Root and rhizosphere responses of iron‐efficient or ‐inefficient apple genotypes to solution pH

Solution culture with four pH levels was employed in this experiment to evaluate root and rhizosphere responses of Malus xiaojinensis [iron (Fe)‐efficient species] and M. baccata (Fe‐inefficient species) in order to pursue some of their physiological mechanism for Fe absorption. The results showed that M. xiaojinensis had a higher fresh weight per seedling than M. baccata at any of the solution pH levels tested and the differences were significant between the two species with increasing of the solution pH levels, particularly at the pH of 7.4 or 8.4. The reducing abilities of root exudates for the two species under test were decreased with increasing of the solution pH from 5.4 to 8.4, in which the reducing abilities for M. xiaojinensis were always more than two times higher than those for M baccata. The significant decrease of the reducing ability was found only at pH of 8.4 for M. xiaojinensis or at both 7.4 and 8.4 for M. baccata, respectively. Malus xiaojinensis had significantly higher respiration rates than M. baccata at the higher solution pH levels. Both rhizosphere pH and rhizosphere redox potential were influenced by the solution pH levels remarkably in distances of 0–4 mm to root surface or in distances of 5–10 mm along the root from the root tip, respectively. Genotypic differences in these two parameters were clearly showed at the solution pH of 7.4, in which rhizosphere pH of M xiaojinensis was clearly lower than that of M. baccata, while the rhizosphere redox potential of the former was much higher than that of the latter.     

外源GA3对高原夏季胡萝卜肉质根发育的影响

为了揭示外源GA3对胡萝卜肉质根发育的影响机理,并为高原夏季胡萝卜安全高效栽培技术研究提供参考理论,本试验以耐先期抽薹的胡萝卜品种为试材,采用酶联免疫吸附法(ELISA),研究了外源GA3对高原夏季胡萝卜肉质根膨大、木质化及其内源激素含量的影响。结果表明,在叶片旺盛生长期和肉质根迅速膨大期分别喷施5.78×10-4 mol·L-1外源GA3 1次,或在苗期、叶片旺盛生长期和肉质根迅速膨大期喷施5.78×10-4 mol·L-1外源GA3 1~3次,能显著降低高原夏季胡萝卜苗期肉质根日鲜重增长速率与库活力,促进肉质根木质化。与对照相比,喷施外源GA3,可显著降低苗期肉质根内源GA3、IAA、GA4、ABA、DHZR与IPA含量,显著提高肉质根内源ZR含量;显著降低叶片旺盛生长期肉质根内源GA3、IAA、GA4、IPA含量,显著提高内源ZR含量;显著提高迅速膨大期肉质根内源IAA、GA4、ZR含量;显著降低肉质根迅速膨大期之前的IAA/ZR和GA4/ZR比值。随着外源GA3喷施次数的增多,IAA/ZR和GA4/ZR比值在肉质根迅速膨大期有逐渐增高的趋势。外源GA3通过改变内源激素含量及其平衡状态来影响高原夏季胡萝卜肉质根的发育。     

棉株不同器官中几种内源激素的变化及相关关系

本试验以转Bt基因抗虫棉GK 1 2为试材 ,研究不同生育期棉花幼叶、功能叶、衰老叶片、根组织和伤流中内源激素的变化。结果表明 :①细胞分裂素两组分iPA +iP和ZR +Z对叶片、根系建构及功能的调控作用是协同互补关系 ,在幼叶、功能叶、衰老叶片和根组织中iPA +iP和ZR +Z的含量变化趋势相反。iPA +iP和ZR +Z均呈单峰曲线变化趋势 ,其中iPA +iP开口向下 ,ZR +Z则开口向上。②赤霉素两组分GA3 和GA4在幼叶、功能叶、衰老叶片和根组织中的变化趋势相似 ,其中GA3 主要调控着根系和叶片的建构与功能 ,GA4参与调控叶片的衰老。③IAA和ABA在幼叶、功能叶、衰老叶片和根组织中的变化趋势不一致。盛花期之后 ,幼叶和功能叶片中的IAA和ABA含量上升 ,衰老叶片和根组织中的含量下降。ABA启动叶片和根系的衰老过程 ,启动后ABA含量下降。④伤流液中iPA +iP、ZR +Z、GA3 、GA4、IAA和ABA的变化动态均呈单峰曲线。     

