Correlation of leaf glucose content with mineral nutrients uptake of South African geranium (Pelargonium sidoides)

Abstract

Pelargonium sidoides is a medicinal plant grown in Kenya for export to Germany where it is used in the manufacture of drugs for lung related diseases. The farm contributes to the well being of the local community by providing permanent employment to for over 80 persons, with 80 percent being women. It also offers free pre-primary education to their children including the ones from the neighbourhood. The broad spectrum of activity against viruses and bacteria may be caused by the coumarins and phenolic acids from a root of a healthy plant. Health of P. sidoides is controlled by appropriate mineral uptake and glucose concentration in the leaves. This concentration is governed by soil nutrients concentration and plant uptake capacity. Inorganic and organic fertilizers are normally applied to the crop. The relationship between nutrients uptake, glucose, and chlorophyll contents has not been established. This study aimed at finding out the correlation between P. sidoides leaf glucose, chlorophyll contents and plant mineral nutrients uptake. P. sidoides plants from a selected field site, where the soil N, P, K and Ca contents had prior been analysed, were dressed with both inorganic and organic fertilizers (worm leachate) of known nutrient levels. Leaf glucose contents before and after application of the mineral nutrients was measured by colorimetry and results verified by high performance liquid chromatography fitted with a refractive index detector (HPLC). Mehlich Double Acid Extraction Method was used for the determination of P, Mg, Mn, Ca, K and Na on soil samples. P was determined colorimetrically, K and Na by flame photometer, and Mg, Mn and Ca by FAAS and N by Kjeldahl Method. Predictions for nutrients in the soil and plant tissues were done by DRIFT FTIR. FTIR predictions closely matched the soil’s wet chemistry data. Leaf chlorophyll measurements were done by SPAD. The data obtained was subjected to GENSTAT software for the ANOVA to find out whether there were any statistical significant differences in the means. Uptake of calcium fertilizer reflected the highest increase of glucose while that of worm leachate had the least effect. Chlorophyll content was also found to increase with nutrients uptake. Change in glucose level was evident within an hour after application, suggesting the possibility of predicting nutrients uptake within a short period of time. The study opened way for real time analysis of plant status and allowed for real time interventions where necessary.