An experiment of sink-source modifications was performed in field-grown wheat at flowering on five varieties (four Triticum aestivum and one T. durum); among these, two varieties were non-awned. The sink-source modifications were blade removal (treatment B) and blade deletion and stalk and sheaths darkening (treatment C). Intact plants (treatment A) acted as a control. In the three awned varieties, the effect of awn removal was also analysed. Two lots of tests were initiaUy performed, with awns (treatments A+, B,, C,) or with awns removed (treatments A _ , B-, C-). Yields and carbon and nitrogen isotope compositions were then determined on seeds harvested at maturity. Blade deletion reduced the yield by one third whereas additional staIk and sheaths darkening led to a two thirds decrease. Nitrogen yield was similarly af€ected but the deprivation due to treatment C was less marked for nitrogen than for carbon. Thus, treatment C produced grains which were notably richer in nitrogen than plants which had received treatment A and B. For each of the five varieties, the decrease in yield was highly correlated with a I3C enrichment of grains (roughly from -28 to -25%). In contrast with the 13C variations, there was no general trend for ISN evolution among treated plants. The final yieId for treated T. durum plants was strongly modified when the awns were removed at flowering whereas no &@cant variations were noted in the other T aestivum awned varieties. Z durum seeds obtained from plants deprived of awns were notably depleted in ' C and in I5N compared to control plants. Isotope compositions of C and N of the Merent pools supplying the grain Wing were estimated and discussed in the context of the physiology of the mother plants between flowering and maturity.

Effects of salt and water stress on seed germination of Hedysarum flexuosum (Fabaceae ).— Hedysarum flexuosum L ., commonly called Sulla has been the subject of numerous studies which have demonstrated its forage and pastoral potential . Previous researches on the biochemical composition of this species have revealed a high nutritional value and positioned it as an alternative to the imported food for goat and sheep raising . The authors mention the richness of Sulla in proteins (22.5 % g / Kg of dry matter ), lipids and minerals . They also note a digestibility rate very similar to those of other forage legumes grown such as alfalfa . The species H . flexuosum or Sulla is reported in Algeria and Morocco on marl and marl-limestone substrates in regions with average rainfall greater than 550 mm . This study consists of an ecophysiological evaluation of the seed germination phase of H . flexuosum through the effects of salt and water stress on the germination rate (GT ) of this species . H . flexuosum pods were collected at maturity at a station in Ouadhia commune in northern Algeria . The seeds extracted from the pods were treated with 5 % sodium hypochlorite for 5 minutes and then rinsed three times with distilled water . In order to avoid any integumentary dormancy , a slight scarification of the seed surfaces was carried out . They were then watered with increasing concentration NaCl solutions (2 , 4 , 6 , 8 , and 10 g / l ), for the salinity test and by solutions of polyethylene glycol 6000 (PEG -6000 ) corresponding to pressures of : -1 bar, -3 bars, -7 bars , -9.25 bars respectively for the water stress . A batch of control seeds was watered with distilled water . The results of the germination rate (GT ) and mean germination time (MGT ) were analysed by an ANOVA using the stat box software (one parameter analysis : NaCl concentration for salt stress and PEG concentration for water stress ). The ANOVA analysis was completed by the Newman and Keuls test when it reveals a significant variation . Results show that GT variation as a function of NaCl concentrations is highly significant (P < 0.001 ). Seed GT decreases in response to increased NaCl concentration in the imbibitions substrate . The higher osmotic pressure is , the greater the rate of reduction of the germinative capacity increases . The influence of salinity is in fact significantly perceptible from 2 g / l with a GT of 74 % corresponding to a reduction rate of 18.7 %. The concentration inducing the reduction of the germination of 50 % (LD 50 ) is between 4 and 6 g / l of NaCl . The germination is practically inhibited at the highest concentration tested (10 g / l ). Analysis of the variance of the MGT factor of H . flexuosum shows that it increases significantly with elevated environmental salinity . In the controls , MGT is 2.37 days but extends to 8 days at the dose of 10 g / l of NaCl . The effect of salinity on germination kinetics is manifested by the germination retardation caused by the increasing concentrations of NaCl and PEG substrate (first phase of germination ). It could be explained by the prolongation of the latency phase corresponding to the time required for the imbibition of the seeds to trigger the germination process . Our results show that the highest GT is obtained in the control seeds (94 %). At the osmotic pressure of -1 bar , the germinative capacity is reduced by 60.63 % compared to the control . GT decreases with increasing osmotic pressure of the seed imbibitions substrate . At the pressure of -3 bars the germination drop reached 90.42 %. The germination is completely inhibited at the pressure of -9.25 bars . Like GT , the MGT required for H . flexuosum seeds increases with osmotic pressure . This is tripled at -7 bars pressure compared to the controls . H . flexuosum appears to be more sensitive to salinity compared to several Tunisian cultivars of H . coronarium (LD 50 to -2.11 bars for water stress ).

