Renata Rauber

Cadmium and mineral nutrient accumulation in potato plantlets grown under cadmium stress in two different experimental culture conditions

In order to evaluate the effect of cadmium (Cd(2+)) toxicity on mineral nutrient accumulation in potato (Solanum tuberosum L.), two cultivars named Asterix and Macaca were cultivated both in vitro and in hydroponic experiments under increasing levels of Cd(2+) (0, 100, 200, 300, 400 and 500 microM in vitro and 0, 50, 100, 150 and 200 microM in hydroponic culture). At 22 and 7 days of exposure to Cd(2+), for the in vitro and hydroponic experiment, respectively, the plantlets were separated into roots and shoot, which were analyzed for biomass as well as Cd(2+), and macro (Ca(2+), K(+) and Mg(2+)) and micronutrient (Cu(2+), Fe(2+), Mn(2+) and Zn(2+)) contents. In the hydroponic experiment, there was no reduction in shoot and root dry weight for any Cd(2+) level, regardless of the potato cultivar. In contrast, in the in vitro experiment, there was an increase in biomass at low Cd(2+) levels, while higher Cd(2+) levels caused a decrease. In general, Cd(2+) decreased the macronutrient and micronutrient contents in the in vitro cultured plantlets in both roots and shoot of cultivars. In contrast, the macronutrient and micronutrient contents in the hydroponically grown plantlets were generally not affected by Cd(2+). Our data suggest that the influence of Cd(2+) on nutrient content in potato was related to the level of Cd(2+) in the substrate, potato cultivar, plant organ, essential element, growth medium and exposure time.

Oxidative stress is an early symptom triggered by aluminum in Al-sensitive potato plantlets.

The objective of this study was to evaluate whether the oxidative stress caused by aluminum (Al) toxicity is an early symptom that can trigger root growth inhibition in Macaca (Al-sensitive) and SMIC148-A (Al-tolerant) potato clones. Plantlets were grown in a nutrient solution (pH 4.00) with 0, 100 and 200mg Al L(-1). At 24, 72, 120 and 168h after Al addition, root length and biochemical parameters were determined. Regardless of exposure time, root length of the Macaca clone was significantly lower at 200mg Al L(-1). For the SMIC148-A clone, root length did not decrease with any Al treatments. Al supply caused lipid peroxidation only in Macaca, in both roots (at 24, 72, 120 and 168h) and shoot (at 120 and 168h). In roots of the Macaca, catalase (CAT) and ascorbate peroxidase (APX) activity decreased at 72 and 120h, and at 24, 72 and 120h, respectively. At 168h, both activities increased upon addition of Al. In roots of the SMIC148-A, CAT activity increased at 72 and 168h, whereas APX activity decreased at 72h and increased at 24, 12 and 168h. The Macaca showed lower root non-protein thiol group (NPSH) concentration at 200mg Al L(-1) in all evaluations, but the SMIC148-A either did not demonstrate any alterations at 24 and 72h or presented higher levels at 120h. This pattern was also observed in root ascorbic acid (AsA) concentration at 24 and 120h. The cellular redox status of these potato clones seems to be affected by Al. Therefore, oxidative stress may be an important mechanism for Al toxicity, mainly in the Al-sensitive Macaca clone.

Effect of cadmium on growth, micronutrient concentration, and δ-aminolevulinic acid dehydratase and acid phosphatase activities in plants of Pfaffia glomerata

