Resumo em Inglês:

Six aquaporin (AQP) homologues were identified in three coffee species (Coffea arabica, C. Canephora, and C. racemosa), including four plasma membrane intrinsic proteins (PIP1;1, PIP1;2, PIP2;1, and PIP2;2) and two tonoplast intrinsic proteins (TIP1;1 and TIP1;2). In order to better understand the role of these genes in coffee, C. arabica cvs Catuaí and Mundo Novo, C. canephora cv. Apoatã, and a graft of Mundo Novo on Apoatã were water stressed, and the expression levels of PIP1;2, PIP2;1, PIP2;2, and TIP1;2 were analyzed in the roots and leaves. The expression of PIP2;1 and PIP2;2 was clearly up-regulated in the leaves and roots by water deficit, suggesting the possible involvement of these genes in controlling the water status of plants and in the post-stress recovery of irrigated plants. The most strongly induced expression in roots was found in both grafted and non-grafted Apoatã plants. Interestingly, the level of PIP2;1 transcripts in roots continued to rise even after the plants were watered and were, therefore, no longer subjected to the water stress, suggesting that this gene may be actively involved in the regulation of water uptake in coffee tree roots, especially when there is a water deficit in the soil.

Resumo em Inglês:

Physiological differences in the Cordia oncocalyx tree growing at different densities in two distinct areas were investigated. An agrosilvopastoral system (AGP) and a secondary forest (SF) were studied. Under both types of land-use, C. oncocalyx presented a relative frequency of approximately 50%, and absolute densities of 670 and 80 individuals per hectare, respectively. Net photosynthesis (A), stomatal conductance (g s), and transpiration (E) were measured, and the SPAD index was recorded in sun leaves from the canopy and shade leaves from the lower canopy, in both the wet and dry seasons. We quantified the dry biomass of leaves and fruit on a per-tree basis at the end of the wet season. Net photosynthesis was higher in shaded leaves in the AGP in the wet season, reaching an average of 4.8 μmol m-2 s-1 against 3.2 μmol m-2 s-1 under SF. As trees began to shed their leaves at the beginning of the dry season and more radiation reached the shaded leaves, there was an increase in SF for A, depending on the intensity of light reaching the leaves. In the sun leaves, gas exchange was similar for the land-use systems during the wet season, but stronger in AGP than under SF during the dry season. This happened when the leaves in AGP retained more relative water content during a period of low gravimetric levels of the soil water. The lower tree density in AGP promoted a higher SPAD index and dry biomass in both the sun and shaded leaves, and allowed greater A, E and g s rates in the sun leaves at the beginning of the dry period.

Resumo em Inglês:

Seedlings of Stylosanthes guianensis CIAT 184 (Stylo 184) were germinated under salt-stress conditions (0-170.9 mM NaCl), and germination and ion content (Cl-, Na+, Ca2+, Mg2+ and K+) were measured after seven days. The salt treatment had no effect on the germination percentage, but the seedling showed reduced growth and displayed variation in ion uptake, thus accumulating Na+ and Cl- in the roots. Callus produced from seedlings selected as salt sensitive (T1) or salt tolerant (T2, T3, T4 and T5) was examined for growth and ion content under the influence of NaCl (0-256.4 mM NaCl) after 15 days. The sensitive clone (T1) contained the lowest Na+ and Cl- content with the highest percentage of K+ contributing to osmolality, suggesting it possesses an ion regulation mechanism that is typical of glycophytes; i.e., osmotic potential was adjusted by accumulating K+. The other clones (T2, T3, T4 and T5) expressed different strategies (osmotic adjustment) to cope with salt stress. T5 showed the highest mean dry weight on salt medium and displayed more effective ion regulation by maintaining low Na+:K+ and Na+:Ca2+ ratios. T2 expressed high Na+ and Cl- with the highest percentage of Na+ contribution to osmolality and water content (succulence). T3 and T4 had lower growth rates but similar ion regulation in relation to T5. Results indicated that the ion content can be used to discriminate salt sensitive and salt tolerant clones of Stylo 184.

Resumo em Inglês:

Among commercial fruits, papaya (Carica papaya L.) is notably one of the most common ones around the world. The aim of the current study was to establish a somatic embryogenesis protocol for the hybrid UENF/CALIMAN 01, elucidating the effects of sucrose and 2,4-dichlorophenoxyacetic acid (2,4-D) on the induction of embryogenic cultures and the effect of polyethylene glycol (PEG) on somatic embryo maturation. Immature zygotic embryos of C. papaya hybrid UENF/CALIMAN 01 were cultured in MS culture medium supplemented with different concentrations of sucrose (30 and 60 g L-1) and 2,4-D (0, 20, 40 and 80 μM). The combination of 30 g L-1 sucrose and 20 μM 2,4-D resulted in the highest induction rates and the largest callus diameters. Furthermore, this combination was associated with the greatest potential to form somatic embryos. To promote maturation, cultures were inoculated in MS medium and exposed to different concentrations of PEG (0, 30 and 60 g L-1). The 60 g L-1 PEG treatment group had the highest average for the number, maturation and conversion of somatic embryos that resulted in plantlets at the end of the process. The addition of PEG to MS medium led to increased protein synthesis. These results are unprecedented for C. papaya hybrid UENF/CALIMAN 01 as the current study demonstrates the development of somatic embryogenesis in this high quality hybrid.

