Quality of field experiments data dependent upon adequate experimental design. This study investigated the relationship between the size of the basic unit for exploratory experiments and the optimum plot size, and the experiment precision with potato crop. Tuber yield of 24 rows, 144 mounds, were used to arrange experimental units of one, two, three, four, six, eight and 12 mounds. Tuber yield data of different mounds were used to arrange plot sizes with different numbers of basic units. The model CV(x)=A/X B was adjusted, in which CV(x) was the coefficient of variation among plots with different numbers of basic units. Optimum plot size was estimated with the modified maximum curvature method of the function CV(x)=A/X B , allowing completely random design. Experimental precision was estimated though the Hatheway method for different experimental arrangements. Based upon the modification of the maximum curvature method, for a fixed total experimental area, experimental unit size of potato initial experiments affects optimum plot size estimations with the same experimental precision and variable number of treatments.
Resumo -O objetivo deste trabalho foi estimar a relação entre dimensões da área dos ensaios em branco, as estimativas do tamanho ótimo de parcela e a precisão de experimentos com a cultura da batata. O ensaio de uniformidade foi conduzido na área de produção de batata, da Fundação Estadual de Pesquisa Agropecuária, em Júlio de Castilhos, RS. A produtividade de tubérculos de batata em 3.456 covas (24 linhas de 144 covas) foi usada para planejar dez ensaios com variações no número de linhas (largura) e de covas por linha (comprimento). Em cada ensaio, foram estimados o tamanho ótimo de parcela e a diferença entre médias de tratamentos. As análises de correlação linear e de trilha permitiram verificar que o tamanho dos ensaios com a cultura da batata, medido em número de covas, não influencia a estimativa do índice de heterogeneidade do solo e a estimativa do tamanho ótimo de parcela. Áreas experimentais com maior número de covas por linha permitem planejar experimentos mais precisos quanto à avaliação da produtividade de tubérculos de batata. Parcelas com seis covas na linha e a adoção da linha como bloco aumentam a precisão dos experimentos com batata.Termos para indexação: Solanum tuberosum, planejamento de experimento, tamanho de parcela; área experimental limitada. Potato trial dimensions and optimum plot size estimationsAbstract -The objective of this work was to assess the relationship among experimental area in uniformity trial dimensions, optimum plot size estimations and experimental precision of potato trials. A homogeneity trial was carried out at the production site of Fundação Estadual de Pesquisa Agropecuária, Júlio de Castilhos, RS, Brazil. Tuber yield of 3,456 hills (24 rows of 144 hills) was quantified and data were used for planning ten different size trials, in which the number of rows and hills per row varied. Estimations of optimum plot size and differences between means of treatments were done for each trial. Based on linear correlation and path analysis, the size of potato trial using different hill numbers does not affect the estimation of soil heterogeneity index and the estimation of optimum plot size. Experimental areas with high number of hills per row can be used to improve precision of potato yield evaluations. One row with six hill plots and treatments distributed in the row, taken as block, increase experimental precision in potato.
Toxic effects of copper (Cu) were analyzed in young plants of Inga subnuda subs. luschnathiana, a species that is highly tolerant to flooding and found in Brazil in wetlands contaminated with Cu. Plants were cultivated in fully nutritive solution, containing different concentrations of Cu (from 0.08 μmol to 0.47 mmol L(-1)). Symptoms of Cu toxicity were observed in both leaves and roots of plants cultivated from 0.16 mmol Cu L(-1). In the leaves, Cu clearly induced alterations in the thickness of the epidermis, mesophyll, palisade parenchyma, and intercellular space of the lacunose parenchyma. Also, this metal induced disorganization in thylakoid membranes, internal and external membrane rupture in chloroplasts, mitochondrial alterations, and electrodense material deposition in vacuoles of the parenchyma and cell walls. The starch grains disappeared; however, an increase of plastoglobule numbers was observed according to Cu toxicity. In the roots, destruction of the epidermis, reduction of the intercellular space, and modifications in the format of initial cells of the external cortex were evident. Cell walls and endoderm had been broken, invaginations of tonoplast and vacuole retractions were found, and, again, electrodense material was observed in these sites. Mineral nutrient analysis revealed higher Cu accumulation in the roots and greater macro- and micronutrients accumulation into shoots. Thus, root morphological and ultrastructural changes induced differential nutrients uptake and their translocations from root toward shoots, and this was related to membrane and endoderm ruptures caused by Cu toxicity.
Palavras-chave: Solanum tuberosum L., índice de h e t e r o g e n e i d a d e , p l a n e j a m e n t o experimental, precisão experimental. ABSTRACT
A redução do erro experimental e o conseqüente aumento da precisão experimental podem ser obtidos com a aplicação do tamanho ótimo de parcelas experimentais. O objetivo deste trabalho foi investigar as relações da largura e do comprimento sobre a estimativa do tamanho ótimo de parcela na cultura de batata pelo método da regressão múltipla. Doze ensaios de uniformidade de batata da cultivar Macaca foram conduzidos na estação experimental da Fundação Estadual de Pesquisa Agropecuária em Júlio de Castilhos, Rio Grande do Sul. Cada ensaio foi constituído por 12 linhas com 24 covas. Foram estimados o ponto crítico e a natureza da função de superfície de resposta do coeficiente de variação em relação às diferentes larguras e comprimentos das parcelas planejadas. A análise de causa e efeito foi feita usando-se o tamanho ótimo de parcela como variável dependente e as estimativas dos parâmetros da função de superfície de resposta como variáveis independentes. O tamanho ótimo de parcela pode ser estimado procedendo-se a colheita das covas em linhas independentes. O efeito linear do comprimento é quem define o tamanho ótimo de parcela na cultura da batata. O tamanho ótimo de uma parcela experimental de batata é de 24 covas distribuídas em uma linha.
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