SUMMARYChanges in sugar content during water stress and recovery were examined in leaves of two varieties of durum wheat {Triticum durum). The drought-resistant Mohamed Ben Bachir (MBB) from Algeria and the droughtsensitive European variety Capdur differed in the time and type of sugar increase during water stress. Glucose accumulated at a rate closely corresponding with decreasing water potential but more rapidly and to a higher concentration in MBB than in Capdur. Sucrose content correlated less well than that of monosaccharides with changes in water potential. Glucose and, to a lesser extent, fructose appeared to play an important role during water stress and to be more sensitive indicators of the degree of stress and of potential tolerance than proline which increased later and to the same extent in both varieties. After rewatering, the amounts of accumulated solutes in leaves of both types fell quickly to normal, coincident with relatively rapid growth.

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SUMMARYThe effect of water stress on growth of Triticum durum L, was in\estigated in relation to sugar accumulation and water status ot wheat plants before, during and after a ptriud of water stress. The slight decrease in water potential in the first few days after withholding water had no detectable efTect on growth. Inhibition of growth was only apparent when the water content started to decline. Dry weight continued to increase during water stress, even under severe stress (after day 27) which was associated with a sharp rise in sugar content, accounting for 20 "o of the gain in dry matter between days 27 and 31, The increase in leaf length and leaf area of stressed plants following re-watering, from day 31, was owing to the leaves regaining turgidity after wilting. Growth inhibition coincided with a considerable increase in sugar content. The role of growth inhibition and other factors in sugar accumulation under water stress is discussed. Photosynthesis rather than reserve starch might be the major source of sugar accumulated under water stress in durum wheat.Key words: Water stress, sugars, growth, wheat. INTRODliCTIONSoluble sugars have been shown to increase in the leaves of wheat under water stress (Munns & Weir, 1981; Drossopoulos, Karamanos & Niavis, 1987;Kameli & Losel, 1993). They are also considered to play an importatit role in osmotic adjustment which is widely regarded as an adaptive response to water stress conditions (Turner & Jones, 1980; Morgati, 1984;Kameli & Losel. 1993, 1995. Factors which have been suggested to contribute to this increase under water stress include reduced translocation of sugars out of the leaves, slower utilization because of decreased growth and other changes, such as starch hydrolysis. These might contribute individually or together, under different conditions and in different plant species.The extent to which growth inhibition might be responsible for a rise in sugar concentration under water stress was investigated in this study by comparing the timing of the two responses in the same species. Changes in soluble and insoluble carbohydrates were examined, during and after water stress, in relation to growth. * Prtsent address: Depariement de Btologie, Ecoie Normale Superieure, Vieux-Kouba, Algiers, Algeria, t To whom correspondence shotild be addressed. M.^TERIALS AND METHODSSeeds of durum wheat {Triticum durum L.) \ariety MBB from Algeria were soaked for 24 h and gertninated m vermicuhte for 6 d. The seedlings were planted in pots of mixed compost and vermiculite (2:1 y/y), as described previously (Kameli & Losel, 1993). After 17 d of grow^th with normal water supply, stress was applied by withholding water from half of the pots, selected in a randomized manner. Stressed plants were again watered from day 31. Control plants received full water treatment throughout the period of the experiment. The plants were grown under fluorescent tubes (Osram white, 65/80 W) with irradiance 9()-100 //mol m"' s"', day and night temperatures 22 + 2 and 18 + 2 °C respectively, an...

Nitrogen is one of the major growth-limiting nutrients for plants: The main source of nitrogen in most of the higher plants is nitrate taken up through roots. Nitrate can be reduced both in the chloroplasts (photosynthetic tissues) and in proplastes (nonphotosynthetic tissues) such as roots. Ferredoxin-nitrite reductase (NiR) catalyses the reduction of nitrite to ammonium in the second step of the nitrate- assimilation pathway. Homology model of Ferredoxin-nitrite reductase has been constructed using the X-ray structure (PDB code: 2akj) a s a template and MODELLER 9v5 software. The resulting model assessed by PROCHECK, PROSAII and RMSD that showed the final refined model is reliable: has 81% of amino acid sequence identity with template, 0.2Å as RMSD and has (-10.37) as Z-scores, the Ramachandran plot analysis showed that conformations for 99.5 % of amino acid residues are within the most favored regions. The model could prove useful in further functional characterization of this protein.AbbreviationsPDB - Protein Data Bank, NMR - Nuclear Magnetic Resonance, NiR - Nitrite Reductase, RMSD - Root Mean Squared Deviation, Fd - ferredoxin.

Lipase inhibitors have generated a great interest because they could help in the prevention or the therapy of lipase-related diseases. Therefore, the aim of this work was to evaluate the inhibitory effect of secondary metabolites extracts such as phenolic compounds and saponins of three Algerian medicinal plants: Achillea santolina, Inonotus hispidus and Zizyphus lotus, indeed their antiradicalaire activity using DPPH• (1, 1-diphenyl-2-picryl-hydrazyl). The phenolic extracts have shown a strong antiradicalaire activity than the saponin extracts with EC50 values ranged from 6 to 11 µg/ml and from 51 to 82 µg/ml, respectively. The enzymatic inhibition produced by these plant extracts is described here for the first time. The results have shown that the phenolic extracts are more potent than the saponin extracts with Ki values ranged from 0.011 mg/ml to 0.027 mg/ml for phenolic extracts, and ranged from 0.071 mg/ml to 0.69 mg/ml for saponin extracts. The nature, mechanism and possible physiological relevance of lipase inhibition by extract components are discussed.

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