Plântulas de Pfaffia glomerata (Spreng.) Pedersen foram cultivadas em cinco niveis (0, 20, 40, 60 e 80 μM) de cadmio (Cd) em um sistema hidroponico durante 7 d, visando-se analisar o crescimento, as concentracoes de micronutrientes, clorofilas e carotenoides, bem como as atividades da desidratase do acido δ-aminolevulinico (ALA-D; E.C.4.2.1.24) e fosfatase acida (AP; E.C.3.1.3.2) nas plantas. A concentracao de Cd, na parte aerea e raizes, aumentou com o incremento dos niveis de Cd. A concentracao de Cd nas raizes foi, em media, 12 vezes maior do que na parte aerea. O comprimento das raizes nao foi afetado pelos tratamentos de Cd. Em contraste, a biomassa seca da parte aerea e raizes aumentou significativamente pela adicao de 20 e 40 μM Cd. Alem disso, a biomassa seca total das plantas somente diminuiu no nivel de 80 μM Cd em relacao a das plantas-controle. Por outro lado, a biomassa radicular diminuiu significativamente pela adicao de Cd a niveis superiores a 40 μM. Constatou-se resposta dependente do orgao e do micronutriente a toxicidade de Cd. As concentracoes de Zn e Cu na parte aerea e raizes nao foram alteradas pela presenca de Cd. A absorcao de Mn foi diminuida pelo estresse de Cd, porem sua translocacao nao foi alterada. Um efeito sinergistico do Cd na concentracao de Fe nas raizes foi observado nos niveis de 20 e 80 μM Cd. As atividades da ALA-D e AP foram diminuidas com o incremento dos niveis de Cd, porem a ALA-D foi mais afetada. Naquelas concentracoes de Cd, a concentracao de clorofila tambem foi diminuida. Houve uma correlacao positiva entre as concentracoes de carotenoides e clorofila. Os resultados indicam que a P. glomerata parece ter algum grau de tolerância ao Cd.

Physiological and oxidative stress responses of four potato clones to aluminum in nutrient solution

Aluminum toxicity is a serious problem in Brazilian soils and selecting potato clones is an important strategy to produce this crop on these kinds of soils. Potato clones, Macaca, SMIC148-A, Dakota Rose, and Solanum microdontum, were grown in a nutrient solution (pH 4.0) with 0, 50, 100, 150 and 200 mg Al L-1. After 7 d, Al concentration in both root system and shoot of all clones increased linearly with increasing Al levels. Based on relative root growth, S. microdontum and SMIC148-A were considered Al-tolerant clones, whereas Macaca and Dakota Rose were considered Al-sensitive. Shoot growth in Macaca linearly decreased with increasing Al levels. Root H2O2 concentration in both Al-sensitive clones increased with increasing Al supply, whereas in Al-tolerant clones it either decreased (SMIC148-A) or demonstrated no alteration (S. microdontum). Shoot H2O2 concentration increased linearly in Macaca, whereas for Dakota Rose it showed a quadratic relationship with Al levels. On the other hand, shoot H2O2 concentration in the Al-tolerant clones either demonstrated no alteration (S. microdontum) or presented lower levels (SMIC148-A). Root catalase (CAT) activity in both Al-sensitive clones increased with increasing Al levels, whereas in Al-tolerant clones it either demonstrated no alteration (SMIC148-A) or presented lower levels (S. microdontum). Shoot CAT activity in the S. microdontum increased curvilinearly with increasing Al levels. In all potato clones, chlorophyll concentration showed a curvilinear response to Al supply, where in Al-sensitive clones it decreased upon addition of Al exceeding 100 mg L-1, but in SMIC148-A it increased at levels between approximately 100 and 150 mg L-1, and decreased in S. microdontum regardless of the Al level. Carotenoid concentrations in the Al-sensitive clones were linearly decreased with increasing Al levels. Aluminum supply caused root lipid peroxidation only in the Al-sensitive clones, whereas in the shoot it increased linearly in the Al-sensitive clones and in S. microdontum it only increased at around 50 mg L-1. Most of root protein oxidation was only observed in the Al-sensitive clones. However, shoot protein oxidation was increased with increasing Al levels for all potato clones. These results indicate that oxidative stress caused by Al in potato may harm several components of the cell, mainly in Al-sensitive clones.

Caracterização das exigências nutricionais de mudas de Pfaffia glomerata em Argissolo Vermelho distrófico arênico pela técnica do nutriente faltante

