Fecundity and factors regulating germination of Vernonia cinerascens and V. cinerea
2004
Shaukat, S.S. (Karachi Univ. (Pakistan). Dept. of Botany) | Siddiqui, I.A. | Ali, Z. | Sikander, S.
Fecundity of Vernonia cinerascens and V. cinerea was dependent upon a number of reproductive characteristics and was, in general, greater in V. cinerascens compared to V. cinerea. The influence of various factors, including intrinsic factors and extrinsic factors, on germination of the two Vernonia spp. was investigated. The rate and final germination percentage of both the species was greater in light compared to dark. Greater stimulatory effect of light was observed for V. cinerea. The most suitable constant temperature for both the species was 30 degree C while among the alternating temperature regimes tested highest germination percentage was recorded at 30/25 degree C day (14h)/night. Increasing moisture stress and salinity provided unsuitable conditions for germination of Vernonia species. Redrying moistened achenes delayed germination but the final germination percentage remained unaffected. Germination as well as hydration of achenes of both the Vernonia species were higher when the dispersal unit was placed with achene-proper touching the water supplying substrate than when it was placed vertically with pappus facing downwards thereby lifting the achene- proper away from the substrate. Removal of pappus resulted in marked decrease in the rate as well as the final germination percentage. The rate of hydration of achenes was remarkably higher in seeds with pappus than those where pappus was detached suggesting that pappus plays a significant role in water absorption in addition to its role in the protection of ovary and seed dispersal.
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