Submitted to: American Journal of Botany
Publication Type: Abstract Only
Publication Acceptance Date: August 5, 1995
Publication Date: N/A
Technical Abstract: Dormancy in wild Helianthus species insures that achenes do not germinate in temperate climates until conditions are optimal for seedling survival. Wild ancestors of crop species are a valuable genetic resource for the cultivated species, but high achene dormancy may preclude their use. Techniques to overcome this dormancy in two annual sunflower species, H. annuus and H. petiolaris that are of potential value to the cultivated sunflower were investigated using different germination substrates. The influence of achene maturity of germination was also evaluated. Germination of untreated achenes of different ages of H. annuus averaged 32%, while H. petiolaris averaged only 17%. A chemical substrate of 1 mM gibberellic acid (GA3) doubled the germination of different age achenes of H. annuus compared to an untreated control. In the case of H. petiolaris, the GA3 treatment tripled achene germination. The second most effective substrate to enhance germination was a 20 mM solution of KNO3. A 1 mM sodium azide (NaN3) solution was detrimental to all achenes and did not allow any germination in either species. In both species, early maturing achenes (collected 10 days after petal drop) generally had higher germination than late maturing achenes (collected 30 days after petal drop). Achenes of both species of different ages stored at different temperature and time responded similarly to the chemical treatments suggesting that these treatments would be effective over a wide range of achene ages and storage times.