The effect of paclobutrazol on plant height and seed yield of oil-seed rape (Brassica napus L.)

Abstract

The effect of paclobutrazol (applied at several concentrations and timings) on stem length and the seed yield of oil-seed rape was explored in three field trials during 1981-4. Spring applications were most effective in reducing plant height, but they had an adverse influence on the yield components. Autumn applications increased seed yield in one season, but were less effective in the final trial when soil conditions were much drier at establishment. Data indicated that autumn treatments may increase the productivity of the uppermost racemes. Future studies must investigate the persistency of paclobutrazol in the soil, and its possible influence on subsequent arable cropping.

Sunflower response to repeated foliar applications of Paclobutrazol

“…These results are in agreement with Weiss (2000), who reported that certain growth regulators generally reduced height of sunflower plants at maturity by affecting the internode length, although a different reaction to the chemical used or to the rate applied may exist, depending on the cultivar. In addition, Scarisbrick et al (1985) found that PBZ significantly reduced the lengths of earlyformed internodes of oilseed rape at the base of the plant, whereas later internodes in the middle and at the top of plants became longer than those of the control. Stem diameter of sunflower plants was not affected in either year; this is in line with Sanvicente et al (1999) who studied the influence of plant growth regulators on culm diameter of winter barley.…”

“…A recent study (Spitzer et al, 2011) found that sunflower plant height was reduced by as much as 63 cm with double application of CCC plus ethephon and by as much as 35 cm with ethephon alone. Spring applications of PBZ in oilseed rape (Brassica napus) prior to a period of rapid crop development reduced plant height, but they had an adverse effect on the yield components and they offered no practical advantage in the commercial production of oilseed rape (Scarisbrick et al, 1985). By contrast, foliar application of PBZ in Ethiopian mustard (Brassica carinata), apart from reducing plant height, increased seed yield per plant primarily due to an increase in the number of siliquae (i.e., pods) per plant and secondarily due to an increase in total dry matter of plants and partitioning coefficients (Setia et al, 1995).…”

“…In addition, the inconsistent performance of many plant growth regulators in the field and the diverse effects on plant growth related to the timing of application (i.e. crop growth stage), the application rate of plant growth regulators, as well as the variable effects of the environmental conditions are considered major limitations in the use of many plant growth regulators (Scarisbrick et al, 1985;Leitch & Kurt, 1999;Elkoca & Kantar, 2006) and require studies under diverse environmental conditions. Data on the use of PBZ for reduction of plant height in sunflower under field conditions are limited.…”

Physiological Constraints and Their Genetic Manipulation

“…Improvement in yield might therefore be achieved through selection of an inflorescence structure permitting greater light penetration of the pod canopy. B. napus inflorescences can be markedly modified by various growth regulators such as paclo-butrazol (Scarisbrick et al 1985) and 14 Clabelled assimilate distribution and utilization has been monitored in treated and untreated plants of a B. napus winter cultivar (Addo-Quaye et al 1985). Increased amounts of 14 C0 2 assimilation by leaves and reproductive parts of treated plants may have been achieved as a result of improved light interception by a more efficient crop canopy.…”

“…Can J Plant Sci 63: 377-384 Adams MW ( 1967) Basis of yield component compensation in crop plants with special reference to the field bean, Phaseolus vulgaris. Crop Sci 7: 505-510 Addo-Quaye AA, Daniels RW, Scarisbrick DH (1985) The influence of paclobutrazol on the distribution and utilization of 14 C-Iabelled assimilate fixed at anthesis in oilseed rape (Brassica napus L.). J Agric Sci Camb 105: 365-373…”