Physiology and Yield of Confection Sunflower under Different Application Schemes of Mepiquat Chloride

Spyridon D Koutroubas,Christos A Damalas

doi:10.3390/agriculture10010015

Abstract

The use of plant growth regulator mepiquat chloride (MPC) has been a widespread practice for the control of vegetative growth in cotton production for several decades. As a growth retardant, MPC could potentially provide a means of controlling plant height in field sunflower (Helianthus annuus L.), but this possibility has not been studied. Field experiments over two years were conducted in northern Greece to study the influence of MPC at rates of 37.5 plus 37.5 g ha−1 (named double application) and 37.5 plus 37.5 plus 37.5 g ha−1 (named triple application) on sunflower growth and yield. MPC provided a height reduction of 9.5% (25 cm) with the double application and a height reduction of 14.4% (49.2 cm) with the triple application at maturity. The number of nodes was also reduced, indicating shorter plants, whereas stem width did not show a consistent response. Moreover, MPC resulted in increased crop growth rate with the triple application scheme. MPC reduced nitrogen utilization efficiency in both growing seasons. However, a reduction in achene yield per plant by 19.9% was observed with the triple application scheme. The achene yield reduction resulted by the reduction in the 100-achene weight (22.3%), given that the number of filled achenes was similar to control. None of the application schemes reduced seed nitrogen and oil content. The results from testing application schemes could be a basis for further research on the use of MPC in this crop, e.g., different timing of applications could be tested for benefits to height reduction.

Highlights

Plant growth regulators, both promoters and inhibitors, are chemicals designed to manipulate plant growth and development [1]
The present study shows the importance of evaluating different mepiquat chloride (MPC) application schemes to control excess vegetative growth of sunflower
MPC application rates used in the present study either did not provide any practical advantage, in terms of height reduction of sunflower plants, or the height reduction achieved was followed by a major reduction in achene yield

Summary

Introduction

Both promoters and inhibitors, are chemicals designed to manipulate plant growth and development [1] These regulators have been applied for specific purposes, e.g., to control plant height, to eliminate excessive vegetative growth, and to enhance flowering [2]. One of their main effects, of the so-called growth retardants, is to limit stem growth (i.e., to shorten internode length). Applying plant growth regulators at incorrect rates or time can produce stunted plants that are of poor market suitability This is often apparent for products that are effective at very low concentrations, such as paclobutrazol

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