Growth Responses of Spiderplant (Cleome gynandra L.) to Salinity

Abstract

Seeds of spiderplant (Cleome gynandra L.) were sown in soil-filled 20-litre plastic pots. The study was conducted to investigate the effect of salinity (NaCl) on the growth, development and adaptation of C. gynandra. The experimental design was based on randomized complete block design (RCBD) with replications. Two to four A weeks after germination, the plants were subjected to five levels of salinity. Salinity was applied by irrigating the pots daily with salt solutions of concentrations: 0 mol/kg (control), 0.07 mol/kg, 0.13 mol/kg, 0.20mollkg and 0.26 mol/kg, which exerted osmotic potentials of 0 MPa (control), -0.3MPa, -0.6MPa, -0.9MPa and -1.2MPa in the rooting medium, respectively. Data on growth parameters was collected weekly, including fresh and oven-dried weights of the whole plant as well as roots, shoots and leaves; water content, chlorophyll content, leaf number, leaf weight ratio, root/shoot ratio and days to 50% flowering. Results showed that salinity significantly decreased the growth of the whole plant as well as the growth of roots, shoots and leaves; and retarded flower emergence. The Chlorophyll content was also reduced by salinity. Water content was initially reduced, but recovered after some time, which was attributed to reduction oftranspiratory water loss and osmotic adjustment. It also showed that spiderplant does possess a moderate degree of salt resistance since plants were able to survive, grow and reproduce when subjected to up to -0.9 MPa of salt stress in the soil. Factors contributing to this resistance may include the species' capacity for osmotic adjustment and the presence of a C4 photosynthetic (Hatch-Slack.) pathway. The age at which plants are exposed to salinity may also be a factor in salt resistance. The Spiderplant was concluded to possess a poor capacity both for regulating the passive entry and translocation of salts, and also of compartmentalizing them, thus allowing large amounts of salt to be absorbed and translocated to the shoots and leaves, where they exerted such effects as retarding or inhibiting the processes of cell division and expansion as well as decreasing photosynthesis and increasing respiration. Observed root death was attributed to the deterioration of soil structure in the presence of high concentrations of sodium ions.