Bacteria-inducing legume nodules involved in the improvement of plant growth, health and nutrition

Bacteria-inducing legume nodules are known as rhizobia and belong to the class Alphaproteobacteria and Betaproteobacteria. They promote the growth and nutrition of their respective legume hosts through atmospheric nitrogen fixation which takes place in the nodules induced in their roots or stems. In addition, rhizobia have other plant growth-promoting mechanisms, mainly solubilization of phosphate and production of indoleacetic acid, ACC deaminase and siderophores. Some of these mechanisms have been reported for strains of rhizobia which are also able to promote the growth of several nonlegumes, such as cereals, oilseeds and vegetables. Less studied are the mechanisms that have the rhizobia to promote the plant health; however, these bacteria are able to exert biocontrol of some phytopathogens and to induce the plant resistance. In this chapter, we revised the available data about the ability of the legume nodule-inducing bacteria for improving the plant growth, health and nutrition of both legumes and nonlegumes. These data showed that rhizobia meet all the requirements of sustainable agriculture to be used as bio-inoculants allowing the total or partial replacement of chemicals used for fertilization or protection of crops

Culture under optimized conditions of the red algae <Gracilaria gracilis> (Stackhouse) Steentofr et al. in the Bizerte lake

La culture de Gracilaria a été réalisée selon le mode de bouturage dans la partie Nord-Est du lac de Bizerte du 15 Avril au 31 Mai 2006 afin de déterminer l'effet des conditions initiales optimisées sur le rendement final. Ces conditions initiales, sont caractérisées par une culture sur le fond (sur cordes tendues), un poids initial des touffes de 200 g, une distance entre les rangées de culture de 50 cm et un écartement entre les touffes de 30 cm; de ce fait, la densité initiale est de 1,4 kg/m². Au terme de 46 jours de culture, nous avons enregistré un accroissement du poids de 200 g à 1280 g engendrant un taux de croissance spécifique de 4,03 %/j et une densité finale de 9,1kg/m² (soit 91t poids frais/ha).تم استزراع طحلب الغراسيلاريا بطريقة الأفتسال في المنطقة الشمالية الشرقية لبحيرة بنزرت من 15 أفريل إلى 31 ماي 2006 لتحديد مفعول الظروف الأولية المحسنة على المردود النهائي. تتمثل تلك الظروف في استزراع فسائل مربوطة على حبال في قاع البحر. تزن تلك الفسائل 200 غ وتبعد الواحدة على الأخرى 30 صم في حين حددت المسافة بين الحبال ب 50 صم. وخلال 46 يوما من الأستزراع مر وزن الفسائل من 200 غ إلى 1280 غ مسجلا بذلك معدل نمو نوعي وكثافة نهائية يقدران تباعا ب 4.03 بالمائة في اليوم و 9.1 كغ في المتر المربع.The culture of Gracilaria has been done by the propagation method in the north-eastern part of the Bizerte lake from 15 april to 31 may 2006 so as to detrminate the effect of the optimized initial conditions on the final output. These intial condtions are characerized by a culture on tight rope on the substrate, a weight of tufts of 200 g, the culture row are 50 cm away from each other and the distance between the tufts is 30 cm. So, the initial density is 1,4 kg/m². After 46 days of culture, the tufts have 1280 g of weight, 4,03 %/j for specific growth rate and 9,1 kg/m² of final density (that is 91 t of wet biomass).PublishedGracilaria gracili