对腰果叶面喷施尿素的叶龄、浓度和吸收时间的研究

<正> 腰果的叶面施肥效果,包括叶龄、施用浓度和施用时间等因素,对此进行研究:当新叶刚萌发时,选择生势和树冠均一致的8株树,在萌发后一周对2株树进行处理;叶龄2周时,对选出的另2株树进行了相同的处理。随后在叶龄3周和4周时分别进行相同的处理。取叶片样品分析,发现叶龄和尿素浓度的差异极显著,吸收时间则不重要。根据这项研究,可以认为,在腰果叶龄为3周时喷施4％的尿素有好的效果。     

辐射松的隐座霉疫病

世界上人口不断增长,对植物资源,包括木材的需要不断增加,在满足人类木材要求方面,辐射松(Pinus radiata D.Don)起着重要的作用。辐射松每年每公顷生长量可高达24立方米,而且造林容易,成本低廉,是一个优良的造林树种。辐射松在原产地仅分布于加利福利亚滨海以及瓜德罗普沿岸岛屿大约4000余公顷的地区,而且形状和大小也并不出众。但在十九世纪后期引种到许多其它国家后,其生长一般比原产地好,智利、新西兰、澳大利亚和东非等国家和地区都采用它作为营造大面积商品林的树种。迄今为止,辐射松栽植最广的地区是智利和新西兰,这两个国家都有25万公顷以上的辐射松林,生产木材和发展造纸业。澳大利亚也有10万公顷以上的辐射松林,大部分     

森林立地潜力中的生物气候因子

在阿巴拉契亚和澳大利亚流域对干燥度口(即每年净辐射总量与年降雨量的潜热总量之比率)辐射指数的分配其与森林地上部分生物量之间的关系进行了比较与研究。对应坡向的干燥度β与生物量分配格局在两个流域都是相似的(如北半球的西南坡向与南半球的西北坡向相对应)。小气候日程对相应坡向的生物生产力的影响有其相似性。对于阿巴拉契亚流域,干燥度β平均值0.75相应是适宜的生长条件。对于澳大利亚流域,β平均值1.75相应为生长的限制条件。     

Photosynthetic responses to needle water potentials in Scots pine after a four-year exposure to elevated CO(2) and temperature

Effects of needle water potential (Psi(l)) on gas exchange of Scots pine (Pinus sylvestris L.) grown for 4 years in open-top chambers with elevated temperature (ET), elevated CO(2) (EC) or a combination of elevated temperature and CO(2) (EC + ET) were examined at a high photon flux density (PPFD), saturated leaf to air water vapor pressure deficit (VPD) and optimal temperature (T). We used the Farquhar model of photosynthesis to estimate the separate effects of Psi(l) and the treatments on maximum carboxylation efficiency (V(c,max)), ribulose-1,5-bisphosphate regeneration capacity (J), rate of respiration in the light (R(d)), intercellular partial pressure of CO(2) (C(i)) and stomatal conductance (G(s)). Depression of CO(2) assimilation rate at low Psi(l) was the result of both stomatal and non-stomatal limitations on photosynthetic processes; however, stomatal limitations dominated during short-term water stress (Psi(l) < -1.2 MPa), whereas non-stomatal limitations dominated during severe water stress. Among the nonstomatal components, the decrease in J contributed more to the decline in photosynthesis than the decrease in V(c,max). Long-term elevation of CO(2) and temperature led to differences in the maximum values of the parameters, the threshold values of Psi(l) and the sensitivity of the parameters to decreasing Psi(l). The CO(2) treatment decreased the maximum values of V(c,max), J and R(d) but significantly increased the sensitivity of V(c,max), J and R(d) to decreasing Psi(l) (P < 0.05). The effects of the ET and EC + ET treatments on V(c,max), J and R(d) were opposite to the effects of the EC treatment on these parameters. The values of G(s), which were measured simultaneously with maximum net rate of assimilation (A(max)), declined in a curvilinear fashion as Psi(l) decreased. Both the EC + ET and ET treatments significantly decreased the sensitivity of G(s) to decreasing Psi(l). We conclude that, in the future, acclimation to increased atmospheric CO(2) and temperature could increase the tolerance of Scots pine to water stress.     

