| The present study investigated the effect of the following four factors on the rooting propensity of stem cuttings in T. mongolica set under mist: (1) cutting length and ages, (2) cutting positions, (3) leaf retention, and (4) different auxin treatment. The study was undertaken with the objective of revealing the mechanism of adventitious root formation T. mongolica stem cuttings by means of examining changes in content of nutrients, plant endogenous hormone and enzymes activity during rooting phase.1. The finding of this investigation suggested that cutting length and ages, cutting positions, leaf retention, and different auxin treatment significantly affected hardwood rooting in Tetraena mongolica. The rooting ratio of two- or three-year old cuttings was larger than more than for four-year old cuttings. The rooting ratio of the cuttings obtained from the distal portions of shoots was significantly larger than those obtained from the middle and the basal portions of the same shoots. Leaf retention played an important role in rooting characteristics of cuttings in T. mongolica, and the rooting rate of cuttings became greater as the leaf retention increased. The effect of external hormone treatment on rooting was obvious; the rooting ratio of cuttings was increased, especially when treated by 600?1000ppm NAA or 600?800ppm IAA, in which case, the rooting ratio reached 100 percent.Cutting length and leaf retention also significantly affected softwood rooting in T. mongolica. The maximum rooting ratio was observed in cuttings that were 15 cm long. Leaf retention also played an important role in rooting in T. mongolica softwood cuttings, and the rooting rate of cuttings became greater as the leaf retention increased. Softwood cuttings rooted more easily than hardwood cuttings, and external auxin treatment had limited role in increasing root ratio of cuttings but it can obviously increase the mean number of adventitious roots.2. The morphological variables associated with rooting revealed that there were about three main processes consisted of callus formation, callus accumulation at the base of cuttings, and root emergence. It was noticed that T. mongolica was a faster rooting species (100 percent after 16 days) when compared to many other species.3. Considerable metabolic activity occurs as new root tissues appeared and the roots grow through and out of the surrounding stem tissues. SOD, POD and IAAO activity changes obviously during rooting phase. Hormone treatment significantly increased SOD and POD activity during adventitious root formation and is conducive to the initiation and development of adventitious roots.4. It's a process that need consuming energy during adventitious rooting, in which, the content of total soluble sugar and starch significantly decreased and the content of protein increased significantly during rooting phase in the rooting zone of Tetraena mongolica stem cuttings. The content of total soluble sugar and protein were increased and by auxin treatment, and the use of starch was promoted through hydrolysis.5. The level of the IAA in cuttings presents rose at first, then decreased to rising trend during adventitious rooting in general. IAA accumulated to rooting cuttings base induced the differentiation of adventitious roots. Exogenous hormones treatment improves the IAA level, promote the IAA to accumulate at the base of the cuttings,and induce differentiation of adventitious roots. The ABA levels decreased sharply in rooting process, and were reduced by exogenous hormones to a certain extent. ZR and GA3 level at the base of the cuttings firstly decreases, then increases in cutting rooting process, and exogenous hormones treatment did not affect significantly the ZR and GA3 level. IAA, ABA, ZR, and GA3 and other plant endogenous hormonbes collaboratively participated in the occurrence of adventitious roots. |
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