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Two cultivars of sweetpotato [Ipomoea batatas (L.) Lam.], Commensal and Salyboro, were subjected to salt stress using axillary bud cultures. The salt levels ranged from 0–150 mM. After 10 weeks of growth, plantlet shoot height, dry weight, number of nodes, levels of proline, soluble carbohydrate, and protein; and metal ions sodium, potassium, magnesium, and calcium, were measured. In both cultivars, proline accumulation was higher in the shoot. There was a positive correlation between the increase in soluble carbohydrates and proteins in `Commnesal', but not in `Salyboro'. More sodium accumulated in the shoots of `Salyboro' compared to `Commensal'. The accumulation of sodium reduced the calcium and potassium, but not magnesium levels. Increase in sodium levels correlated with the increase in soluble carbohydrate levels is `Salyboro', but not in `Commensal'. A similar trend was evident with praline and sodium accumulation. Based on these and previous results, the cultivar `Salyboro' appears to be more susceptible to salt stress.
Two cultivars of sweetpotato, `Commensal' and `Salyboro', were subjected to salt stress using axillary bud cultures. The salt levels ranged from 0 to 10 g·L-1. After the initial experiments, levels of calcium in the medium were changed from 3 mm in the MS medium to 1.5, 6, and 12 mm. After 10 weeks of growth, plantlet shoot height, dry weight, number of nodes, levels of proline, soluble carbohydrate, and protein were measured. `Commensal' was tolerant to salt levels up to 4 g·L-1, but `Salyboro' was sensitive to concentrations of salt even at lower concentrations as evidenced by the growth and dry weight. Proline accumulation was higher in the shoot than in the root. The protein: carbohydrate ratios did not change much in `Commensal', but levels of carbohydrates increased in `Salyboro'. Reduction in calcium levels had a synergistic affect on salt-stressed cultivars. Enhanced levels of calcium reduced the inhibitory affects of salt stress. This was more pronounced in `Salyboro', which was susceptible. Proline levels were higher in plants subjected to salt stress and higher levels of calcium than controls, but lower than the plants subjected to salt stress. These and other metabolic changes suggest that calcium can reduce the adverse affects of salt stress in these two sweetpotato cultivars.
Scotch Bonnet pepper is a valuable commodity for Jamaica and the Caribbean, both for local consumption and for export because of its unique flavor and pungency. It is a valuable cash crop for small farmers who supply most of the fruit needed for processing and export. Azolla is a small water fern that grows on the surface of water bodies or on moist soil. Due to the presence of the nitrogen-fixing cyanobacterium Anabaena azollae, it fixes molecular nitrogen. This fern is used as biofertilizer for rice in millions of hectares in Asia. In the present work, experiments were carried out to determine the suitability and usefulness of both fresh and dried Azolla as biofertilizer for Scotch Bonnet pepper. A control without any fertilizer and a fertilizer control with 100 kg N/ha, supplied as ammonium sulfate, were used in 2-m2 plots, with three replicates for each treatment. Fertilizer was supplied in three split doses. Fresh Azolla was spread at the base of each plant and the soil was kept moist for the duration of the study. Dry Azolla was spread like a mulch around the base of the plant and used as a split treatment similar to inorganic fertilizer. Both the fresh and dry Azolla increased the marketable fruit yield over the control without fertilizer. Dry Azolla resulted in a similar yield as the fertilizer treatment [80%] while the fresh Azolla had a 60% increase in the yield over the control. In addition, dry Azolla resulted in early anthesis by 3 days over the fertilizer control. The dry weights of the whole shoot also showed increases similar to fruit yield. The dry Azolla also helped to improve the soil conditions and retained moisture for long periods. The results suggest that dry Azolla can be successfully substituted for chemical fertilizer for pepper. The cost of preparing Azolla to be used as fertilizer is calculated to be about 10% to 15% of the cost of chemical fertilizer for small farmers.
The Production of the cut flowers of Anthurium andreanum was in decline after Hurricane Gilbert in 1988 and the subsequent wide-spread problem of bacterial blight in Jamaica and the Caribbean. New methods of cultivation and new varieties were necessary for the development of the industry. In addition, with the destruction of coconut trees, the supply of commonly used coconut husk became difficult. The present work has focused on the development of alternative media to coconut husk and on the development of cultural and fertilizer practices that increase plant productivity and reduce incidence of disease. The variety Honduras was chosen for the study. A 3 × 3 latin square design was used to evaluate four media—coconut husk, brick chips, gravel, and basalt igneous rock—two methods of cultivation—pots and beds; at three levels of fertilizer—244, 448 and 896 kg N/ha per year. While the coconut husk was still the better medium, the other media have resulted only in about 15% decline in the marketable blooms. This was offset by the requirement for low maintenance and lower fertilizer rates in inorganic media compared to coconut husk. Pot culture proved to be better for management purposes as well as production for the same area of production, as density of the plants could be increased and the incidence of disease could be easily managed. These results will be discussed with emphasis on a simple cost–benefit analysis of various combinations of cultivation methods and practices for commercial cultivation of A. andreanum var. Honduras in the Caribbean.