Al-sensitive Cultivar Research Articles

Patterns of Root Respiration Associated with the Induction of Aluminium Tolerance inPhaseolus vulgarisL.

Aluminium (Al) tolerance in an Al-tolerant cultivar of Phaseolus vulgaris L. («Dade») was found to be an inducible trait. Upon exposure to 10 μM Al, the rate of root elongation was inhibited in comparison to controls. During the following 72 h, the rate of elongation returned to levels comparable to controls. In contrast, root elongation of an Al-sensitive cultivar («Romano») did not recover after exposure to Al. In Dade, the resumption of root elongation following exposure to Al was accompanied by increased rates of root respiration, whereas respiration rates slowly declined over the 72 h treatment period in Romano

Aluminium effects on growth, nutrient net uptake and transport in 3 rice (Oryza sativa) cultivars with different sensitivity to aluminium

Varietal differences in net nutrient uptake rate and transport efficiency in the presence of aluminium have seldom been investigated in rice. Therefore, effects of Al on growth, uptake and transport of macronutrients (K, P, Ca, and Mg) and micronutrients (Fe, Zn, Cu, and Mn) were evaluated in 3 rice cultivars (BG35, DA14 and IR45) with different Al sensitivity. The plants were grown in nutrient solution at pH 4.1. An initial growth was completed in the time interval 1 to 5 days immediately before the addition of Al. The final growth period with Al (0, 140, 280 or 560 μM) was completed on day 26. With Al, a comparatively high P accumulation occurred in shoots and roots of the Al tolerant cultivar BG35. In contrast, the Al sensitive cultivar IR45 maintained a relatively high Ca accumulation during the Al treatment. A reduced total net uptake rate of P and Ca by IR45 in the time period 5 to 26 days was due to both a reduced root fresh weight and a reduced net uptake rate per g fresh weight of root. Moreover, net Ca transport to the shoots higher than net uptake rate in DA14 and IR45 at > 140 μM Al during the test period suggests restricted Ca uptake by the roots in combination with a continuous net loss of Ca from the roots to the shoots as time proceeds. In the case of Mg and Mn, there was a general reduction of net uptake rates, irrespective of Al sensitivity of cultivars. With Al treatment, comparatively high accumulation of Fe, Zn and Cu occurred in the roots of IR45, concomitant with a high net Zn and Cu uptake rate. It is concluded that differences in Al sensitivity among rice cultivars BG35, DA14 and IR45 are not primarily linked to the depressed internal Mg or Mn status of the plants but rather to changes in the uptake and distribution of Ca and P.

Effects of Biological Inhibitors on Kinetics of Aluminium Uptake by Excised Roots and Purified Cell Wall Material of Aluminium-Tolerant and Aluminium-Sensitive Cultivars of Triticum aestivum L.

The effects of biological inhibitors on the kinetics of aluminium (Al) uptake by excised roots and purified cell-wall material of two Al-tolerant and two Al-sensitive cultivars of Triticum aestivum were investigated. In excised roots, treatment with 2,4-dinitrophenol (DNP) increased rates of Al uptake by 52% and 73% in Al-tolerant cultivars, but only by 7% and 25 % in Al-sensitive cultivars. Gramicidin increased rates of Al uptake by 22% and 61% in Al-sensitive cultivars, while those of Al-tolerant cultivars were not affected. The combined effects of gramicidin and DNP on Al uptake were synergistic in Al-tolerant cultivars and multiplicative in Al-sensitive cultivars. Further investigations included fract ionation of excised roots after absorption and desorption in vivo . In these experiments, kinetics of Al uptake in purified cellwall material was unaffected by gramicidin, while increased uptake in the cell wall fraction was observed with DNP and DNP plus gramicidin. In contrast, in vitro uptake of Al by purified cell-wall material was unaffected by both DNP and gramicidin, suggesting that accumulation of Al in the cell-wall depends on the existence of a functional plasma membrane and/ or cellular integrity. In all experiments with purified cell-wall material, no differences were observed between Al-tolerant and Al-sensitive cultivars. Thus, differences in the kinetics of Al uptake by excised roots could not be accounted for simply by differences in Al uptake into the cell wall. While the physiological basis of Al tolerance is still not clear, the effects of biological inhibitors on the kinetics of Al uptake by excised roots and purified cell-wall material in Al-tolerant and Al-sensitive cultivars provide exp erimental evidence that is consistent with the op eration of an energy-dependent exclusion mechanism.

