Phenotyping vigour control capacity of new peach rootstocks by xylem vessel analysis

In peach, xylem anatomical characteristics have been shown to be related to vigour of selected rootstocks. The goal of this research was to determine if xylem characteristics of a new set of rootstocks that exhibit a range of size-controlling potential and have a different genetic background from previously examined material would also exhibit similar differences in xylem characteristics. If so, then anatomical analysis of xylem may be a useful means of predicting the vigour control capacity of selected peach rootstock genotypes. Samples of xylem tissue were taken from roots, trunks and shoots of four new rootstocks that were derived from a genetic cross between ‘Harrow Blood’ and ‘Okinawa’ peaches and compared with tissue from ‘Nemaguard’, a vigorous control. Xylem samples were sectioned and analysed by optical microscope. The number and dimensions of vessels in recently developed xylem of each rootstock were measured and compared. The more dwarfing rootstocks had fewer large vessels and more small vessels than the more vigorous rootstocks. Weighted mean vessel diameter (Wm) and calculated hydraulic conductance (K_h) differed among rootstocks: more vigorous rootstocks had higher K_h and Wm than dwarfing rootstocks. Rootstock xylem vessel dimensions varied in relation to the vigour they imparted to a common scion cultivar (‘O’Henry’). After the ‘Nemaguard’ control, ‘HBOK 50’ was the most vigorous rootstock followed by ‘HBOK 10’, ‘HBOK 32’ and ‘HBOK 27’, respectively. Thus, as was seen in previous research with a separate set of rootstocks, the vigour-control capacity of this new series of peach rootstocks was strongly related to their xylem hydraulic characteristics and it appears likely that it would be possible to use xylem anatomical characteristics of shoots or roots of young trees to pre-select for size-controlling potential in a rootstock development program.     

木质部汁液pH调控蒸腾速率的信号作用

采用压力室加压收集番茄木质部汁液,并测定和调节木质部汁液pH及叶片蒸腾速率变化的结果显示,对比原汁液,用KOH溶液调高pH(0.6~1.4)的蒸腾速率平均降幅大于14%;用盐酸调低pH(0.6~1.0)的蒸腾速率平均下降7%以上;用柠檬酸溶液调低pH(0.7~1.2)的蒸腾速率基本不变;用KOH溶液调高pH且加盐酸使pH复原后的蒸腾速率未见恢复。这表明汁液pH升高抑制蒸腾的效果可能被伴随的离子浓度变化对蒸腾的效果所抵消。     

不同栽培袋材料对袋培黄瓜生长、产量及品 质的影响

以黄瓜品种津优30 为试材,以玉米秸秆∶牛粪∶炉渣=3V∶1V∶1V 为栽培基质,分别采用
底部（透水、不透水）编织袋、无纺布和双色膜为4 种栽培袋材料,进行日光温室黄瓜营养基质袋式栽培
试验,研究了不同栽培袋材料对黄瓜植株生长、伤流液、产量和品质的影响。结果表明：采用底部不透水
编织袋为栽培袋材料时,定值后40 d 及55 d 黄瓜的株高显著高于其他3 个处理,并且其植株地上部鲜质量、
地下部干质量、黄瓜伤流液中养分含量也显著高于其他3 个处理,果实可溶性蛋白、VC 含量都高于其他
处理。因此,底部不透水编织袋是适宜黄瓜袋培的栽培袋材料。     

Endogenous cytokinin levels of table grape vines during spring budburst as influenced by hydrogen cyanamide application and pruning

Cytokinins play an important role in budburst, flowering and fruit set in table grapes. Rest-breaking treatments with hydrogen cyanamide and pruning practices modify budburst and reproductive development in table grapes, especially in regions with low and often inadequate winter chilling. The effect of these treatments on the xylem sap and bud Zeatin riboside (ZR) content was determined during late winter and budburst in ‘Sultanina’, ‘Sunred Seedless’, and ‘Alphonse Lavalleé’ canes in a total of nine trials conducted between 1997 and 2001. Bud ZR levels of hydrogen cyanamide treated ‘Sultanina’ canes showed an earlier and increased cytokinin peak, in particular in the distal buds. Large ZR peaks before budburst and noticeable differences between distal and proximal buds were absent on non-sprayed canes. The xylary ZR content of long pruned ‘Sultanina’, ‘Sunred Seedless’, and ‘Alphonse Lavaleé’ canes showed a significantly higher and earlier cytokinin peak than in short pruned spurs. By contrast, the bud ZR content tended to be higher in spurs than canes. Pruning and rest-breaking treatments enhanced budburst and increased endogenous cytokinins in these experiments. Long pruning in ‘Sultanina’ and ‘Sunred Seedless’ (both parthenocarpic) is necessary for acceptable fruit set and yields. Possibly, in longer canes more cytokinin is available for reproductive development. ‘Alphonse Lavaleé’ (seeded) is sufficiently fruitful and produces adequate yields following spur pruning.     