CHANGES IN ENDOGENOUS HORMONAL STATUS IN CORN (ZEA MAYS) HYBRIDS UNDER DROUGHT STRESS

Corn has several mechanisms that allow it to perceive the incoming water deficit and rapidly regulate its growth and physiology to cope with this stress. Among these regulated physiological responses, phytohormones, such as abscisic acid (ABA), gibberellin (GA₃), indole acetic acid (IAA), and zeatin (ZT) have important roles. To evaluate changes in hormonal status of corn hybrids under different drought stress levels, a greenhouse study was conducted at the College of Agriculture, Shiraz University, Iran, during summer 2010. Treatments consisted of drought stress in five levels: 100% field capacity (F.C.) as control, 80, 60, 40, and 20% F.C. and three corn hybrids, including single cross 704 (SC704), Maxima, and double cross 370 (DC370). Results showed that drought stress significantly affected phytohormones concentration, ABA concentration was increased and GA₃, IAA and ZT concentrations were decreased. Indeed, there was an initial increase (about 13.5% more than control) in IAA concentration. In severe drought condition, ABA concentration was eventually decreased (37.8% less than the first drought level, i.e., 80% F.C.). The ratios of GA₃, IAA and ZT to ABA concentration were also decreased. Among hybrids, SC704 showed the highest phytohormone concentrations and DC370 had the highest ratios of GA₃, IAA, and ZT to ABA concentrations. Overall, the results of this study suggest that although mild drought stress was associated with greater ABA concentration, it had negative impact on GA₃, IAA, and ZT concentrations. Furthermore, SC704 hybrid appeared to be more resistant to drought stress than the other hybrids.     

Factors related to iron uptake by dicotyledonous and monocotyledonous plants. I. pH and reductant

Some plants respond to Fe‐deficiency stress by inducing Fe‐solubilizing reactions at or near the root surface. In their ability to solubilize Fe, dicotyledonous plants are more effective than monocotyledonous plants. In this study we determined how representative plants differ in their response when subjected to Fe‐deficiency stress in a calcareous soil and in nutrient solutions. Iron‐inefficient genotypes of tomato, soybean, oats, and corn all developed Fe chlorosis when grown in soil, whereas Fe‐efficient genotypes of these same species remained green. The same genotypes were grown in complete nutrient solutions and then transferred to nutrient solutions containing N (as NO₃ ^‐) and no Fe.

The T3238 FER tomato (Lycopersican esculentum Mill.) Fe‐efficient) was the only genotype that released significant amounts of H from the roots (the pH was lowered to 3.9) and concomitantly released reductants. Under similar conditions, Hawkeye soyhean [Glycine max (L.) Merr.] released reductants but the solution pH was not lowered. Both Fe‐inefficient and Fe‐efficient genotypes of oats (Avena sativa L.) and corn (Zea mays L.) released insufficient H or reductant from their roots to solubilize Fe; as a result, each of these genotypes developed Fe‐deficiency (chlorosis).

The marked differences observed among these genotypes illustrate the genetic variability inherent within many plant species. A given species or genotype may accordingly not be adapted to a particular soil. Conversely, a given species or genotype may be found (or developed) that is precisely suited for a particular soil. In this event, the need for soil amendments may be reduced or eliminated.     

Sorghum seedling root growth as influenced by H+, CA++, and MN++ concentrations 1

Root response mechanisms for acid soil tolerance adaptability are generally unknown. Sorghum [Sorghum bicolor (L.) Moench] cultivars (Funk G522DR, GP140, SC599, TAM428, SC283, and SC574) were grown in white quartz flintshot sand and watered with 0.01M sodium acetate buffer at pH 4.0, 4.5, 5.0, 5.5, or 6.0 and Ca⁺⁺ (0, 10, 100 mgl^‐1 as CaCl₂) or Mn⁺⁺ (0, 1.4, or 140.0 mgl^‐1 as HnCl₂). At the acid soil tolerance impact response phase (< 10 days old), Ca⁺⁺ did not influence initial root growth. Increased H⁺ concentration inhibited juvenile root growth equivalently in all six cultivars. This inhibition was reversed by exogenous GA₃ in Funks G522DR but not in SC283 or SC574. Excess Mn⁺⁺ (140 mgl^‐1) further decreased root growth. Induction of an auxinase inhibitor by GA₃ would support a hypothesis of H⁺ concentration influence on IAA transport and/or availability. Root growth matched IAA water partitioning and exogenous IAA (10^‐10 and 10^‐9 M) reversed the H⁺ concentration influence on root growth of SC283. We suggest that low pH (<4.8) soil influence on root growth is explicable as an influence on IAA synthesis and/or transport and that excess Mn⁺⁺, which is known to induce IAA oxidation, further exacerbates the deleterious growing conditions.     

