Abstract
The use of growth regulators in wheat aims to reduce problems caused by the lodging of plants. The aim of this study was to evaluate the growth and vigor expression of wheat seeds treated with a growth regulator and the fertilization of plants to achieve high yields. The cultivar used was OR Topázio, the treatments consisted of the combination of five rates of the trinexapac-ethyl [0 – no application; 200; 400; 600 e 800 mL of the commercial product ha-1] and eight harvesting dates [14, 28, 42, 56, 70, 84, 98 e 112 days after emergence ]. The experimental design was completely randomized, in a factorial scheme 5 x 8 (five rates and eight harvest dates) with four repetitions. The total dry matter, dry matter production rate, relative growth rate, net assimilation rate, conversion efficiency of solar energy, photoassimilate partition, harvest index, and seedling emergence index were evaluated. Allocation of total dry matter, relative growth rate, plant height and harvest index were reduced by the growth regulator, with varied intensity according to the rate applied. The net assimilation rate was reduced in plants subjected to 400, 600 and 800 mL ha-1. The seedling emergence and the speed of emergence index were not affected by the action of the growth regulator.
Highlights
The nutritional status of plants greatly influences the partition of carbohydrates and dry matter between different plant structures, and it is an important factor in producing high quality seeds (Sawan, 2013)
On wheat the five treatments, the total dry matter plants adjusted to the logistic tendency w(Witht) of the a high coefficient of determination (Table 1), with more pronounced effects at the end of the cycle of plant development under the effect of T2 and T4 comparatively to the plants that were not subjected to application of the product (T1) (Figure 1c)
The plants under all the treatments had a phase of slow growth until the 42 DAE, which was followed by a phase of intense growth, in which plants of T2 the values of Wt were superior to those in T1 at 56 days after emergence (DAE)
Summary
The nutritional status of plants greatly influences the partition of carbohydrates and dry matter between different plant structures, and it is an important factor in producing high quality seeds (Sawan, 2013). Under certain environmental conditions, such as excessive rainfall and high nutrient availability, the structure of plant stalk does not support the increase in the dry matter of the plant during the period of seed formation, causing plant lodging (Chastain et al, 2014). Reduction in gibberellin levels causes a reduction in plant growth due to the fact that the gibberellins are responsible for cell division and elongation (Taiz & Zeiger, 2010). These synthetic substances perform similar actions as plant hormones (Chorbadjian, Bonello & Herms, 2011) and act promoting, inhibiting or modifying physiological and morphological processes of plants (Taiz & Zeiger, 2010). There are few studies reporting changes in the physiological processes related to plant performance due to growth regulator use
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