膜下滴灌棉花根系吸水模型研究

通过室内三组桶栽水平试验,在不同生育期对棉花根系进行取样,得到棉花根长密度分布函数,并在每次灌水前后对试验桶进行取土样及称重,进而得到土壤剖面的含水量和棉花的蒸腾量;由根长密度分布函数、土壤含水量及棉花蒸腾量,选定根系吸水模型为Feddes模型,经模型计算:土壤水分的模拟值与实测值吻合较好,该模型能够准确地描述膜下滴灌棉花根系吸水,表明建立的棉花根系吸水模型是可行的。     

镉对两蕹菜品种生长的影响

[目的]探讨镉处理对不同品种蕹菜的影响差异。[方法]测量镉处理后蕹菜品种QLQ和T308株高、根长及叶绿素含量的变化。[结果]与对照相比,镉处理后2个品种株高均在0.05水平显著降低;QLQ根长在0.05水平显著增加,T308根长在0.05水平显著降低;QLQ中的叶绿素a、叶绿素b和总叶绿素含量在0.05水平显著降低,T308中只有叶绿素b含量在0.05水平显著降低。[结论]两蕹菜品种地上部对镉处理的响应相似,而根对镉处理的响应相差较大。     

海南地方猪POU1F1基因多态性与体质量的相关性

采用 PCR–SSCP、PCR–RFLP 技术,对海南五指山猪封闭群及其近交系、海南黑猪2个品系(临高猪、屯昌猪)的 POU1F1基因外显子4、外显子5、外显子6、内含子3的多态性进行研究.结果表明:猪 POU1F1基因外显子5、外显子6不存在多态性,内含子3、外显子4存在2个等位基因和3种基因型;在外显子4基因座上,五指山猪、临高猪、屯昌猪呈 Hardy–Weinberg 平衡状态,五指山猪近交系呈不平衡状态,4个猪种群的遗传多态性均处于中度多态(0.250.5);利用 SPSS 软件分析五指山猪 POUIF1基因内含子3和外显子4基因的多态性与其3个生长阶段体质量的相关性,发现引物 P1与 P4不同基因型个体体质量的差异均不显著     

Causal relationship between juvenile shoot growth characters in picea abies

The causal relationships between shoot growth variables were analysed on the basis of a study in the Phytotron where six full‐sib families of Picea abies L. (Karst.) were grown for six growth periods. Phenotypic correlations and path analysis were used for the analysis of causes. The phenotypic correlations were estimated in three different ways: 1) separate analyses within each growth period based on individual tree data, 2) based on family means at different growth periods (0, and 3) using differences in family means between two consecutive growth periods (dt). The two methods based on t or dt‐values gave different results in a number of cases. We argue that, because of the rapid concurrent changes that occurred between growth periods, we could not conclude that the correlations based on family means (t) reflected causal relations and, also, that the method based on dt‐values gives a better indication of causal relationships between different variables. Using dt‐values, the variation in shoot elongation period was mainly explained by the variation in free growth (82%) while the variation in shoot growth initiation only explained a minor fraction. Variation in leader length was mainly explained by growth rate and only to a minor extent by shoot elongation period, meaning that the observed decrease in shoot elongation period did not cause a corresponding changé in leader length. One conclusion from this finding is that we do not necessarily lose growth capacity if we breed for a better adapted growth rhythm (i.e. shorter shoot elongation period) of the seedlings.     

The effect of release cutting on the growth and external quality of the dominant trees in a Pinus sylvestris stand established by spot sowing

The effect of the number of Pinus sylvestris trees in seed spots on the growth and external quality of the dominant trees was studied. The trees were monitored during the period between release cutting and the first commercial thinning. The treatments were one, two and four of the tallest seedlings retained per seed spot, and a control. The mean height of the dominant trees was highest in the one‐tree and two‐tree treatments. Diameter at breast height (DBH) increased with increasing spacing. On average, the stump diameter was 1.5–4.7 cm greater in the one‐tree treatment than in the control. Slenderness (height/DBH) was highest in the control treatments. The average living crown limit of the dominant trees was 4.6 m, and was at its highest in the two‐tree treatment. The results indicate that the competition in seed spots decreases the height growth of the dominant trees.     

Vegetative propagation of Dalbergia sissoo: effect of growth regulators, length, position of shoot and type of cuttings on rooting potential in stem cuttings

The effect of auxins (IAA or IBA at 100,200,500 mg L 1) on rooting and sprouting parameters differed significantly (p < 0.05).Rooting and sprouting percentages were higher in some treatments while other parameters were significantly higher in other treatments.The results of the present study revealed that rooting was significantly (p < 0.05) affected by the length of cuttings,as well as the position of shoots and type of cuttings.On average,86.0 per cent rooting was observed in the 30-cm long cuttings compared to the other two lengths of cuttings,i.e.,20 and 25 cm,irrespective of any auxin treatment.In a control set,without any auxin treatment,a maximum of 60.0% rooting was recorded in the 30-cm long cuttings and a minimum of 40.0% of the cuttings rooted in the 20-cm long cuttings.Similarly,cuttings collected from the lower and upper portions of shoots resulted in 72.5 and 52.5 per cent rooting respectively,irrespective of auxin treatments.Maximum rooting was observed in the lower portion (40.0%) of cutting compared to the upper portion (30.0%) in the control set without auxin treatment.Leafless branches produced maximum (72.0%) rooting compared to the leafy cuttings (35.0%),irrespective of the auxin treatment.The leafy cuttings produces a minimum of 15.0% sprouting and rooting in the control set.     

仙湖肉鸭A系皮脂率与体重、体尺的相关及通径分析

本研究对仙湖肉鸭(A系)7周龄的皮脂率、体重、体尺指标等8个性状进行了相关分析和通径分析。结果表明:仙湖肉鸭公鸭的体斜长、胸宽、胫长与皮脂率均呈中等正相关,且相关关系显著(0.01相似文献   

旋切单板的长度计算

提出了两种精确计算旋切单板长度的数学方法：①分析刀具在原木上的旋切曲线,通过对旋切曲线的积分计算单板长度;②计算原木段端面的单板面积,通过面积计算单板长度。借助Microsoft Mathematics软件对两种算法进行对比分析,结果表明给出的算法准确可靠,可供实际生产和相关科研参考。