Effect of reduced oxygen concentration on the germination behavior of vegetable seeds

Abstract

Oxygen (O2) in the soil is necessary for the germination of seeds, but it can be reduced by excessive water contents, compaction, compression, and hard surfaces. Reduced O2 concentrations may change the germination success (proportion of seeds germinated; d) and speed (time to reach 50% germination; t 50) of seeds. Independent laboratory experiments tested the germination of nine economically valuable vegetable species at five O2 concentrations (20.9, 15, 10, 5, and 2.5%). Members of the Asteraceae (butterhead lettuce and iceberg lettuce) and Brassicaceae (broccoli and white cabbage) families germinated best at 20.9% O2 and 15% O2, but were also able to germinate at 5-2.5% O2. Members of the Apiaceae (carrot, celeriac, and parsley) were sensitive to 5-2.5% O2 concentrations, which reduced their d and increased their t50. The germination rate of Swiss chard (Amaranthaceae) consistently declined as O2 concentrations reduced from 20.9% O2 to 2.5% O2. There was a slight variation in the germination response to O2 concentration between the morphotypes of Brassica oleracea, (white cabbage, broccoli and cauliflower), although it was unclear whether this was related to seed age, genetic variation, or the conditions experienced during seed production or storage. The seeds of the Brassicaceae (broccoli and white cabbage) and Asteraceae (butterhead lettuce and iceberg lettuce) were less sensitive to reduced O2 concentrations and therefore may be more suitable for soils suffering from low O2 concentrations, such as compacted soils with hard surfaces or waterlogged soils.