A Study on Photoblastism in Seeds of Some Tropical Weeds

Abstract

The influence of light on germination of seeds of a number of tropical weeds was studied. The same types of light sensitivity known from seeds of plants of the temperate zone were found.In addition to the expectation that the behaviour of tropical seeds resembles that of the temperate zone, also was found that seeds of Ruellia tuberosa probably show a very fast "inverse dark reversion" and that gibberellic acid may delay or inhibit the onset of a secundary dormancy.

Germination variability and the effect of various pre-treatment on germination in the perennial spurge Euphorbia nicaeensis All.

“…1000-1600) and a widespread distribution, especially in subtropical and warm areas (Steinmann and Porter, 2002;Webster, 1994). Most studies about germination in Euphorbia have been carried out on annual species (Brenchley and Warington, 1930;Brecke, 1995;Capon and Van der Asdall, 1967;Heit, 1942;Kigel et al, 1992;Kivilaan and Bandurski, 1981;Krueger and Shaner, 1982;Van der Rooden et al, 1970;Sen and Chatterji, 1968;Voigt, 1977;Washitani and Masuda, 1990). However, only a few perennial species have been studied, such as Euphorbia caducifolia, E. characias and E. esula (Best et al, 1980;Go´mez and Espadaler, 1997;Selleck et al, 1962;Sen and Chatterji, 1966).…”

Survival, germinability and fungal colonization of dimorphic achenes of the annual weedGalinsoga parvifloraburied in the soil

“…This pattern would also agree with an HRLR syndrome if the differences in detaching time would result in different dispersal distances between achene types. For both achene types our results suggest that the non-dormant character shown by unburied achenes (Van Rooden et al, 1970;Baskin & Baskin, 1981, 1998 is lost once they are buried. This acquired dormancy lasted for variable periods and once it was broken, it apparently could be induced again.…”

“…For both achene types our results suggest that the non‐dormant character shown by unburied achenes (Van Rooden et al. , 1970; Baskin & Baskin, 1981, 1998) is lost once they are buried.…”

“…Ray achenes are slightly larger than disc achenes (2.0 mm vs. 1.7 mm). Achenes have no dormancy when they are produced in autumn but they require light to germinate (Van Rooden et al, 1970;Baskin & Baskin, 1981, 1998. Achenes germinate well over a range of temperatures 10-35°C (Mes, 1954, cited in Andersen, 1968.…”

The Importance of the Red-Far Red Antagonism in Photoblastic Seeds

“…But a great many non-photoblastic seeds which will eventually germinate for 100%in darkness, can be completely inhibited by far red. Some instances are tomato, cucumber (SPRUIT & MANCINELLI 1969), Calotropis procera, Ruellia tuberosa, Bidens cynapiifolia, Mentzelia aspera, Synedrella nodiflora (VAN ROODEN et al 1970), but there are a great many more.…”