SPAD INDEX AS AN INDIRECT ESTIMATE OF CHLOROPHYLL CONTENT IN OKRA PLANTS

A clorofila, molécula responsável pela atividade fotossintética das plantas, pode ser quantificada por métodos diretos e indiretos. O objetivo do estudo foi relacionar os resultados do conteúdo de clorofila obtidos por diferentes métodos de determinação em folhas de quiabo. Foi estimado o conteúdo de clorofila através do índice SPAD (não-destrutivo) e da extração dos pigmentos foliares com acetona (destrutivo). As análises foram realizadas em folhas de quiabo (cultivar Santa Cruz 47) do terço médio de plantas no estágio reprodutivo com coloração variando de amarela a verde escuro, em condição de sequeiro. Determinações pelo método não destrutivo foram realizadas com equipamento SPAD-502 e as determinações por método destrutivo foram realizadas por espectrometria, utilizando acetona como extrator. Foi realizada análise descritiva, correlação e regressão nos dados. O índice SPAD variou de 20,93 a 49,03, e apresentou correlação linear com o conteúdo de pigmentos foliares. O índice SPAD apresentou correlação positiva com os teores de clorofila b e clorofila total, entretanto para o conteúdo de clorofila a foi observado relação negativa. A variação do conteúdo de carotenoides não apresentou relação direta com o índice SPAD. A estimativa do conteúdo de clorofila por método não destrutivo apresenta relação direta com o conteúdo absoluto em folhas de quiabo.Chlorophyll, the molecule responsible for the photosynthetic activity of plants, can be quantified by direct and indirect methods. The study aimed to relate the results of chlorophyll content obtained by different determination methods in okra leaves. Chlorophyll content was estimated using the SPAD index (non-destructive) and leaf pigments extraction with acetone (destructive). Analyzes were carried out on okra leaves (cultivar Santa Cruz 47) from the middle third of plants during the reproductive stage, varying colors from yellow to dark green under rainfed conditions. Determinations by the non-destructive method were conducted with SPAD-502 equipment, and determinations by the destructive way were carried out by spectrometry. Descriptive analysis, correlation, and regression were performed on the data. SPAD index ranged from 20.93 to 49.03 and showed a linear correlation with leaf pigments content. SPAD index showed a positive correlation with chlorophyll b and total chlorophyll contents. However, a negative relationship was observed for chlorophyll a content. Variation in carotenoid content was not directly related to the SPAD index. Estimating chlorophyll content by the non-destructive method directly correlates with the absolute content in okra leaves

Leaf pigments in cauliflower cultivated with different water conditions and silicon applications

Environmental factors and crop management can influence the characteristics of plant morphology and physiology, altering photosynthetic efficiency and mass accumulation. The study aimed to analyze the contents of leaf pigments in cauliflower cultivated under different conditions of water availability and silicon (Si) applications. The experiment was carried out in a protected environment in the city of Maringá-PR. A randomized block design, in a 3x4 factorial scheme, with three replacement conditions [40, 70 and 100% of crop evapotranspiration (ETc)] and four Si doses (0, 50, 100 and 150 kg ha-1), with four repetitions. The cauliflower cultivation, cultivar Sharon, was carried out in dystroferric RED NITOSOL. Daily evapotranspiration was determined with a constant level water table lysimeter and water replacement was performed with drip irrigation. Si was applied in split doses in three applications (initial, intermediate and final phases). At flowering, leaf tissue from the upper third of the plant was collected, with pigment extraction performed with pure acetone and determination in a spectrophotometer. At harvest, the leaf area of ​​the plants was determined. Data were subjected to analysis of variance and regression analysis. Cauliflower crop under water-deficient reduces leaf area development and alters chloroplast pigments dynamics. Silicon use in the soil increases leaf development, chlorophyll a and b contents, and reduces carotenoids concentration. Under water stress conditions, silicon addition to the soil improves cauliflower performance