Crescimento inicial de plantas de pequi após aplicação de 2,4-D

Abstract

Resumo -O ácido 2,4-diclorafenóxacético (2,4-D) tem causado efeitos tóxicos em várias culturas cultivadas vizinhas ao local na qual foi destinado, devido à deriva durante sua aplicação. Objetivou-se, nesta pesquisa, avaliar o efeito da deriva simulada por meio de subdoses do herbicida 2,4-D em plantas de pequi (Caryocar brasiliense, Camb.). Testaram-se em blocos completos casualizados com seis repetições as doses de 0; 1, 67; 3,35; 6,70; 16,75; 33,50; 67,00 e 134,00 g ha -1 de equivalente ácido do herbicida. A unidade experimental foi de um vaso contendo uma planta de pequi. A aplicação de 2,4-D causou sintomas leves de epinastia nas folhas, com valores entre 6,25 e 13,33% de fitointoxicação nas plantas de pequi; contudo, ocorreu a recuperação das plantas a partir dos 15 dias após a aplicação. Foi observado efeito hormético para as variáveis área foliar, área foliar específica e razão de área foliar. Porém, com o aumento das doses, verificou-se redução no crescimento das mudas, caracterizada pela diminuição nas variáveis foliares e massa seca total das plantas. Comparado ao controle (dose zero) foram observados maiores valores da partição de fotoassimilados para a parte aérea das plantas. Initial growth of Caryocar brasiliense plants after application of 2,4-DAbstract -The 2,4-dichlorophenoxy acid (2,4-D) causes toxic effects on various cultivated crops surrounding the place in which it is sprayed due to drift. This work evaluated low doses of 2,4-D herbicide in simulated drifting on Caryocar brasiliense, Camb. seedlings. They were tested in a randomized complete block design with six replications, using herbicide acid equivalent doses of 0; 1. 67, 3.35, 6.70, 16.75, 33.50, 67.00 and 134.00 g ha -1 . The experimental unit was a vessel containing one C. brasiliense plant. The application of 2,4-D caused low epinasty in leaves with values between 6.25 to 13.33% phytotoxicity in C. brasiliense. However, there was full recovery of the plants 15 days after application. Hormesis effect was observed for leaf area, specific leaf area and leaf area ratio variables. However, with increasing doses there were reductions in seedlings growth characterized by reduction in leaf variables and plants total dry matter. Compared to control (zero dose) higher values of assimilates partition for aerial part of the plants were observed.

Effect of pre-emergent graminicide herbicides on germination and early development of native species

“…Polini et al (2018) evaluated the selectivity of herbicides in native forest species of the Cerrado biome and concluded that herbicide imazapyr, when applied at low doses in post-emergence, is selective for tree species Schinus terebinthifolia, Peltophorum dubium, and Handroanthus albus; at high concentrations, however, it may affect their survival differently. Tavares et al (2017) observed that the initial growth of Caryocar brasiliense plants was benefited from the application of 2,4-D subdoses for the variables leaf area, specific leaf area, and leaf area ratio. However, with increasing doses, there was a reduction in seedling growth, characterized by a decrease in leaf variables and in the total dry weight of plants.…”

Hormesis effect of 2,4-D choline salt on soybean biometric variables

“…Known as a growth regulator, synthetic auxin or hormonal herbicide, 2,4-D belongs to the class of auxin-mimicking herbicides, because at low concentrations it has physiological and biochemical effects similar to those of the indole-3-acetic acid (IAA), the main natural auxin present in plants (Vanneste and Friml, 2009). Thus, it is expected that the hormesis effect of the 2,4-D herbicide may cause an increase of auxins production and activity, with adverse impacts on the plant's growth and development (Tavares et al, 2017).…”

Hormesis of 2,4-D Choline Salt in Biometric Aspects of Cotton

“…Auxin-based herbicides, such as 2,4-D, are examples of chemicals that enhance growth at nontoxic concentrations but are lethal at higher rates (Americo et al, 2017). Thus, such responses may be expected with increased auxins production and activity and may interfere with the plants' growth and development (Tavares et al, 2017).…”