Study On The Phosphorus Efficiency Physiological Mechanisms Of Brassica Napus Root Mutants

Oilseed rape (Brassica napus L.) is one of the most important oil crops in China and showed sensitive to phosphorous (P) deficiency. It required more P, but the Olsen-P content in the soil in the major production land is very low. Therefore, it is very important to explore the P efficiency mechanism to improve the breeding of P-efficient Cultivars. Crop P efficiency, including P acquisition efficiency and utilization efficiency, is defined as the ability to produce more biomass or higher grain (seed, et al) yield under certain condition with low or high available P. Two Brassica napus root mutants insensitive to exogenous cytokinin, Irnl (a mutant with more lateral roots) and prll (a mutant with an elongated primary root), were identified and they could produce more shoot dry weight and root dry weight than wild type at both low and normal P and showed P efficiency (Shi TX et al.,2012).In this study, firstly, the phenotype of Irnl and prll were identified; secondly, difference in microanatomical character of the root of both mutants at6-BA were observed; thirdly, some aspects of achieving P of the mutants were further studied. The main results are as follow:1The phenotype of Irnl and prll is stability. At DAG9, there was no significant difference in primary root length among plants of M4, M5, M6generation of prll at6-BA, and the primary root length of all the three generations of prll was longer than that of the WT. There was no significant difference in lateral root number and lateral root density among plants of M4, M5, M6generation of Irn1at6-BA, and the lateral root number and lateral root density all the three generations of lrnl is more than that of the WT.2Significant differences in the root microanatomical character were observedamong Irnl, prll and wild type. At DAG3, the root hair length and root hair density of two mutans and WT at0.2μM6-BA were longer (more) than that of them at ddH20. The root hair length and root hair density of Irn1and prll were lower than that of WT at0.2uM6-BA. At DAG6, the meristem area of of two mutans and WT at0.2μM6-BA were larger than that of them at ddH20. At DAG6, the meristem area of WT was smaller than that of Lrn1and prl1at0.2μM6-BA. Moreover, the structure disorder of xylem bundle and the plerome of WT were observed.3P efficiency physiological mechanisms of Irn1and prll. Root tips, total root length, total root surface area, total root volume of lrnl, and only root tips and total root length of prll were more than that of the WT at LP. The root-secreted total acid exudation, H+and acid phosphatases of Irnl were significantly more than that of WT at LP. The root-secreted rate of total acid exudation and H+of prll were higher than that of WT at LP. Irnl could have a big root system and produce more root exudates at LP. prll has the ability to produce H+and total acid very quickly at LP. There existed significant differences in the response to6-BA and low P between lrnl and prll.