Aluminum Ions Induce Oat Protoplasts to Produce an Extracellular (1→3)β-d-Glucan

Aluminum chloride induced mesophyll protoplasts of oat (Avena sativa) to produce an extracellular polysaccharide (EPS). EPS induced by AlCl(3) appeared identical to that produced in response to the phytotoxin victorin (JD Walton, ED Earle [1985] Planta 165: 407-415). Al ions at 1 millimolar were toxic to protoplasts, but maximum EPS production occurred at a sublethal concentration of 200 micromolar, assayed at pH 6.0. As measured by incorporation of [(14)C]glucose, AlCl(3) stimulated EPS production 10- to 15- fold. Pretreatment of protoplasts with cycloheximide prevented EPS production but not cell death in response to AlCl(3), indicating that protein synthesis was necessary for EPS production but not for the phytotoxicity of Al ions. The trivalent salts of Y, Yb, Gd, and In also induced EPS production but those of Sc, Fe, Ga, Cr, and La did not. Mesophyll protoplasts from an acid-soil tolerant oat cultivar, Coker 83-23, produced less EPS in response to AlCl(3) than the acid-soil sensitive cultivar Fla 501. EPS was also produced by wheat (Triticum aestivum) and barley (Hordeum vulgare) protoplasts in response to AlCl(3). An Al-tolerant cultivar of wheat, Atlas, produced less EPS than an Al-sensitive cultivar, Scout, but an Al-tolerant cultivar of barley, Dayton, produced more than the Al-sensitive cultivar Kearney. Therefore, production of EPS by protoplasts in response to Al ions did not appear to be related to Al ion tolerance at the level of whole plants. EPS fluoresced in the presence of Calcofluor and Sirofluor and was degraded by purified laminarinase [(1-->3)beta-d-glucanase] but not pectinase (polygalacturonase). EPS was composed solely of glucose in 1-->3 linkages; hence it is a (1-->3)beta-d-glucan (callose).

Kinetics of Aluminum Uptake by Excised Roots of Aluminum-Tolerant and Aluminum-Sensitive Cultivars of Triticum aestivum L.

Uptake of aluminum (Al) by excised roots of two Al-tolerant cultivars and two Al-sensitive cultivars of Triticum aestivum L. (wheat) was biphasic, with a rapid phase of uptake in the first 30 minutes followed by a linear phase of uptake up to 180 minutes. At the end of the uptake period, higher concentrations of Al were found in roots of the Al-sensitive cultivars (Neepawa and Scout-66) than in the Al-tolerant cultivars (Atlas-66 and PT-741), but differences were small. Experiments testing the effectiveness of several desorption agents demonstrated that citric acid was most effective in desorption of loosely bound Al (the putative apoplasmic compartment) followed by others in the order tartaric acid > EDTA > CaSO(4) = ScCl(3). In all cultivars, 30 minutes of desorption with citric acid depleted the rapidly exchanging, putative apoplasmic compartment, although some tightly bound Al remained in that compartment. The relationship between Al remaining after desorption and time in the uptake medium was nearly linear and no distinction was observed between Al-tolerant and Al-sensitive cultivars. However, uptake of Al by the Al-tolerant cultivars was increased by treatment with the protonophore 2,4-dinitrophenol (DNP), while uptake of Al by Al-sensitive cultivars was relatively unaffected. Such results suggest the possible involvement of an active exclusion mechanism in Al-tolerant cultivars of T. aestivum.

