Effect of silicon and methyl jasmonate on some morphological traits and photosynthetic parameters in common purslane (Portulaca oleracea L.)

Common purslane is one of the valuable medicinal plants for its abundant effective substances (Stephan et al., 1994). Since the use of silicon as a beneficial element (Ma et al., 2000) and methyl jasmonate as an elicitor (Creelman and Mullet, 1997) can increase some of the most desirable traits of medicinal herbs, in this study, the effect of simultaneous treatment of methyl jasmonate and silicone on different growth characteristics and photosynthetic parameters of common purslane has been investigated.

This research carried out in a factorial format based on complete block randomized design with two factors and three replications in greenhouse conditions. The first factor was methyl jasmonate spray at three levels (M0: control, M75: 75 µm, M150: 150 µm) and the second factor was silicon in five levels (S0: control, Sf1: fertigation of 1 µm, Sf2: fertigation of 2 mM, SS1: spray of 1 mM, SS2: spray of 2 mM) in one step, when the plants had six developed true leave. Morphological traits including stem fresh weight (g), leaf fresh weight (g), length and width of leaf (cm) stem length (cm) and root length (cm), and photosynthetic parameters including leaf relative humidity (rh), transpiration rate (E), stomatal conductance (GH2O), carbon dioxide absorption rate (A), photosynthetic active radiation in top surface of the leaf (PARtop), photosynthetic active radiation in bottom surface of the leaf (PARbot), Ambient photosynthetic active radiation (PARamb) and photosynthetic pigments including chlorophyll a, b, total chlorophyll and carotenoids. Data analysis was performed using SAS software and comparison of meanings by Duncan's multiple range test at 1 and 5 percent probability level.

The results showed that M0Ss2, M0Sf2, M150S0 and M150Sf2 treatments had the highest stem length with no significant difference among each other (Table 2). The fresh weight of the stem was significantly higher in M75Sf1 and M150S0 compared to the control and all other treatments (Table 2).  M75Ss1 treatment showed the least fresh weight of leaf, however, it was not significantly different with M0S0 and M150Ss1 treatments (Table 2). Transpiration rate (E) was significantly higher in treatments using 2 mM silicium fertilizer (M0Sf2, M75Sf2 and M150Sf2) than control (Table 4).  The lowest stomatal conductance (GH2O), was seen in M150S0 treatment which was significantly less than control (Table 4).  The highest chlorophyll a was observed in M150Ss1 treatment which had no significant difference with M75S0 and M150S0, and all three treatments were superior to control (Table 6).  The highest amount of chlorophyll b was observed in the treatment of M150Ss1 which showed significant difference with M75Ss2 and M75Sf1 (Table 6).  In terms of total chlorophyll content, M150Ss1 was significantly higher and the highest amount of carotenoids was observed in M0Ss2 (Table 6).

As a whole, M150Ss1 treatment has been shown to improve on yield and photosynthetic traits in common purslane and it is a suitable treatment for spraying on this plant.