Abstract
Carry-over effects of paclobutrazol on various vegetative parameters of sweet cherry were studied. Paclobutrazol was applied on the basin of the trees as per trunk diameter during early spring and gibberellic acid was sprayed at full bloom. The treatment application was carried out during the first year only to assess carry-over effect during the next year. Trunk cross-sectional area, tree height and spread, tree volume, number of nodes on a linear shoot, and internode length decreased both in the year of treatment application and during the next year when no treatment was applied. Lowest increment in trunk cross-sectional area (3.37 cm),tree height (0.21 m), tree spread (0.17 m), and tree volume (3.33 m3) during the carry-over year were recorded with the maximum concentration of paclobutrazol (0.3 g/cm). Maximum number of nodes (8.67) and shorter intermodal length (2.33 cm) were observed with 0.2 g/cm TD PBZ treatment, both of which are desirable parameters for better fruit set.
INTRODUCTION
Cherries are one of the glamorous fruits of the temperate region of the world and are divided into two main groups: sweet cherry (Prunus avium L.) and sour cherry (Prunus cerasus L.). The areas having good winter rains and dry cool summers are ideal for its cultivation. Commercial cultivation is mostly confined to Europe, USA, and to a lesser extent, Turkey and Japan. In India, the Jammu and Kashmir areas contribute 95% of the total commercial production. The application of paclobutrazol inhibits terminal growth while enhancing cropping efficiency. Reduced vegetative growth can reduce pruning requirements and improve light penetration in the tree canopy resulting in improvement in fruiting and fruit color. Bearing trees of ‘Bigarreau Noir Gross’ (‘Misri’) cherry were selected during the 2001 and 2002 cropping years to evaluate the carry-over effect of paclobutrazol on the vegetative production of cherry.
MATERIALS AND METHODS
Cherry trees of uniform age and vigor were identified. Twenty-four trees were selected and growth regulators were applied during the first year only. A single tree was allotted to each treatment and each treatment was replicated three times. Paclobutrazol was applied to the basin of the trees as per trunk diameter in early spring and gibberellic acid was applied at full bloom.
The treatment details are as follows:
Trunk cross-sectional area, tree height and spread, tree volume, number of nodes on a linear shoot, and internodal length were measured before flowering and after the growing period. Trunk cross-sectional area of each tree was measured by using the formula: girth = 3.1416 d, cross sectional area = 0.7854 d (CitationWestwood, 1993). Tree height was measured in meters by measuring from the ground to top and spread by measuring the outer periphery from one side to another. Volume of the tree was calculated from height and spread measurements as 4/3 ab and 3/4 ab for a tree that is taller than wide and for a tree that is wider than tall, respectively. The number of nodes was counted and the distance between nodes was measured before flowering on a 20-cm-long shoot.
RESULTS AND DISCUSSION
The yearly increment in trunk cross-sectional area was decreased by all the levels of paclobutrazol. Carry-over effect was less pronounced compared to the first year. The lowest yearly increment of 3.37 cm was noticed at 0.3 g/cm TO PBZ during the second year when The treatment application was not applied (). The application of paclobutrazol resulted in reduced growth attributes, which may be due to systematic inhibition gibberellin effect on growth (CitationKim et al., 1990). The observed response is in conformity with the findings of CitationMarini (1987) who observed that tree trunk cross-sectional area was suppressed by the application of paclobutrazol in the peach. Application of 20 ppm of gibberellic acid resulted in an increase of the tree trunk cross-sectional area. Paclobutrazol application resulted in a significant reduction in the yearly increment of tree height. Increment of tree height of 0.21 m was recorded at 0.3 g/cm TO PBZ as compared to 0.59 m in control in the second year when treatments were not repeated. These findings are in accordance with the findings of CitationGreene (1991) who observed reduction in the length of apple shoots with multiple sprays of paclobutrazol. It is believed that paclobutrazol inhibits gibberellin biosynthesis and it is, therefore, likely that the presence of paclobutrazol in the apical part of the shoot would interfere with the gibberellin system controlling shoot extension growth (CitationRichardson and Quinlan, 1986). Tree height showed a response to gibberellic acid during both the years of application. Increment in tree spread was significantly reduced by the application of paclobutrazol both in the year of application and in the year when treatment was not applied. The least tree spread 0.17 m was recorded with the highest dose of paclobutrazol as compared to 0.61 m in control in the year when treatments were not repeated. The apparent increase in reduction of tree shoot growth in later years may have been due to the residual effect of first year treatments (CitationWebster et al., 1986). Application of gibberellic acid modified the growth decreasing effect of paclobutrazol.
Table 1 Influence of Single Year Consecutive Application of Paclobutrazol and Giberellic Acid and Their Carry-Over Effect during Next Year on Increment in Trunk Cross Sectional Area, Tree Height, Tree Spread, and Tree Volume of Sweet Cherry
Reduction in the yearly increment in tree volume was observed both in the first year of treatment application and in the next year when treatment application was not repeated (). Tree volume was reduced due to the fact that paclobutrazol decreased tree height and shoot number, which ultimately contribute in reduction of volume. This is in conformity with CitationGrochowska and Houdun (1997). The gibberellic acid almost changed the effect of paclobutrazol and increased significantly the yearly increment in tree volume.
The effect of paclobutrazol on the number of nodes per 20 cm linear growth was found to be non-significant during the single year application, but was significant in the second year when treatment application was not repeated (). The number of nodes increased from 7.50 per 20 cm linear growth in control to 8.50 with 0.3 g cm TD PBZ. Internode length decreased significantly with an increase in the dose of paclobutrazol. The lowest internodal distance of 2.38 was observed with 0.3 g cm TD PBZ as compared to 2.68 cm in control in the second year when no treatment was applied. Similar findings were observed in apple by CitationSteffens et al. (1985).
Table 2 Influence of Single Year Consecutive Application of Paclobutrazol and Giberellic Acid and Their Carry-Over Effect during Next Year on Number of Nodes per 20 cm Linear Growth and Internode Length (cm) of Sweet Cherry
It was observed that paclobutrazol reduced trunk cross-sectional area, tree height, spread, volume, and number of nodes in the year of application. But its carry-over effect was much more pronounced when treatment application was not repeated. Application of gibberellic acid modified the paclobutrazol effect.
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