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Articles by Saida Ammar
Total Records ( 2 ) for Saida Ammar
  Jemaa Essemine , Saida Ammar and Sadok Bouzid
  The aim of the present study was to follow the early growth of wheat seedlings at different temperatures regimes and to assess the threshold of sensitivity of the wheat seedlings to heat constraints during the early stage of development. Obtained results showed that solely temperatures 15° and 25 °C allow early growth of wheat seedlings, while this growth was inhibited at all other temperatures 5°, 35° and 45 °C. The following of the mineral ionic content in K+ and Ca2+ as function of time showed, after 2, 4 and 6 days of germination at 25°C, a decrease in the amount of potassium and calcium in both roots (R) and aerial parts (AP) or shoots of the young wheat seedlings. The drop in the content of Ca2+ is more pronounced, particularly, in the shoots of the seedlings. The temperature 15 °C caused a significant decrease of the ionic contents (K+ and Ca2+) of roots and shoots of seedlings obtained in the 6th day with regard to those obtained in the 4th day of early growth. After 6 days of growth at 25 °C, we obtained content in Ca2+ more important in the roots than that in the shoots, whereas at 15 °C the opposite was observed. The peroxidasic activity in roots and AP (shoots) of wheat seedlings obtained from seeds have germinated either at 15 ° or at 25 °C, decreases as function of time. After 4 days of the early growth at 15 °C, the activity of the total soluble peroxidases of R and AP is higher than that of R and AP of seedlings grown at 25 °C. After 6 days, this enzymatic activity increased solely in the R of seedlings grown at 25 °C if compared to those (R) obtained from seedlings established at 15 °C.
  Jemaa Essemine , Saida Ammar and Sadok Bouzid
  The present study investigated the effect of heat stress on different stages of growth in wheat, such as germination under various temperature regimes and precocious development of wheat seedlings. The behaviors of two wheat cultivars (Triticum durum, cultivar Karim and Triticum aestivum, cultivar Salambô) were studied, particularly at the physiological, biochemical levels. Temperature stress caused a harmful effect to plant metabolism, by disrupting cellular homeostasis. A direct result of stress-induced cellular changes is the enhanced accumulation of toxic compounds in cells that include reactive oxygen species. In our investigation made on two wheat cultivars, we were found a similarity in the response to heat stress either at the germination stage or the early development (coleoptiles and first leaf). According to literatures, our results have shown that 10 or 15°C above the optimum of temperature doesn’t allow the establishment of wheat seedlings. Furthermore, reserve mobilization, seems to be damaged following heat stress by affecting the enzymes implicated in the starch breakdown and abolish giving nutrients to the wheat embryos. This was demonstrated in our work, in which we were shown that both 5 and 45°C affected the reserve mobilization but this effect is less pronounced after heat treatment of 35°C. At the photosynthetic level, heat stress generated ROS, which could damage both PS I and PS II. The detrimental effect of ROS might be alleviated by antioxidant enzymes and the sequestration of other components in plant cells. Furthermore, adaptation to temperatures changes, at the molecular level, was accompanied by the degradation of the normal proteins and the synthesis of Heat Shock Proteins (HSPs) involved in the mechanism of defence in plants.
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