铜对不同苹果砧木实生苗生长的影响差异研究

在网室采用盆栽的方法研究了当年生八棱海棠、平邑甜茶 (M .hupehensis Rehd .)、莱芜难咽及海棠果 4种苹果砧木实生苗在外源铜 0、75、15 0mg kg处理下对植株相对株高、胸径、生物量 ,细胞膜透性及根茎叶中的铜、钙、铁矿质元素含量等的影响。结果表明 ,海棠果比平邑甜茶、莱芜难咽和八棱海棠等 3种砧木实生苗具有较强的抗铜毒害能力。     

不同施氮水平对矮化富士苹果幼树生长、氮素利用及内源激素含量的影响

【目的】矮化中间砧是目前我国苹果栽培中主要的致矮手段,但在提早结果的同时存在树势早衰的现象,而有关矮化中间砧的果树氮素需求规律及其氮素与树体生长和内源激素之间的关系研究较少。本文研究氮素施用量对矮化中间砧苹果幼树的生长、氮素吸收利用及内源激素的影响,以期为苹果矮化中间砧的果树栽培中氮肥的科学施用和高效利用以及防止树体早衰提供理论依据。【方法】利用15N同位素示踪技术,以三年生宫藤富士/SH6/平邑甜茶(Borkh cv.Fuji/SH6/M.hupehensis Rehd)为试材,于春梢萌芽前,设置3个氮肥施用水平(N 50、100、200 kg/hm2,分别以N50、N100、N200表示),同时每棵树施15N-尿素0.5 g。于春梢旺长期、春梢缓长期,采用酶联免疫法测定茎尖和细根的激素含量;植株停止生长时,测其春、秋梢长度,并整株解析,称量各部分鲜重、干重,测植株全氮及其15N丰度。【结果】研究结果表明,不同施氮水平与植株生长及氮素吸收利用密切相关,春、秋梢长度、树体鲜重及植株全氮均以N50处理最低,N100次之,N200最高,但15N的利用率趋势正好相反,为N50N100N200;细根鲜重以N100处理(34.06 g)最高,N200(28.36g)次之,N50(22.47g)最低。施氮水平对茎尖和细根的赤霉素(GA)、玉米素核苷(ZRs)、脱落酸(ABA)和吲哚乙酸(IAA)的含量变化及其比值有较大影响。春梢旺长期和春梢缓长期茎尖、细根中的IAA和GA含量均为N50N100N200,而ZR和ABA的含量则随氮肥用量的增加而降低,表现为N50N100N200;春梢缓长期与春梢旺长期相比,除细根中GA含量(N50、N100、N200处理分别为5.13、5.68、6.17 ng/g,Fw)有所升高外,各器官的IAA、GA、ZR的含量均明显降低,且差异显著;两时期茎尖和细根的ZR/GA、ABA/GA比值均以N50处理最大,N100处理次之,N200处理最小;同一器官不同处理间(IAA+GA+ZR)/ABA比值也存在差异,N200处理显著高于其他处理。【结论】氮肥施用量在50 kg/hm2到200 kg/hm2范围内,随着氮肥用量的增加矮化中间砧苹果幼树的生长促进型激素含量、植株全氮和植株生物量显著增加,但15N利用率显著降低,且ZR/GA、ABA/GA比值逐渐降低。本试验条件下施氮量为N100 kg/hm2是矮化中间砧苹果幼树的适宜施氮量,有利于提高氮素利用率,促进细根生长,同时可延缓树势衰老,促进成花,保证苹果矮化密植集约化栽培中的氮肥充足和均衡供应。     

