Taxonomical and Chemical Characterization of Panicum maximum L. from Different Agro- Ecological Zone of Sri Lanka

Chemical and taxonomical characteristics of Panicum maximum L. originated from seven contrasting agro-ecological zones of Sri Lanka were investigated representing the low country-wet zone (LW), mid country-wet zone (MW), up country-wet zone (UW), low country-intermediate zone (LI), mid country-intermediate zone (MI), up country-intermediate zone (UI) and low country-dry zone (LD). The levels of leaf nutrients namely, nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), magnesium (Mg), copper (Cu), iron (Fe), manganese (Mn) and zinc (Zn) were determined on a dry weight basis. Assuming linear relationships, some significant interelement relationships were detected in P. maximum leaves. The leaf anatomy and the mesophyll to bundle sheath cell ratio were studied using the light microscopy, whereas the vein density was determined by stereo microscopy. The foliar nutrient contents of P. maximum varied significantly (P<0.05) among different populations collected from diverse climatic zones. The highest nutrient contents were detected in the plants growing in the low country-wet zone, and the lowest in the low country-dry zone. Values of foliar δ13C within populations from warmer and cooler climates had an average of – 14% showing typical C4 photosynthesis with little evidence for adaptive divergence of the photosynthetic mode. Mesophyll cell to bundle sheath cell ratio of the leaves from different climatic zones had an average of 2.35 and the M: BS ratios were not significantly varied under different climatic conditions. Mean values of the vein densities of the leaves were 1.72 veins cm-2 and the highest vein density was obtained from the leaves of low country-wet zone and the lowest was from the leaves of up country-wet zone.