Nutritional status of ‘Hass’ and ‘Fuerte’ avocado (Persea americana Mill.) plants subjected to high soil moisture

Abstract

In this study, the effect of increased soil moisture on the nutritional status of two key commercial avocado (Persea americana Μill.) cultivars, ‘Fuerte’ and ‘Hass’, was examined. The results revealed that prolonged exposure of plants to high soil water content conditions (waterlogging) reduced the total nutrient content (absolute quantity) of almost all of the nutrients in scion’s tissues (leaves and stems) of both cultivars. The decrease of nutrient content in the ‘Fuerte’ leaves was more prominent/severe compared to the ‘Hass’ leaves, which could be the outcome of the reported higher sensitivity of the cultivar to soil waterlogged conditions in previous studies. Interestingly, the inability of ‘Fuerte’ avocado plants to withstand high soil moisture conditions was not reflected in the relative concentrations of most nutrients, both in leaves and stems. Indeed, significantly higher concentrations of P, K, B, Fe, and Zn were found in the leaves of ‘Fuerte’ waterlogged plants than in well-watered ones. This fact reveals that under marginal/stressful conditions, like waterlogging, nutrient concentration in tissues does not reflect potential negative effects on total nutrient uptake of avocado plants, obviously due to concentrated nutrient phenomena primarily created by the stress-dependent growth inhibition. Therefore, total nutrient content is proposed as a more representative indicator for assessing plant response to waterlogged conditions.     

Die n-versorgung der getreidepflanzen im iosdv?-?tartu?-?pflanzenanalysen und n-bestimmung im boden

Der Internationale Organische Stickstoffdauerdüngungversuch (IOSDV) Tartu wurde 1989 mit den N-Stufen: 0-40-80-120-160 kg N/ha und den verschiedenen organischen Düngungsstufen: 400 dt/ha Rübenblatt, 40 dt/ha Stroh und 600 dt/ha Stallmist auf einer Fahlerde angelegt. Es wurden NH₄- und NO₃- N im Humushorizont des Bodens untersucht und der N-Gehalt im Aufwuchs von Sommerweizen und Sommergerste. Die mineralische und die mineralische-organische Düngung beeinflussten die Bestockung und Blüte der Getreidepflanzen. Die Getreidepflanzen waren während dieser Zeit ausreichend mit Stickstoff versorgt. Die gemessenen Werte stimmten mit den Angaben zur optimalen N-Versorgung in der Literatur überein (<citeref rid="b1">Bergmann, 1986</citeref>). Die N-Gehalte im Korn korrelierten positiv mit den Erträgen. Die N_min-Werte im Boden zeigten erwartungsgemäß im Herbst eine bessere Korrelation zum Ertrag von Sommergerste als die im Frühjahr gemessenen N_min-Werte. Sie wurden stärker durch den mineralisch gedüngten Stickstoff als durch die Nachwirkung der organischen Düngung beeinflusst. Die Ertrag von Sommerweizen war mehr durch die Witterungsbedingungen während der Vegetationszeit beeiflusst. The aim of the international organic-nitrogen long-term experiment (Internationaler organischer Stickstoffdauerdüngungsversuch (IOSDV), initiated in 1989) is to compare the effects of different forms of mineral nitrogen fertilizer (0-40-80-120-160 kg N/ha) with different organic amendments (beet leaves, 400 dt/ha; straw, 40 dt/ha; and FYM, 600 dt/ha) on loamy Podzoluvisol (FAO). The ion-exchangeable NH₄-nitrogen and NO₃-nitrogen content in humus layer and N-content in shoots of different stages of spring barley and spring wheat were studied. Mineral and organic fertilization influenced N-uptake at anthesis and tillering stage. Cereal plants had a sufficient supply of nitrogen at this time. Measured data are well in accordance with published results (Bergmann, 1986). Results of optimal N-content of shoots at different stages correlated positively and significantly with grain yields. N_min content in the humus layer in autumn was correlated better as in spring with grain yields of spring barley. In the vegetation period, N_min content correlates better with treatment with mineral nitrogen fertilizer than with use of organic amendments. In addition, yield of spring wheat is significantly correlated with weather conditions.     