Antimicrobial flavonoids from the stem bark of Erythrina burttii

The chloroform extract of the stem bark of Erythrina burttii showed antifungal and antibacterial activities using the disk diffusion method. Flavonoids were identified as the active principles. Activities were observed against fungi and Gram(+) bacteria, but the Gram(-) bacteria Escherichia coli was resistant.     

Effects of temperature and nutrient availability on plasma membrane lipid composition in Scots pine roots during growth initiation

We studied the effects of root zone temperature (RZT) and nutrient availability on free sterols and phospholipids in the plasma membrane (PM) and on PM-ATPase activity in roots of 1-year-old Scots pine (Pinus sylvestris L.) seedlings during growth initiation in the spring. Seedlings were grown for 6 weeks in hydroponic cultures with low (0.5 mM N; LN) or high (3 mM N; HN) nutrient availability. The root zone was subjected to slow warming (SW) and fast warming (FW) treatments while maintaining similar air temperatures in both treatments. Decreases in the amount of phospholipids and in the phospholipid/free sterol ratio, an increase in the degree of saturation of phospholipid fatty acids and changes in free sterol composition were observed during root growth initiation. Changes in lipid composition of the PM associated with the cold deacclimation process were detected at RZTs above 9 degrees C. Nutrient availability affected the lipid composition of the PM only when RZT was increased slowly. When RZT increased from 4 to 6 degrees C in the SW treatment, the degree of saturation of phospholipid fatty acids decreased, especially in HN seedlings. The sitosterol/stigmasterol ratio remained higher in HN seedlings than in LN seedlings. After an RZT of 9 degrees C had been reached in the SW treatment, HN caused increases in the saturation of phospholipid fatty acids and root PM-ATPase activity, and a decrease in the phospholipid/free sterol ratio. Possible effects of changes in PM lipid composition on root growth and PM-ATPase activity are discussed.     

Essential oil composition and antioxidant activity of endemic Ziziphora taurica subsp. cleonioides

The essential oil of Turkish endemic Ziziphora taurica subsp. cleonioides aerial parts was found to contain (+)-pulegone (81.86%), limonene (4.48%) and piperitenone (2.30%) activity. The essential oil showed relevant antioxidant activity.     

Daily time course of whole-shoot gas exchange rates in two drought-exposed Mediterranean shrubs

Effects of drought on water relations, whole-shoot gas-exchange characteristics, and pigment and zeatin concentrations were investigated in the Mediterranean shrubs rosemary (Rosmarinus officinalis L.) and lavender (Lavandula stoechas L.). Two-year-old, greenhouse-grown plants were placed in a whole-shoot gas-exchange measurement system and subjected to 10 days of drought, resulting in severe water stress, and then re-watered for 5 days in order to study their recovery. Water stress resulted in a significant decline in maximum whole-shoot net CO2 assimilation rates (An) for both species that was associated with reductions in leaf area and stomatal conductance. Because shoot dark respiration rate (Rd) was less sensitive to water stress than An, shoot Rd/An ratio increased from about 15 to 95% during water stress. No major changes in chlorophyll and carotenoid concentrations of rosemary leaves were observed during the experiments, but chlorophyll and carotenoid concentrations fell significantly in water-stressed lavender leaves. Zeatin concentrations were higher in rosemary leaves than in lavender leaves during water stress. After re-watering, whole-shoot An and Rd rapidly recovered to their pre-drought rates.     

Hydraulic architecture and water relations of a flood-tolerant tropical tree, Annona glabra

Hydraulic architecture parameters, water relation parameters and wood anatomy were studied in roots and shoots of the flood-tolerant tree Annona glabra L. on Barro Colorado Island, Panama. Hydraulic conductivity, leaf specific conductivity, and Huber value were similar to the corresponding values for tree species living in non-flooded habitats. The vulnerability of stems to loss of hydraulic conductivity resulting from embolism was low (50% loss of conductivity at -3.3 MPa). The lowest leaf water potential measured in the field was about -1.0 MPa, indicating that A. glabra has a large margin of safety from embolism, which may provide protection against rare drought events, or may be an adaptation to brackish mangrove habitats. Low absolute conductivity of roots was compensated for by an increase in the number of roots. More than two-thirds of whole-plant resistance to water flow was located in the roots.     

Antidiarrhoeal activity of the bark extract of Careya arborea Roxb

The methanol extract of the Careya arborea Roxb. bark significantly reduced castor oil-induced diarrhoea in mice. This effect supports the local traditional use of the plant against diarrhoea.