Leaf Photosynthetic Potential of Sala (Salacca spp.) cv. ‘Nern Wong’ and ‘Sumalee’

Abstract

Leaf photosynthetic capacity of ‘Sumalee’, a new and increasing popular Sala cultivar was evaluated in comparison to the original cultivar ‘Nern Wong’. The maximum net photosynthesis rate was attained from the first frond onwards, with frond number 10–11 showing full development in both cultivars. Maximal gross photosynthesis rates were similar at 12–13 μmol CO₂ m^-2 s^-1, but ‘Nern Wong’ required higher level of light saturation (700 μmolPPF m^-2 s^-1). Under shadier environment, ‘Sumalee’ showed more robust growth, as it had lower dark– and photo–respiration rates, lower ratio of oxygenation to carboxylation, lower level of CO₂ compensation but higher carboxylation efficiency. During light response measurement, repeated incidents were found that both cultivars were sensitive to high radiation (2000 μmolPPF m^-2 s^-1). A period of longer than 3–5 minutes under intense radiation would induce the stomatal closure, limiting the rates of net photosynthesis, transpiration and electron transport. Measurement protocol had to be modified to initially expose the leaf to lower intensity of 1000 μmolPPF m^-2 s^-1.