Effects of Salinity on the Growth and Visocosity of Fruits of Okra (Abelmoschus esculentus L.)
A local okra variety (Ishiagu early) of Abelmoschus esculentus L. seeds were collected from Ishiagu in Ebonyi State in the southeastern region of Nigeria and were grown in plastic horticultural bags filled with a mixture of top garden soil, poultry manure and river sand as growth media. Seven days after germination, the plants were subjected to different levels of salt stress (control, 20mM, 50 mM, 100 mM and 200 mM Nacl). The growth parameters were measured at 2, 4, 6, 8, 10 weeks after planting. The growth parameters considered were germination percentage, shoot height stem girth, leaf length and width, fresh and dry weight of the plants, fresh pod yield and viscosity of the mucilage extracted from the fruits. Increasing salinity caused a reduction in plant growth. Germination was 100% in the control, however there was a sharp reduction as the level of salinity increased with 30% germination seen in 200nM treated soil. Shoot height decreased continuously with increment in the salinity level with a minimum of 38.54 cm in control and a maximum of 24.30cm in 200 nm treated saline soil. The shoot thickness also decreased considerably as the salinity level increased (control – 1.88 cm, 30 mM – 1.4 cm, and 200 mM – 1.30 cm). The fresh weights of the shoots of the plants were drastically affected and this is evident from the wide margin seen in 30 nm and 200 nm saline soil (16.76g and 4.12 respectively). A similar trend was observed in the dry weight. The pod weight was also affected negatively (25.94 g and 20.93 g for 30 nM and 200 nM treated soil respectively). The viscosity of the mucilage of the fruits was affected by the salinity of the soil. There was a reduction in the viscosity of mucilage as the salinity level increased. The highest was observed in control soil (198 mPa.s) and the lowest was in 200 nM treated soil (191 mPa.s). Visible physiological changes were also observed on the leaves, such as yellowing of older leaves, reduction in thickness and senescence of the older leaves with increase in salinity. The salt stress generally affected the okra germination rate, plant growth, development and yield as well as the viscosity of mucilage of the fruit of okra.