Track A Basic Science

Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/138319/1/jia218438.pd

Amido no megagametófito de Araucaria angustifolia (Bert.) O. Ktze: degradação durante a germinação e desenvolvimento do esporófito Starchy reserve of the megagametophyte of Araucaria angustifolia (Bert.) O. Ktze: mobilization during germination and on the developing sporophyte

O pinheiro brasileiro possui um diásporo de grandes dimensões, o pinhão, rico em reservas amiláceas. A mobilização dessas reservas pelo embrião foi quantificada em secções transversais do megagametófito, em cinco estágios de desenvolvimento da plântula, sob dois tratamentos, na luz e no escuro. Na luz, o consumo das reservas do megagametófito pela plântula é mais rápido do que no escuro e, existe uma tendência ao consumo do amido realizar-se primeiro na região do megagametófito próxima ao embrião.<br>The parana pine has a very large dispore, the "pinhão", rich in starchy reserves. The mobilization of these reserves by the embryo was quantified in transversal sections of the megagametophyte, in five stages of seedling development, sampled in the light and in the darkness. The consuption of starch grains was in plantlets grown in light than those grown in darkness. There was a tendency to quicker use up of the the megagametophyte starch near to embryo

Respostas morfológicas e produtivas do capim-marandu adubado com doses combinadas de nitrogênio e enxofre Morphological and productive responses of marandugrass to combined rates of nitrogen and sulphur

Avaliaram-se os efeitos de combinações de doses de nitrogênio com doses de enxofre nas respostas morfológicas e produtivas de Brachiaria brizantha cv. Marandu cultivada em solução nutritiva, utilizando-se sílica como substrato, em um experimento em casa de vegetação no período da primavera. Utilizou-se o esquema fatorial 5² fracionado, com 13 combinações para nitrogênio e enxofre na solução nutritiva, em mg L-1: 14 e 3,2; 14 e 32; 14 e 80; 126 e 12,8; 126 e 64; 210 e 3,2; 210 e 32; 210 e 80; 336 e 12,8; 336 e 64; 462 e 3,2; 462 e 32; e 462 e 80, as quais foram distribuídas segundo o delineamento estatístico de blocos ao acaso, com quatro repetições. As avaliações foram realizadas em dois estádios de crescimento das plantas. Os resultados demonstraram que o fornecimento de enxofre é fundamental quando se aplica o nitrogênio. Para a maximização do número de perfilhos e de folhas, da produção de massa seca de folhas, de colmos+bainhas e da parte aérea, da área foliar e da taxa de aparecimento de folhas do capim-marandu, a combinação deve ser, no mínimo, de 358 mg L-1 para nitrogênio com 56 mg L-1 de enxofre. A taxa máxima de aparecimento de folhas para o capim-marandu ocorreu na dose de enxofre de 42 mg L-1.<br>This experiment was carried out in a greenhouse during the spring to study combinations of nitrogen and sulphur rates on Brachiaria brizantha cv. Marandu growing in nutrient solution and using ground quartz as substrate. It was set in a fractionated 5² factorial arrangement, with five rates of nitrogen and five rates of sulphur. The resulting 13 combinations were, in mg L-1: 14 and 3.2, 14 and 32, 14 and 80, 126 and 12.8, 126 and 64, 210 and 3.2, 210 and 32, 210 and 80, 336 and 12.8, 336 and 64, 462 and 3.2, 462 and 32, and 462 and 80. The experimental units were set in randomized blocks design, with four replications. Plants had two growth periods. The results showed that high availability of sulphur is required when nitrogen is supplied for total tiller number, leaf number, leaf dry matter yield, stems plus sheaths and plant tops, leaf area and leaf appearance rate. In order to maximize these variables for the marandugrass, it is necessary the minimum combination of 358 mg L-1 of nitrogen with 56 mg L-1 of sulphur. The highest leaf appearance rate for marandugrass occurred in the sulphur rate of 42 mg L-1

Root system characteristics of Marandu palisadegrass supplied with nitrogen and magnesium rates

The development of root system of forage grasses is influenced by the supply of mineral nutrients. The experiment was carried out in a greenhouse in Piracicaba, São Paulo State, with the objective of evaluating the effect of nitrogen and magnesium rates on dry mass yield, total length and surface, specific length and surface, and concentrations of nitrogen, magnesium, calcium and potassium in the root system of Brachiaria brizantha Stapf. cv. Marandu. It was studied five rates of nitrogen (2, 9, 16, 23 and 30 mmol L-1) and five rates of magnesium (0.05, 0.70, 1.35, 2.00 and 2.65 mmol L-1) in nutrient solutions in an incomplete 5² factorial arrangement, which resulted in the following combinations: 2/0.05; 2/1.35; 2/2.65; 9/0.70; 9/2.00; 16/0.05; 16/1.35; 16/2.65; 23/0.70; 23/2.00; 30/0.05; 30/1.35 and 30/2.65. The experimental design was a randomized block with four replications. Plants had two growth periods, and after the second harvest the roots were separated from the plant tops. Combination of the high rates of nitrogen and magnesium resulted in expressive increases in rooty dry matter yield, in the length and in the root surface of marandu palisadegrass. High rates of nitrogen and magnesium resulted in short root specific length and surface. Combinations of high rates of nitrogen and magnesium increased nitrogen concentration or decreased potassium concentration in the roots. Calcium concentration in the roots was increased by nitrogen rates and decreased by magnesium rates. Magnesium rates resulted in increase in magnesium concentration in the roots of marandu palisadegrass