27 research outputs found

    Application of plant growth regulators at pre-harvest for fruit development of 'PĂŠRA' oranges

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    The aim of the present work was to evaluate the effects of auxins and gibberellins when applied at pre-harvest to the fruit development, and to the ripening and natural fall of the fruit, in 'Pêra' oranges. Trees of Citrus sinensis Osbeck cv. Pêra, 5 years old, were utilized. The treatments applied were: GA3 + 2,4-D 12.5mg L-1 of each; GA3 + 2,4-D 25mg L-1 ; GA3 + 2,4-D 37.5mg L-1; GA3 + NAA 12.5mg L-1; GA3 + NAA 25mg L-1; GA3 + NAA 37.5mg L-1; NAA + 2,4-D 12.5mg L-1; NAA + 2,4-D 25mg L-1; NAA + 2,4-D 37.5mg L-1; and water (control). The treatments were applied 3 times, at intervals of 45 days. The variables evaluated were: rate of natural fall (%), fruit length and diameter (mm), and fresh fruit weight (g). None of the treatments promoved alterations in the development of the fruits, but they did reduce the natural fall rate, when compared to control, up to 78.05%, inhibiting the fruits' abscision as much as 3 months.<br>O trabalho objetivou avaliar os efeitos de auxinas e giberelinas, combinados e aplicados em pré-colheita no desenvolvimento e na taxa de queda natural de frutos de laranjeira 'Pêra'. Foram utilizadas árvores de laranjeira (Citrus sinensis Osbeck) cultivar Pêra com 5 anos de idade. Os tratamentos foram: GA3 + 2,4-D 12,5mg L-1 de cada; GA3 + 2,4-D 25mg L-1; GA3 + 2,4-D 37,5mg L-1; GA3 + NAA 12,5mg L-1; GA3 + NAA 25mg L-1; GA3 + NAA 37,5mg L-1; NAA + 2,4-D 12,5mg L-1; NAA + 2,4-D 25mg L-1; NAA + 2,4-D 37,5mg L-1 e testemunha (água). Durante todo o período experimental foram realizadas três aplicações a intervalos de 45 dias. As variáveis avaliadas foram: Taxa de queda natural dos frutos (%), comprimento (mm), diâmetro (mm) e massa fresca dos frutos (g). Nenhum dos tratamentos proporcionaram alterações no desenvolvimento final dos frutos, mas reduziram a taxa de queda natural em comparação com a testemunha em até 78,05%, inibindo a abscisão dos frutos em até três meses

    Plant architecture, its diversity and manipulation in agronomic conditions, in relation with pest and pathogen attacks

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    Abstract Plant architectural traits have been reported to impact pest and disease, i.e., attackers, incidence on several crops and to potentially provide alternative, although partial, solutions to limit chemical applications. In this paper, we introduce the major concepts of plant architecture analysis that can be used for investigating plant interactions with attacker development. We briefly review how primary growth, branching and reiteration allow the plant to develop its 3D structure which propertiesmay allow it (or not) to escape or survive to attacks. Different scales are considered: (i) the organs, in which nature, shape and position may influence pest and pathogen attack and development; (ii) the individual plant form, especially the spatial distribution of leaves in space which determines the within-plant micro-climate and the shoot distribution, topological connections which influence the within-plant propagation of attackers; and (iii) the plant population, in which density and spatial arrangement affect the micro-climate gradients within the canopy and may lead to different risks of propagation fromplant to plant. At the individual scale,we show how growth, branching and flowering traits combine to confer to every plant species an intrinsic architectural model. However, these traits vary quantitatively between genotypes within the species. In addition, we analyze how they can bemodulated throughout plant ontogeny and by environmental conditions, here considered lato sensu, i.e. including climatic conditions and manipulations by humans. Examples from different plant species with various architectural types, in particular for wheat and apple, are provided to draw a comprehensive view of possible plant protection strategies which could benefit from plant architectural traits, their genetic variability as well as their plasticity to environmental conditions and agronomic manipulations. Associations between species and/or genotypes having different susceptibility and form could also open new solutions to improve the tolerance to pest and disease at whole population scale
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