Abstract:
Chlorophyll fluorescence transient measurement has proved a strong technique to investigate
the photosynthesis functions and integrated measurement to identify the stress responses. This
technique uses the energy flux theory in the photosynthesis apparatus. Plectranthus
scutellarioides (L.) R.Br (coleus) is famous as a landscape plant and the appearance of this plant
is determined by environmental factors, especially by light intensity. An experiment was
conducted to assess the influence of two contrasting light conditions on photosynthesis activities
of three Plectranthus scutellarioides (L.) R.Br (coleus) varieties through the chlorophyll
fluorescence transient analysis measurements. Also there was an objective to assess the
applicability of OJIP method for plant physiological analysis under stress conditions imposed by
different light intensities. “Alabama sunset”, “Velvet red”, “Finger paint” varieties were arranged
in 0% (Full sunlight) and 70% shade levels as two-factor factorial completely randomized
design. Sixty days after exposure to 0% and 70% light conditions, chlorophyll fluorescence
parameters were measured in fully expanded leaves using Hansatech pocket PEA chlorophyll
fluorometer. Resulted values of OJIP transients were analyzed according to the JIP test and the
most important functional parameters such as quantum efficiencies (φEo, φPo, ψo) and
Performance index (PIAbs). Analyzed data showed that from derived parameters, φEo, φPo,
quantum efficiencies and PIAbs values were significantly affected by light conditions and
varieties. Higher quantum efficiencies and the higher Performance index were observed under
70% shade compared to the 0% shade (full sunlight). Overall, the contrasting light conditions
influence the photosynthesis performance of the coleus varieties and different parameters of
OJIP chlorophyll fluorescence transient analysis can successfully be used to study the stress
responses for different light intensities in the photosynthesis process.
