule number, an indirect measure of the number of amyloplasts in the endosperm, has correlated with final kernel mass in several cereal grain species, including maize (14), wheat (18,19), and barley (5). In the present studies, culturing kernels on medium containing ABA had no apparent effect on the number of starch granules per endosperm during the period of most rapid starch granule initiation (ABA treatment from 11 DAP, Fig.…”

“…Decreases in final kernel mass in response to environmental stresses have correlated well with decreases in endosperm cell number in maize (14), as well as in other cereal grain species (5,18,19). Perhaps in the present case also, the ABA-induced decrease in endosperm cell number limited the maximal storage capacity of the kernel, and in tum, decreased the mature dry mass (Table II), even though fresh weight growth and starch granule initiation were relatively unaffected.…”

“…3A). At 14 DAP, kernels in both treatments (ABA from 5 or from 8 DAP) had about 30% fewer endosperm cells than controls. Transferring the kernels to ABA-containing medium at 11 DAP had no effect on the number of endosperm cells observed at 14 DAP, probably due to the near completion of endosperm cell division at the time of transfer.…”

“…Both cell division and cell expansion may be important in determining the storage capacity of the kernel. Water or I temperature stress during early kernel development decreases the number of endosperm cells and starch granules (5,14,18,19) and also decreases dry matter accumulation (18,28). Since ABA accumulates in plant tissues subjected to water deficit and other types of stress, it is plausible that the effects of water deficit on kernel development may be due, in part, to elevated levels of ABA in the kernel.…”

Influence of shading during different periods upon ear development, grain yield and its components in two wheat cultivars

“…FRIEND (1965) (1970). BROCKLEHURST et al (1978) found that reduced irradiance during the cell production phase decreased grain weight by 13 07o when sampled 14 days after anthesis, while in our results grain weight was only reduced 5.3 %, a non-significant change (table 4) …”