Este trabalho teve por objetivo caracterizar as exigencias nutricionais de mudas de ginseng brasileiro (Pfaffia glomerata (Spreng.) Pedersen) em Argissolo Vermelho distrofico arenico pela tecnica do nutriente faltante. Plantas de P. glomerata produzidas in vitro e aclimatizadas ex vitro foram usadas como material inicial para o experimento em casa de vegetacao. Aos 10 dias apos o transplante para o solo, atraves de solucoes nutritivas, foram realizadas as adubacoes correspondentes a nove tratamentos: controle (sem adubacao), adubacao completa (com macro e micronutrientes) e as omissoes individuais de N, P, K, Ca, Mg, S e dos micronutrientes (Zn, B, Cu, Fe, Mn e Mo). Aos 60 dias de cultivo, avaliaram-se os parâmetros de crescimento das plantas. O numero de folhas por planta foi o parâmetro de crescimento mais afetado pela ausencia dos nutrientes N, K, S e P na adubacao. O efeito da omissao dos nutrientes na adubacao foi diferenciado quanto a particao de biomassa entre os orgaos da planta. A biomassa acumulada pela parte aerea obedeceu a seguinte ordem decrescente, em relacao a omissao do nutriente: Mg @ micronutrientes > Ca @ adubacao completa > P > S > K > N @ controle. Ja a biomassa radicular obedeceu a seguinte ordem decrescente: Mg @ adubacao completa ³ P ³ micronutrientes ³ S ³ Ca > N > K @ controle. Plantas jovens de P. glomerata cultivadas em Argissolo Vermelho distrofico arenico apresentaram grande reducao no crescimento pela ausencia de N, K, S e P na adubacao. As omissoes de Mg e dos micronutrientes na adubacao nao foram limitantes para o crescimento das plantas jovens.

Micronutrient concentration in potato clones with distinct physiological sensitivity to Al stress

The objective of this study was to evaluate the effects of aluminum (Al) on the zinc (Zn), manganese (Mn), iron (Fe) and copper (Cu) concentrations in four potato clones (Macaca and Dakota Rose: both Al-sensitive clones; and SMIC148-A and Solanum microdontum: both Al-tolerant-clones), grown in a nutrient solution (pH 4.00) with 0, 50, 100, 150 and 200mg Al L-1. Root Zn and Fe concentrations decreased linearly with the increase of Al levels in Macaca, SMIC148-A and Dakota Rose and increased linearly in S. microdontum. Shoot Zn concentration showed a quadratic relationship with Al in S. microdontum and SMIC148-A, but a curvilinear response in Dakota Rose. Shoot Fe concentration showed a quadratic relationship with Al in S. microdontum, SMIC148-A and Dakota Rose. Root Mn concentration decreased linearly in Macaca and SMIC148-A, and increased linearly in S. microdontum with Al levels. Mn concentration showed a quadratic relationship with Al in roots of Dakota Rose and in shoot of SMIC148-A, and increased curvilinearly with Al levels in shoot of Dakota Rose. In shoot, there was no alteration in Zn, Fe and Mn in Macaca and Mn concentration in S. microdontum. Roots and shoot Cu concentration increased linearly in Dakota Rose, and showed quadratic relationship with Al in Macaca. Roots Cu concentration showed a quadratic relationship with Al levels in S. microdontum and SMIC148-A. Shoot Cu concentration increased linearly in S. microdontum, and decreased linearly in SMIC148-A. Therefore, the excessive Al accumulation affected the uptake and distribution of Zn, Fe, Mn and Cu in roots and shoot of potato clones.The response of shoot Cu concentration to Al was less altered in the Al-tolerant clones than was in Al-sensitive clones. Aluminum tolerance in S. microdontum may be connected with greater levels of Zn, Fe and Mn in the roots.

Effect of aluminum on the in vitro activity of acid phosphatases of four potato clones grown in three growth systems

The aim of this study was to assess the effect of aluminum on the in vitro activity of acid phosphatases (APases) of four potato clones, Macaca and Dakota Rose (Al-sensitive), and SMIC148-A and Solanum microdontum (Al-tolerant), grown in vitro, in hydroponics or in a greenhouse. The enzyme was assayed in vitro in the presence of 0, 1.85, 3.70, 5.55 and 7.40 mM Al. In plantlets grown in vitro, root APases were inhibited by Al in all clones, while shoot APases were inhibited by Al in S. microdontum and Dakota Rose and increased in Macaca at all Al concentrations. In plantlets grown in hydroponics, root APases increased in Macaca at 1.85 mM Al, whereas decreased at all Al levels in S. microdontum. In greenhouse plantlets, root APases decreased at 7.40 mM Al in S. microdontum and SMIC148-A, and at 3.70, 5.55 and 7.40 mM Al in Dakota Rose. Shoot APases decreased in Macaca and SMIC148-A. Conversely, in Dakota Rose, APases increased at 1.85 and 3.70 mM Al. These results show that the effect of Al toxicity on in vitro APase activity depends not only on Al availability but also on the plant organ, genetic background, and the growth conditions. Therefore, it suggests that acid phosphatases activity assessed in vitro might not be a good parameter to validate the screening for adaptation of potato clones to Al toxicity.