Comparative assessment of five methods of determining sap flow in peach trees

Five different methods of determining sap flow (SF), three based on heat pulse (compensation heat pulse, New Zealand—cHP–NZ; compensation heat pulse, Greenspan/Australia—cHP–G (South oriented), and cHP–G–EW (East and West oriented, average); non-compensation heat pulse, Ariel/Israel—ncHP), one based on stem heat balance (Dynamax/USA—SHB), and another based on heat dissipation (Granier/France—HD) were compared in an experiment performed on peach trees in Northeast Spain. Two irrigation treatments (drip-irrigated) were applied: a control and a stress treatment, the latter consisting of withholding water from day 190 to 199. Between 1 and 3 different systems were installed in some trees of both, the control and stress treatments. All the techniques reflected the evolution of water stress in the stressed trees with a very similar tendency and in agreement with the evolution of predawn water potential (Ψp). Ψp correlated well with sap flow (SF) determined with all the systems (r² > 0.65) in the stress treatment, indicating that all the SF techniques detected changes in tree water status. The cHP–NZ system was the first to detect a SF reduction through the outer xylem vessels, as a response to water withholding. In control trees, daily SF rates provided by the three heat pulse and heat balance methods were well correlated with ETo and somewhat less with global radiation; all regressions improved on an hourly basis. Daily pattern and magnitude of mean SF rates monitored by the three heat pulse systems were quite similar in control trees. This was reflected by high regression coefficients when compared with each other. Higher SF rates recorded by ncHP methods in comparison with cHP–G and cHP–NZ might be attributed to technical limitations and to different sensor orientation. In an accompanying experiment, substantial differences between East and West location of the cHP–G sensors were observed, but when taking the mean value of those daily SF rates, differences between ncHP and cHP–G–EW were lower. Mean monthly crop coefficients, calculated by using SF data computed with ncHP method and soil evaporation as determined with microlysimeters, were 0.64 in July and 0.67 in August. SF systems can be used to detect plant water stress related to control, and might be useful for irrigation scheduling based on plant water status. The SF techniques analysed showed potential to better determine actual plant water necessities than other traditional methods, but a preceding calibration is needed.     

水肥对高产无性系油茶果实产量的影响

以肥料氮(N)、磷(P)、钾(K)不同施用量和灌溉水量(H2O)为试验因子,采用二次通用旋转组合设计,研究了水肥对油茶鲜果产量的影响。结果表明,N、P、K和H2O的用量对油茶鲜果产量均存在显著的影响,且N与K、K与H2O对油茶鲜果产量存在显著的互作效应。试验因子间的交互作用使油茶鲜果产量明显提高,达到最大值时4个因子的编码值分别为:N为1.03、P为0.62、K为1.19、H2O为0.92,即全年每株油茶施有效养分N 181.8 g、P2O5 48.6 g、K2O 287.1 g,灌水29.2 kg,相当于每hm2施用N 795 kg、P2O5 80 kg、K2O 474 kg,灌水48 m3。采用该方案,油茶鲜果产量可达到最大为5 131 kg hm2。     

Does accelerated soil organic matter decomposition in the presence of plants increase plant N availability?

Plant roots can increase microbial activity and soil organic matter (SOM) decomposition via rhizosphere priming effects. It is virtually unknown how differences in the priming effect among plant species and soil type affect N mineralization and plant uptake. In a greenhouse experiment, we tested whether priming effects caused by Fremont cottonwood (Populus fremontii) and Ponderosa pine (Pinus ponderosa) grown in three different soil types increased plant available N. We measured primed C as the difference in soil-derived CO₂-C fluxes between planted and non-planted treatments. We calculated “excess plant available N” as the difference in plant available N (estimated from changes in soil inorganic N and plant N pools at the start and end of the experiment) between planted and non-planted treatments. Gross N mineralization at day 105 was significantly greater in the presence of plants across all treatments, while microbial N measured at the same time was not affected by plant presence. Gross N mineralization was significantly positively correlated to the rate of priming. Species effects on plant available N were not consistent among soil types. Plant available N in one soil type increased in the P. fremontii treatment but not in the P. ponderosa treatment, whereas in the other two soils, the effects of the two plant species were reversed. There was no relationship between the cumulative amount of primed C and excess plant available N during the first 107 days of the experiment when inorganic N was still abundant in all planted soils. However, during the second half of the experiment (days 108-398) when soil inorganic N in the planted treatments was depleted by plant N uptake, the cumulative amount of primed C was significantly positively correlated to excess plant available N. Primed C explained 78% of the variability in plant available N for five of the six plant-soil combinations. Excess plant available N could not be predicted from cumulative amount of primed C in one species-soil type combination. Possibly, greater microbial N immobilization due to large inputs of rhizodeposits with low N concentration may have reduced plant available N or we may have underestimated plant available N in this treatment because of N loss through root exudation and death. We conclude that soil N availability cannot be determined by soil properties alone, but that is strongly influenced by root-soil interactions.     

