Control of Stretching of Tomato (Lycopersicon esculentum Mill.) on Cylindrical Paper Pot Seedling Using High-Salinity Potassium Fertilizers

Abstract

This study was conducted to examine the potential of inducing salinity stress on cylindrical paper pot tomato seedlings to inhibit overgrowth. Potassium fertilizers, sulfate of potash (K2SO4), muriate of potash (KCl), and monopotassium phosphate (KH2PO4), were prepared as two solutions of (5 and 10) dS·m-1 salinity level, respectively, to investigate the influence on tomato (Lycopersicon esculentum Mill.) seedling growth. We also investigated the adaptability and survivability of treated tomato seedlings with high-salinity potassium (10 dS·m-1 KCl) to harsh environmental conditions (water deficit, low temperature, and storage conditions). Repeated addition of high-salinity level KCl, K2SO4, or KH2PO4 markedly decreased the dry matter of shoot and root, leaf area, and net assimilate rates (NAR) but increased the stem diameter of seedlings. Among the three sources, the relative growth rate of plant height (RGRH) was most sensitive to KCl addition; increasing salinity levels of KCl solution decreased the RGRH of seedlings. The compactness, which directly reflects the stocky growth index, increased in KCl or KH2PO4 treatments. After a week’s water deficit, severely wilted seedlings were observed in control seedlings (untreated with KCl), but no wilted seedlings were observed in the KCl treated seedlings, and the relative water content (RWC) of the untreated seedlings significantly decreased by 23 %, while that of the pretreated seedlings only decreased by 8 %. The increase in ion leakage of KCl treated seedlings at low temperatures was less than that of untreated seedlings. Furthermore, there was far lower damage proportion on pretreated seedlings at (9, 12, and 15)°C storage temperatures after 20 days, compared with on unpretreated seedlings. Our results suggest that high-salinity potassium fertilizer, especially KCl, is effective in preventing tomato seedling overgrowth, while it also improves tolerance.