西藏农业区?ngstr?m-Prescott公式参数选取研究

针对西藏地区地域广阔、辐射站点少且分布不均匀等特征,为获得适用于西藏主要农业区的太阳总辐射计算模型参数,基于拉萨、狮泉河、那曲、昌都站1961—2004年的逐日太阳总辐射及日照时数数据,采用最小二乘法对?ngstr?m-Prescott(AP)中的参数进行率定,利用2005—2016年的逐日观测数据对率定结果进行验证,并根据不同农业区划,由已知站点的参数值推求无辐射数据典型站点的经验参数,进而选取不同农业区划的经验参数。结果表明,FAO推荐的参数值并不完全适用于西藏地区,4个站点2个参数率定值的变化范围分别为0.18～0.26以及0.55～0.64。经验参数受纬度影响最大,其次是经度、海拔。拉萨站和昌都站计算值与实测值的吻合较好。5个不同农业区2个参数值变化范围分别为0.18～0.25及0.55～0.64。FAO推荐值在高原温带半湿润区以及高原温带半干旱区适用性较好。该研究成果可为无辐射实测地区的太阳辐射值和作物腾发量的计算提供依据。     

什么是 PPm?

PPm 是英文 parts per million 的缩写,它表示百万分之(几),或百万分率。PPm 与百分率(%)所表示的意思相似,只是它的比例数比百分率大而已。PPm 是一个比例数,不是一个固定值。有时人们为了避免繁杂的小数,通常不用百分率而用 PPm 值来表示某些化合物中某一成分的含量。如在一百万斤土壤中含有5斤氮素,则氮素在土壤中占的比例就是百万分之五,即5PPm。     

怎样科学调运粮食?

有四个公社需将公粮交到粮站,粮站有两个,甲站大一点,可收容710万斤;乙站稍小,可收容390万斤.四个公社根据耕地和产量多少,A 公社应交270万斤,B 公社应交180万斤,C 公社应交290万斤,D 公社应交360万斤。这四个公社距甲、乙二粮站的路程     

什么叫pH值?

在化学上常采用氢离子(H~ )浓度的负对数来表示溶液的酸碱性,叫做溶液的 pH 值。pH=-lg(H)。例如纯水:[H~ ]=[OH~ ]=1×10~(-7) M.它的 pH 值是:pH=-lg10~(-7) =-(-7) .通常可用酸碱指示剂、pH 试纸或 pH 计来测得溶液的 pH 值.pH值为7时,溶液呈中性;pH 值小于7时,溶液中氢离子数量多于氢氧根离子数量,溶液呈酸性;PH 值愈小酸性愈强;pH 值大于7时,溶液呈碱性,pH 值愈大碱性愈强.     

秋水仙素诱导党参四倍体?

以党参（Codonopsis pilosula (Franch.) Nannf.）为诱变材料,用改良秋水仙素涂抹法进行多倍体诱变以获取四倍体,研究了秋水仙素对党参的诱导效果以及变异株的形态学与细胞学变化。本试验利用0.2%秋水仙素琼脂凝胶处理党参幼苗获得了四倍体材料,结果表明党参经秋水仙素诱导后,以处理24h加倍率最高,为34.14%。四倍体植株形态学变异表现为苗期生长受阻,叶片变大变厚,叶形指数变小;花器变大,茎杆加粗,茎节变短;结实率下降而千粒重增加等。党参四倍体植株的细胞学表现为叶下表皮气孔器变大,气孔密度下降,保卫细胞内叶绿体的含量增加;花粉粒变大而花粉育性降低;根尖细胞有丝分裂染色体数目为2n=4x=32,其对照为2n=2x=16。四倍体党参减数分裂染色体行为复杂,同源染色体出现了多种联会方式。     

A Future for Sustainability?

Sustainability has become a focal topic and important goal for many people concerned about environmental issues. It is, therefore, important for educators, and others, to talk about sustainability with their students and colleagues—about its meaning, curricular application, and practice. However, I do not think this is sufficient. In this paper I will examine limitations of the language of sustainability and implications for environmental thinking. Before launching into a critique, I do acknowledge the importance of "sustainability" and the usefulness of this concept. Many ecological processes are not sustained—not kept going continuously. Species are going extinct at an alarming rate and whole ecosystems are at risk. So, sustainability is important. However, we must also pay attention to what sustainability is not. And, we should consider why these limitations matter. For example, "education for sustainability" has gained rapid acceptance, yet little critical attention has been given to the term. Just as many environmental educators have expressed reservations about "education for sustainable development," I believe there are serious problems associated with allowing our work to be subsumed by the term "education for sustainability." In this presentation I will explore reasons for educators, and others, to be concerned about relying on the language and goals of sustainability. These areas of concern, or limitations, are discussed in terms of determinism, exclusivity, and conceptualization. Some suggestions are provided to help refocus our direction.     

