No abstract

Leaf yellowing associated with early senescence is a major problem associated with cut decorative leaves and flowers of many tropical plant species. Effect of postharvest application of benzylaminopurine (BAP), gibberellic acid (GA 3), silver-thiosulphate (STS) and silver nitrate (AgNO 3) on vase life of cut leaves of three Dracaena species Dracaena marginata 'bi colour', Dracaena sanderiana 'white' and Dracaena deremensis were investigated. Deionized water (DIW) was used as the control. All the BAP treatments (25, 50 and 100 M) applied either as 10 minutes immersion or as 24 h pulse improved the vase life of all three species examined. Application of STS (2 mM) and AgNO 3 (10 mM Ag ions) did not increase the vase life of D. marginata 'bi colour' and D. sanderiana 'white' significantly while GA 3 (50, 100 and 250 M) either as a pulse or immersion, significantly reduced the postharvest life of D. deremensis compared to untreated leaves. Results suggest that the application of 25 M BAP as a pulse treatment for 24 h can be recommended to prolong the postharvest life through delayed leaf senescence and thus enhance the marketability of cut leaves of Dracaena marginata 'bi colour', Dracaena sanderiana 'white' and Dracaena deremensis.

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).

An efficient protocol was developed for the micropropagation of Cryptocoryne beckettii and Cryptocoryne bogneri, two endemic threatened aquatic herbs of Sri Lanka, highly valued as aquarium plants. Rhizomes of C. beckettii and C. bogneri were established on full strength Murashige and Skoog (MS) medium with 3% sucrose and regenerated shoots were cultured on MS medium supplemented with combinations of 6-benzylaminopurine (BAP) 2, 5, 8, 10 mg l -1 and 0.1 mg l -1 indole acetic acid (IAA) for multiple shoot regeneration. For root induction and shoot growth, agar solidified full and half strength MS medium and a soil-based medium were used. The presence of growth regulators in MS medium had a significantly high (p<0.05) effect on shoot multiplication in both species. Lowest mean number of shoots proliferated per shoot explant (C. beckettii 10.4 and C. bogneri 4.2) was observed in the absence of growth regulators. BAP alone or IAA alone in the medium also had no significant effect. Presence of both BAP and IAA in the medium significantly increased the shoot number. Highest mean number of shoots proliferated per single shoot explant (43.0) was observed in the combination of 5.0 mg l -1 BAP with 0.1 mg l -1 IAA for C. beckettii while the combination of 5.0 mg l -1 BAP with 0.1 mg l -1 IAA or 8.0 mg l -1 BAP with 0.1 mg l -1 IAA had highest mean number of shoots proliferation (51.8, 50.4) for C. bogneri. Mean number of roots induced per plant was highest (C. beckettii 8.4: C. bogneri 7.8) in the soil based medium consisting of a mixture of equal parts of 2 mm size ground brick fragments: sand: charcoal: top soil (medium A) with half strength MS and 0.1 mg l -1 NAA. Treatments of soil based medium had a significantly high effect on root and shoot development than the agar solidified media in both species. The plants were acclimatized with 90 % survival in C. beckettii and 100% survival in C. bogneri.

Based on the scientific information available, E. trinervium is currently of conservation concern since it shows poor seedling growth even under satisfactory seed germination. Ex-situ cultivation is therefore recommended as a conservation strategy. This study aimed to (i) investigate the effective pre-sowing 6-Benzylaminopurine (BAP) treatment that enhances the seed germination and seedling vigour and (ii) to study morphological traits that can be used in assessing healthy seedlings of E. trinervium. The experiment was conducted in a completely randomized design under both laboratory and green house conditions with BAP concentrations of 1.0, 2.0 and 3.0 mgL -1 as pre-sowing treatments and distilled water as the control with different exposure durations i.e. 18, 24 and 30 hours. The results showed that there was no significant effect of BAP treatments on seed germination percentage under laboratory and nursery conditions. The lowest average mean germination time (MGT) was obtained 24 h exposure duration for the green house condition. Seedling dry weight and seedling Vigour Index (SVI) were significantly (P<0.05) higher for BAP concentration of 3.0 mgL -1 under 24 h exposure duration. Growth parameters i.e. number of leaves, plant height, root length, number of primary roots, dry weight and fresh weight of E. trinervium were significantly (P<0.05) induced by BAP concentration and exposure duration. Accordingly, BAP concentration of 3.0 mgL -1 under 24 h exposure duration proved to be the optimum BAP treatment for the increase of seedling vigour of E. trinervium under the green house conditions. Therefore, the present study suggests that BAP treatment may be involved metabolically in the stimulation of germination and then to increase the seedling vigour of E. trinervium.