Physiological Responses of Young Plants of Carpobrotus edulis (L.) N.E. Br (Aizoaceae) to Salt and Water Stress

Abstract

Coastal sand-dune ecosystems have a high conservational value worldwide, but are frequently subjected to the introduction of exotic floral species by man. One of these species, cohabiting successfully with the native flora of Mediterranean-type coastal habitats, is the succulent Carpobrotus edulis. This species is native to South Africa and is considered an invasive species due to its capability to compete with the local flora, invading and quickly establishing itself in cleared areas. Studies at the ecological level, on the impact of this species and its hybrids on native flora of different countries, are available in the literature. However C. edulis seemingly competitive advantages remain poorly characterized at the physiological level. To investigate the responses of this species to the main stresses present in sand-dune habitats, C. edulis plants, grown from seed under controlled conditions, were subjected to water stress and salt stress. Rapid light response curves, shoot growth and concentration of photosynthetic pigments and soluble protein were determined, and the detection of differentially expressed genes was initiated. It was found that both types of stress did not negatively affect photosynthetic electron transport rate and shoot concentration of photosynthetic pigments in this species. However, shoot soluble protein concentration was significantly decreased by salt and water stress, in relation to control levels. Both types of stress induced differential gene expression. Although work is still under way, the set of genes affected by water stress appears to be different from the set of genes affected by salt stress.