PHOSPHATE FERTILIZATION AND INTER-RELATIONSHIPS OF THE AGRONOMIC AND PHYSIOLOGICAL CHARACTERS OF AMARANTH SEEDS

The objective of this work was to evaluate the effect of different doses of phosphorus in the growth and development of plants and in the physiological quality of the seeds produced, as well as to identify the interrelationships between the morphological and physiological attributes. The experiment was carried out in the agricultural crop 2016/2017 in Federal University of Pelotas. The experimental design was a randomized block in which the treatments were arranged in five replications. The analysis of variance revealed a significance of 5% probability through the characters, plant height, dry mass of the plant shoot, seed yield, germination and accelerated aging these results demonstrate that these attributes are influenced by the P2O5 doses, in contrast, the chlorophyll index. The Amaranthuscruentus species expresses variability to the morphological attributes, yield components and seed quality produced in relation to the use of phosphate fertilization. Doses comprising 100 to 200 kg ha-1 of P2O5 tend to potentiate plant height, dry biomass accumulation, yield, germination and vigor of the seeds produced. Plants with greater stature and accumulation of biomass increase the proportion of photosynthetic pigments, being these determinants for the production and quality of seeds produced of amaranth in the extreme south of Brazil

Treatment of seeds, herbicides, air temperature and its effects on rice.

The sowing time is a major factor to be considered to obtain high yields in irrigated rice. However, when sowing is performed early, low temperatures can cause stress to culture, reducing its emergence rate and the shelf plants and reduce the selectivity of herbicides applied. Seed treatment can be an alternative to increase rice emergence speed and improve the selectivity to herbicides in the initial phase of development of culture. In view of the above, the objectives of this study were to make a literature review about the seed treatment (Chapter I); evaluate the effect of seed treatment on germination and early establishment of rice seedlings in different sowing times and selectivity to herbicides (Chapter II); characterize the biochemical parameters of oxidative stress in rice subjected to low temperatures and the application of herbicides (Chapter III); and evaluate the initial performance resulting from the application of fertilizers in the herbicide selectivity in irrigated rice. Based on the results obtained it can be concluded that the treatment of seeds with gibberellic acid positive influence on the initial growth of the rice seedlings, the optimum temperature (25 °C) and suboptimal (17 °C) and treatment with the combination of dietholate dietolate + fipronil + carboxin + thiram, adversely affected the germination and vigor at both temperatures, reducing the physiological performance of rice seeds in the laboratory. In the field the seed treatments had no effect on phytotoxicity and selectivity of herbicides, which temperature is the determining factor. The bispyribac-sodium herbicide was more toxic to plants when planting occurred at the beginning of September, since when sown in October the major symptoms of phytotoxicity were presented by plants treated with the herbicide profoxidim. Seed treatment does not influence in plant defense responses and the herbicide treatments induce different responses in rice plants by stimulating the secondary metabolism of the same. Low temperature situations with herbicide application may impair the absorption by the plant. The application of liquid fertilizer in rice does not influence the initial development and the sensitivity of the rice herbicide culture. The application of herbicide profoxidim was the treatment that presented the highest level of phytotoxicity in rice.Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPESA época de semeadura é um dos principais fatores a ser considerado para a obtenção de altas produtividades em arroz irrigado. Contudo, quando a semeadura é realizada precocemente, as baixas temperaturas podem causar estresse à cultura, reduzindo sua velocidade de emergência e o estante de plantas, além de reduzir a seletividade de herbicidas aplicados. O tratamento de sementes pode ser uma alternativa para aumentar a velocidade de emergência do arroz e melhorar a seletividade a herbicidas na fase inicial de desenvolvimento da cultura. Em vista do exposto, os objetivos deste trabalho foram: efetuar uma revisão de literatura a cerca do tratamento de sementes (Capítulo I); avaliar o efeito do tratamento de sementes na germinação e estabelecimento inicial de plântulas de arroz irrigado em diferentes épocas de semeadura e na seletividade à herbicidas (Capítulo II); caracterizar os parâmetros bioquímicos do estresse oxidativo em arroz irrigado submetido a baixas temperaturas e a aplicação de herbicidas (Capítulo III); e avaliar o desempenho inicial decorrente da aplicação de fertilizantes na seletividade de herbicidas na cultura do arroz irrigado. Com base nos resultados obtidos pode-se concluir que o tratamento de sementes com ácido giberélico influenciou positivamente o desenvolvimento inicial das plântulas de arroz, na temperatura ótima (25°C) e subótima (17°C), tratamento com dietholate e a combinação de dietolate+fipronil+carboxina+tiram, influenciaram negativamente a germinação e o vigor em ambas as temperaturas, diminuindo o desempenho fisiológico das sementes de arroz em laboratório. À campo os tratamentos de sementes não influenciaram na fitotoxicidade e seletividade de herbicidas, sendo a temperatura o fator determinante. O herbicida bispiribaque-sódico apresentou maior toxicidade às plantas quando a semeadura ocorreu no início do mês de setembro, já quando semeadas em outubro os maiores sintomas de fitotoxicidade foram apresentados pelas plantas tratadas com o herbicida profoxidim. O tratamento de sementes não influencia nas respostas de defesa das plantas e os tratamentos herbicidas induzem respostas distintas nas plantas de arroz, estimulando o metabolismo secundário das mesmas. Situações de baixa temperatura juntamente com a aplicação do herbicida podem prejudicar a absorção pela planta. A aplicação de fertilizantes líquidos na cultura do arroz não influencia no desenvolvimento inicial e na sensibilidade da cultura do arroz irrigado a herbicidas. A aplicação do herbicida profoxidim apresenta elevado nível de fitotoxicidade na cultura do arroz