Multispectra Analysis
In higher
plants, chlorophyll a, chlorophyll b and carotenoids are the pigments
that carry out the reactions of photosynthesis. Chlorophyll a serves as
the primary donor for the reaction center in photosystem II and it or
something close to it serves, as primary donor of Photosystem I. Chlorophyll
b is involved in the inductive resonance reactions that funnel light energy
to the reaction centers. Due to flooding chlorophyll breakdown provides
the most visible and easily measurable sign of the onset of plant stress.
However, the establishment of
leaf color changes using visual observations is very subjective. Therefore,
in this area our work is concentrated in comparing techniques to allow
a better estimation of plant stress level and recovery ability during
and after flooding. We are using the SPAD-502 chlorophyll meter, multispectral
analysis of leaf digital images and chlorophyll extractions.
Our preliminary experiments
support the concept that leaf digital images multispectral analysis is
a potential technique to assess differences among soybean genotypes regarding
flooding tolerance. We obtained a considerable relationship between the
SPAD-502 chlorophyll meter and the leaf red color (Fig. 1). However, both
parameters were low correlated with the
leaf
chlorophyll content. Unlike the SPAD system, the value obtained using
the leaf digital images represents the total leaf image instead of a single
point on the leaf. We are currently working in establishing algorithms
to estimate chlorophyll content using leaf digital images. The leaf multi-spectral
analysis method appears more efficient than the SPAD system for multiple
reasons: i) the leaves are digitally stored, ii) their analysis can be
any time without the alteration of the results and iii) digital images
can be used for further analysis using different computational methods.