Aluminum inhibition of shoot lateral branches ofGlycine max and reversal by exogenous cytokinin

Aluminum effects on the morphological development of soybean (Glycine max (L.) Merr.) were characterized in greenhouse and growth chamber experiments. An Al-sensitive cultivar, ‘Ransom’, was grown in an acid soil (Aeric Paleudult) adjusted to 3 levels of exchangeable Al. Lateral shoot development at the nodes of the main stem was extensive in the limed soil containing 0.06 cmol(+) Alkg−1. However, lateral shoot length and weight were severely inhibited in the unlimed soil containing 2.19 cmol(+) Alkg−1, and in the unlimed soil amended to 2.63 cmol(+) Alkg−1 with AlCl3. This inhibition by the high Al/low pH condition was reversed by the exogenous application of a synthetic cytokinin 6-benzylaminopurine (BA). The daily application of 20 μg mL−1 BA applied locally to the lateral meristems of plants grown in the unlimed soil stimulated lateral shoot growth substantially, such that it was either comparable to or greater than that observed in the limed treatment without BA. Accumulation of K, Ca, and Mg in lateral shoot branches was also stimulated by the local application of BA. The inhibitory effects of Al on lateral shoot development were confirmed in solution culture. In addition, differential sensitivity to Al was evident among the primary root, first order lateral roots, and second order lateral roots. The length of the primary root was only slightly decreased by increasing concentrations of Al up to 30 μM. In contrast, the length of basipetally located first order lateral roots was restricted to greater extent; up to 50% by 30 μM Al. Second order lateral lengths were inhibited even more severely; up to 86% by 30 μM Al. Substantial evidence in the literature indicates that the root apex is a major site for the biosynthesis of cytokinin that is supplied to shoots, and cellular function and development in this region of the root are impaired during Al toxic conditions. This suggests that one mode of action by which Al may affect shoot growth is by inhibiting the synthesis and subsequent translocation of cytokinin to the meristematic regions of the shoot. The present observation of a reversal of Al-inhibited lateral shoot development by exogenously applied cytokinin supports this hypothesis. However, the inability of applied cytokinin to counter the restriction imposed by Al on total shoot dry matter production implies the impairment by Al toxicity of other root functions, such as ion and water transport, also played an important role in altering shoot morphology.

Responses of Al-tolerant Dayton and Al-sensitive Kearney barley cultivars to calcium and magnesium during al stress

Responses of Al-tolerant Dayton and Al-sensitive Kearney barley cultivars to calcium and magnesium during al stress

Melhoramento do trigo: XIV. Correlações entre a tolerância à toxicidade a dois níveis de alumínio e altura das plantas com outros caracteres agronômicos em trigo

Visando estimar as correlações entre a altura das plantas com sete caracteres agronômicos e aquelas entre a tolerância a 1 e 3 mg/litro de Al3+ em solução nutritiva com produção de grãos, altura das plantas e número de grãos por espigueta, foram efetuados, no Centro Experimental de Campinas, em 1983, cruzamentos entre o cultivar de trigo BH-1146, com Siete Cerros e Tobari-66. Plântulas representando os pais e as gerações F1 e F2 foram testadas para a reação a 1 e 3 mg/litro de Al3+ em solução nutritiva no laboratório. As plântulas, devidamente identificadas, foram transplantadas em número de quatro por vaso, empregando-se no total 164 vasos dispostos em quatro blocos ao acaso. Os dados referentes à produção de grãos e a outros caracteres agronômicos foram obtidos de plantas individuais em 1984. Os valores da herdabilidade no sentido restrito para comprimento da espiga, número de grãos por espiga, número de grãos por espigueta e número de espigas por planta foram de 0,79; 0,75; 0,73 e 0,68 respectivamente, e de 0,58; 0,53 e 0,50 para número de espiguetas por espiga, altura das plantas e peso de cem grãos respectivamente. Para produção de grãos, o valor estimado foi de 0,38. Nas populações estudadas, a altura das plantas foi correlacionada com todos os caracteres agronômicos estudados, com exceção de número de grãos por espigueta e peso de cem grãos na população BH-1146 x Tobari-66. A tolerância ao alumínio não foi associada com altura das plantas, número de grãos por espigueta e produção de grãos (com exceção da população BH-1 146 x Tobari-66, quando se utilizou a concentração de 3 mg/litro de Al3+), sugerindo ser possível selecionar plantas que combinam a tolerância ao Al3+, porte semi-anão e alto potencial produtivo para serem cultivadas nos solos ácidos. Entretanto, grandes populações F2 seriam necessárias para assegurar a freqüência dos recombinantes desejáveis.

