Endosperm cell number in barley
Grain weight is one of the major components of grain yield and it has been suggested that in wheat, final grain weight may be a function of endosperm cell number1. If grain weight is to be increased by increasing the rate and/or duration of endosperm cell division, it is important to establish the stage of development at which maximum endosperm cell number is attained. Evers2 reported that no cell division occurred in the endosperm of wheat later than 16 days after anthesis and other workers3,4 have come to a similar conclusion using cell counts. However, biochemical analyses5 have shown that the maximum DNA content of wheat endosperm is not reached until 25 days after anthesis and both Donovan6 and Radley7 have suggested that endosperm cell division may continue until about 30 days after anthesis. We have estimated the number of endosperm nuclei in developing caryopses of barley and have examined transverse sections of endosperms of different ages. We report here that cell division in barley endosperm continues until 28–30 days after anthesis.
Relationship Between Grain Nitrogen, Non-Protein Nitrogen and Nucleic Acids During Wheat Grain Development
Eight wheat varieties which normally produce grain of different final percentage nitrogen content were grown under field and glasshouse conditions. The final percentage grain nitrogen of the field grown varieties ranked in the expected order; however, total nitrogen/grain, DNAIgrain, RNA/grain and non-protein nitrogen/grain during grain development differed between varieties. DNA/grain reached a maximum value in all varieties between 21 and 28 days post- anthesis, suggesting a longer period of cell division than previously reported. There was no apparent relationship between final percentage grain nitrogen and either DNA, total grain RNA or the concentration of grain amino acids during development. Heads from glasshouse grown wheat were detached at 8 days postanthesis and grown in liquid culture under conditions where the nitrogen concentration of the culture medium was varied. Fresh weight/grain, DNA/grain, RNA/grain and total grain nitrogen all increased with increasing nitrogen concentration in the culture medium, but grain dry weight remained constant at the different nitrogen concentrations. The changes in fresh weight/grain, DNA/grain and RNA/grain were not the same for all varieties. A possible relationship between total grain nitrogen and DNA/grain and RNA/grain during seed development exists for heads grown in culture for individual varieties. This apparent relationship for individual varieties cannot be used to explain intervarietal differences in total grain nitrogen because in some cases different varieties grown under identical culture conditions, although producing grain of equivalent total nitrogen, had widely differing levels of both DNA and RNA per grain.
The Physiology of Growth in the Wheat Plant I. Seedling Growth and the Pattern of Growth at the Shoot Apex
Seedling growth of wheat in a constant environment is studied over a period of 21 days. Dry weights of leaves, leaf sheaths, stem, and roots are given for 11 occasions. The pattern of dry weight change is also presented in terms of the changing ratios of plant parts.