Seed germination and seedling emergence of giant sensitiveplant (Mimosa invisa).
Giant sensitiveplant is a dominant weed in many tropical and subtropical countries because it is highly competitive and is difficult to clear by hand. Experiments were conducted to determine the effect of various environmental factors on giant sensitiveplant seed germination and seedling emergence. Light was not required for germination, though germination was stimulated by seed scarification, suggesting that inhibition of germination is mainly due to the seed coat. Germination of scarified seed was not influenced by a range of alternating temperatures. Germination increased by exposure to higher temperatures, such as might occur when vegetation is burnt, as simulated by placing nonscarified seed in an oven for 5 minutes. Germination increased as exposure temperature increased from 25 to 120°C but declined progressively with further increases and there was no germination after exposure to 200°C. Moderate salinity and osmotic stress did not inhibit germination and some seeds germinated at 250 mM sodium chloride (55%) and osmotic potential of -1.0 MPa (13%). Germination was greater than 79% over a pH range of 4 to 10. Seedling emergence was 80 to 94% at depths of 0 to 2 cm but decreased progressively at deeper depths, and no seedlings emerged from seeds buried at 10 cm. The results of this study identify some of the factors enabling giant sensitiveplant to be a widespread and problematic weed in the humid tropics and provide information that could contribute to its control.