15 research outputs found
Profiles of radiation intensity and absorption in a cylindrical photoreactor diffusely illuminated from the outside, in consideration of light refraction at the border of the reactor
Produção de bulbinhos de cebola em bandejas de isopor Production of onion bulb sets in styrofoam trays
Com o objetivo de estudar a viabilidade de produção de bulbinhos de cebola sob ambiente protegido em diferentes tipos de bandejas de poliestireno expandido foram instalados dois experimentos. No primeiro, trabalhando com a cultivar Serrana, foram avaliadas trĂȘs tipos de bandejas com diferentes nĂșmeros de plantas por cĂ©lula: uma planta/cĂ©lula na bandeja de 288 cĂ©lulas, trĂȘs a cinco plantas/cĂ©lula na de 128 e cinco a nove plantas/cĂ©lula na de 72 cĂ©lulas. No outro experimento, testaram-se nove cultivares, semeadas somente em bandejas de 128 cĂ©lulas com trĂȘs plantas por cĂ©lula. Utilizou-se o delineamento em blocos ao acaso com quatro repetiçÔes no primeiro ensaio e cinco no segundo, sendo cada parcela constituĂda por uma bandeja. Observou-se que quanto maior a densidade de plantio menor o tamanho do bulbinho (diĂąmetro e peso). O manejo adequado de adubaçÔes em cobertura pode viabilizar, tecnicamente, a produção de cinco bulbinhos com 1,3 cm de diĂąmetro (2 g) por cĂ©lula, na bandeja de 128 cĂ©lulas. Quanto ao ensaio de cultivares, âCrioulaâ da Agroflora, âCrioulaâ da Granja LotĂĄrio e âHoustonâ apresentaram 83%, 67% e 81% de plantas bulbificadas, enquanto que nas demais (âAuroraâ, âBaia Periformeâ, âBrownsvilleâ, âPetrolineâ, âPira Ouroâ, âPiranaâ e âSerranaâ) obteve-se 100% de bulbificação. As principais vantagens na produção de bulbinhos em bandeja foram: uniformidade, ausĂȘncia de plantas daninhas e de patĂłgenos. Ă um sistema que pode ser Ăștil aos viveiristas que tem entressafra de mudas nos meses de agosto a novembro, perĂodo de produção dos bulbinhos. PoderĂĄ, tambĂ©m, ser uma alternativa na produção de bulbinhos para conserva, no controle de qualidade de lotes de sementes e em programas de melhoramento de cebola.<br>One objective was to study the production of onion Allium cepa L.. bulb sets in a protected environment in a seedling system with trays with different number of cells: 288 (1 plant/cell), 128 (3 to 5 plants/cell) or 72 cells (5 to 9 plants/cell) using the cultivar Serrana. The second purpose was to compare nine cultivars, grown in trays of 128 cells, with 3 plants per cell. In the first experiment, five replications were used in the trial of types of trays and densities, while four replications were used in the experiment concerning cultivars which was set out in a randomized block design. Each plot was represented by one tray. It was observed that at the higher the plant density, there was a smaller bulb set size (diameter and weight). With good fertilizer management it was possible to produce bulb sets with a diameter of 1.3 cm (2g) in a tray of 128 cells and 5 plants/cell. Among the nine cultivars examined, Crioula - AF, Crioula - GL and Houston had 83%, 67% and 81% bulb formation, respectively. The other cultivars (Aurora, Baia Periforme, Brownsville, Petroline, Pira Ouro, Pirana and Serrana) produced no thick stems. The main advantages of producing bulb sets in this system over the traditional system were: relatively higher uniformity and absence of weeds or pathogens. This system may be a good alternative for producing bulb sets for processing, for controlling seed quality and for use in the onion breeding programs
Stomatal behaviour, photosynthesis and transpiration under rising CO2.
Definitions of the variables used and the units are given in Table 1 The literature reports enormous variation between species in the extent of stomatal responses to rising CO2. This paper attempts to provide a framework within which some of this diversity can be explained. We describe the role of stomata in the short-term response of leaf gas exchange to increases in ambient CO2 concentration by developing the recently proposed stomatal model of Jarvis & Davies (1998). In this model stomatal conductance is correlated with the functioning of the photosynthetic system so that the effects of increases in CO2 on stomata are experienced through changes in the rate of photosynthesis in a simple and mechanistically transparent way. This model also allows us to consider the effects of evaporative demand and soil moisture availability on stomatal responses to photosynthesis and therefore provides a means of considering these additional sources of variation. We emphasize that the relationship between the rate of photosynthesis and the internal CO2 concentration and also drought will have important effects on the relative gains to be achieved under rising CO2
Hysteresis in the response of stomatal conductance in Pinus sylvestris L. needles to light: observations and a hypothesis.
