Study On The Histology And Immunity Histochemistry During The Rhizogenesis Of Walnut

Juglans is difficult to induce to produce adventitious root, therefore there are somedifficult for asexuality multiplication of elite cultivars. After successfully inducing adventitiousroot of in vitro walnut, researches centering on the regulation mechanism of adventitious rootwas carried out. The main results about the histology, hormonal regulation andimmunohistochemistry are the below.1,The in vitro stems of 'Xinzaofeng', a walnut variety was induced by two-stage rootingprotocol to root, and the development of the adventitious roots of their in vitro seedling wasanatomically examined. The results showed that:(1)No dormant root primordial was founded in the in vitro tender stems of walnut.(2)The primordial of the adventitious roots originated in the cambium, especially thecambium part over against the pithy rays, thus then they were induced root primordial andoccurred in mono-sites.(3)The lateral roots of the adventitious roots originated in the pericycle cells.(4)The development of the adventitious roots of the in vitro stems could be divided intofour stages:①the cambium cells divided;②the cells from the division transformed intocambium cell groups (root initials);③the cambium cell groups developed into visible rootprimordial;④the root-tip shape formed by the continuous division of the cells in the rootprimordial, and vascular bundles developed inside the root tips, which grew outward,penetrated through the cortex and broke through the stem epidermis.(5)The structure of the adventitious roots induced under the conditions of tissue culturewas a typical primary structure and the secondary structure appeared for the first time 68 daysafter their transplanting.(6)Whether the in vitro seedlings grew root hairs or not depended on chemical andphysical properties of the substrates, i.e. ecological conditions could decided the occurrenceand shape of a tissue.2,The walnut cotyledons of "Jinlongyihao" (Julanas regia L) was induced to root on the 1/4 DKW medium. The histological and morphological characters during the rhizogenesisof walnut cotyledon were investigated. The results are below.The top, middle and basal section of the cotyledon can all root on the medium suppliedwith IBA, and they cannot root after treated with 6—BA. This confirmed that exogenous auxincan induce and promote adventitious roots again, and 6-BA inhibits the occurrence of theadventitious. Cotyledon produce meristem, which is the district of root morphologicaloccurrence, around the vascular bundle and on the brink of cotyledon after treated with IBA,and no meristem appear after treated with 6-BA. In conclusion, the development of theadventitious roots of the cotyledon could be divided into three stages, forming meristem,forming root primordial, appearing adventitious root.3,The walnut cotyledons of "Jinlongyihao" (Julanas regia L) was induced to root on the1/4 DKW medium. The distribution of IAA during the rhizogenesis of walnut cotyledon wasinvestigated. The result is below.The IAA was distributed in the all walnut cotyledon, but mainly in immature reticularvascular tissue. After the vascular bundle mature, the IAA was mainly distributed in themeristem around the vascular. And the signal of IAA in the top section of the cotyledon is moststrong, and the signal gradually decreased from the top section to the basal section.The movement trace of IAA during the rhizogenesis of walnut cotyledon is below:immature vascular tissue→the annular meristem around the mature vascular tissue→rootprimordial→pericycle→growth point of root tip.