Cristiane Elizabeth Costa de Macêdo

GERMINAÇÃO IN VITRO DE MANGABEIRA (Hancornia speciosa Gomez) EM DIFERENTES MEIOS DE CULTURA

Culture media studies that facilitate recalcitrant seed germination are very important to the fruit crops. Mangabeira (Hancornia speciosa Gomez) is a native specie from Brazilian Northeast. Its propagation by traditional methods is difficult because its seeds are recalcitrant and the fruit pulp has an inhibitory effect on seed germination. Trying to maximize its in vitro germination percentage, it was tested the influence of sucrose (0; 10; 30; 60 e 90 g/L), giberelic acid (0; 0.1; 0.3 e 0.5 mg/L), and different culture media (distilled water, coconut water, solid MS and liquid MS). It was also tested the scarification effects (seeds with or without tegument). The seeds obtained from mature fruits were scarified or not and inoculated in media containing different treatments. The germination rate was calculated 30 days after the seed inoculation. Seeds without tegument obtained higher germination percentage in all studied culture media being the highest one obtained from MS liquid treatment. The exclusion of sucrose favored the germination in MS solid medium as well in MS liquid. The highest seed germination percentage in MS supplemented with giberelic acid, in both MS solid and MS liquid media, occurred at 0.1 mg/L concentration. The highest in vitro germination rates were obtained upon removal of the seed tegument and posterior inoculation in MS liquid medium supplemented by 0.1 mg/L of giberelic acid.

Concentrações de ANA e BAP na micropropagação de abacaxizeiro L. Merrill (Ananas comosus) e no cultivo hidropônico das plântulas obtidas in vitro

The effect of different ANA and BAP concentrations on in vitro and hydroponic cultures were studied. Pineapple shoots derived from Perola explants variety were inoculated in MS media containing BAP and ANA in different concentrations. Growth parameters of shoots and plantlets were measured for in vitro and hydroponic cultures. Showed a highest multiplication rates of shoots and consequently highest fresh matter production were obtained with BAP and ANA at the concentrations of 1,0 and 0,5 mg L-1 respectively. However, the shoot length as well as the root number formed were higher in the T2 (0,5 de BAP + 0,25 de ANA) and T3 (0,25 de BAP + 0,12 de ANA) treatments. The results showed that after sixty days of hydroponic culture and in the presence of T1 treatment, all plantlets had good developing that was observed in the majority of morphological growth parameters evaluated. The results showed that it is possible to obtain high quantities of shoots and then plantlets which could be cultivated in hydroponic culture using the pineapple micropropagation procedures methods.

Salt-induced changes in antioxidative enzyme activities in root tissues do not account for the differential salt tolerance of two cowpea cultivars

The salt stress effect in root growth and antioxidative response were investigated in two cowpea cultivars which differ in salt tolerance in terms of plant growth and leaf oxidative response. Four-day-old seedlings (establishment stage) were exposed to 100 mM NaCl for two days. The roots of the two cultivars presented distinct response in terms of salt-induced changes in elongation and dry weight. Root dry weight was only decreased in Perola (sensitive) cultivar while root elongation was mainly hampered in Pitiuba (tolerant). Root relative water content remained unchanged under salinity, but root Na+ content achieved toxic levels as revealed by the K+/Na+ ratio in both cultivars. Then, root growth inhibition might be due to ionic toxicity rather than by salt-induced water deficit. Although electrolyte leakage markedly increased mainly in the Perola genotype, lipid peroxidation decreased similarly in both salt-stressed cultivars. APX and SOD activities were reduced by salinity in both cultivars reaching similar values despite the decrease in Pitiuba had been higher compared to respective controls. CAT decreased significantly in Pitiuba but did not change in Perola, while POX increased in both cultivars. The salt-induced decrease in the CAT activity of Pitiuba root is, at principle, incompatible to allow a more effective oxidative protection. Our results support the idea that the activities of SOD, APX, CAT and POX and lipid peroxidation in cowpea seedling roots were not associated with differential salt tolerance as previously characterized in terms of growth rate and oxidative response in plant leaves.

Differences in Cowpea Root Growth Triggered by Salinity and Dehydration are Associated with Oxidative Modulation Involving Types I and III Peroxidases and Apoplastic Ascorbate

