The effect of nitrogen application on resistance of endemic species Excentrodendron hsienmu under cadmium stress in Karst areas was studied by using pot-culture method.Results indicated that contents of solu-ble sugar,soluble protein and chlorophyll significantly reduced under cadmium stress,which reduced by 19.0%,12.0% and 33.3%,respectively under high cadmium stress(120 mg/kg).The content of MDA,pro-line(Pro)and superoxide dismutase(SOD)activity significantly increased,which increased by 65.3%, 72.9% and 12.1%,respectively under high cadmium stress.Under low cadmium stress(30 mg/kg),com-pared with control group,the chlorophyll content,soluble protein content and SOD activity reached the high-est in the treatment of low nitrogen(0.4 g/kg),which increased by 8.6%,8.8%,4.1%,respectively,and MDA content reached the lowest,which reduced by 19.9%,and all indexes existed significant differences in addition to chlorophyll(P<0.05).The Pro decreased with the increase of nitrogen application,but soluble sugar content increased.Pro reduced by 9.2% and soluble sugar content increased by 51.5% with the high nitro-gen treatment(0.8 g/kg),but there was no significant difference between low nitrogen and high nitrogen.The content of chlorophyll and soluble protein as well as Pro decreased with the increase of nitrogen application un-der high cadmium stress.The content of chlorophyll and soluble protein as well as Pro decreased by 19.3%, 25.0% and 38.2%,respectively with application of high nitrogen treatment.The SOD significantly decreased, while soluble sugar content significantly increased,but MDA had no significant effect with the increase of ni-trogen application.E.hsienmu increased the content of soluble sugar in order to adapt to environment with ni-trogen application under cadmium stress.The adaptation of E.hsienmu promoted under low cadmium stress by adding low nitrogen.It was harmful for E.hsienmu under high cadmium stress by adding nitrogen or under low cadmium stress by adding high nitrogen.

桉树具有用途广泛、速生、耐瘠薄和丰产等多种特性和优势,因此被我国各地区广泛引种种植.然而,随着我国桉树林种植范围和面积不断扩大,林内病虫害发生率和害虫种类也不断增多,其中油桐尺蠖便是对桉树危害最大的害虫之一,油桐尺蠖属于杂食性害虫,每年可繁衍三四代,并对多种林果植物会产生严重的危害,为此有关林业部门需重视油桐尺蠖对桉树危害的影响,并积极探寻有效的防治对策,进而促使桉树林业得到安全、可靠的发展.本文主要简述油桐尺蠖与桉树的概念,分析油桐尺蠖危害对桉树生物量和木材材积的影响,最后探究几点关于桉树油桐尺蠖危害防治对策.

尾巨桉DH32-29无性系是种植面积最大的优良桉树无性系,本文通过对尾巨桉DH32-29无性系林多年的测定,利用Logistic模型对该无性系的树高,胸径和蓄积量进行拟合,确定3个性状的Logistic模型的参数,在此基础上确定速生期,为该无性系制定合理的水肥管理等抚育措施及确定其合理的采伐期提供了理论依据.

WRKY转录因子参与植物生长发育、抗病虫、耐逆境等众多过程,并在其中起重要作用.为了研究WRKY在赤桉中的结构和功能,本研究利用电子克隆的方法克隆了赤桉与AtWRKY50高度同源的一个WRKY基因Ec WRKY50,并利用生物信息学方法对该基因编码蛋白的氨基酸组成,理化性质,亚细胞定位和高级结构等方面进行预测和分析.结果表明,Ec WRKY50基因全长为585 bp,包含一个480 bp的开放阅读框,编码159个氨基酸,该基因蛋白分子量为18.187KD,理论等电点为5.45.该蛋白含有一个WRKYGKK的保守结构域和C2H2结构域,属于GroupⅡc成员,很可能在细胞质中起转录和转录调控的作用;并对该蛋白进行了同源性分析.这些研究为该基因功能的进一步分析奠定了坚实的基础.

By using a chronosequence approach, this paper studied the nutrients accumulation, allocation, and cycling in 7-, 17-, 31-, and 51-year-old Masson pine plantations, aimed to analyze the dynamics of nutrients in Masson pine plantation at its different developmental stages. The results showed that 1) nutrient accumulation was not synchronized with biomass accumulation, with the accumulation rate of biomass being 3.3, 5.4, 3.3, 3.7, and 9.8 times of that of N, P, K, Ca, and Mg from age 17 to 51, respectively, 2) nutrient allocation to a specific component was related to the growth rate of the nutrient pool in the component, and the nutrient allocation to stem as well as the ratio of nutrient allocation to root/shoot increased with plantation age, and 3) the biomass production per unit nutrient, i. e., nutrient use efficiency, and the nutrient cycling coefficient also increased with plantation age, being higher for 51-year-old plantation than for younger plantations, suggesting that shortening the rotation length could reduce the possibility to raise the nutrient use efficiency. It was suggested that both extending the current rotation length to as long as 50 years and reducing the harvest intensity could be helpful to conserve the nutrients and to maintain long-term productivity.