对蜂蜜中主要抗褐变因子的探讨

选用ＡＧ５０Ｗ－Ｘ８阳离子交换树脂，并以批处理的方式，成功地将蜂蜜中的肽类物质与其它组合得到了分离。抗褐变实验结果清楚地表明，蜂蜜中的肽类成分完全没有抑制褐变的活性。这与以前的报道截然不同。     

Fruit Quality at Harvest of “Jonathan” Apple Treated with Foliarly-Applied Calcium Chloride

Abstract

The response of “Jonathan” apple trees (Malus domestica, Borkh.) grafted on EMLA 111 to frequent application of calcium chloride (CaCl₂) was studied at Topeka, Emporia, and Conway Springs, Kansas, orchards in 2002. Trees were sprayed one to eight times with foliar applications of calcium chloride at the rate of 8.971 kg ha^?1. First spray was made when fruits were 1.4, 0.9, and 1.6 cm diameter at Topeka, Emporia, and Conway Springs, respectively. More than six applications of CaCl₂ improved fruit quality at harvest. Improvement included an increase in fruit weight, size, appearance, skin redness, and reduction of scald incidents. Although CaCl₂ applications had no effect on percent of soluble solids, the ratio of soluble solid content to titratable acidity was increased by frequent CaCl₂ application. Fruit skin redness was the most improved quality of “Jonathan” apple as the result of CaCl₂ applications. No symptoms of fruit russetting or leaf scalding resulting from frequent CaCl₂ application were observed. Increase in fruit quality was attributed to a linear increase in Ca concentrations in fruit and leaf tissues. Increase in Ca concentrations in fruit and leaf tissues of treated trees coincided with increases in potassium (K), magnesium (Mg), phosphorus (P), and nitrogen (N) concentrations compared with untreated control trees. Potassium, Mg, P, and N were correlated with fruit quality as much as, or in some cases more than, Ca. This information suggests that changes in mineral balance with CaCl₂ applications contributed to improvement of fruit quality and is evidence that frequent Ca application improved “Jonathan” apple quality in Kansas.     

Diversity of leaf unfolding dynamics among tree species: New insights from a study along an altitudinal gradient

Leaf unfolding is a key ecosystem parameter controlling carbon and water fluxes and affecting forest dynamics. This parameter is highly sensitive to temperature and, consequently, often used as an indicator of global change. In this paper, we analyzed weekly leaf unfolding dynamics for seven temperate species (Fagus sylvatica L., Acer opalus Mill., Sorbus aria L., Quercus pubescens Willd. Abies alba Mill., Pinus sylvestris L., Pinus nigra Arnold). The effects of temperature on leaf unfolding were studied in situ using several methods and proxies. First, in a spatial approach, leaf unfolding dates were measured along two altitudinal gradients situated on the north and south face of the Mont Ventoux to test altitudinal and slope effects. Second, in a temporal approach, the year effect was analyzed on the north face by comparing two contrasted years (2006 and 2007). Finally, the role of temperature was investigated directly by linking leaf unfolding patterns and temperatures recorded during the leaf unfolding process itself.Two major conclusions were obtained. First, three distinct leaf unfolding patterns were revealed: a rapid sigmoid pattern for the deciduous species group, a slow kinetic pattern for the pines and an intermediate pattern for A. alba. Second, we found an unexpected pattern of variation in the response to spatial or temporal variation of temperature. The more sensitive a species was to temperature variations between years, the less sensitive it was to temperature variations due to altitude. Finally, we discuss that these results can be correlated to two major life history traits: evergreen vs. deciduous and shade tolerant vs. shade intolerant.     