The aim of this work was to investigate the balance between the activities of ascorbate peroxidase (APX) and phenol peroxidases (POD) and cowpea root growth in response to dehydration and salt stress. Root growth and indicators of oxidative response were markedly changed in response to salinity and dehydration. Salt treatment strongly inhibited root elongation, which was associated with an increase in lignin content and a significant decrease in the concentrations of apoplastic hydrogen peroxide (H2O2) and ascorbate. In conditions of extreme salinity, cytosol–APX activity was significantly decreased. In contrast, cell-wall POD activity was greatly increased, whereas lipid peroxidation was unchanged. These results indicate that POD could be involved in both H2O2 scavenging and the inhibition of root elongation under high salinity. In contrast, dehydration stimulated primary root elongation and increased lipid peroxidation and apoplastic ascorbate content, but it did not change APX and POD activities or H2O2 concentration. When cowpea roots were subjected to salinity followed by dehydration, the water and pressure potentials were decreased, and lipid peroxidation was markedly increased, highlighting the additive nature of the inhibitory effects caused by salt and dehydration. The proline concentration was markedly increased by dehydration alone, as well as by salt followed by dehydration, suggesting a possible role for proline in osmotic adjustment. Salinity and dehydration induce contrasting responses in the growth and morphology of cowpea roots. These effects are associated with different types of oxidative modulation involving cytosolic-APX and cell-wall POD activities and apoplast H2O2 and ascorbate levels.

Atividade de enzimas antioxidantes e inibição do crescimento radicular de feijão caupi sob diferentes níveis de salinidade

Phenol peroxidase (POX) is a dual enzyme that is involved with hydrogen peroxide scavenging and lignin biosynthesis, contributing to growth inhibition by secondary wall thickening. In order to relate growth inhibition to salt-induced oxidative modulation, the activities of superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX) and POX were evaluated in cowpea roots under salinity. Four-day-old seedlings of the Pitiuba and Perola cultivars were exposed to 0, 25, 50, 75 and 100 mM NaCl in germination paper under controlled conditions. After two days of treatment, root length was reduced under 100 mM NaCl by 56 and 26% in Pitiuba and Perola, respectively, which was associated with enhanced electrolyte leakage and cell death in the root apex. NaCl salinity did not trigger lipid peroxidation, indicating that cell death was probably due to membrane damage instead of oxidative stress. Salt stress reduced the activity of SOD, CAT and APX and increased the POX activity, demonstrating that this enzyme plays a role in oxidative protection in cowpea roots exposed to NaCl salinity. In conclusion, salt-induced growth inhibition in cowpea roots could be attributed, at least in part, to a coordinate action involving an increase in POX activity and a drop in CAT and APX activities.

Effects of aluminium on root growth and apical root cells in rice (Oryza sativa L.) cultivars. Reliability of screening tests to detect Al resistance at the seedling stage

The effects of Al2(SO4)3·18H2O on growth of root and apical root cells were studied in seedlings of rice cultivars differing in Al resistance including I Kong Pao and Aiwu (Al-sensitive) and IRAT 112 and IR6023-10-1-1 (Al-resistant). Inhibition of root growth was a typical effect of Al, and the extent of the inhibition depended on both cultivar and Al concentration. Al impaired the activity of the root meristem as indicated by reductions in its size, mitotic activity and the diameter of the meristematic cell nucleoli. Cell size in the elongation zone of the root was also reduced by Al. The reliability of the haematoxylin staining method to classify rice cultivars according to their Al-sensitivity failed to discriminate the Al-resistant IR6023-10-1-1 cultivar from the two sensitive cultivars. The results are discussed in relation to the Al resistance mechanisms operating in rice.

Efeito do cultivo in vitro na presença de NaCl em plantas de abacaxizeiro na fase de aclimatação

3 Depto. de GenOtica e Biologia Celular, UFRN 4 Embrapa Semi-`rido Resumo: A cultura de tecidos tem sido utilizada como ferramenta para gerar e selecionar variabilidade genOtica que confira maior toler‚ncia das espOcies cultivadas ‡ salinidade. Plantas de abacaxi das variedades POrola e Smooth Cayenne foram micropropagadas em meio de cultura contendo zero, 12,5 e 25 mM de NaCl e avaliadas durante a fase de aclimataAao quanto ‡s alteraAies induzidas pelo NaCl durante o cultivo in vitro e para determinar o melhor par‚metro para quantificar estas alteraAies. Foram avaliados os caracteres altura das plantas, di‚metro da roseta foliar, nœmero de folhas, comprimento e largura da folha eDi aos 0, 15, 45, 75 e 105 dias apUs a instalaAao do experimento. Observou-se que as plantas micropropagadas em meio com NaCl e sem NaCl apresentaram mOdias e taxas de crescimento semelhantes, mas diferiram quanto ‡s correlaAies entre os caracteres e ‡s vari‚ncias fenotIpicas. Os resultados indicaram que a vari‚ncia fenotIpica foi o par‚metro mais adequado para avaliar o impacto da seleAao in vitro sobre caracteres aparentemente nao relacionados com a salinidade em plantas de abacaxi. Palavras-chave: Ananas comosus, cultura de tecidos, salinidade Effects of in vitro culture in the presence of NaCl in pineapple plants during the acclimatization phase Abstract: Plant tissue culture has been used to induce and select genetic variability in order to increase the level of salinity tolerance in several species. Pineapple plants from POrola and Smooth Cayenne varieties were micropropagated for six months in a medium with 0, 12.5 and 25 mM of NaCl and evaluated during the acclimatization phase to verify the changes induced by NaCl during in vitro cultivation and to determine the best parameter to quantify these changes. The traits evaluated for plant height, plant diameter, leaf number, length and width of the D leaf at 0, 15, 45, 75 and 105 days after the installation of the experiment. There was no effect of different levels of NaCl during the micropropagation on the traits and mean growing rates. Differences were found in the correlation coefficients between the characters and mainly, in the phenotypic variances. The results indicated that the phenotypic variances were more adequate to evaluate the impact of in vitro selection for NaCl tolerance on traits apparently not related to salinity in pineapple plants.

