The study concerns the impact of herbivory on the root systems of 3 perennial grasses, huffelgrass (Cenchnrs ctiti), digitgrass (Digitaria commutata) and needlegrass (Stipa lagascae), growing in the arid zones of Tunisia. The study simulated animals feeding of the grasses by affecting cuttings at various times throughout the spring growing period. The following effects on the root systems of the grasses were observed.When there is continual overgazing (simulated by cutting all sprouts down the ground level-along the spring), more than 65% of the roots off all 3 species are found in the salty upper 15 cm of soil.In case of medium average grazing (simulated by 2 to 3 cuttings), the root system again remains superficial for buffelgrass (C. c&z&), with 58 to 67% of the roots located in the upper 15 cm of soil. Digitgrass (Digitaria commutata) and needlegrass (Stip Zugascae), however, develop deeper roots with 68 to 86% in the upper 30 cm of soil.When grazing is light (just one cutting), all 3 species perform all most exactly as if there had been no grazing compared to (a control plot) with 85% of the root system located in the upper 50 cm and about 15% at 50 to 75 cm of ground depth.On the basis of this experiments, it is suggested that grazing on these grasses should be allowed just once each spring, thereby allowing : l-To take advantage of the aboveground contained in these grasses in spring.2-Preservation of a deep root system with will thereby have a much better chance of getting through the water stress summer $zl?axlIl.
In the southern suburb of Sfax (Tunisia), almond and pomegranate trees grow in the vicinity of a phosphate fertilizer-producing factory. In order to reveal strategies adopted by these fruit species to live in restrictive conditions, we investigated the effect of fluoride pollution on the distribution of some elements during the growing season. The results show that calcium and magnesium play an important role in trapping fluoride and delaying the appearance of necroses. Sensitive fruit species, like the almond tree, tend to reduce (F − ) toxicity by increasing leaf Mg content, following a decrease in leaf calcium. Since the Mg has multiple roles in the plant metabolism, the Mg-F affinity seems to be temporary and constitutes, in the long run, a limiting factor for the main physiological processes. Therefore, it appears that resistant species, like pomegranate, have the ability, during fluoride intoxication, not only to assimilate calcium ions but also to maintain Mg concentrations at an adequate level, thus ensuring the cell smooth running. When calcium is no more available, Mg is taken from the chlorophyll molecule as MgF 2 , and so damage may appear as marginal necroses. By comparing fluoride content of necrotic and healthy leaf slices, it appears that marginal necroses represent typical symptoms of fluoride pollution. By increasing their phosphorus concentration, sensitive fruit species tend to reduce damage intensity, whereas resistant ones tend to avoid F − toxicity. To cite this article: F.
Accumulation du cadmium par quelques espèces végétales cultivées aux environs d'une usine d'engrais phosphatés à Sfax (Tunisie) Accumulation of cadmium by some cultivated vegetable species around a factory producing phosphate fertilizers in Sfax (Tunisia) Imed MEZGHANI , Makki BOU KHRIS , Mohamed CHAIEB* RÉSUMÉ La pollution des écosystèmes terrest res par du cadmium d'origine industriell e (usine d'engr ais phosphatés) se traduit par des tach es nécrotiques au nivea u des feuilles et par une accumulation importante de cet élément dans ces feuilles et dans les horizons superficiels du sols. À proximité de la source d'émi ssion , les taux de cadmium dans le sol dépassent 10 fois les va leurs normale s. Au niveau des feuilles, elles sont 10 à 30 fois plus élevées que chez les témoins et dépendent de la nature de l'espèce, de la distance (corrélation négative) et des conditions topog raphiques.
Les effets d'une pollution atmosphérique par des composés fluorés ont été étudiés sur des cultivars d'une vigne locale, Vitis vinifera L. 'Asli', cultivée aux environs d'une usine de production d'engrais phosphatés. L'étude a pour objectif de déterminer les mécanismes permettant à ces vignes autochtones de survivre dans la zone polluée. Elle a consisté à suivre le comportement de ces cultivars dans deux parcelles : l'une soumise aux fumées d'une usine polluante et l'autre au loin de toute pollution. Les paramètres mesurés sont la conductance stomatique, la teneur des feuilles en F -et en Ca 2+ et l'activité photosynthétique des zones foliaires saines. Nos résultats suggèrent que la survie de la vigne est liée à une compartimentation du fluor dans les bordures et les extrémités des feuilles, avec une tendance de la plante à contourner les nouveaux tissus nécrosés par un liseré de transition conduisant au développement d'auréoles concentriques de zones nécro-sées donnant au limbe un aspect de mosaïque. Ce dernier peut donner des informations intéressantes sur la qualité de l'air et l'état des plantes. Ce comportement est concomitant à une aptitude des zones foliaires saines à conserver la capacité photosynthétique de la plante, tant que les nécroses ne dépassent pas 10 % à 20 % de la surface foliaire. Outre le piégeage du fluor dans des régions foliaires particulières, la fermeture temporaire des stomates semble également contribuer à la restriction de l'accumulation de ce polluant. Par ailleurs, le parallélisme entre l'accumulation du fluor et celle du calcium suggère que ce cation est impliqué dans le piégeage et la détoxication du fluor en le séquestrant sous forme de CaF2. Enfin, nos résultats ne plaident pas en faveur d'une remobilisation foliaire du fluor qui demeure séquestré dans les feuilles les plus âgées. D'ailleurs, la contamination des baies semble se faire directement par les fumées de l'usine, et non par apports endogènes. Abstract:The effects of atmospheric pollution by fluoride compounds were studied on a local grapevine cultivar, Vitis vinifera L. 'Asli', grown in the vicinity of a factory that produces phosphate fertilizer. The objective of this study was to determine mechanisms allowing these indigenous grapevines to survive in the polluted area. The response of this cultivar was monitored during growth on two plots of land, one exposed to fumes from the polluting factory, and the other far away from the pollution. Measured parameters were stomatal conductance, leaf fluoride and calcium content, as well as photosynthesis of healthy leaf areas. Our results suggest that survival of grapevine was related to the partitioning of fluoride in leaf boundaries and extremities with plant tendency to delimit the new necrotic tissues by a narrow dark violet borderline, leading to the development of concentric halos of necrotic zones, and giving the blade a mosaic aspect. These symptoms may be useful as an indicator of air quality and plant state. This response occurs concomitantly with the ability of health...
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.