Effect of Potassium Silicate on Growth and Leaf Epidermal Characteristics of Begonia and Pansy Grown in Vitro

This study was carried out to investigate the effect of potassium silicate on the growth and leaf epidermal characteristics of horticultural crops viz., begonia (Begonia semperflorens Link et Otto) 'Super Olympia Red' and 'Super Olympia Rose' and pansy (Viola × wittrockiana Hort.) 'Matrix White Blotch' and 'Matrix Yellow Blotch' in vitro. Seeds after germination were grown on a quarter strength MS medium supplemented with potassium silicate (K₂SiO₃) at 0, 100, 200, or 300 mgㆍL-¹ and were maintained under a photoperiod of 16 hours at 25℃. Growth parameters such as plant height, root length, chlorophyll content, fresh, and dry weights have been recorded after a growth period of 58 days for begonia and 94 days for pansy. In begonia, fresh weight was significantly greatest in the 200 mgㆍL-¹ K₂SiO₃ treatment in both 'Super Olympia Red' and 'Super Olympia Rose'. In both pansy cultivars, fresh weight was the greatest in the 200 mgㆍL-¹ K₂SiO₃ treatment than other treatments. Chlorophyll content was significantly greater in the 100 mgㆍL-¹ K₂SiO₃ treatment for both the cultivars of begonia. Leaf area significantly increased with the higher concentrations of K₂SiO₃ treatment in both cultivars of pansy. Stomatal structures on the leaf epidermis were observed with scanning electron microscopy (SEM). In begonia 'Super Olympia Rose', the structure of stomata were more compact in size in the 300 mgㆍL-¹ K₂SiO₃ treatment than in the control. Similarly, in pansy 'Matrix White Blotch' the surface of stomata appeared to be smoother in the 300 mgㆍL-¹ K₂SiO₃ treatment than those wrinkled appearance in the control. The surface of the leaf epidermis appeared to be compact due to Si deposition, and thus results indicated that Si positively affected the growth and biomass production of these species. Our data show that the effect of Si on growth parameters is strongly dependent on cultivar of the plant species tested.