Pre-germination effects on mechanically impeded root growth of barley (Hordeum vulgare L)

Abstract

The effects of conditions pre-dating germination on growth rate of impeded barley cv. Harrington roots were measured using an agar-capillary tube technique. Seedling root tips were directed into glass capillary tubes twothirds filled with agar at eight concentrations ranging from 1.6 to 9.6%, equivalent to penetrometer resistances of 25 to 1240 kPa. The rate of unrestricted root elongation (growth in air) of seed stored for 13 months (old seed), and of seed grown for a second generation without subsequent storage (new seed) was compared with growth in agar over a 24-hour interval. Root elongation rate of old and new seed was identical in the absence of resistance. At low to intermediate agar concentrations, elongation was significantly slower in roots from old, compared with new seed. At high agar concentrations root growth of old and new seed was the same. In both old and new seed, root growth through agar was greater in seed that germinated after 24, compared with 48 h. Differences in impeded root growth between old and new seed were lost in progeny of the test seed. Environmental factors that pre-date germination are an important influence on the ability of seedling roots to elongate through soil.