| Directed against the question of rooting difficulty and strain mixing etc on breeding and propagation, breeding of easy rooting triploid, characters and cutting propagation of the triploids Section Leuce were studied. The research results were as follows: 1) The Section Leuce hybrid 989 clone, bred through P. alba×P. tomentosa crossing, appeared the obvious superiority in growth, resistance to adversity and rooting character at seedling stage. It's seedling height and breast diameter exceeded P.tomentosa 34.02%and 19.94% respectively under the same condition, and it was not obvious difference with triploid P. tomentosa. The cell plasma membrane was damaged little under high temperature, drought or low temperature condition. It was better than P. tomentosa and the triploid, and had no obvious difference with it's parent P. alba at the character of root primordia, primary root number and induced root number. The giant quality of 989 was very obvious through morphology and microscope observation. The chromosome of 989 was more than 50. 989 was a potential triploid. 2) Based on detailed observation and measurement of the morphology organ of every clone, the 6 triploid clones were divided into two groups ——leaf-crack type and leaf-round type, the former's leaf was bigger, and its leaf shape was irregular and had 3-5 cracks, and it had more lateral branches. The later,'s leaf was smaller, and leaf shape was regular and had no cracks, and it had less lateral branches. According to the typical characteristic of every clone, we named them as palm-leaf triploid P.tomentosa(S1), vertical-verve triploid P.tomentosa (S2), more-down triploid P.tomentosa(S3), triangle-leaf P.tomentosa(S4), brown-stem triploid P.tomentosa(S5), and wrinkle-leaf triploid P.tomentosa (S6), whose characteristic were obvious and easy to be recognized. 3) The 6 triploidS P. tomentosa had obvious difference in growth and resistance. Totally, the type of leaf-crack is better than that of leaf-round. The growth increment of S1, S2, S3and S4 were bigger than that of S5 and S6. The drought-resistance abilities of 6 clones from high to low were S3>S2>S1>P.tomentosa>S6>S5, the cold-resistance abilities order was S2>S2>S3>S4>S5> P.tomentosa >S6. The standardized index average of each resistance indexes of clones showed that S1, S2 and S3 belonged to same type on drought resistance, S5 and S6 belonged to same type, and on cold resistance S1 and S2 belonged to same type, and S3, S4 and S5 belonged to same type. 4) The rooting ability of triploid P.tomentosa was affected extremely by variety, cutting's position and artificial factors. There was a great difference in rooting rate among 6 triploid clones. The variation range was from 45.9% to 73.1%, and the heritability of rooting characters was more than 0.75. So, selecting easy rooting clone from triploid population may be better. The cuttings at the base of triploid stem had a relative higher rooting ability compared with cuttings at the top, and the survival rate of cuttings at the base was higher 33% than that of the top. Treating cuttings with paraffin wax could increase the survival rate of cuttings and quality of seedlings remarkably. Compared with the contrast, the survival rate, height and breast diameter of seedlings were increased respectively 29.4%, 18.4% and 17.4%. The reason of wax increasing survival rate was that it can promote bark rooting, postpone the time sprouting, the mechanism is developing the cuttings water condition. Auxin can promote bark rooting but had no effect on callus rooting. A small amount of cytokinin added to auxin could result in stimulating the development of the callus and adventitious root formation from callus. Through wax and NAA+BA (2:1) (concentration 250-750ppm) treatment, the survival rate of cutting was increased average 65.4%, and the biggest is up to 82.3%. 5) The variation of the population genetic structure and its effect under the condition of poplar mixed strain cutting propagation were pro... |
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