The effect of seed scarification and soil-media on germination, growth, storage, and survival of seedlings of five species of Prosopis L. (Mimosaceae)

Prosopis L. (Mimosaceae) species are important Vegetation elements in arid and semi-arid environments where they offer shade, firewood, timber and food for man, wildlife and livestock. Many species, specially South-American ones, have been included in afforestation programmes and agroforestry-silvopastoral systems. Within this scope, there is a need of information on eco-physiological responses related to growth and development. The objective of this study was to assess the influence of seed scarification method and growing media on germination, seedling growth, survival and some physiological variables of three Prosopis species native to South America: P. alba, P. chilensis and P. flexuosa, and two native to North America: P. velutina and P. pubescens. All scarification methods can be used to promote germination in the species evaluated in this study, except for the chemical treatment for P. chilensis and the thermal treatment for the North American species. Nursery soil mix should be preferred to the soil under the canopy of Prosopis trees, since germination, plant size, and plant survival were higher in this growth media. An increase in biomass partition to above ground structures was an important mechanism that allowed for the superior response of plants in nursery mix. The addition of nutrients to Prosopis soil did not improve the rate of leaf appearance or biomass, or changed the shoot:root ratio. Both reserve carbohydrates and C:N ratio were lower in fertilized plants. Prosopis flexuosa showed a significant increase in plant biomass with the addition of nutrients to the growth media. (C) 2001 Academic Press.