Resumo em Inglês:

When glyphosate is added to the soil, it is absorbed by roots and transported by xylem causing growth inhibition in plants. Mycorrhiza is the beneficial association between roots of most plants and soil fungi. The methylphosphonic group of the glyphosate could compete with inorganic phosphates for sorption sites in the soil. The aim of this work was to study the effect of phosphorus availability and glyphosate residues in soil on pepper plant growth, and on physiological parameters, in plants non-inoculated or inoculated with Glomus mosseae or G. intraradices. The phytotoxic effects of the glyphosate were assessed by a bio-indicator as shikimic acid. At high doses, glyphosate (6.32 μM) reduced root colonization, and this effect was increased by higher levels of phosphorus in the soil. The effects of herbicide on shikimic acid accumulation and on shoot growth began 24 hours after glyphosate treatments (HAT). At 24, 48, and 72 HAT, inoculated plants grown without glyphosate showed higher growth compared to the non-inoculated ones. At high glyphosate (6.32 μM) and 96 HAT, the growth was completely inhibited. The shikimic acid accumulated in the upper leaves of non-inoculated plants, treated at 3.16 μM glyphosate, was significantly higher at high P level, related to inoculated ones. These results suggest that the remobilization of glyphosate residues in the soil by the addition of phosphate should be considered a serious problem for crops in treated soils. The mycorrhization increases the pepper plant's tolerance to high glyphosate concentration in the substrate, and may allow support to this stress condition.

Resumo em Inglês:

Trypsin inhibitors (TI) have crucial functions in plant defense against pests, and recent studies reveal their diversity in stress response. Disease and herbivore infestations are harmful to plant growth, but the response of TI in Cicer arietinum (L.) in Central India has been less studied. In the present study, we partially characterized the TI from Cicer arietinum (L.) seeds and evaluated its insecticidal potential against Helicoverpa armigera (Hübner). A 20 kDa trypsin inhibitor was purified to homogeneity by ammonium sulfate precipitation and chromatographies with Sephadex G-100 and diethylaminoethyl cellulose (DEAE-cellulose-52) ion-exchange column. TI assay categorized 17 cultivars in three groups: with high (more than 70%), intermediate (16-70%) and very low (0-15%) TI activity. Moreover, results from the TI activity coincided with herbivore attack studies carried out in J.N.K.V.V. fields earlier. Together, our results suggest that the presence of TI triggers a signal that leads the dynamics of stress response and, in turn, regulates pest resistance in plants. Feeding experiments conducted with 5th instar larvae suggested dose-dependent decrease for both the larval weight and the survival of the larva.

Resumo em Inglês:

Eucalypt plantations in Venezuela occupy 14% of land covered by savannas. Since water use by plantations in the savannas of Mapire (Venezuelan Llanos) was apparently similar to or lower than in the natural vegetation, evaluating how carbon fixation by plantations compares to the natural vegetation could help to elucidate whether plantations have higher water-use efficiency (WUE) than the savanna. We aimed to determine, using measurements of leaf gas exchange, the seasonal changes in photosynthetic rate (P N) and WUE of a seasonally dry savanna in Mapire, composed mainly of the grass Trachypogon vestitus and the tree Curatella americana, and trees of Eucalyptus urophylla growing in an experimental plantation. Daily integrated WUE (WUEint) was highest in C. americana and similar between T. vestitus and E. urophylla during both seasons. The Gross carbon fixation (GCF) at the leaf level in T. vestitus was similar to C. americana and lower than E. urophylla during the dry season, whereas during the rainy season it was nearly as high as in E. urophylla and both higher than C. americana. Gross carbon fixation (GCF) in T. vestitus was higher than in C. americana, but lower than in E. urophylla during the dry season, while it was much higher than the other two species during the rainy season. The contribution to savanna GCF of C. americana was small and constant throughout the seasons. The GCF in eucalypts was 15% higher than in the savanna during the dry season, but 45% lower during the rainy season, GCF averaging 85% of that in the savanna. Since water use by plantations is lower than in the savanna, they have a large potential for C sequestration without significantly altering ground water availability.

Resumo em Inglês:

Cymbopogon citratus (lemongrass) is an aromatic species whose essential oil is rich in citral, with industrial applications due to its lemon scent. The effects of environmental factors on the percentage and composition of essential oils are the main challenges in commercial cultivation. Various studies have indicated the positive effect of cytokinin on terpene production. The present work aimed to evaluate the effect of N6-benzylaminopurine (BAP) associated with light intensity on the production and composition of essential lemongrass oil. Plants were grown under field conditions (FIELD) and shade (SHADE). The study employed a 2x7 factorial scheme with two growing environments, seven BAP concentrations, and five replicates. After seven months of growth, a single application of the synthetic cytokinin BAP was performed at concentrations 0, 30, 60, 90, 120, 150, and 180 mg L-1. One week after the BAP application, plants were harvested and the essential oil was extracted in a Clevenger apparatus. The chemical composition of the essential oil of plants treated with 60, 120, and 180 mg L-1 of BAP was determined by Gas Chromatography (GC). The essential oil percentage was not affected by the treatments, showing 1.08% on average. On the other hand, the citral percentage was negatively influenced by BAP, and light intensity had no effects. In plants treated with 60 mg L-1 of BAP, citral percentage was 72%, on average, while in plants treated with 180 mg L-1, the mean percentage of citral was 33%.