Abstract
A factorial split plot 4 × 3 experiment was designed to examine and characterize the relationship among production of secondary metabolites (total phenolics, TP; total flavonoids, TF), carbohydrate content and photosynthesis of three varieties of the Malaysian medicinal herb Labisia pumila Benth. namely the varieties alata, pumila and lanceolata under CO2 enrichment (1,200 µmol mol-1) combined with four levels of nitrogen fertilization (0, 90, 180 and 270 kg N ha-1). No varietal differences were observed, however, as the levels of nitrogen increased from 0 to 270 kg N ha-1, the production of TP and TF decreased in the order leaves>roots>stems. The production of TP and TF was related to increased total non structural carbohydrate (TNC), where the increase in starch content was larger than that in sugar concentration. Nevertheless, the regression analysis exhibited a higher influence of soluble sugar concentration (r2 = 0.88) than starch on TP and TF biosynthesis. Photosynthesis, on the other hand, displayed a significant negative relationship with TP and TF production (r2 = -0.87). A decrease in photosynthetic rate with increasing secondary metabolites might be due to an increase in the shikimic acid pathway that results in enhanced production of TP and TF. Chlorophyll content exhibited very significant negative relationships with total soluble sugar, starch and total non structural carbohydrate.
Highlights
Labisia pumila Benth., popularly known as Kacip Fatimah, is a sub-herbaceous plant with creeping stems from the family Myrsinaceae that is found widespread in Indochina and throughout the Malaysian forest [1]
The objective of this study was to examine the effects of different nitrogen levels under CO2 enrichment on photosynthesis rate, photosynthesis-nitrogen use efficiency (PNUE), C/N ratio, chlorophyll content, primary and secondary metabolite synthesis in three varieties of L. pumila
Results of the present study showed that a decrease in photosynthesis could have stimulated the production of plant secondary metabolites, as shown by the negative correlation coefficient (Table 2)
Summary
Labisia pumila Benth., popularly known as Kacip Fatimah, is a sub-herbaceous plant with creeping stems from the family Myrsinaceae that is found widespread in Indochina and throughout the Malaysian forest [1]. L. pumila has been used by Malay women to induce and facilitate childbirth as well as a post-partum medicine [2]. Stone [3] had categorized three varieties of this herb in Malaysia, namely L. pumila var. Each of the varieties has a different usage. The varieties most universally utilized by the traditional healers are the first two, L. pumila var. The other uses of this herb are treatment for dysentery, dysmenorrheal, flatulence, and gonorrhea treatments [4]
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