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The current study provides a particular characterization of the floristic features, ecological features and economic potentialities of five selected Zygophyllum species namely: Zygophyllum decumbens, Zygophyllum simplex, Zygophyllum coccineum Zygophyllum aegyptium and Zygophyllum album growing naturally in the Deltaic Mediterranean coastal desert of Egypt and in North Galala Desert in the Northern sector of the Eastern Desert of Egypt.
The total number of the listed plant species survyed in the current study was 135 species belonging to 401 genera and related to 14 families, Asteraceae, Poaceae, Chenopdiaceae, Fabaceae. These are the prime four families which represent about 51.11 % of the total registered plant species in the study areas.These registered species include 75 perennial (55.56%) species, 3 biennial species (2.22%) and 57 (42.22%) annual species.
The life-forms of the flora of the registered species were ranked into six types as follows: therophytes, cryptophytes, hemicryptophytes, chamaephytes, nanophanerophytes and parasites. The floristic dissection of the study areas showed that, 65 species (about 48.15% of the total number of species) were Mediterranean taxa. These taxa were either Biregional (29 species = 21.48%), Pluriregional (21 species = 15.56%) or Monoregional (15 species= 11.11%). It has been also found that, 34 species or about 25.19% of the total number of recorded species were Saharo-Sindian taxa.
The Two Way Indicator Species Analysis (TWINSPAN) was the application technique applied here, resulted in the recognition of four vegetation groups, Group A comprises 16 stands codominated by Zygophyllum coccineum and Zilla spinosa. Group B includes 14 stands codominated by Zygophyllum simplex, Zygophyllum coccineum and Haloxylon salicornicum. Group C consists of 23 stands dominated by Zygophyllum aegyptium Group D includes 17 stands dominated by Zygophyllum coccineum.
The economic potentialities of the five Zygophyllum species in family Zygophyllaceae that occurring naturally in the study areas have been estimated. The allelopathic bioassay of Zygophyllum spp was detected by investigating the phytotoxic effects of phenolic extracts on seed germination and seedling development (shoot and root) of two targeted nuisance weeds. In Echinochloa crus-galli, Zygophyllum simplex attained the highest allelopathic potential on seed germination, Zygophyllum album showed the highest allelopathic potential on shoot growth and Zygophyllum aegyptieum gave the highest allelopathic potential on root growth at concentration 40 g/l. On the other hand, in Lactuca sativa; Zygophyllum aegyptium showed the highest allelopathic potential on seed germination, Zygogphyllum coccineum showed the highest allelopathic potential on shoot growth and Zygophyllum simplex gave the highest allelopathic potential on root growth at concentration 40 g/l. The antioxidant activity was estimated by using DPPH free radical scavenging activity for testing the radical scavenging activity of the five methanolic Zygophyllum extracts. It has been founded that the extract of Zygophyllum album showed a moderate antioxidant activity, while other Zygophyllum extracts showed weak scavenging activity.