Root and Leaf Ferric Chelate Reductase Activity in Pond Apple and Soursop

Abstract

Root and leaf ferric chelate reductase (FCR) activity in Annona glabra L. (pond apple), native to subtropical wetland habitats and Annona muricata L. (soursop), native to nonwetland tropical habitats, was determined under iron (Fe)-sufficient and Fe-deficient conditions. One-year-old seedlings of each species were grown with 2, 22.5, or 45 µM Fe in a nutrient solution. The degree of tolerance of Fe deficiency was evaluated by determining root and leaf FCR activity, leaf chlorophyll index, Fe concentration in recently mature leaves, and plant growth. Root FCR activity was generally lower in soursop than in pond apple. Eighty days after plants were put in nutrient solutions, leaf FCR activity of each species was lower in plants grown with low Fe concentrations (2 µM) than in plants grown with high (22.5 or 45 µM) Fe concentrations in the nutrient solution. Leaves of pond apple grown without Fe became chlorotic within 6 weeks. The Fe level in the nutrient solution had no effect on fresh and dry weights of soursop. Lack of Fe decreased the leaf chlorophyll index and Fe concentration in recently matured leaves less in soursop than in pond apple. The rapid development of leaf chlorosis in low Fe conditions and low root and leaf FCR activities of pond apple are probably related to its native origin in wetland areas, where there is sufficient soluble Fe for adequate plant growth and development. The higher leaf FCR activity and slower growth rate of soursop compared to pond apple may explain why soursop did not exhibit leaf chlorosis even under low Fe conditions.     

Effects of Lead,EDTA, and IAA on Nutrient Uptake by Alfalfa Plants

ABSTRACT

The element concentrations of alfalfa plants exposed for 10 d to 40 mg lead (Pb) L^{? 1} from lead nitrate [Pb(NO₃)₂] alone, or combined with ethylenediaminetetraacetic acid (EDTA) and indole-3-acetic acid (IAA), was determined by inductively coupled plasma-optical emission spectroscopy (ICP-OES). Indole-3-acetic acid at 10 μ M and Pb/EDTA/IAA at 10 μ M increased potassium (K) concentration in roots by 87% and 94%, respectively (P < 0.05). However, IAA at 100 μ M decreased K concentration in leaves (P < 0.05). Plants exposed to 100 μ M IAA, Pb/IAA at 100 μ M, and Pb/EDTA/IAA at 100 μ M had, respectively, 30%, 55%, and 40% more sulfur (S) in leaves than control plants (P < 0.05). Lead and Pb/IAA reduced Ca concentration in stems and leaves (P < 0.05). Conversely, Pb and Pb/EDTA increased Cu concentration in roots and stems. IAA at 100 μ M, Pb, and Pb/EDTA/IAA decreased Zn concentration in roots (P < 0.05). Manganese (Mn) and molybdenum (Mo) concentration in roots and stems was lower in plants treated with Pb and Pb/IAA (P < 0.05). Pb and Pb/IAA reduced (P < 0.05) the iron (Fe) concentration in roots. However, the addition of EDTA and IAA at 10 μ M reduced the negative effects of Pb on Fe absorption.     

Effect of Burkholderia sp. KCTC 11096BP on some physiochemical attributes of cucumber

Plant growth promoting rhizobacteria (PGPR) has been a focus of research for its potential as an eco-friendly alternative to chemical fertilizers in the agriculture industry. In current study, the effect of culture suspension (CS) of a novel gibberellins (GAs) producing bacterial strain Burkholderia sp. KCTC 11096BP, was observed on shoot length, shoot fresh and dry biomass, root fresh and dry biomass, chlorophyll contents, endogenous bioactive GAs (GA₁ and GA₄) and their immediate precursors, abscisic acid (ABA), soluble sugar contents and crude protein contents of cucumber (Cucumis sativus L.). We found that growth attributes of cucumber were significantly promoted by the application of CS of Burkholderia sp. KCTC 11096BP. The quantity of GA₁ and GA₄ and their immediate precursors GA₂₀ and GA₉ respectively, were also significantly promoted as compared to their respective controls. Contrary to GAs, the quantity of endogenous free ABA in cucumber leaves was much lower in bacterial CS treated plants. Soluble sugar contents and crude protein contents of cucumber leaves were also significantly higher in bacterial CS treatments as compared to control. It was concluded that Burkholderia sp. KCTC 11096BP can be used as an eco-friendly bio-fertilizer in our farming systems.     

