The effect of moisture content in the substrate on rooting of seedlings in plug trays.

摘要

The effects of moisture level in the plug substrate on the root morphology of 6 species grown in 288-plug trays were studied. Two species per substrate moisture class, i.e. dry (Verbena and Zinnia spp.), medium (Coleus and Petunia spp.) and wet (Begonia and Impatiens spp.), were selected based on the recommended moisture level. After radicle emergence, the moisture content of the substrate was maintained at 3 different moisture levels within each class (experiment 1), or the plug substrate was allowed to dry out until one of the 3 moisture levels was attained before the trays were rewetted to the original moisture level for germination (experiment 2). The number and position of lateral and adventitious roots on the primary root, total root length, and length of the primary root were determined after the first leaf had fully expanded (3 weeks). The number of lateral and adventitious roots, and dry weights of the root and shoot were evaluated after 6 weeks. The number of adventitious roots was reduced in Verbena sp. (dry) and Coleus sp. (medium moisture), total root length was reduced in Coleus sp., and the primary root length was reduced in Impatiens (wet) as moisture stress increased (experiment 1). The total root length decreased for Coleus (medium) and Impatiens (wet) with increased moisture stress (experiment 2). Root dry weight after 6 weeks was not affected by moisture stress in either experiment. The increased moisture deficit had no effect (Zinnia, Petunia and Begonia spp.) or reduced the number and total length of adventitious and lateral roots. The different moisture deficits had no effect on the position of lateral and adventitious roots on the primary root.