Abstract
The vegetative propagation of ornamental plants can be accelerated by applying plant growth regulators. Amongst them, the use of auxins, plant hormones with physiological effects on cell elongation and rooting have stood out. Alternatively, the application of humic acids, bioactive fraction of soil organic matter, also results in increases in rooting cuttings of ornamental plants. The objective of this work was to study the growth characteristics and the nutritional contents of croton and hibiscus plants during acclimation of seedlings in response to different concentrations of indolebutyric acid (IBA) and humic acid (HA) applied to cuttings for rooting. The experiment was conducted in greenhouse, and the apical stem cuttings were treated with solutions with concentrations of 0, 250, 500, 1000 and 2000 mg L-1of IBA and 0, 10, 20, 30 and 40 mg L-1 of C from HA. At 45 days of rooting in carbonized rice husk, they were individually transferred to plastic bags of 2.0 dm3 containing a mixture of soil: sand: manure (2: 1: 1) as substrate. At 90 days of acclimation, the plants were collected for measurement of growth and nutritional variables. The results showed that the application of the IBA stimulates the absorption of nutrients and growth of croton cuttings and transplanted hibiscus, contributing to formation of vigorous seedlings. A similar response occurred with the application of HA in hibiscus cuttings
Highlights
According to Ibraflor (2012), the area used for growing plants and ornamental flowers all over Brazil is 12 thousand hectares, with around nine thousand farmers and a farm average size of 1.5 hectares
For growth traits of croton seedlings at 90 days of acclimation, in response to the application of indobultiric acid (IBA) and humic acid (HA), no differences for most of the analysed variables were found, when compared to the control (Table 1). In this same table, when comparing the use of plant regulators, it was possible to verify that IBA application incremented crown diameter (CRD) by 11.33% and number of leaves (NL) by 20.82%, in croton plants, in comparison to HA application
Endogenous levels of auxins in croton plants are sufficient to stimulate the formation of adventitious roots, allowing this species to be classified as one with easy vegetative propagation by cutting (Baldotto et al, 2012), which can be seen in the acclimation period, when there is a lack of differences during growth among plants treated or not with IBA or HA
Summary
According to Ibraflor (2012), the area used for growing plants and ornamental flowers all over Brazil is 12 thousand hectares, with around nine thousand farmers and a farm average size of 1.5 hectares. With the objective of increasing yield and optimization of acclimation phase of ornamental seedlings, the following has been studied: the use of fitted substrates (Yamamoto et al, 2007; Lima et al, 2008) and containers (Cunha et al, 2005), the association between plants with micorhizal fungi and diazotrophic bacteria (Weber et al, 2003; Baldotto, 2010), the use of growth regulators (Lima et al, 2008), among others The objective of such efforts is to accelerate plant growth and to reduce the impact of transference from nursery to the field, increasing yield and seedling quality in less time and at lower costs. Because such plants are very appreciated by the population, they need fast propagation methods, with low cost and that assures the formation of vigorous, high-quality seedlings
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