| Abstract: | The effects of incorporating a hydrogel polymer into sand onthe development of selected horticultural plants grown undersaline conditions has been demonstrated. In separate experiments,the seeds of tomato (Lycopersicon esculentum Mill.), lettuce(Lactuca sativa L.) and cucumber (Cucumis sativus L.) were germinatedin sand/swollen hydrogel polymer mixture (25: 75, v: v) withadded Hoagland nutrient solution. At cotyledon + first trueleaf stage, the plantlets were transplanted into polythene growbagscontaining a range of sand/swollen hydrogel polymer combinations(0: 100, 25: 75, 50: 50, 75: 25 and 100: 0, v: v). Saline solutionscontaining NaCl, CaCl2 and MgCl2 were prepared as molar solutionsand applied at combined concentrations as follows; Control (Hoagland),2000, 4000, 8000, and 32 000 ppm. Application of the appropriatesolution to the growbags was made twice per week, alternatingwith a comparable watering regime. Harvesting was carried outafter 14 and 28 d. Polymer incorporation encouraged growth ofall species under all saline conditions, the order of effectivenessof the polymer contents being as follows; 75%>50% 25% 100%>0%.At high salinity (32 000 ppm) plants of the test species werereduced in growth but appeared to be tolerant at all levelsof polymer incorporation; in pure sand the level of tolerancein tomato and cucumber was <8000 ppm and in lettuce <4000 ppm. Generally, dry weight, leaf area, succulence, chloroplastpigments (chlorophyll a, chlorophyll b, and carotenoids), photosyntheticactivity, total amino acids, proline, and protein contents wereincreased with polymer incorporation compared with pure sand.This hydrogel polymer appears to be highly effective for useas a soil conditioner in horticulture, to improve crop toleranceand growth in a sand or light gravel substrate under salineconditions. It is intended to confirm the results of these studiesby field trials. Key words: Tomato (Lycopersicon esculentum Mill.), lettuce (Lactuca sativa L.), cucumber (Cucumis sativus L.), salinity, hydrogel, polymer, salt tolerance, growth, free amino acid, free proline, and protein |