Selection for bulb maturity in onion Seleção para maturidade de bulbos em cebola
It is possible to produce onions (Allium cepa) all over the year in Brazil, but most of the Brazilian cultivars have poor quality bulbs, a fact that favours onion imports from Argentina, a producer of Valenciana type cultivars that does not bulb in Brazil, but please Brazilian consumers. To study the effect of selection for bulb maturity, seventeen half sib progenies selected for early maturity and twenty five for late maturity, from the intervarietal triple cross [Crioula x (Pira Ouro x Valenciana Sintetica 14)] were grown, along with the triple cross itself and the cultivars Pira Ouro (short-day), Crioula (intermediate-day) and Armada (long-day). A total of forty six treatments were tested in a randomized block design with three replications of 32 plants per plot. The progenies selected for earliness had cycles from 67 to 83 days, whereas those selected for lateness had cycles of 85 to 103 days. This difference was evident when comparisons were made for the percent thick neck bulbs, which varied from 0 to 6.2% and from 8.1 to 59.8% for the early and late progenies, respectively. High heritability estimates were obtained for all characters and they varied from 0.65 (thick neck percentage, in the late selection) to 0.80 (average bulb weight, in the early selection). Progenies of higher bulb weight and maturity similar to the standard cultivars were obtained. Selection for maturity was highly efficient and the population selected for early maturity has potential to originate adapted cultivars, with bulb yield and quality superior to the available cultivars.<br>Embora seja possĂvel produzir cebola (Allium cepa) o ano inteiro no Brasil, a maioria dos cultivares nacionais apresentam bulbos com baixa qualidade, o que proporcionou grande importação de cebola da Argentina, do tipo Valenciana, que nĂŁo bulbifica no Brasil, mas que agradou os consumidores brasileiros. Para estudar o efeito da seleção para maturidade de bulbos baseada em progĂȘnies de meios irmĂŁos obtidas do hĂbrido triplo intervarietal [Crioula x (Pira Ouro x Valenciana SintĂ©tica 14)] foram semeadas 17 progĂȘnies selecionadas para maturidade precoce e 25 para tardia, alĂ©m da geração F1 e dos cultivares Pira Ouro (dias curtos), Crioula (intermediĂĄrios) e Armada (dias longos), totalizando 46 tratamentos. O delineamento foi em blocos ao acaso, com trĂȘs repetiçÔes de 32 plantas por parcela, cultivadas em bandejas de isopor. As progĂȘnies precoces apresentaram ciclo mĂ©dio variando de 67 a 83 dias e as tardias de 85 a 103 dias. Na comparação da porcentagem de plantas improdutivas esta diferença tambĂ©m foi evidente, variando de 0,0% a 6,2% nas precoces e de 8,1% a 59,5% nas tardias. Os coeficientes de herdabilidades obtidos foram elevados, variando de 0,65 (porcentagem de plantas improdutivas, na seleção tardia) a 0,80 (peso mĂ©dio de bulbo, na seleção precoce), sendo, em mĂ©dia, superiores na população selecionada para maturidade precoce. Foram obtidas progĂȘnies com peso de bulbo superior Ă s testemunhas 'Pira Ouro' e 'Crioula' e com ciclo que nĂŁo diferia destas. A seleção para maturidade foi altamente eficiente e a população selecionada para maturidade precoce apresenta grande potencial de originar cultivares adaptados, com produção e qualidade de bulbos superiores Ă s disponĂveis no mercado brasileiro
Changes in Photon Flux Can Induce Stomatal Patchiness
Images of chlorophyll fluorescence were used to detect the occurrence of stomatal patchiness in leaves from eight species under variable photon flux conditions. Pronounced stomatal patchiness was induced within 5â10 min after PFD was changed from intermediate (âŒ450 ÎŒmol quanta mâ2 sâ1) to low (âŒ150 ÎŒmol quanta mâ2 sâ1) levels. This effect was completely reversible by returning PFD to intermediate levels. The pattern of heterogeneous fluorescence for each leaf was usually similar during repeated applications of medium and low PFD. In three species, stomatal patchiness could only be induced in slightly water-stressed plants. Leaves of more severely water-stressed Xanthium strumarium plants in low air humidity exhibited oscillations in fluorescence that corresponded with oscillatory changes in leaf diffusion conductance for water vapour. Stomatal patchiness was also induced by illuminating dark-adapted leaves with low PFD (below 200â300 ÎŒmol quanta mâ2 sâ1). Infiltration of leaves with distilled water showed that heterogeneous chlorophyll fluorescence was caused by changes in stomatal apertures