Regulador de crescimento em plantas de trigo: reflexos sobre o desenvolvimento vegetativo, rendimento e qualidade de grãosReguladores de crescimento podem ser utilizados com o intuito de evitar o acamamento do trigo, porém, podem apresentar outros benefícios, em função da melhoria da interceptação de luz e da realocação de carbono. O objetivo deste trabalho foi avaliar a influência do regulador de crescimento (trinexapac-etil) sobre o desenvolvimento vegetativo, os componentes da produção e a qualidade de grãos de dois cultivares de trigo distintos em relação à susceptibilidade ao acamamento. Um experimento foi realizado em casa de vegetação e outro a campo. No experimento em casa de vegetação, foram avaliadas as variáveis de desenvolvimento vegetativo (estatura de planta, relação entre raiz e parte aérea, áreas foliares unitária e total, comprimento e matéria seca de raízes) em plantas de trigo, com e sem a aplicação de trinexapac-etil, em estádio de primeiro nó visível e segundo nó perceptível. A campo foram avaliadas variáveis de desenvolvimento vegetativo (clorofila, estatura e área foliar), rendimento (número de espigas, massa de mil grãos e produtividade) e qualidade (massa do hectolitro e conteúdo de proteína), em plantas de trigo com variações de aplicação de trinexapac-etil (testemunha sem aplicação, perfilhamento e primeiro nó visível e segundo perceptível). O regulador de crescimento trinexapac-etil aumenta a relação entre raiz e parte aérea do cultivar Mirante e a produtividade dos cultivares Quartzo e Mirante. Porém, não interfere na qualidade de grãos desses cultivares. Palavras Growth regulator in wheat: effects on vegetative development, yield and grain qualityGrowth regulators can be used to avoid wheat lodging, but can also bring benefits such as increase in intercepted radiation and carbon reallocation. The aim of this study was to evaluate the effect of a growth regulator (trinexapacethyl) on the vegetative development, production components and grain quality of two wheat cultivars with different susceptibility to lodging. Two experiments were carried out; one in a green house and another in the field. In the green house experiment, the vegetative development variables (plant height, leaf area, root: shootratio, length and dry mass of roots) were evaluated with and without application of trinexapac-ethyl on the first visible node and on the second noticeable node. The following characteristics were evaluated in the field: vegetative development, yield and quality grain variables (hectoliter mass and protein content) with varying trinexapac-ethyl applications (untreated control, tillering, first visible node and second notice able node). The growth regulator trinexapac-ethyl increased the root: shoot ratio in the cultivar Mirante and increased the yield in the cultivars Quartzo and Mirante. However, the growth regulator did not influence the grain quality of these cultivars.

Adverse factors cause a decrease in the productive potential of crops. For soybean [(Glycine max (L.) Merrill], the excessive growth is a factor that results in plants with low effective efficiency. Thus, plants with an architecture that favours greater interception of solar radiation and deposition of pesticides tend to be more productive. The objective of this study is to evaluate the different application of lactofen, which is used as a growth inhibitor, improve the productive efficiency of soybeans by increasing the biological activity of the leaves. The study was conducted in the field with soybean cultivars NA 5909 RG and BMX Potência RR. The experiment followed a randomized complete block design with four treatments and five replicates: T1: control; T2: application of 140 g a.i ha-1 of lactofen in phenological stage V3; T3: application of 140 g a.i ha-1 of lactofen in phenological stage V6; and T4: application of 70 g a.i ha-1 of lactofen in phenological stage V3 + 70 g a.i ha-1 of lactofen in phenological stage V6. The interception of photosynthetically active radiation in the lower layer increased in all treatments. Lactofen application increased the percent area covered and the number of phytosanitary products spray droplets per cm² in the middle and lower layers of the plants. The lower third of the plants experienced the greatest effect of the treatments with regard to the number of pods, grains and grain weight, with treatment T2 presenting significant increases. The use of lactofen as a growth inhibitor at the beginning of pod development in soybean caused changes to plant architecture and root development, consequently enhanced the productive efficiency of the plant, primarily due to increased grain production in the lower layer. Future research using lactofen in different phenological stages and cultivars may provide more insights in to the performance of this growth inhibitor in soybean.

An important limitation to increased soybean [Glycine max (L.) Merr.] grain yield is excessive plant growth. The use of growth regulators and population adjustment is imperative for the management of soybean. This study aimed to evaluate whether lactofen, used as a growth regulator, and a reduction in plant population affected the architecture of soybean and increased its production efficiency. The study was carried out under field conditions during the 2017–2018 and 2018–2019 seasons. The experimental design was in completely randomised blocks with five treatments and five replications: T1 (control), T2 (application of 140 g a.i. ha−1 of lactofen at phenological stage V3), T3 (application of 140 g a.i. ha−1 of lactofen at phenological stage V6), T4 (plant population 20% lower than recommended) and T5 (plant population 40% lower than recommended). The plant height, the number of nodes, the number of branches, stem diameter, and the internode distance were affected by lactofen application at stage V3. Lactofen use at stage V3 also increased the coverage percentage and the number of droplets per square centimetre of phytosanitary products. The interception of solar radiation was higher with lactofen application at stage V3 and that treatment provided the highest yield. Therefore, the use of lactofen as a growth regulator improves soybean grain yield. A reduction in plant population had the greatest effect on grain number and weight. Plant density should be maintained as recommended to avoid a decrease in grain yield