Growth regulator losses from cotton plants due to rainfall

Abstract

Plant growth regulators (PGRs) applied to cotton plants (Gossypium hirsutum L.) can be washed off by rainfall. It is expected that the closer the rainfall to spraying time, the higher the product loss and the higher the amount of product to be reapplied to reach the desired growth rate. The objective of this study was to evaluate the effects of time between rainfall and application of either mepiquat chloride or chlormequat chloride to cotton on plant growth, as well as, estimate the need for PGR reapplication. Cotton was grown in 12-L pots with soil in a greenhouse. PGRs were applied forty days after seedling emergence, when 50% of plants had one pinhead square. Rainfall was simulated 1, 2, 4, 6, or 24 h after spraying. Plant height was measured just before PGR application and then at 3-d intervals for 30 d. At harvest, the number of reproductive branches and structures were counted before dry matter phytomass determination. Both growth regulators reduced cotton dry matter yields regardless of rainfall interval. PGRs controlled excessive plant growth; however, their efficiency was reduced as the time elapsed until rainfall was shorter. Product losses were detected after all rainfall intervals, which, in field conditions would require PGR reapplication. Mepiquat chloride rates to be reapplied after rain were on average 17% higher than chlormequat chloride rates. Key words: Gossypium hirsutum L., mepiquat chloride, chlormequat chloride Perdas de reguladores de crescimento no algodoeiro devido à chuva RESUMO: Reguladores de crescimento aplicados às plantas de algodoeiro (Gossypium hirsutum L.) podem ser lavados em função da ocorrência de chuvas. Chuvas que ocorrem próximas à época de aplicação podem ocasionar elevada perda e necessidade de reaplicação dos produtos visando à taxa de crescimento desejada. Avaliou-se o efeito do intervalo de tempo entre a ocorrência de chuva simulada e a aplicação de cloreto de mepiquat e cloreto de chlormequat no algodoeiro no crescimento das plantas, além de estimar a necessidade de reaplicação dos reguladores. Plantas de algodão foram cultivadas em vasos de 12 L que permaneceram em casa de vegetação. Os reguladores de crescimento foram aplicados 40 dias após a emergência, quando 50% das plantas apresentavam botão floral. A chuva foi simulada 1, 2, 4, 6 e 24 horas após a aplicação dos reguladores. Determinou-se a altura das plantas antes da aplicação dos produtos e a cada 3 dias até o 30º dia. Na colheita, foi avaliado o número de ramos e estruturas reprodutivas, com posterior determinação da massa da matéria seca. Também foi determinado o crescimento acumulado e taxa de crescimento das plantas. Os dois reguladores reduziram a massa da matéria seca das plantas, independente do intervalo para ocorrência da chuva. O crescimento excessivo das plantas foi controlado, porém, com eficiência reduzida quanto menor o intervalo para simulação de chuva. Em todos os períodos avaliados houve perda de produtos, com necessidade de reaplicação. A taxa de reaplicação de cloreto de mepiqua...

Plant growth regulator losses in cotton as affected by adjuvants and rain

“…For MC, the adjuvant had no effect on the amounts to be replaced, which were lower than 10%. Conversely, a study evaluating MC and CC losses on cotton showed higher losses for MC up to 6h without rain (GARCIA et al, 2010). Using the same application rate used in this study (15g i.a ha -1 ), SOUZA & ROSOLEM (2007) also observed that for a 30mm rainfall 1.5h after the application of MC without adjuvant, less than 13% of the dose applied would have to be re-applied.…”

“…A greenhouse experiment was conducted in Botucatu, SP, Brazil (22º51' S, 48º26'O) in 12L pots with a Rhodic Ferralsol (FAO, 2006 (GARCIA et al, 2010) was composed of a 3-m high, 2-m wide metal frame with a carriage coupled 2.5m overhead. A rainfall simulator bar with 3 high-flow nozzles (TK-SS-20) 0.5m apart was fixed onto the carriage.…”

“…Without rain Average LSD GARCIA et al (2010) with MC and CC without adjuvant, as the period without rain was increased. The longer the time without rain after PGR application, the lower the rate that would have to be Ciência Rural, v.42, n.12, dez, 2012.…”

Development of Poly(ionic liquids) Based on Mepiquat Chloride with Improved Rainfastness and Long-Lasting Activity on Growth Regulation of Cotton Plant

“…11,12 In addition, being a highly water-soluble organic compound, MC is easily rainwashed before it could be absorbed by the green parts of plants. 13,14 And the loss of MC exhibits a certain extent of risk to aquatic organisms due to its toxicity to Daphnia magna with an acute 48 h EC 50 value of 68.5 mg L −1 . 15 Therefore, for maintaining long-lasting activity and minimizing unwanted loss of MC, there is an urgent need to prepare new effective formulations of MC.…”

“…Plant growth regulators (PGRs) are naturally occurring or synthetic organic chemical compounds, such as naphthaleneacetic acid, gibberellic acid, chlormequat chloride, and so on, which are widely used to modify the life processes of plants in agriculture and horticulture by the application of low concentrations. , As one of the PGRs, mepiquat chloride (MC), N , N- dimethylpiperidinium chloride, is a gibberellin biosynthesis inhibitor, and has become one of the most useful tools for managing the plant geometry during cotton growth and development. , Application of MC to cotton can balance the vegetative and reproductive growth by reducing main stem nodes, shorting internode elongation, and decreasing leaf expansion and leaf area, thus leading to the formation of a more compact plant and improvement in cotton yield. , However, due to the short effective period of MC, it needs be used more than once during cotton growth including the seeding, squaring, early bloom, full bloom, and so on. , In addition, being a highly water-soluble organic compound, MC is easily rain-washed before it could be absorbed by the green parts of plants. , And the loss of MC exhibits a certain extent of risk to aquatic organisms due to its toxicity to Daphnia magna with an acute 48 h EC 50 value of 68.5 mg L –1 . Therefore, for maintaining long-lasting activity and minimizing unwanted loss of MC, there is an urgent need to prepare new effective formulations of MC.…”