Search

Leaf explants of Caladium ‘Pink Cloud’ were cultured in vitro on MS medium containing various auxins (NAA, IBA, IAA, 2,4,5-T and 2,4-D) in combination with cytokinin (BA). NAA gave the most vigorous in vitro propagation of this plant, and only 15% of the plants were leaf-colour variants on the medium containing 0.5 μmol NAA. Leaf colour variation was observed in all plants regenerated on the medium containing 2,4-D at 0.5–4.5 μmol. In hormone-free medium, only a few leaf-colour variants (6%) occurred, but the rate of plant regeneration was very low. Application of 0.5 μmol NAA together with 4.5 μmol BA seemed to be the most appropriate for in vitro propagation of Caladium ‘Pink Cloud’ with only a few leaf-colour variants. [Copyright &y& Elsevier]

Morphological changes during the development of pseudoembryos in parthenocarpic fruits of the genetic parthenocarpic tomato cultivar, ‘Severianin’, were observed. Pseudoembryos that originated from division of the innermost integument cells were formed in the ovule cavity. These cells were highly stained with toluidine blue O and actively divided until 20 days after anthesis. Uniconazole, an inhibitor of gibberellin biosynthesis, applied at anthesis decreased the setting ratio of fruits and inhibited the development of pseudoembryos. Uniconazole applied at 3 days after anthesis inhibited fruit growth entirely and suppressed pseudoembryo development. Gibberellin treatment at 2 days after uniconazole treatment reversed the inhibitory effect of uniconazole on fruit growth and pseudoembryo development in ‘Severianin’. The inhibitory effect of uniconazole on fruit growth and pseudoembryo development in auxin-induced fruits of ‘Kyouryoku-Kyokkou’, a commercial cultivar without genetic parthenocarpy, was weaker than that in ‘Severianin’. Application of gibberellin also reversed the inhibitory effect of uniconazole in this cultivar. Well-developed pseudoembryos were always observed in the well growing fruit in both cultivars. These results indicate that the development of pseudoembryos is closely related to the growth of parthenocarpic fruit. [Copyright &y& Elsevier]

Capsiate is a capsaicin-like ingredient of a non-pungent cultivar of red pepper, CH-19 sweet. To elucidate the mechanisms underlying the non-pungency of capsiate, we investigated whether capsiate activates the cloned capsaicin receptor, TRPV1 (VR1). In patch-clamp experiments, capsiate was found to activate TRPV1 expressed transiently in HEK293 cells with a similar potency as capsaicin. Capsiate induced nociceptive responses in mice when injected subcutaneously into their hindpaws with a similar dose dependency as capsaicin. These data indicate that the non-pungent capsiate is an agonist for TRPV1 and could excite peripheral nociceptors. In contrast to this, capsiate did not induce any significant responses when applied to the skin surface, eye or oral cavity of mice, suggesting that capsiate requires direct access to nerve endings to exhibit its effects. Capsiate was proved to have high lipophilicity and to be easily broken down in normal aqueous conditions, leading to less accessibility to nociceptors. Another highly lipophilic capsaicin analogue, olvanil, was similar to capsiate in that it did not produce irritant responses when applied to the skin surface, although it could activate TRPV1. Taken together, high lipophilicity and instability might be critical determinants for pungency and so help in understanding the effects of capsaicin-related compounds. [Copyright &y& Elsevier]

Explants from various parts of Caladium bicolor Ait. plants were cultured on MS medium containing 1 ppm naphthalene acetic acid (NAA) and 1 ppm 6-benzyladenine (BA). Variations in the shape and color pattern were observed in the regenerated plants. In plants regenerated from shoot tip explants including the two youngest leaves, young leaves (third and fourth leaves from the top), unexpanded leaves (fifth or sixth leaves), expanded leaves and petiole, the frequency of the occurrence of variants was 14, 24, 41, 53 and 70%, respectively. Plants regenerated from young leaves of lateral buds or root tips also produced only a few variants (12–14%). Thus, explants from younger tissue having meristematic tissue produced fewer variations than explants from older tissue. The mode of variation (color pattern and shape of leaves) also varied with the age of the explant. We conclude that young tissue should be used to propagate Caladium plants by tissue culture. [Copyright &y& Elsevier]