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Effects of reduced plant height on breeding requirements and ...

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the effect <str<strong>on</strong>g>of</str<strong>on</strong>g> seeding rate <strong>on</strong> yield is affected by the<br />

envir<strong>on</strong>ment, in particular, the amount <str<strong>on</strong>g>of</str<strong>on</strong>g> water avail-able.<br />

Pelt<strong>on</strong>'s (t969) results with lower seed.ing rates gíving<br />

better yields when under moisture stress are evidence <str<strong>on</strong>g>of</str<strong>on</strong>g><br />

this. Kirby (19?O) reported no difference in total water<br />

use for the growing seas<strong>on</strong> with barley seeded at various<br />

rates i however, he did report that differences existed in<br />

water use at different times <str<strong>on</strong>g>of</str<strong>on</strong>g> the seas<strong>on</strong> for the different<br />

densities. He suggested that the higher density <str<strong>on</strong>g>plant</str<strong>on</strong>g>ings<br />

used more v;ater earl-y in the growing period, <strong>and</strong> may then<br />

suffer moisture stress during the grain filling stage. This<br />

could present a problem in dry years or dry areas.<br />

Ðay <strong>and</strong> Thomps<strong>on</strong> (19?0), from work with winter barley,<br />

reported that seeding date also had an effect <strong>on</strong> the optimum<br />

seeding rate. They indicated that as the seeding date was<br />

delayed the seeding rate should be increased.<br />

Briggle <strong>and</strong> Vogel (1968) indicated that <strong>on</strong>e <str<strong>on</strong>g>of</str<strong>on</strong>g> the<br />

problems with the semi-dwarf wheats in the Pacific Northwest<br />

was that they did not emerge well from deep <str<strong>on</strong>g>plant</str<strong>on</strong>g>ing,<br />

apparently due to shorter coleoptile length.<br />

A close positive correlati<strong>on</strong> between culm length <strong>and</strong><br />

coleoptile length was reported by Allan et al. (1962),<br />

sunderman (1964), Burleigh et al. (L964), <strong>and</strong> $than (L9?6).<br />

in wheat studies, <strong>and</strong> by Takahashi (L946) in bartey experi-<br />

ments .<br />

JI

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