Application Methods of Calcium Supplements Affect Nutrient Levels and Calcium Forms in Mature Tomato Fruits

AZ‐Germ Salt II, a salt tolerant line of alfalfa (Medicago sativa L.) at the germination stage, was compared with its parent line Mesa Sirsa in sand culture at the germination and seedling stages and in hydroponic culture at the adult stage under greenhouse conditions. The sodium chloride (NaCl) treatments used were 0 or 100 mol/m³ in half strength Hoagland nutrient solution. AZ‐Germ Salt II was superior to Mesa Sirsa in biomass production at all three stages. AZ‐Germ Salt II had significantly greater chloride (Cl) in the plumules and radicle than Mesa Sirsa at the germination stage. The two lines did not differ in shoot and root sodium (Na) and shoot Cl at the seedling stage. However, at the adult stage AZ‐Germ Salt II accumulated significantly higher Na in the shoots and roots and Cl in the shoots compared with Mesa Sirsa. The two lines did not differ in tissue potassium/sodium (K/Na) ratios in all three experiments, although K concentrations were higher in the seedling shoots and roots, and in the plumules of AZ‐Germ Salt II than Mesa Sirsa. The K versus Na selectivities were higher in the plumules and seedling shoots and roots of AZ‐Germ Salt II compared with Mesa Sirsa, whereas at the adult stage the reverse was true. The lines also did not show any difference in tissue calcium (Ca) concentrations at any stage. It is concluded that salt tolerance in these two lines is not age‐dependent. The pattern of ion accumulation varies with the change in growth stage. Generally there is a positive correlation between Na and Cl accumulation and growth in alfalfa.     

Factors influencing fruit size in the strawberry (Fragaria ananassa Duch.)

Summary Fruit size is one of the most important characteristics of highly productive strawberry cultivars. The aim of the experiments was to establish the factors responsible for the expression of this trait. The total yield of large fruits correlates closely with the total yield of all fruits and depends mainly on the mean fruit weight of all fruits. The position of fruits on the inflorescence influences the decline of fruit size to a larger extent in small-fruited clones than in the large-fruited ones. The size of the fruit is controlled by the dimension of the receptacle and number of achenes. The stimulating effects of achenes are quite different in various genotypes and the fruit weight per achene declines with the inferior blossom position. The large-fruited clones have bigger leaves, a larger photosynthetic area, and thicker petioles and flower stalks. Their cells are larger, which is common for the giant genotypes. The results suggest that there exists a possibility for indirect selection of fruit size on the basis of some additional parameters, which can be useful particularily in the years of unsuitable weather conditions.     

The role of border areas for dendrochronological investigations on catastrophic snow avalanches: A case study from the Italian Alps

Snow avalanches are common in mountain environments, sometimes affecting inhabited areas and infrastructures (e.g. roads, bridges, and ski slopes). Their study is widespread and involves the use of a variety of different techniques, including dendrochronological methods. The aim of such investigations is principally to date past events, but also to detect variation in avalanche frequency as well as their spatial distribution. Trees affected by snow avalanches generally have scars, tilted trunks and broken branches, which allow past events to be dated to within a year. In this work tree rings were used to investigate a disruptive snow avalanche which occurred in 2001 in Val Mala in the Italian Alps. The event almost completely removed forest along the flow path, while the snow powder component of the avalanche also impacted on the adjacent forest. Comparison of tree reaction in surviving plants along the flow path and vegetation on the border showed i) the production of reaction wood even in apparently undisturbed trees and ii) the usefulness of border plants for dating past events. Different dendroecological indicators were investigated (i.e. reaction wood, scars, traumatic resin ducts, and variations in stem eccentricity) and reaction wood is evidently concentrated from 2001 not only in damaged trees but also in adjacent plants. The potential to investigate past snow avalanches by collecting samples from trees growing in border areas is presented: in the specific case of Val Mala, vegetation bordering the flow paths reacted to produce reaction wood in 2001, in a similar manner to plants along the flow track, demonstrating their usefulness in such investigations. Their response to the 2001 event confirms the possibility of applying dendrochronological techniques to trees adjacent to the flow path, even if they appear morphologically undisturbed, and proposes to use only border areas in cases of an absence of sufficient trees along the avalanche track.     

柑橘类果汁中柚皮苷的分析

柚皮苷是柑橘汁中主要的苦味物质之一,其含量高低影响果汁的色泽、口味、稳定性等.通过分光光度法分析了9种柑橘类果汁中柚皮苷的含量,研究结果表明：胡柚汁中柚皮苷含量最高,为3.018 g/L,芦柑汁中柚皮苷含量最低,为0.310 g/L.在此基础上,用数学统计的方法对9种柑橘类果汁中柚皮苷含量差异性分析表明：脐橙汁与象山橘汁,椪柑汁与蜜柚汁柚皮苷含量无差别;椪柑汁比芦柑汁高,蜜柚汁比芦柑汁高,差异显著;其余种类果汁间柚皮苷含量均有极显著差异.