Control of water-use efficiency by florigen

A major issue in modern agriculture is water loss through stomata during photosynthetic carbon assimilation. In water‐limited ecosystems, annual plants have strategies to synchronize their growth and reproduction to the availability of water. Some species or ecotypes of flowers are early to ensure that their life cycles are completed before the onset of late season terminal drought (“drought escape”). This accelerated flowering correlates with low water‐use efficiency (WUE). The molecular players and physiological mechanisms involved in this coordination are not fully understood. We analyzed WUE using gravimetry, gas exchange, and carbon isotope discrimination in florigen deficient (sft mutant), wild‐type (Micro‐Tom), and florigen over‐expressing (SFT‐ox) tomato lines. Increased florigen expression led to accelerated flowering time and reduced WUE. The low WUE of SFT‐ox was driven by higher stomatal conductance and thinner leaf blades. This florigen‐driven effect on WUE appears be independent of abscisic acid (ABA). Our results open a new avenue to increase WUE in crops in an ABA‐independent manner. Manipulation of florigen levels could allow us to produce crops with a life cycle synchronized to water availability

Foliar anatomy of neotropical Salicaceae: potentially useful characters for taxonomy

The taxonomy of neotropical Salicaceae, a family that now includes the majority of the former Flacourtiaceae, has been problematic, especially because they display very diverse morphology and have several characteristics in common with many other families. Recent phylogenetic studies have proposed substantial changes at both family and generic levels. Considering the importance of anatomy as an aid for taxonomy, the gathering of anatomical data for the family is fundamental to help clarify the taxonomic problems. Leaves belonging to Abatia americana (four samples), Banara brasiliensis (2), Casearia arborea (4), C. decandra (5), C. gossypiosperma (2), C. obliqua (1), C. sylvestris (3), C. ulmifolia (3), Prockia crucis (3), and Xylosma prockia (4) and the closely related Carpotroche brasiliensis (3) from Achariaceae, were studied by standard microscopy techniques. The leaves were anatomically described, emphasizing their differences and similarities. Similar characters for the neotropical Salicaceae (former Flacourtiaceae) and Salicaceae strictu sensu were recognized, such as the presence of salicoid leaf teeth, brachyparacytic stomata, secondary growth of the petiole, abundance of crystals, collateral and arch-shaped vascular system at the midrib, and sclerenchyma accompanying the bundles. These data demonstrate that leaf anatomy can provide evidence to assist with the taxonomy of Salicaceae, at family, generic, and specific levels

Desenvolvimento de Pasteuria penetrans em Meloidogyne spp. parasitando diferentes espécies vegetais

A bactéria Pasteuria penetrans é um parasita obrigatório do nematóide das galhas (Meloidogyne spp.) e produz esporos que persistem por anos no solo. A sua produção por cultivo in vitro ainda é inviável e a produção de inoculo requer o seu cultivo in vivo em nematóides parasitando plantas em vasos. Neste trabalho, buscou-se, por meio do estudo histológico de raízes, averiguar diferenças no desenvolvimento de P. penetrans em Meloidogyne spp. parasitando raízes de tomateiro (Lycopersicon esculentum), maxixe (Cucumis anguria) e camapu (Physalis angulata), e possíveis razões para estas diferenças, como forma e tamanho de células gigantes e das fêmeas do nematóide. O maxixe foi o pior dentre os hospedeiros em teste para a produção de inóculo e apresentou células gigantes anormais. A estrutura das células gigantes assim como o desenvolvimento da bactéria foram semelhantes no camapu e no tomateiro, entretanto o ciclo de vida de P. penetrans foi ligeiramente mais curto no tomateiro.The bacterium Pasteuria penetrans is an obligate parasite of root-knot nematodes and produces spores that persist in soil for many years. At present, in vitro cultivation is not feasible, thereby requiring inoculum production in vivo cultivation, inside nematode parasitizing potted plants. In this work, the differences in the development of P. penetrans in Meloidogyne spp. parasitizing roots of tomato (Lycopersicon esculentum), gherkin (Cucumis anguria) and "camapu" (Physalis angulata) were evaluated by histopathology of infected roots. Possible reasons for the differences found were analyzed, such as change in the giant cells or nematode females. The gherkin was the worst host for inoculum production and presented abnormal giant cells. The anatomy of giant cells and the bacterium development were similar in tomato and "camapu" root systems, but the P. penetrans life cicle was slightly shorter in tomato than in camapu

