Abstract:
Individual grain weight of wheat kernels differs with their positions on a spike.
Cultivation practices (such as fertilizer nitrogen and plant growth regulators application)
can be used to improve weight of basal and distal kernels. For this purpose, two
experiments based on randomized complete block design were carried out with three
replications. The aim of this research was to study the mechanisms related to sink
strength as well as the regulatory factors affecting sink activity. One cultivar of a
facultative wheat, cv Yangmai15, was used. Treatments of the experiments included
application of nitrogen (two levels) and plant growth regulators [abscisic acid (ABA) and
Fluridone (inhibitor of ABA synthesis)] in basal and distal kernels, respectively. Results
showed that nitrogen application increased grain yield and its components. Grain filling
in basal kernels started earlier and its rate was higher than that of the distal kernels.
Nitrogen fertilizer increased the individual kernel weight both in basal and distal kernels,
and the rate of increment was higher than the control, even in distal kernels. The
application of ABA resulted in increase in grain weight, whereas a considerable decrease
in grain weight was observed in response to Fluridone compared to the control. Nitrogen
application together with ABA application enhanced the activity of SuSase, AGPase, SSS,
and SBE in basal and distal kernels and the increment in the activity was higher in distal
kernels. It is concluded that simultaneous application of nitrogen and ABA enhanced
grain weight by regulating the activity of key enzymes involved in starch synthesis.
Keywords: Basal and distal kernels, Grain growth, Plant growth regulators, Sink activity,
Wheat (Triticum aestivum L.).
