Seminal root number in cultivated barley

In well-matured seeds of cultivated barley the average number of seminal roots of 72 pure-line varieties ranged from 5.4 in the six-rowed Winter Club to 8.9 in the two-rowed varieties Alpha and White Smyrna. Within a variety the number was relatively uniform, seldom varying by more than 2 roots among individual seeds. Because of the low variability within a variety and the high correlation between the same varieties grown under different environments, it appears that seminal root number is a varietal character. Within a species the varieties of H. distichon, with the widest diversity of forms and sources of origin, ranged from 5.6 to 8.9 seminal roots. H. deficiens and H. irregulare both had a varietal range of variation of but 1.5 roots. The species H. intermedium and H. vulgare each had a varietal range of variation of 2.1 roots. A single strain of a six-rowed natural tetraploid had an average of 6.8 roots, a number characteristic of the diploid varieties of the vulgare group. This indicated that doubling of the chromosome number did not affect the formation of seminal roots. No association was apparent between seminal root number and density of spike, color of seeds, adherence of lemma and palet, or character of lemma tip. The area of the absorptive surface of the scutellum of eight widely different varieties was not correlated with a seminal root number. Lack of consistently significant intervarietal correlations would indicate that in mature seed, seminal root number is independent of both the length of developmental period and seed weight. Within a variety the number of seminal roots increases with number of days after pollination. In Manchuria barley the earliest viable immature stage showed 3 roots in sections and produced on germination a maximum of 3 roots. With further growth and development of the seed, the number increased to the maximum for the variety when the seeds were plump and well-matured. In nine field samples of Wisconsin Barbless barley a correlation coefficient of .776 was found between kernel weight, as indicating stage of development at harvest, and number of seminal roots. This value is significant at the P = .02 level. No correlation was found between number of seminal roots and malting quality as measured by diastatic power or by percentage of wort nitrogen produced in 30 samples of malting barley representing 12 varieties grown in 3 years at three different places. A similar lack of correlation was found among nine samples of the Wisconsin Barbless variety.