SPAD index as an indirect estimate of chlorophyll content in okra plants

Abstract

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.