| The diploid Gossypium arboreum L. was used to induce autotetraploid with colchicine technique, and the comparison of morphology and cytology characters between obtained tetraploid and diploid control was studied in this paper. The main results were showed as follows:1. Polyploid inducing conditions:The seedling tip bud of diploid G. arboreum were induced by colchicine solution at different concentration of0.1%,0.2%,0.3%,0.4%respectively under three treatment time of Id,2d and3d. Statistic analysis were also conducted in this study. It showed that the treatment group of0.1%and1d was the best and the mutant rate was up to42.31%2. Comparing with contrast, there were many morphology changes of mutant plant (1)The growth rate of mutated plant in different period were all slower than contrast.(2) The strain height of mutated plant in different period were all lower than contrast.(3)The functional leaf area of mutated plant in different period were all smaller than contrast and its SPAD value also decreased. The mutated leaf thickness decreased by12.45%to84.40±5.18μm compared to96.40±4.04μm of the contrast.(4)The internode length of mutated plant became smaller than contrast. The main stem diameter also changed obviously.(5) The petal area of mutated plant were almost twice of the contrast. The length, area, jaggies number of mutated bract changed by-11.40%,+96.06%,-58.33%respectively. The pistil and stalk length of mutated plant changed by+10.40%and-74.74%. Anther number per flower of the mutated plant decreased. Proportion of cotton ball with two bracts changed from2.74±1.82%of the contrast to86.64±8.19%of the mutated.(6) Single seed weight of each plant changed from0.082±0.008g of the contrast to0.124±0.011g of the mutated, increased by51.22%. Fiber weight of single seed of the mutated decreased by72.22%, and fiber length decreased by25.64%to2.32±0.24cm. Seeds number per boll and boll number each plant of the mutant all decreased.3. There were many cytology differences between mutated plant and contrast:(1) the pollen grains of the control developed uniformly and nearly spherical with the average diameter of83.04±11.16μm. The pollen grains of mutants developed uneven with specially big and extremely small ones. The diameter of specially big pollen grains was200.00μm, and that of extremely small pollens was25.83μm.Its proportion of abnormal pollen grain is4.28%.(2) Compared to the control, the mutant had lower stomatal density, higher length-width ratio, higher approximate area and higher chloroplast number in each stomatal.(3) By chromosome observation of root tip cells, it showed that the chromosome number of mutated plant was2n=4x=52, but the chromosome number of contrast was2n=2x=26. The karyotype formula of contrast and mutated were K=2n=2X=26=18m+6sm(4SAT)+2st(2SAT), K=2n=4X=52=8M(4SAT)+44m(8SAT) and belonged to2B and1B karyotype respectively.(4) The meiosis behavior of the induced tetraploid G.arboreum L. was much more complex than that of the diploid. Especially at diakinesis, some univalent, trivalent and polyvalent were also observed besides divalent and quadrivalent. There were different kinds of polyad in tetraspore period of the mutant. The dissociate chromosomes existed during metaphase Ⅰ and metaphase Ⅱ, the unbalance separation of chromosomes existed during anaphase Ⅰ and anaphase Ⅱ.Conclusion:From this study, we successfully obtained tetraploid of G. arboreum L. by the chromosome comparison between the diploid (2n=2x=26) and the mutant plant (2n=4x=52), the main pattern of two divalents and quadrivalents at diakinesis, and finally separating by two/two style at anaphase Ⅰ and anaphase Ⅱ following with its morphology character. |
PDF Full Text Request