Experimental reports on using "Penzhangjing" for Larix loptolepis

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Experimental reports on using “Penzhangjing” forLarix loptolepis

Experiments on spaying Penzhangjing on seedlings ofLarix leptolepis was conducted for a year. The height growth and diameter at foot of experimental seedlings increased by 34.3% and 35.5%, respectively, compared with control seedlings. Variance analysis concludes that Penzhangjing have obvious effect on growth of height and diameter at foot of seedlings. (Responsible Editor: Chai Ruihai)     

Manipulating phenology and water relations in <Emphasis Type="Italic">Senna spectabilis</Emphasis> in a water limited environment in Kenya

The effect of shoot pruning on leaf phenology, stem wood anatomy and sap flow was investigated on Senna spectabilis (DC.) Irwin and Barneby in Machakos, Kenya. Unpruned trees (single stem) were compared to hedges (two to four stems), pruned 4 times a year during two rainy seasons (April–June, 1997 and November, 1997–January, 1998) separated by a dry season (July–October 1997). Trees attained peak leaf area of 55 m² plant⁻¹ during the rainy seasons, and shed all their leaves naturally during the dry season. Maximum hedge leaf area was 4 m² plant⁻¹ between pruning events and 5.2 m² plant⁻¹ during the dry season. Pruning induced multiple stems and narrow xylem vessels with low hydraulic conductivity. Average cross sectional area of conducting wood per plant was at least 1.8 times greater in trees than in hedges. Xylem lumen diameter at 5 mm depth below the cambium was significantly (P < 0.001) larger in trees (53.6 ± 6.21 μm) than that in hedges (36.2 ± 8.21 μm). Maximum sap flow occurred in the wet season for trees (4800 g d⁻¹ plant⁻¹) and in the dry season for hedges (1400 g d⁻¹ plant⁻¹). Wet season pruning suppressed crown expansion and modified the natural phenology of senna, reducing transpiration rate and therefore soil water depletion, causing crowns to grow. This enhanced the ecological combining ability of senna managed as hedges with annual crops.     

Decay development in living sapwood of coniferous and deciduous trees inoculated with six wood decay fungi

Development of decay and/or discoloration was assessed in the functional sapwood of one coniferous and three deciduous trees after wounding and artificial inoculation with six wood decay fungi. Living stems of mature Douglas fir, beech, oak, and sycamore trees were wounded in spring 2002 and immediately inoculated with brown, white, and soft rot fungi. Extent of discoloration and decay, wood weight loss, and total phenols in the reaction zone (zone of active response at a dynamic interface between living sapwood and wood colonized by decay fungi) were assessed 16 and 28 months after inoculation.     

内聚力学说不可能成立的依据

利用压力室技术测到的水势是缺乏修正的数值,比实际水势要高出许多,用该方法测定水势,只能反映出水势的大小变化,而不能用其代表木质部内真实的负压。蒸腾使木质部产生的负压最大不会超过-0．1Mpa,木质部内巨大负压的存在缺乏理论依据和直接的实验证据。空穴的必然发生使水柱无法保持连续,故连续水柱不存在。蒸腾状态下木质部水分的移动方式是自上而下分段依次移动的,这一现象与内聚力原理相抵触。蒸腾产生的负压能保持到蒸腾停止后继续使根系吸水。     

Comparative monitoring of temporal and spatial changes in tree water status using the non-invasive leaf patch clamp pressure probe and the pressure bomb

Real-time monitoring of plant water status under field conditions remains difficult to quantify. Here we give evidence that the magnetic-based leaf patch clamp pressure (LPCP) probe is a non-invasive and online-measuring method that can elucidate short- and long-term temporal and spatial dynamics of leaf water status of trees with high precision in real time. Measurements were controlled remotely by telemetry and data transfer to the Internet. Concomitant measurements using the pressure chamber technique (frequently applied for leaf water status monitoring) showed that both techniques yield in principle the same results despite of the high sampling variability of the pressure chamber data. There was a very good correlation between the output pressure signals of the LPCP probe and the balancing pressure values (on average r² = 0.90 ± 0.05; n = 8), i.e. the external pressure at which water appears at the cut end of a leaf under pressure chamber conditions. Simultaneously performed direct measurements of leaf cell turgor pressure using the well-established cell turgor pressure probe technique evidenced that both techniques measure relative changes in leaf turgor pressure. The output pressure signals of the LPCP probe and the balancing pressure values were inversely correlated to turgor pressure. Consistent with this, the balancing pressure values and the cell turgor pressure values could be fitted quite well by the same firm theoretical backing derived recently for the LPCP probe (Zimmermann et al., 2008). This finding suggests that use of the LPCP probe technique in agricultural water management can be built up on the knowledge accumulated on spot leaf or stem water potential measurements.