Seed dormancy and appropriate germination protocol for Vernonia galamensis (Asteraceae).

Abstract

ernonia galamensis (Cass.) Less., (Asteraceae) is a new potential industrial oil crop that originated in eastern and south-eastern parts of Ethiopia and is endemic primarily to East African countries. On a dry mass basis, Vernonia seed contain 35 to 45% of a triglyceride oil which is rich in vernolic acid, a naturally epoxidized fatty acid, useful in the formulation of oil-based paints to reduce emissions of volatile organic compounds. In addition, the meal left after oil extraction is a valuable source of crude protein, carbohydrate and major minerals (calcium, potassium, magnesium and phosphorus) and therefore has potential for use as animal feed. The seed of this species are however dormant and lack synchrony in germination. Therefore to facilitate further investigation of the suitability of this species as a crop it is necessary to understand the regulation of seed germination. This study tested the hypotheses that V. galamensis seed are dormant and require cold stratification and/or dry-after-ripening for dormancy release as well as responding to light, alternating temperatures and nitrate. We also tested whether secondary dormancy can be induced by incubation in the dark. We tested these hypotheses using seed from two sub species of V. galamensis, V. galamensis subsp. nairobiensis and V. galamensis subsp. afromontana var. gibbosa grown at two distinct locations in Kenya. The studies revealed that seed germination of two sub-species of V. galamensis is affected by temperature during seed development with non-deep physiological dormancy of these light and nitrate sensitive seed being broken by dry-after-ripening and cold stratification.