Effects of Different Colchicine Concentrations on Latex Amount and Changes in Certain Stomata Characteristics of Hevea brasiliensis Muell. Arg. Seedlings In Vivo

Abstract

The effect of colchicine upon certain morphological characteristics of rubber tree (Hevea brasiliensis) seedlings aged 13 mth was studied. Different concentrations of 0.01, 0.02, 0.04, 0.06, 0.08, 0.1, 0.3 and 0.5% colchicine together with 1% volume by volume dimethyl sulfoxide (DMSO) were applied once with different application times of 6, 12 and 24 hr. This arrangement was chosen to ascertain the optimal concentration and application time for the induction of polyploid seedlings. The results for the rubber tree seedlings at age 17 mth showed a significant increase in latex amount at concentrations of 0.01 and 0.5% of the mixture. In particular, the concentration of 0.01% was superior to those of the control groups without any change in the latex quality. At colchicine concentrations of 0.01 and 0.08%, the stem diameter difference 5 cm above and below the chemical-treated area was significantly larger than the control. The largest increase was at the concentration of 0.01% which was correlated with the observed latex amount. In all treatments, the number of stomata in the treated plants was significantly greater than those of the control, especially at the concentration of 0.01%, at which the highest number was recorded. The stomatal length was significantly smaller than the control in most treatments including the 0.01% concentration; furthermore, the width of stomata was less, although the difference was not significant and the length-width ratio of the stomata at 0.01% had nearly the same value as the control group. Flow cytometric determination of the DNA content of the control and the treated rubber seedlings was carried out. The results showed the control seedlings were all diploid with 2 n. Of the treated seedlings, the concentrations of 0.01, 0.04 and 0.5% colchicine gave a similar pattern of aneuploid cells, but also haploid plants appeared at concentrations of 0.08 and 0.3%.