CORESTA Congress, Shanghai, 2008, APPOST 07

Effect of plant growth regulators on maturation, harvesting, yield and quality of Oriental (sun-cured) tobacco

Aristotle University of Thessaloniki, Greece.
Maturation and senescence in tobacco leaves can be accelerated or retarded by applied chemicals and plant growth regulators. Until now, research was focused only on the "yellowing" effect of ethylene on tobacco types other than Oriental. This work was conducted in order to evaluate the effects of ethephon, jasmonic acid (JA) (senescence-enhancing agents), aminooxyacetic acid (AOA), aminoethoxyvinylglycine (AVG) and benzyladenine (BA) (senescence-inhibiting agents), on maturation, number of primings, yield, quality and chemical characteristics of Oriental tobacco (Basma type, cv. BZ7) in a two-year (2001 and 2002) field experiment. The above chemicals - growth regulators were applied by a single spray on the whole tobacco plants after the strip off of the lowest and pale ground leaves (prior to the harvest of the first priming). An additional treatment with ethephon application after the harvest of the first priming was also studied. Each of the six treatments was replicated three times, in a randomized complete blocks design (RCB).The ethephon, foliarly applied, promoted the maturation of the 7-9 lower leaves of plant and forced their harvest within 1-3 days after the application. Moreover, ethephon reduced the number of primings. The effect of ethephon on yield, quality and leaf chemical composition depended not only on the weather conditions, but also on the time of application and the stage of plant growth. The early application of ethephon (prior to the harvest of the first priming), showed more harmful and detrimental effects on yield and quality in comparison with the late application. Yield, quality index and chemical composition of cured product were not affected by the late application of ethephon (after the harvest of the first priming). The JA application promoted the maturation and the time of harvest of the 5-7 lower leaves, reduced the number of primings and did not affect the yield, quality and chemical composition. The AVG and BA delayed the ripeness and harvest of the 5-7 and 7-9 lower leaves, respectively, reduced the number of primings but the yield was not affected. In both years the effect of AOA was not significant.