Chlorophyll fluorescence of the testa of Brassica oleracea seeds as an indicator of seed maturity and seed quality

H Jalink,A Frandas,J.B Bino,R Van Der Schoor

doi:10.1590/s0103-90161998000500016

Abstract

Chlorophyll fluorescence of the testa of seeds is proposed as a non-invasive method for the determination of maturity and quality of seeds. In this study cabbage seeds (Brassica oleracea) were sorted individually based on the chlorophyll fluorescence signals into four subsamples labeled with respect to their chlorophyll fluorescence signal (low, medium, high and very high). The results show that the magnitude of the chlorophyll fluorescence signal was inversely related to the quality of the seeds, expressed as germination %, normal seedling %, germination rate (T50) and uniformity of germination (T75-T25). The seed lot could be improved from 90 to 97% normal seedlings by sorting out 13% of the seeds with very high chlorophyll fluorescence signals. Advantages of the chlorophyll fluorescence method for sorting seeds are the high sensitivity, the method being fully non-destructive, the high speed at which the fluorescence is generated and measured and the specificity for only chlorophyll. Other pigments or substances which can influence seed colour but do not fluoresce at the specific wavelengths of excitation and emission of chlorophyll, will not contribute to the fluorescence signal. These characteristics make chlorophyll fluorescence highly suitable as a new sorting technique.

Highlights

An important quality property of seeds is the maturity status
Seed material: Seeds of white cabbage (Brassica oleracea L.) of variety Ernando were used for this research, since this particular seed lot contained a small fraction of about 10% of seeds that showed higher values in chlorophyll fluorescence signals compared to the average chlorophyll fluorescence signal of the sample
With the combination of two interference filters of 656 and 730 nm, the background signal of the system due to stray light of the LED was suppressed to a current of about 1 pico ampere, which was low compared to the average fluorescence signal of 12 pA of the seed lot

Summary

Introduction

An important quality property of seeds is the maturity status. Seeds which are immature or not fully mature are generally speaking of lower quality as mature seeds. During development the total chlorophyll content of the seed coat (as measured by the optical density of seed coat extracts) decreased. Because of this correlation, Steckel et al proposed a simple field test using colour cards to assess the chlorophyll content of seed extracts to estimate the optimal harvest date. At the same time the colour of the seed changes from green to a colour which depends on the species and varies with the cultivar. The chlorophyll breakdown in the seed, is poorly understood (Ward et al, 1995)

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Discussion

Conclusion