Arnóbio Gonçalves de Andrade

Atividade enzimática em variedades de cana-de-açúcar cultivadas in vitro sob diferentes níveis de nitrogênio

Nitrogen is considered the most abundant mineral element in the plants and an essential component to biomolecules and several enzymes. The objective of this work was to estimate nitrogen assimilation efficiency process and to identify biological fixation potential parameters on sugar cane varieties cultivated in vitro. The sugar cane varieties used were RB 842021, RB 83102, RB 75126, RB 882980, CO 997, besides Brachiaria arrecta (witness), cultivated in vitro in different nitrogen levels [M1 (9.83 mM), M2 (2.46 mM), M3 (0.49 mM), M4 (0.0 mM)]. All the varieties and plant witness (Brachiaria arrecta) exhibited redutase nitrate activity and glutamina sintetase, even in the ammonium and nitrate absence culture media. The RB 842021 variety showed the highest activity of nitrate reductase and the higher chlorophyll a and b contents, whereas RB 882980 variety showed the highest glutamine sintetase activity when cultivated without nitrogen, representing a higher potential assimilation of nitrogen.

Metabolismo de plantas de cana-de-açúcar cultivadas in vitro sob diferentes concentrações de nitrogênio

Variedades de cana-de-acucar (RB 732577, RB 83102, RB 75126, CB 45-3, Caiana e Co 997) foram cultivadas in vitro em meio nutritivo basico MS com diferentes concentracoes de N (9,83 mM, 7,37 mM, 4,92 mM, 2,46 mM, 0,49 mM e 0,0 mM), com o objetivo de avaliar a eficiencia no processo de assimilacao desse elemento. Apos 45 dias de cultivo, foram determinados os ganhos de biomassa e os teores de amonio, aminoacidos e acucares soluveis. A variedade Co 997 apresentou maior ganho de biomassa e maior quantidade de N incorporado em aminoacidos livres em relacao as demais variedades, sugerindo maior eficiencia no processo de assimilacao. Os teores mais elevados de amonio foram observados nas variedades RB 83102 e RB 75126, quando cultivadas em meio desprovido de N, mostrando-se menos eficientes no processo de assimilacao uma vez que apresentaram os menores valores de aminoacidos livres nas mesmas condicoes de cultivo.

RESPOSTA DE GENÓTIPOS DE MILHO AO ESTRESSE SALINO EM CONDIÇÕES HIDROPÔNICAS

Four maize (Zea mays L.) genotypes, Jatina C3 anao, BR-201, V-190 and LW-1, grown under hidroponic conditions, were evaluated for their tolerance to saline stress imposed by three salt levels (0, 50 and 100 mM NaCl). Plants submitted to 100 mM NaCl for 29 days had 50% lower dry matter production and 75% reduced leaf area, as compared to the control (0 mM NaCl) plants. Among the four genotypes studied, LW-1, a pure line, produced the least dry matter and leaf area. The increase salt levels in solution decreased the growth rate of both shoot and root in all genotypes. Roots had the largest sodium concentration and also showed the largest decrease in the relative growth rate, demonstrading the negative effect of sodium accumulation. The number and size of the stomata were not affected by saline stress.

Plantas de cana-de-açúcar cultivadas in vitro com antibióticos

A contaminacao por microrganismos e conhecida como um dos mais serios problemas da cultura de tecidos de plantas, especialmente, em especies tropicais. Com o objetivo de eliminar bacterias endofiticas, propagulos das cultivares de cana-de-acucar Co 997, SP 70-1143 e apices caulinares isolados de plantas, provenientes de semente botânica biparental (RB 818004 x SP 71-6949), foram cultivados in vitro, em meios de cultivo com antibioticos. No primeiro experimento, propagulos das cultivares Co 997 e SP 70-1143 foram cultivados em meio de cultivo contendo 200 e 300 mg.L-1 de amoxicilina e cefatoxima sodica durante 30 dias. Num segundo experimento, utilizou-se apenas a amoxicilina em concentracoes mais elevadas ( 300, 600 e 1000 mg.L-1), com as mesmas plantas utilizadas no primeiro experimento, permanecendo em cultivo por mais 30 dias. No terceiro experimento foram utilizados apices caulinares isolados de plantas provenientes de semente botânica biparental (RB 818004 x SP 71-6949), cultivados em meio de cultivo contendo 1000 mg.L-1 de amoxicilina, por um periodo de 120 dias. Apos estes periodos de cultivo, testes de infeccao e observacoes histologicas revelaram que o isolamento do apice caulinar associado ao uso de antibiotico no meio de cultivo nao foi suficiente para eliminar as bacterias endofiticas.