Variação estrutural quantitativa no lenho de Terminalia ivorensis A. Chev., Combretaceae

Com o objetivo de analisar a variação anatômica ao longo do caule de Terminalia ivorensis, estudaram-se amostras de madeira de três indivíduos, nos planos radial e axial. Para tal, corpos de prova foram obtidos a partir de discos de madeira, de 2 em 2cm, no sentido medula-câmbio. A metodologia usada para desenvolver o trabalho foi aquela tradicionalmente recomendada para estudos em anatomia vegetal. A descrição anatômica realizada seguiu as recomendações do IAWA Committee. No sentido radial do caule, alguns elementos anatômicos apresentaram tendências de variação definidas e significativas estatisticamente quando aplicado o teste Tukey para comparação de médias. São eles: freqüência, diâmetro e comprimento dos elementos de vaso, freqüência de raios/mm linear, comprimento dos raios em número de células, e comprimento e espessura da parede das fibras. Já no sentido axial, todas as variáveis analisadas não se mostraram estatisticamente significativas. Os resultados observados devemse, principalmente, à caracterização bem definida dos lenhos juvenil e adulto na madeira de Terminalia ivorensis

Diagnostic and prognostic characteristics of phytotoxicity caused by fluoride on Spondias dulcis Forst. F. (Anacardiaceae)

The goal of this study was to determine the symptoms and microscopic damage caused by fluoride on Spondias dulcis, a fluoride-sensitive species. The plants were exposed to simulated fog with fluoride (0, 5, 10, 15 and 20 mg L-1) for 20 min daily during four consecutive days. Samples from leaflets without any apparent fluoride injury were collected to microscopic analysis. The percentage of necrosed leaf area was measured, and the level of pollutant in the dry matter from the basal and apical portions of the plant was determined. The necroses began 24 h after the first simulation mainly from the base of the leaflets. A higher level of necrosis was observed at the apical portion of the plants, a region of higher fluoride accumulation. The damage on the surface of the leaflets was characterized as plasmolysis, erosion of the epicuticular waxes and epidermal rupture. Structurally, the noticeable accumulation of granules and droplets green stained by toluidine blue in the spongy parenchima and the boundaries of ending veinlets was observed. The limb thickness reduction occurred due to plasmolysis in the mesophyll, showing an apparent correlation with the damage observed on the surface. The parameters observed in the laboratory are promising for field biomonitoring studies

Tifton grass yield on constructed wetland used for swine wastewater treatment

It is the purpose of this study to evaluate the agronomic behavior and yield of the Tifton 85 grass (Cynodon dactylon Pers), when used in the treatment of swine wastewater (SW) with constructed wetland systems (CWs). For this purpose, five tanks were built measuring 24 x 1.1 x 0.7 m, damp-sealed with PVC canvas and filled with 0.4 m crushed stone. In two of these tanks, Tifton grass was cultivated: one of the tanks (CW 3) contained the grass, and in the other (CW4) the grass was only cultivated in the final third part of the tanks, being preceded by Alternanthera (Althernanthera philoxeroides) and cattail (Thypha latifolia L.). The SW was previously treated by means of a filtration process that consists of 0.7 m - high organic filters; the filtering beds were made of chopped sugarcane bagasse. The filter effluents were applied to CWs at a 0.8 m³ d-1 flow rate, corresponding to a hydraulic detention time of about 4.8 days. During the experimental period, three cuttings were done in CWs plants in order to evaluate the dry matter yield and the nutrient extraction capacity. All plants showed satisfactory performance in dry mass yield (86.3 and 65.3 t ha-1, in CW3 and CW4 respectively) and nutrient extraction, as well as in dry matter yield. Except for the case of Zn, the cultivation of other vegetable species in the same tank did not alter the capacity of the Tifton 85 grass extraction of the SW macro and micronutrients removal