学术论文
Abdallah ATIA, Mokded RABHI, Ahmed DEBEZ, Chedly ABDELLY, Houda GOUIA, Chiraz CH
In Tunisian arid regions, plant life forms, ecotypes, physiological types and photosynthetic pathways (C3, C4 or CAM) remain unclear. Understanding the characters of these plant species could be important for land restoration. A literature survey was conducted for 105 species from arid regions of Tunisia. These plant species belong to several eco-types: halophytes, xerophytes, gypsophytes, psamophytes, xero-halophytes, gypso-halophytes, psamo-halophytes, psamo-xerophytes, xero-gypsophytes and hygro-halophytes. The variation of photosynthetic pathway types in the 105 studied species shows that 56.2% are C3, 41.0% are C4, 1.9% are CAM and 1.0% are C3-CAM. The C3 pathway is more abundant in the halophytes, whereas the C4 one is more common in the xerophytes, gypsophytes, gypso-halophytes and psamo-halophytes. The ratio of C3 to C4 species (C3/C4 ratio) is 0.2 in the psamo-halophytes, 0.8 in the gypso-halophytes, 1.1 in the xerophytes, 1.6 in the xero-halophytes, 1.8 in the hygrohalophytes, 2.0 in the psamophytes and 3.8 in the halophytes. The annuals are mainly C3 plants whereas most of perennials are C4 ones. The C3/C4 ratio is 1.3 in succulent species and 1.4 in non-succulent species. Thus, succulence seems not to affect the distribution of C3 and C4 pathways within the studied plants. This investigation shows high percentages of C4 plants in plants of Tunisian arid regions. However, there are significant differences in their abundance among ecotypes. Based on C3/C4 ratio, the abundance of the C4 pathway is in the following order: psamo-halophytes, gypso-halophytes, xerophytes, xero-halophytes, hy-grohalophytes, psamophytes, halophytes. In Tunisian arid regions, C4 species are most abundant in xerophytes and less abundant in halophytes. In the Chenopodiaceae the number of C3 plants is 13 and the number of C4 species is 20 and in the Poaceae the number of C3 was 23 and the number of C4 was 19 species. Thus, the most C4 proportion is in the Chenopodiaceae and Poaceae species. This confirms the fact that the Chenopodiaceae and the Poaceae were the leading families that tolerate salinity and aridity.