干旱胁迫及复水对豌豆根系内源激素含量的影响

采用盆栽试验方法,研究了干旱胁迫及复水对豌豆根系脱落酸(ABA)、吲哚乙酸(IAA)、赤霉素(GA)和玉米素(ZT)等4种内源激素含量的影响.结果表明:不同程度的干旱胁迫均导致各生育期豌豆根系ABA和IAA含量增加,GA和ZT含量减少,且随干旱胁迫程度的加重变化量增大.同时对各生育期豌豆根系内源激素比例产生影响,对ZT与ABA、GA与ABA、GA与IAA、ZT与IAA比例影响较大,对ZT与GA、IAA与ABA比例影响较小.旱后复水可对各生育期豌豆根系内源激素含量产生补偿效应,其补偿量决定于豌豆生育时期、干旱胁迫强度和复水历时.同时促进各生育期豌豆根系内源激素比例发生变化.     

Biochemical Responses to True and Bicarbonate-Induced Iron Deficiency in Grapevine Genotypes

ABSTRACT

Biochemical responses to direct or bicarbonate-induced iron (Fe) deficiency were compared in two Tunisian native grapevine varieties, Khamri (tolerant) and Balta4 (sensitive), and a tolerant rootstock, 140Ru. Woody cuttings of each genotype were irrigated with a nutrient solution containing one of the following: 20 μM Fe (control), 1 μM Fe (direct Fe-deficiency), or 20 μM Fe + 10 mM HCO₃ ^? (indirect bicarbonate-induced Fe-deficiency). Under direct Fe-deficient conditions, lower leaf chlorosis score and higher chlorophyll and leaf Fe contents were found in Khamri and 140Ru compared with Balta4. Moreover, indirect Fe deficiency caused similar effects on these parameters, which were more pronounced in Balta4. Both tolerant genotypes, Khamri and 140Ru, showed higher roots-acidification capacity and phenol release under the direct Fe deficiency compared with the bicarbonate-induced condition. In the sensitive variety, Balta4, no significant changes were found between the control and Fe-deficient plants. Root Fe(III)-reductase activity was strongly stimulated by both types of Fe deficiency in Khamri and 140Ru, and displayed no significant changes in Balta4. In the three genotypes, root and leaf activities of two Fe-containing enzymes, catalase and guaiacol peroxidase, were significantly affected under Fe deficiency (either direct or induced), though to a greater extent in the sensitive variety, Balta4. The latter also displayed higher leaf malonyldialdehyde (MDA) content, traducing an important membrane lipid peroxidation.     

Genotypic Variation in Nodule Iron Content of Common Bean (Phaseolus Vulgaris L.) in Response to Phosphorus Deficiency

Common bean (Phaseolus vulgaris L.) can supply all of the iron that humans require for metabolism. Also, it fixes atmospheric nitrogen (N₂) in symbiosis with rhizobia. In order to analyze the relation between phosphorus (P) and iron (Fe) elements in nodules and their roles for the plant N₂-dependent growth, six common bean recombinant inbred lines (RIL) of the cross of BAT477 and DOR364 were inoculated with Rhizobium tropici CIAT 899 (originating from International Center of Tropical Agriculture, Colombia) and grown with sufficiency versus deficiency P supply in hydroaeroponic culture. Under P deficiency, the Fe content in nodules decreased in all studied genotypes and was significantly the highest for RIL 34. The nodule contents of Fe and P were significantly correlated under P deficiency. It is concluded that the regressions of nodule Fe content as a function of P content in nodules, roots and shoots, depend upon P supply and genotype.     

Changes in nutritional homeostasis of Poncirus trifoliata and Ceratonia siliqua as a response to different iron levels in nutrient solution

Abstract

Iron (Fe) deficiency is a nutritional disorder in plants. Poncirus trifoliata is susceptible to Fe deficiency, but symptoms of Fe deficiency are rare in Ceratonia siliqua, a slow-growing species. Specimens of the two species were grown in nutrient solutions containing three Fe concentrations: without Fe (0?µM), 1?µM Fe, and either 10?µM Fe (for Ceratonia) or 40?µM Fe (for P. trifoliata). Growth, the degree of chlorosis, the plant mineral composition, and the activity of the root ferric chelate-reductase (FCR) were assessed. Ceratonia plants exposed to 1?µM Fe were efficient at using Fe in the synthesis of chlorophyll. The activity of FCR was enhanced in the total absence of Fe. In Poncirus a low activity of the FCR was observed in plants with no Fe. The balance between micronutrients in the Ceratonia roots was not affected with 1?µM Fe compared with the higher Fe concentration treatments.     

