Allelopathic effects of the water extract of the perennial herb Achillia santolina on growth and distribution in its rooting area of two selected soil algae namely Chlorella vulgaris (Chlorophyta) and Lyngbya contorta (Cyanophyta) were investigated under controlled laboratory conditions. The algal flora inhabiting the soil under and away of Achellia santolina rooting zone were also identified. Chlorophyta species were dominated only in soils far away of A. santolina, while Cyanophyta and Diatoms species were identified in both types of soil. Chlorella vulgaris and Lyngbya contorta; were chosen because both organisms flourish all the year in their sites. The results cleared remarkable negative allelopathic effect of the water extract of A. santolina shoot on growth of the blue green alga L. contorta, and a detrimental positive effect of it on growth of C. vulgaris. Also, growth of the green alga C. vulgaris was significantly (P ≤ 0.01) inhibited specially at the higher extract concentration. Growth promotion (p ≤ 0.05) of the blue green alga L. contorta was extract dependant. The phytochemical screening of A. santolina plant showed that it contains essential oils, flavonoids, glocosides, phenolic compounds, sterols, triterpenese and tannins. The allelopathic effect, specially inhibitory one of A. santolina may be due to the high concentrations of the flavonoids and total phenolics attained in values of about 7.985 and 29.725 mg/g dm, respectively in the plant extract.
Key words: Allelopathy, Growth, Phytochemical screening, Soil algae,
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