Mature turning tomato fruits (cv. 'Thilina') were treated with four different concentrations of CaCl 2 (0%, 2%, 4%, and 6% aqueous solutions) using different modes of application; dipping, vacuum infiltration and pressure infiltration, with a view to improve the shelf life and quality. Fruits vacuum infiltrated at-20 kPa and treated with the four different concentrations of CaCl 2 were assessed for pH, total soluble solids (TSS) content, percentage titratable acidity (%TA) and firmness. Total calcium content in the inner and outer pericarp tissues was estimated and the path of calcium infiltration was revealed using black ink. Vacuum infiltration was found to be the most effective treatment with respect to shelf life extension. Also,, 6% CaCl 2 treatment at-20 kPa was the best in terms of extension of shelf life (by 92%) and in keeping the postharvest quality of tomatoes compared to the untreated fruits kept at 28 o C. Fruit firmness significantly increased with CaCl 2 application. Delay in fruit colour development, lowering of ethylene production rates and delay in the time taken to reach the ethylene climacteric were observed with increased CaCl 2 concentration. Treatment with CaCl 2 did not have a considerable effect on fruit pH, TSS or %TA. The amount of total calcium in the inner and outer pericarp regions increased significantly with calcium application. The stem end scar was found to be the main pathway of CaCl 2 infiltration in to fruits.

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ABSTRACT1-MCP is a competitive, gaseous ethylene inhibitor, which binds irreversibly to ethylene receptors and thereby blocks effects of ethylene in plants. The potential for 1-MCP to delay ripening in avocado cv. 'Pollock' fruit was examined under tropical ambient storage conditions. Fruits harvested at commercial maturity were exposed to 300 nll -1 1-MCP gas for 20 h under 27± 2 ˚C and then stored under ambient conditions (27± 2 ˚C and relative humidity 65 ± 2%). Fruits were assessed daily for fresh weight, firmness, skin colour, fungal rot development and glossiness. The antifungal activity in diethylether extracts of fruit peel was assessed through thin layer chromatography (TLC) coupled with Cladosporium bioassay. Exposure to 1-MCP extended the shelf life up to 9 days of fruit by 2.2 fold as compared to the shelf life of 4 days of the controls. Stem end rot caused by Botryodiplodia theobromae was found to be the shelf-life determining factor of the fruits. 1-MCP treatment resulted in a significant (p< 0.05) delay in change in peel colour, softening and glossiness of fruit as compared to the controls. Bioassays using Cladosporium fungus revealed the presence of antifungal activity at Rf 0.75 in both 1-MCP treated and control fruits. 1-MCP treatment was effective in delaying the decline of antifungal activity in fruit apparently along with the delay of other ripening-related changes and minimizing losses encountered during storage under warmer ambient conditions.

Rice husk is a natural Silicon (Si) source. This study evaluated the effect of rice husk in two different forms; ground rice husk (GRH) and rice husk ash (RHA) on downy mildew in bitter gourd (Momordica charantia L.) leaves caused by Pseudoperonospora sp. Rice husk was added to the growing medium to achieve the final concentration of 200 mg Si /kg soil. Si accumulation in leaves, disease severity, plant growth parameters, cuticle-epidermal layer thickness, chlorophyll content, total phenolic content, peroxidase (POD) and polyphenol oxidase (PPO) activity of leaves were measured. Husk treatment lowered the downy mildew severity significantly (p < 0.05) in leaves although the difference between the effects of two husk forms was insignificant. Numbers of leaves, flowers and fruits in husk-treated plants were significantly higher (p < 0.05) than those in control plants. Cuticle-epidermal layer thickness in GRH, RHA-treated and control plants were 16.8 ± 1.21, 18.2 ± 0.98 and 13.2 ± 1.27 µm respectively. Total phenol content, POD, PPO activity and chlorophyll content in rice husk-treated plants were significantly (p < 0.05) higher than that of control plants. The enhanced disease resistance in rice husk-treated plants appears to be positively associated with the higher accumulation of silicon and Si-enhanced phenolic content and increased activity of PPO and POD enzymes in leaves.

Effect of soluble silicon (Si) on downy mildew in bitter gourd (Momordica charantia L.) leaves caused by Pseudoperonospora cubensis was tested using three concentrations of liquid potassium silicate (100, 200, 300 mg Si/kg) added to the growing medium containing top soil, compost and sand. Disease severity, plant growth parameters, silicon accumulation on leaves and cuticle-epidermal layer thickness of transverse sections of leaves were measured. Si treated plants exhibited less disease severity than that of control plants and 200 mg Si/kg treatment resulted in highly significant disease suppression (37 -53% reduction against controls). The suppression of the disease strongly correlated with the Si accumulation in leaves. Cuticle-epidermis thickness was higher in Si-treated leaves (17.2 -21.3 µm) against non-treated (10.3 -13.81 µm). Numbers of leaves, flowers or fruits in Si treated plants were significantly higher (p < 0.05) than control plants except in 300 ppm Si level. Structural changes created by Si may at least be partly responsible for reducing the fungal disease severity in bitter gourd leaves.

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Foliage of Calathea aemula, C. lietzei and C. zebrina at four maturity stages, first, second, third and fourth fully expanded leaves (FEL) from the shoot apex, were subjected to vase life assessment in distilled water at 20 °C and 70% RH. Leaf rolling was the factor leading to vase life termination. Chlorophyll content significantly decreased during vase life in all three species. The best harvesting maturity in relation to vase life varied among the species. At the time of harvest, chlorophyll content of the 1 st FEL were significantly less than those of the 4 th FEL in all three species. However, the chlorophyll content at harvest did not show a significant correlation with subsequent Calathea vase life.

To investigate the function of BAP, amount of chlorophyll was quantified using leaf pigment extracts. The vase life of O. japonicus could be extended from 5.1 days to 12.5 days by giving BAP based vase solutions. Chlorophyll contents of leaves dipped in BAP solutions were significantly higher than the control (distilled water). CuSO 4 solutions did not show any significant antibacterial effects compared to the control. According to vase life data, the most effective vase solutions were CuSO 4 .5H 2 O (0.5 mM), sucrose 20 g/L with CuSO 4 .5H 2 O (0.5 mM) as holding treatments, sucrose 20 g/L and 30 g/L as pulsing treatments and BAP treatments (5, 10, 20 mg/L).