Optimizing Silicon Application for Enhancing Growth and Chlorophyll Concentration in Pepper Plants (Piper nigrum L.) Cultivar Kuching

Silicon is known to play a central role in regulating various aspects of plant growth and development, including nutrient uptake, root formation, and growth. Silicon is the second most abundant element found in soil primarily as neutral, monomeric silicic acid, which is the biologically available form for plant uptake. Although silicon is not considered an essential nutrient for the basic life cycle of most plants, its availability can significantly benefits to plant health, growth, and stress tolerance. However, previous research has mainly focused on plants grown in silicon, and silicon occurs naturally as silicon dioxide (SiO2), and is not in a form that is easily absorbed by plants. Therefore, this study investigates the effects of silicon (Si) in silicic acid form (H4O4Si) on the growth and chlorophyll concentration of pepper (Piper nigrum L.) seedlings, particularly the Kuching variety. The Si application had been applied once a week with five different concentrations via root applications; T1 [0.5% Si (v/v)], T2 [1.5% Si (v/v)], T3 [2.0% Si (v/v)], T4 [1.5% potassium silicate (v/v)] as positive control and T5 [negative control (without silicon)] on pepper cutting-grown plants. Growth parameters such as plant height, stem diameter and chlorophyll concentration were observed and collected. Our results showed that the treatment with Si nutrients is promising, as the Si-treated pepper clones showed faster and more robust growth compared to the control plants in the early growth stages. The results indicate that a 0.5% Si concentration (v/v) effectively maintains the high chlorophyll content over four weeks, in contrast to the decreasing trend observed in the control group. This study thus presents the first report on the application of Si in P. nigrum L., demonstrating the feasibility of Si uptake and growth enhancement in pepper plants. The results suggest a stepwise application of Si, starting with low concentrations (0.5% Si v/v) via the root in the early growth stages to strengthen young plants before transplanting to the field. However, foliar spraying could also be considered in future studies as the silicon is absorbed faster compared to root application. Further studies on the passive defence structure (physical barriers such as cuticle, wax, and trichomes) are needed to prove that it can repel pathogens and insects.