Gibberellins and Heterosis in Maize: Quantitative Relationships

Abstract

To investigate the possible relationship between gibberellins (GA) and heterosis, a diailel from four elite maize, Zea mays L., inbreds (A632, B73, CH807 [from Mo17], and CO109) was studied under controlled environment conditions. Heterosis for plant growth was substantial at 25/15 °C (day/night), as hybrid seedlings emerged more rapidly, were taller, had heavier shoots, and larger leaf areas than the parental inbreds. Gibberellic acid (GA3) at 0.1, 0.5, or 1.0 mg per plant was pipetted into the leaf whorls of 14‐d‐old seedlings. The exogenous GA3 promoted ligule and total height in all genotypes, but the inbreds were maximally influenced. Consequently, potence ratios, representing the overall degree of dominance, were reduced from an average of 7.7 to 1.7 following GA3 application, indicating decreased heterosis. In an experiment at 15 °C, imbibition of seeds in GA3 accelerated germination and seedling growth, particularly shoot elongation of the parental inbreds. Endogenous concentrations of GA1 and GA19 were determined by gas‐chromatography‐selected ion monitoring using [2H]GAs as quantitive internal standards. Highly significant regressions of height, leaf area, relative growth rate, and height increment versus the log of GA concentration were observed. These results are consistent with the theory that GA are one factor involved in the regulation of heterosis of shoot growth in maize, a theory that suggests that a partial deficiency in endogenous GA in maize inbreds limits their growth, and is a contributing cause of inbreeding depression.

Arroz Vermelho: Ecofisiologia E Estratégias De Controle

“…O crescimento inicial e a concomitante acumulação de maté-ria seca são dependentes da assimilação de carbono através da fotossíntese e partição de assimilados (CAUSSE et al, 1995). Plântulas com crescimento rápido possuem maior capacidade competitiva devido ao maior porte e área foliar que desenvolvem (ROOD et al, 1990). A maior interceptação de radiação solar pelo arroz ocorre pouco antes da floração, período em que as plantas atingem o nível máximo de área foliar, demonstrando que ocorre desperdício de radiação nos estádios iniciais de desenvolvimento.…”

Relationship among physiological quality, heterosis, and amylase gene expression in maize seeds

“…According to Rood et al (1990), maize lines have less vigor than their hybrid descendants, in part because of gibberellin deficiency. There was a positive correlation between the gibberellin content found in the seedlings and the increases in growth rate, leaf area, and plant height of maize.…”

Qualidade fisiológica de sementes de milho na presença de bioestimulantes

“…Esse produto apresenta em sua composição 0,005% de ácido giberélico. De acordo com Rood et al (1983Rood et al ( , 1990) existe uma correlação positiva entre heterose e teor de giberelina, sendo que o teor de giberelina nas plântulas hibridas é significativamente maior que nas de suas linhagens parentais.…”