Release of phytosiderophores from roots of wheat and triticale under nickel‐deficient conditions

Despite numerous studies on phytosiderophores (PS) there is still an open question whether nickel (Ni) deficiency induces release of PS from graminaceous plant roots. Seedlings of two wheat cultivars (Triticum aestivum L. cvs. Rushan and Kavir) and a triticale cultivar (X. triticosecale) were grown in Ni‐free nutrient solution (Ni‐deficient, Ni–) and with 10 µM NiSO₄ (Ni‐sufficient, Ni+, control). Root exudates were collected weekly for 4 weeks and the amount of PS in the root exudates was measured. The response to Ni deficiency on the release of PS differed between species. Roots of Rushan and triticale exuded higher PS in response to Ni‐deficient conditions. Nickel deficiency significantly enhanced shoot Fe and Zn concentrations in wheat, while it decreased shoot Fe and Zn concentrations in triticale. In Kavir, PS exudation was decreased by Ni deficiency at weeks 3 and 4 and the reduced release of PS from roots of Kavir was accompanied by lower concentrations of Fe and Zn in plant roots but higher Fe and Zn concentrations in shoot tissue. The PS release by Kavir was triggered by a Ni‐induced Zn deficiency particularly in the shoots. According to the results, it is suggested that in the studies concerning the phytosiderophore release under Ni deficiency, special attention should be given to different responses among and within cereals and to the plant Zn or Fe nutritional status.     

Uptake and apoplastic retention of EDTA‐ and phytosiderophore‐chelated chromium(III) in maize

Increasing the mobilization and root uptake of chromium (Cr) by synthetic and plant‐borne chelators might be relevant for the design of phytoremediation strategies on Cr‐contaminated sites. Short‐term uptake studies in maize roots supplied with ⁵¹CrCl₃ or ⁵¹Cr(III)‐EDTA led to higher apoplastic Cr contents in plant roots supplied with ⁵¹CrCl₃ and in Fe‐sufficient plants relative to Fe‐deficient plants, indicating that Fe stimulated co‐precipitation of Cr. Concentration‐dependent retention of Cr in a methanol:chloroform‐treated cell‐wall fraction was still saturable and in agreement with the predicted tendency of Cr(III) to precipitate as Cr(OH)₃. To investigate a possible stimulation of Cr(III) uptake by phytosiderophores, Fe‐deficient maize roots were exposed for 6 d to Cr(III)‐EDTA or Cr(III)‐DMA (2'‐deoxymugineic acid). Relative to plants without Cr supply, the supply of both chelated Cr species in a subtoxic concentration of 1 µM resulted in alleviation of Fe deficiency–induced chlorosis and higher Cr accumulation. Long‐term Cr accumulation from Cr(III)‐DMA was similar to that from Cr(III)‐EDTA, and Cr uptake from both chelates was not altered in the maize mutant ys1, which is defective in metal‐phytosiderophore uptake. We therefore conclude that phytosiderophores increase Cr solubility similar to synthetic chelators like EDTA, but do not additionally contribute to Cr(III) uptake from Cr‐contaminated sites.     

Contribution of N : P ratio and endogenous phytohormones during development of phosphorus toxicity in Brassica campestris spp. parachinensis

Agricultural practices may lead to excessive phosphorus (P) accumulation in soil. The effects of excessive P on Chinese flowering cabbage (Brassica campestris spp. parachinensis) were investigated by exposing plants for 4 weeks in solution containing 1, 2, 3, 5, and 7 mM NaH₂PO₄. Phosphorus concentrations [P] greater than 3 mM produced significantly stunted growth, together with reduced appearance quality due to overaccumulation of anthocyanin in the epidermis of flower stalk. Nitrate concentrations in the flower stalk decreased with increasing solution [P]. Nitrogen (N) concentrations in the roots and potassium (K) concentrations in the leaves, stems, and roots all decreased at [P] higher than 3 mM. Increasing P supply caused great enhancement of root and stem [P], but decreased total plant and root N : P ratios. A positive linear relationship between solution [P] and anthocyanin concentration and a negative linear relationship between root N : P ratio and anthocyanin concentration were also observed. In addition, 3 to 7 mM P caused decreased levels of indole‐3‐acetic acid (IAA) and gibberellin (GA₃) in the leaves, but promoted ethylene production. The average gibberellin concentration was generally correlated with the plant's relative growth rates. Ethylene was negatively correlated with plant growth parameters except for the last day of the experiment. In conclusion, N : P ratio and endogenous phytohormones may be involved in the development of P toxicity in Chinese flowering cabbage plants.     

