Germination of selected African leafy vegetables in response to different dormancy pre-sowing treatments

When the cultivation of weedy species is being considered, knowledge of seed dormancy is important, because dormancy impedes timing and extent of seed germination. In this study the effect of dormancy on seed germination of eight selected African leafy vegetables was investigated. The objective was to determine whether these vegetables had any form of seed dormancy and if so, whether pre-sowing treatments could break seed dormancy. The different factors associated with seed dormancy that were investigated included:-1) physical barriers, such as hardness of the seed coat; (2) physiological dormancy, such as the effect of temperature (thermodormancy) and light (photodormancy) on embryo differentiation and development; and (3) chemical dormancy, such as the presence of chemical inhibitors in the seed cotyledons. Fresh, mature seeds of Amaranthus cruentus, Brassica rapa subsp. chinensis, Citrulus lanatus, Cleome gynandra, Corchorus olitorius, Cucurbita maxima, Solanum retroflexum and Vigna unguiculata were studied, whilst Beta vulgaris var. cicla served as the reference crop. The findings showed that A. cruentus, B. rapa subsp. chinensis, C. gynandra and S. retroflexum exhibited some form of physical, embryo or physiological dormancy within their seed. Scarification improved onset and final germination of A. cruentus and B. rapa subsp. chinensis seed, whilst pre-chilling improved the germination of A. cruentus. Soaking seed in KNO3 improved both onset and final germination of B. rapa subsp. chinensis and S. retroflexum.