Response of Plant Hormone bioassay to Paclobutrazol

Quantitative estimation of a known or suspected biologically active substance (such as a hormone or drug) by measuring its effect on a living organism in standard conditions is known as bioassay. The interaction of gibberellic acid (GA3) and paclobutrazol (PBZ) in lettuce hypocotyl bioassay and 6-benzyl aminopurine (BAP) and paclobutrazol in radish cotyledon enlargement test that paclobutrazol counteracts gibberellin activity when applied exogenously. The radish cotyledon enlargement at low concentration without counteracting BAP action. The reduction of growth to be counteracting of gibberellin activity by paclobutrazol as well as its cytokinin well activity at lower concentration which indicate concentration of gibberellins activity as evidence by their respective bioassay in the present investigation. Paclobutrazol slightly increased radish cotyledon growth at low concentration (up to 0.01 ppm) and could not counteract the growth caused by 1.0 ppm BAP at its 0.001 to 1.0 ppm concentrations suggesting independent effect of paclobutrazol to that of BAP. Furthermore, the activity of paclobutrazol was tested in corn root curvature test and it was found that PBZ concentrations from 0.001 to 10.0 ppm linearly increased the percentage of corn roots showing more than 90° curvature. Therefore, suggession that PBZ conutracted GA3, induced growih and also as IAA and cytokinin at lower concentration0.001 to 100ppm.

Growth responses of excised radish cotyledons to meta-topolin

Meta-topolin (mT) has been established as an active aromatic cytokinin by Strnad et al. (1997). The present investigation assessed the effects of mT on radish cotyledon growth. The effect of mT on cotyledon growth, chlorophyll, N and soluble protein contents were measured. Peroxidase (POD) activity and polyamine (PA) contents were also determined. Treatment at 0.25, 0.5 and 1.0 mM mT concentrations resulted in 44, 50 and 57% increments in cotyledon growth, respectively, compared with control cotyledons. Increase in chlorophyll content per cotyledon was highest at low mT concentrations. Peroxidase activity was highest at 1.0 mM mT. Soluble protein content was reduced by the application of mT. Key words: Cotyledon growth, meta-topolin, polyamine, peroxidase, radish cotyledons

Effect of Fructose on Growth of Papaw Shoot Explants in vitro

The effects on papaw (Carica papaya L.) shoot growth of the carbohydrates sucrose, fructose, glucose and ribose singly and combined, were compared at a range of concentrations, in both autoclaved and filtered media. Fructose (10 g L-1), when autoclaved together with other media components, consistently promoted growth of shoots from buds on nodal sections or buds excised with a wedge of stem tissue. This enhancement was seen if the fructose was used singly or in combination with 10 g L-1 sucrose. By contrast, autoclaved media containing fructose reduced growth of small axillary bud explants. Decreasing the pH of fructose solution from 5.8 to 4.4 before autoclaving enhanced growth of buds from nodal sections. Other sugars in the D-ketose group inhibited papaw shoot growth totally when autoclaved with other media components. A radish cotyledon bioassay of solutions of fructose autoclaved singly or with NH4NO3 (20 mM) showed no evidence of cytokinin effects.