SH6中间砧不同埋土深度对苹果幼树内源激素和氮素利用的影响

【目的】苹果矮化密植集约化栽培已成为国内外现代苹果生产发展的主流和方向。应用矮化中间砧是当前我国果树生产上采用的主要致矮手段,但矮化中间砧苹果存在氮素吸收利用率低、 树势弱、 易衰老等问题,目前我国对于矮化中间砧的栽培标准尚不统一,生产上大都采用的中间砧埋深1/2的措施也缺乏一定的理论依据。因此,研究中间砧不同埋土深度对苹果幼树内源激素和氮素利用的影响,以期为确定SH6中间砧埋土的最适深度提供理论依据。【方法】利用15N同位素示踪技术,以两年生宫藤富士/SH6/平邑甜茶(Borkh cv. Fuji/SH6/M.hupehensis Rehd)为试材,于春梢萌芽前,设置3个埋土深度,其中T1为中间砧全埋,T2为中间砧埋深1/2,T3为中间砧全露,同时每棵施0.5 g 15N-尿素,5次重复。于春梢旺长期、 春梢停长期,采用酶联免疫法测定茎尖和细根的激素含量;植株停止生长时,整株解析,称量各部分鲜重、 干重,测定植株全氮及其15 N 丰度。【结果】中间砧埋土深度与植株生长关系密切,株高、 茎粗、 鲜重、 细根生物量均以全埋(T1)最高,全露(T3)最低,且两者差异显著。中间砧不同埋土深度影响植株内源激素含量,不同处理间存在差异,新梢旺长期和新梢停长期茎尖、 新梢中赤霉素(GA)和生长素(IAA)含量均表现为T1T2T3,而脱落酸(ABA)的含量则相反; 新梢停长期,T2处理茎尖的玉米素核苷(ZR)/赤霉素(GA)比值比T1和T3处理分别升高了8.53%、 6.06%;各时期茎尖和细根的ABA/GA和 ABA/IAA比值均为T3T2T1;新梢旺长期,T1、 T2和T3处理茎尖(GA+ZR+IAA)/ABA比值分别为1.66、 0.83和0.71。植株全氮、 15N吸收量、 氮肥利用率均以T1处理最大,T2处理次之,T3最小;同一器官不同处理间Ndff%值也存在差异,T3处理显著高于其他处理。【结论】SH6中间砧埋深1/2处理的生长促进型激素GA和IAA的含量以及(GA+ZR+IAA)/ABA比值均降低,并且与花芽分化有关的ZR/GA比值明显升高。中间砧埋深1/2处理既能调节植株体内激素平衡,起到矮化效果,又能促进根系对氮的吸收利用、 提早花芽分化。因此生产上SH6苹果中间砧以埋深1/2的效果最好。     

Iron deficiency responses in roots of kiwi

Many dicotyledonous species respond to iron (Fe) deficiency by morphological and physiological changes at root level, which are usually defined as Strategy I. Particularly, these latter modifications include a higher acidification of the external medium and the induction of a high root Fe reductase activity. The aim of this work was to investigate the response of kiwi (Actinidia deliciosa cv. Hayward) plants, which often exhibit Fe chlorosis in the field, to Fe deficiency. Actinidia kept for two weeks in nutrient solution without Fe showed visual deficiency symptoms (leaf chlorosis). Moreover, upon prolonged micronutrient shortage shoot, and to a lesser extent, root dry weight accumulation was greatly impaired. Roots of Fe‐deficient Actinidia showed an increased capacity of net proton extrusion and higher ferric ethylenediaminetetraacetate [Fe(III)EDTA] reductase activity as compared to plants grown in the presence of 10 μM Fe(III)EDTA. Localization of the increased acidification and reductase capacity by means of agar‐technique revealed that these activities are both present in the sub‐apical region of the roots. Re‐supply of Fe after two weeks partially reversed the tendency of the roots to acidify the nutrient solution and to reduce Fe(III)EDTA.