Does ivermectin attract earthworms?

Purpose  

Changes in the behavior of earthworms (for example avoidance of a particular substrate) can influence the soil ecosystem. Our aim was to determine whether the earthworms Eisenia fetida and Lumbricus terrestris are able to avoid ivermectin (a veterinary endectocide belonging to the avermectins). A standard avoidance test with earthworms was conducted using standardized Lufa 2.3 soil (Speyer, Germany) and sandy soil provided by Cinkarna Celje (Slovenia).     

Are lignins optically active?

The accepted derivation of lignins from non(enzymatically)-controlled radical coupling reactions has been recently challenged, and it is relevant to ascertain unequivocally whether lignins are or are not (as normally assumed) optically active. Two approaches were used. First, DFRC (derivatization followed by reductive cleavage) dimers derived from beta-5- and beta-beta-units in pine lignins, which certainly retain unaltered chiral centers (as well as beta-1- and beta-O-4-units where the intactness may be debated), were shown to be optically inactive by circular dichroism (CD) and chiral high-performance liquid chromatography. CD of beta-5-derived dimers following enantiomeric separation readily demonstrated the sensitivity of the method. Second, no optical activity could be detected (above 250 nm to avoid carbohydrate contributions) by CD of lignin isolates from pine, kenaf, maize, or a CAD-deficient pine mutant. Representative lignins are therefore not, within limits of detection by these methods, optically active.     

什么叫配合饲料?

配合饲料是通过对畜禽营养科学的研究,根据畜禽的不同种类(猪、鸡、牛等)、不同生长发育阶段(雏鸡、青年鸡.蛋鸡等)对各种营养物质的需要量,将多种饲料原料按照科学比例配制而成的饲料。     

Which species? What kind of diversity? Which ecosystem function? Some problems in studies of relations between biodiversity and ecosystem function

I examine a number of problems that need to be identified and accounted for when examining the relationships between diversity and ecosystem function. Among these are measures of diversity and complexity in ecosystems: species richness, diversity indices, functional groups, keystone species, connectance, etc, all of which may be difficult to relate to ecosystem function. Several important distinctions, when testing diversity–function relationships empirically, are discussed: Diversity of functional groups, diversity within functional groups vs. total diversity; manipulating variables such as body-size distributions vs. manipulating diversity per se; effects of diversity vs. effects of biomass; and diversity–function relations under stable vs. changing conditions or perturbations. It is argued that for the management and development of sustainable ecosystems, it is probably more important to understand the linkages between key species or functional groups and ecosystem function, rather than focusing on species diversity. This is because there are possible mechanistic relations between what species do in ecosystems and ecosystem function. Diversity, being an abstract and aggregated property of the species in the context of communities and ecosystems, lacks such direct relations to ecosystem functions.     

怎样防止锅台抹灰裂缝?

锅台用水泥砂浆抹面,光洁平滑,但往往烧火不几天便出现裂缝,裂缝首先从灶口、火道等抹灰面狭小、加热量大的地方出现.而且由细变粗,发展很快,原因是水泥砂浆中的砂受热到一定程度后体积要发生膨胀,温度降低之后,体积又收缩.一胀一缩,抹灰层便极易产生裂缝.有     

如何正确利用逆温层植胶?

云南省哀牢山以西坝缘坡地尤其是阳坡,是植胶主要地段,在该区冬季容易生成地面逆温,因有一定厚度,故称作逆温层。由于有逆温存在,在海拔相对较高处(指逆温层)内植胶,胶树冬期寒害轻微,这是问题的一个方面;另一方面,到了雨季(5—10月即橡胶树生长季节)逆温消失,温度恢复了随海拔升高而降低的一般规律,加上云雨随海拔升高而增加,因而在雨季,较高海拔丘陵山地的光热条件就比低海拔地段要差,胶树生长量不如低海拔地区。两者应如何结合,即如何正确利用逆温层植胶?值得探讨。本文就现有资料,对此作初步分析。