International Journal of Biometeorology

Not AvailableIn this study, the response of 6-month-old cocoa (Theobroma cacao L.) seedlings to elevated CO2 concentration [ECO2], elevated temperature [ET], and their interaction with water deficit stress was studied in an open top chamber (OTC). Each OTC was maintained at chamber control (400 ppm CO2), [ECO2] 550 ppm, [ECO2] 700 ppm, ET 3 ?C above chamber control, and ET 3 ?C + [ECO2] 550 ppm. Inside each OTC, a set of plants received moisture at 100% FC, while the other set was at 50% FC, which was the water deficit stress treatment. Increasing the CO2 concentration in cocoa increased photosynthesis (Pn) by 27%, which resulted in high biomass accumulation, thus improving the whole plant water use efficiency (WUE). The impact of high temperature (Tmax), around 39 ?C in ET treatment against 36 ?C in chamber control, is quite severe on Pn, leaf ?, and biomass accumulation. Similarly, water deficit at 50% FC resulted in the leaf ? reducing to ??14.06 bars at which Pn, leaf area, and biomass were significantly reduced. [ECO2] could ameliorate the negative effect of high temperature and water deficit stress to certain extent. However, the relative response of cocoa seedlings to [ECO2] in improving Pn, leaf ?, biomass, and WUE was greater under 50% FC compared to plants at 100% FC suggested additional advantage of [ECO2] to cocoa under water limited conditions

Characterization of exopolysaccharides produced by rhizobacteria

International audienc

Rizobactérias e promoção do crescimento de plantas cítricas Rhizobacteria and growth promotion of citrus plants

Desenvolveram-se três experimentos em casa de vegetação para verificar a possibilidade de as rizobactérias atuarem como promotoras do crescimento de plantas cítricas. Ao todo, testaram-se 10 isolados de Pseudomonas do grupo fluorescente, 13 de Bacillus e sete de outras bactérias rizosféricas em porta-enxertos utilizados na citricultura: tangerineira 'Cleópatra' (Citrus reshni), limoeiro 'Cravo' (Citrus limonia) e limoeiro 'Volcameriano' (Citrus volkameriana). Dependendo do porta-enxerto, sete isolados de Pseudomonas, um de Bacillus e um de outra bactéria rizosférica tiveram efeito benéfico sobre a matéria seca de raízes ou de parte aérea, indicando uma alta proporção de promotores de crescimento entre as bactérias do primeiro grupo. Procedeu-se também à contagem de bactérias fluorescentes do gênero Pseudomonas e de bactérias não-fluorescentes em raízes de tangerineira 'Cleópatra' e de limoeiro 'Cravo', procedentes de viveiro de mudas e do campo. Ambos os grupos bacterianos tiveram sua multiplicação favorecida na rizosfera de tangerineira 'Cleópatra', em condições de viveiro.<br>Three greenhouse trials were carried out to verify if rhizobacteria can promote citrus plant growth. Ten isolates of fluorescent Pseudomonads, thirteen of Bacillus spp. and seven of other rhizospheric bacteria were tested in three rootstocks seedlings: 'Cleopatra' mandarin (Citrus reshni), rangpure lime (Citrus limonia) and Volkamerian lemon (Citrus volkameriana). Depending on the rootstock, seven Pseudomonads, one isolate of Bacillus and one of other rhizospheric bacteria increased the root or shoot dry weight, indicating a high proportion of growth promoters among the fluorescent Pseudomonads. Also, fluorescent Pseudomonads and non fluorescent bacteria were counted in the roots of nursery seedlings and field plants of Citrus reshni and Citrus limonia. The growth of both bacterial groups was favored in the Citrus reshni rhizosphere under nursery conditions