Embriogênese somática in vitro em couve-comum

The aim of this study was to obtain calluses and somatic embryos of common cabbage (Brassica oleracea L., var. leucocephala) and to characterize them by means of histological observations in vitro; foliar explants were cultivated under asseptic conditions in a nutritive MS medium supplemented with various combinations of 2,4-D/BAP and 2,4-D/KIN. During the induction phase of calluses (phase I), there was a development of calluses with embryogenic characteristics derived from the media (5.0 mg/L of 2,4-D), (1.0 mg/L of 2,4-D plus 0.1 mg/L of BAP), (1.0 mg/L of 2,4-D plus 1.0 mg/L of BAP) and (2.0 mg/L of 2,4-D plus 0.05 mg/L of BAP), that were chosen for subcultivation in regeneration media (phase II). In this phase, culture media were supplemented with reduced concentrations of 2,4-D, BAP and GA3, or they were totally deprived of these supplements. In this case, the calluses remained in cultivation for other 30 days. The calluses that were subcultivated in the regeneration media R3 (0.1 mg/L of BAP) and R8 (0.001 mg/L of 2,4-D plus 0.01 mg/L of BAP), derived from the induction media M16 (5.0 mg/L of 2,4-D) and M30 (1.0 and 1.0 mg/L of 2,4-D and BAP), respectively, developed structures similar to embryos. However, this histological characterization revealed the superiority of the interaction between the M30 and R8 media for regeneration of the calluses and somatic embryos.

In vitro somatic embryogenesis of common cabbage

The aim of this study was to obtain calluses and somatic embryos of common cabbage (Brassica oleracea L., var. leucocephala) and to characterize them by means of histological observations in vitro; foliar explants were cultivated under asseptic conditions in a nutritive MS medium supplemented with various combinations of 2,4-D/BAP and 2,4-D/KIN. During the induction phase of calluses (phase I), there was a development of calluses with embryogenic characteristics derived from the media (5.0 mg/L of 2,4-D), (1.0 mg/L of 2,4-D plus 0.1 mg/L of BAP), (1.0 mg/L of 2,4-D plus 1.0 mg/L of BAP) and (2.0 mg/L of 2,4-D plus 0.05 mg/L of BAP), that were chosen for subcultivation in regeneration media (phase II). In this phase, culture media were supplemented with reduced concentrations of 2,4-D, BAP and GA3, or they were totally deprived of these supplements. In this case, the calluses remained in cultivation for other 30 days. The calluses that were subcultivated in the regeneration media R3 (0.1 mg/L of BAP) and R8 (0.001 mg/L of 2,4-D plus 0.01 mg/L of BAP), derived from the induction media M16 (5.0 mg/L of 2,4-D) and M30 (1.0 and 1.0 mg/L of 2,4-D and BAP), respectively, developed structures similar to embryos. However, this histological characterization revealed the superiority of the interaction between the M30 and R8 media for regeneration of the calluses and somatic embryos.

Variedades de cana-de-açúcar cultivadas in vitro com diferentes fontes de nitrogênio

To verify the behaviour of three sugarcane varieties cultivated in vitro using media with different sources of nitrogen, an experiment was carried out under sterile conditions. Twelve treatments were used, represented by three sugarcane varieties: Co 997 (V1), SP 71-6949 (V2) and SP 70-1143 (V3), and four growth media, differing in the source of N: integral MS salts (M1-control); 4,3 g/L of glutamine as the only source of nitrogen (M2); KNO3 of MS salts as the only source of nitrogen (M3) and KNO3 of MS salts + 3,0 g/l of glutamine (M4). Five replicates were used in a completely randomized design. Based on the variables studied (shoot height and number), significant differences existed among the varieties, except for V1 and V2. There were also differences on growth media, except for M2 and M4. With respect to the shoot number/height ratio, the variety (V2) was superior when grown in media M1 and M3.