Melhoramento do trigo: X. Estimativas da herdabilidade e correlações entre tolerância à toxicidade de alumínio e produção de grãos com outros caracteres agronômicos em trigo

Visando estimar a herdabilidade para várias características da planta de trigo (tolerância ao Al3+, altura, produção de grãos, número de espigas, número de espiguetas e de grãos por espiga, número de grãos por espigueta, peso de cem grãos e comprimento da espiga), bem como as correlações entre produção de grãos com sete caracteres agronômicos e aquelas entre tolerância ao alumínio com produção de grãos, altura das plantas e número de grãos por espigueta (fertilidade da espiga), foram efetuados cruzamentos entre o cultivar de porte semi-anão Alondra S-46, e os de porte alto 'IAC-5', 'BH-1146' e 'C-3'. Plântulas representando os pais, as gerações F1 e F2 e os retrocruzamentos para ambos os pais foram testados para a reação a 6mg/litro de Al3+ em solução nutritiva. As plantas, devidamente identificadas, foram transplantadas em número de quatro por vaso, empregando-se no total 500 vasos dispostos em quatro blocos ao acaso. Os dados referentes à produção de grãos e a outros caracteres agronômicos foram obtidos de plantas individuais. Os valores da herdabilidade no sentido restrito para comprimento da espiga, número de grãos por espiga, peso de cem grãos e altura da planta foram 0,885; 0,748; 0,760 e 0,720 respectivamente, e de 0,413 e 0,588 para número de espigas por planta e de espiguetas por espiga. Para os demais caracteres estudados, os valores estimados foram baixos, variando de 0,072 a 0,224. Esses resultados indicaram que grande parte da variabilidade genética total para comprimento da espiga, número de grãos por espiga, peso de cem grãos e altura das plantas está associada a uma ação aditiva dos genes. Nas populações estudadas, a característica produção de grãos foi correlacionada significativamente com todos os caracteres agronômicos estudados com exceção do caráter número de espiguetas por espiga. Nessas populações, a tolerância ao alumínio não foi associada com altura das plantas (com exceção da Alondra S-46 x IAC-5), produção de grãos e número de grãos por espigueta, sugerindo que seria possível selecionar plantas tolerantes ao Al3+, de porte médio, com maior fertilidade da espiga e com o potencial produtivo do cultivar Alondra-S-46.

Differential Effects of Aluminum on the Vegetative Growth of Tomato Cultivars in Acid Soil and Nutrient Solution1

Abstract Tomato cultivars developed in Brazil, Hawaii, and different parts of the continental United States differed significantly in their tolerance to an acid (pH 4.2), Al-toxic Bladen soil. Cultivars showing greatest tolerance included ‘BGH 588’ (Brazil), ‘Ace’ (Calif.) and Owyhee’ (Idaho); those showing low tolerance included ‘BGH 402’ (Brazil), Anahu’ (Hawaii), and Truckers Favorite’. Differential Al tolerances of ‘BGH 588’, ‘BGH 402’, and ‘Truckers Favorite’ were confirmed in nutrient solutions containing a range of Al concentrations. Tolerance to Al-toxic Bladen soil, measured by vegetative growth, was not associated with reported resistance to blossom end rot (Ca deficiency). Cultivars showing the greatest tolerance to acid Bladen soil tended to contain lower concentrations of Al, Ca, and P in their tops than did the more sensitive cultivars. In nutrient solutions containing Al, the tops of Al-tolerant and Al-sensitive cultivars generally contained similar concentrations of Al, P, and Ca. Roots of tolerant cultivars tended to contain lower concentrations of Al and P and sometimes Ca. Results suggest the possibility of developing tomato cultivars specifically for greater tolerance to acid soil environments which cannot be economically corrected. An example would be strongly acid Al-toxic soil zones beneath the plow layer.