Effect of aluminum stress on mineral nutrition in rice cultivars differing in aluminum sensitivity

The effects of aluminum (Al) stress on ion concentration and distribution were investigated in four rice cultivars (Aiwu and IKP, Al sensitive; IRAT112 and IR6023, Al resistant). Macro and micronutrient levels in plant tissues were markedly affected by Al and the magnitude of this effect depended on the cultivar group (Al resistance versus Al sensitivity) and on the concentration of Al in the nutrient solution. Al decreased Ca, P, K, Mg and Mn concentrations in shoot and K, Mg and Mn in root. It increased Ca and P in root and caused an increase in shoot and root Al contents. All these effects were observed in both cultivar groups, but were more apparent in Al sensitive ones. In conclusion, the results support the idea that, compared to the Al sensitive cultivars Aiwu and IKP, Al resistance in IRAT112 and IR6023 could be explained by a limited absorption and translocation of Al from root to shoot and could also be explained by a more efficient transport of Ca, P and Mn from root to shoot. These findings showed clearly that more than one mechanism may contribute to Al resistance in rice plants.

Alterações no perfil de frações nitrogenadas em calos de cana-de-açúcar induzidas por deficit hídrico

The aim of this work was to evaluate the use of physiological and biochemical parameters, in the characterization of water stress in sugarcane (Sacharum sp.) calluses, cultivars RB 72454 (sensible) and SP 813250 (resistant), differing in drought resistance in the field. The experimental design was completely randomized with a factorial scheme 2x5 [cultivar x concentrations of polyethylene glycol (PEG)], with ten treatments and three replicates. Calluses were submitted to PEG concentrations corresponding to osmotic potentials of 0, -0.3, -0.6, -0.9 and -1.2 MPa, during 120 hours. The variation of relative water content and humidity showed no significant differences between the cultivars. However, it was observed a trend of increase in electrolyte leakage, in the resistant cultivar related to diminishig of the osmotic potential in resistant cultivar. In the sensible cultivar, it was observed a trend of increase in proline, while the resistant one showed decrease, though proline levels were not affected by the water deficit. The amino acid concentrations were bigger in the sensible cultivar. There was a decrease of ammonia in both cultivars. Protein levels were not affected by the PEG. The protein profile evaluated by SDS-PAGE showed no PEG-induced increase in the intensity of bands corresponding to peptides between 14 and 66 kDa. The physiological and biochemical parameters were not related to differential degree of resistance observed in cultivars under field conditions.

Modulation of Reserve Mobilization by Sucrose, Glutamine, and Abscisic Acid During Seedling Establishment in Sunflower

We carried out in vitro feeding experiments using sunflower as a model to differentiate the modulatory effects of metabolites (sucrose and glutamine) and hormones (gibberellic acid and abscisic acid) on reserve mobilization, metabolite partitioning, and key enzyme activities. Exogenous sucrose negatively not only modulated the mobilization of carbon reserves (oils and starch), but it also delayed the degradation of nitrogen reserves (storage proteins) in the cotyledons. Similarly, exogenous glutamine negatively not only modulated storage protein hydrolysis, but it also retarded oil and starch degradation. Different from the metabolites, exogenous abscisic acid affected only the mobilization of oils and storage proteins. Sucrose and glutamine caused non-reducing sugar accumulation in the cotyledons and axis, but abscisic acid did not change the content of these compounds in both seedling parts. Curiously, glutamine failed to cause amino acid accumulation in the cotyledons and abscisic acid increased the amino acid content in both cotyledons and axis. Gibberellic acid did not stimulate reserve mobilization and metabolite consumption. Although the mobilization of oils, storage proteins, and starch has been delayed by sucrose and glutamine, these metabolites augmented the activity of isocitrate lyase, acid proteases, and amylases. Only abscisic acid reduced amylase activity and increased glutamine synthetase activity. Accordingly, sucrose and glutamine exert a “crossed effect” on reserve mobilization, that is, sucrose delays storage protein hydrolysis and glutamine retards oil and starch degradation. These effects may be mediated by non-reducing sugars and they are, at least in part, different from those exerted by abscisic acid.