Réponses comparatives à la sécheresse en condition de serre des plantules de Quercus suber de trois provenances algériennes.-Le Chêne-liège est une espèce typiquement méditerranéenne présentant un intérêt économique et écologique. L'existence de mécanismes de tolérance à la sécheresse estivale méditerranéenne chez cette espèce a été démontrée par de nombreuses études réalisées, essentiellement en Europe. Cependant, ces dernières années, d'autres études ont montré que les mécanismes de tolérance diffèrent entre les provenances. Le comportement des provenances algériennes de Chêne-liège a été le sujet de très peu d'études. L'Algérie, étant un pays plus aride que les pays européens, ses provenances pourraient montrer des différences de comportement par rapport aux provenances européennes. L'objectif de ce travail est l'étude de la réponse à une sécheresse estivale des plantules originaires de trois provenances algériennes caractérisées par des étages bioclimatiques différents : Azazga (subhumide), Jijel (humide) et M'Sila (semi-aride). Un arrêt d'arrosage a été appliqué aux plantules, cultivées de façon homogène en serre, pendant 10 semaines, de fin-juin à mi-septembre, pour simuler la sécheresse estivale méditerranéenne. Le statut hydrique et des paramètres morphologiques et biochimiques ont été évalués chez les plantules arrosées (témoins) et non arrosées (stressées) et les taux de survie des plantules non arrosées ont été déterminés pour les trois provenances. Les résultats ont révélé des différences de comportement entre les trois provenances dans les deux conditions d'arrosage et de non arrosage. Dans les conditions d'arrosage, les plantules originaires de M'Sila ont montré la teneur relative en eau la plus élevée ainsi que la meilleure croissance. L'arrêt d'arrosage, ayant provoqué une diminution significative des teneurs en eau du sol, a provoqué une réduction de la teneur relative en eau et de la croissance (hauteur et diamètre de la tige) des plantules originaires de Jijel et d'Azazga alors que seul le diamètre des tiges était réduit chez les plantules originaire de M'Sila. Les feuilles des plantules originaires du site le plus aride, M'Sila, ont montré des modifications morphologiques et physiologiques considérées comme étant des stratégies d'adaptation à la sécheresse : une faible surface foliaire spécifique, une diminution des teneurs en Chlorophylle a, pour éviter une absorption excessive de l'énergie lumineuse, une diminution des teneurs en amidon, une accumulation des protéines, des sucres et de la proline afin de permettre un ajustement osmotique et une augmentation du δ 13 C pour une meilleure utilisation de l'eau. Dans les conditions de non arrosage, les plantules d'Azazga ont montré un comportement intermédiaire entre les plantules originaires de Jijel et de M'Sila. Cependant, contre toute attente, les plantules de M'Sila ont montré le plus faible taux de survie, le meilleur taux de survie étant enregistré pour les plantules d'Azazga. Les écotypes étudiés dans ce travail montrent donc des traits f...

Wheat plants were grown in a greenhouse in containers filled with chalky or loamy soil. Single-labelled ammonium nitrate fertilizer NH415NO3 or 15NH4 NO3 (5 atom% 15N) was applied in a split-dose after the third leaf-stage. Initial soil nitrate levels were lower in chalky soil. At maturity, the amount of N recovered in shoots was lower in chalky plants (CP) than in loamy plants (LP) but N fertilizer recovery was higher in CP than in LP. There was a greater 15NO3 recovery, in CP: 15NO3 / 15NH4 being 1 in LP and 1.3 in CP seeds. This was explained by efficient N mobilization enriched in 15NO3 in CP. Leaf excision or shoot shading at flowering changed the seed 15NO3 / 15NH4 ratio; it increased in CP and decreased in LP for plants with excised leaves whereas it was not modified in CP but decreased in LP for shaded plants. This indicated that grain filling was predominantly via mobilization in CP, whereas a late assimilation was involved in LP. The flag leaf in CP was the site for early and transient storage of NO3- and later a main source of assimilated N for seeds. Benefits previously observed in vegetative wheat plants grown on chalky soils compared to loamy soils with respect to enhanced NO3 utilisation, are also manifest at grain-filling and maturity.

Drought conditions are the major constraint to the early establishment of Quercus suber species. However, drought responses of this species depend on provenances. The objective of this study was to obtain more comprehensive knowledge on the influence of drought conditions on the response of Q. suber L. seedlings originating from Algeria. Soil water status in soil (SWC) and relative water content (RWC) in leaves, morphological parameters for growth evaluation and physiological parameters, and ectomycorrhization were evaluated in two plots of seedlings: watered (W) and none watered (NW). Ten weeks of water starvation induced a reduction in RWC, ectomycorrhization rate and height and diameter growth of none watered seedlings. Under drought conditions, both soluble sugars and proteins were enhanced while polyphenols and %N decreased. The reduction of soil water content was negatively correlated with carbon isotope discrimination. The survival of the seedlings under these drought conditions was due to two strategies: osmotic adjustment through soluble sugars and proteins accumulations in leaves and an increase in carbon discrimination which enhances the water use efficiency (WUE).