The effects of protein kinase C (PKC) inhibitors on the metallothionein (MT) gene expression induced by metals were investigated. When PKC inhibitor (H7 or chelerythrine) was administered to Cd resistant, MT gene-amplified Chinese hamster ovary (Cd ) cells, the induction of MT mRNA by Cd or Zn was blocked. Treating the Cd cells with a PKA-specific inhibitor, HA1004, did not cause an inhibition of metal-induced MT gene transcription. The inhibitory effect was effectuated by adding inhibitors within 40 min of exposing the cells to Cd. Apparently, AP1 was not involved in this down-regulatory effect of PKC inhibitor on MT gene expression since the inducibility of MT promoter was blocked by H7 even in the absence of the AP1-binding sequence. For Cd-treated cells, Cd accumulation in the cell was similar with or without H7 treatment. However, H7 markedly reduced cellular Zn accumulation when the cells were treated with Zn. Cycloheximide treatment increased the level of MT mRNA. This elevation can also be blocked by treating the cell with PKC inhibitor. Results in this study suggest that PKC participates in the process of metal-induced MT gene expression.z 1997 Federation of European Biochemical Societies.

Natural flowering of pineapple is a serious problem for commercial growers of pineapple because it disrupts fruiting schedules, decreases harvesting efficiency and increases costs, and may reduce the percentage of marketable fruit. Aviglycine ([S]-trans-2-amino-4-(2 aminoethoxy)-3-butenoic acid hydrochloride), an inhibitor of ethylene biosynthesis, was applied as a foliar spray to evaluate its potential to prevent natural flowering in 1-year-old `Tainon 18' pineapple. Two experiments were conducted between 10 Oct. and 10 Apr. during the 2001-02 and 2002-03 production seasons. For the 2001-02 season, single or double applications of aviglycine at 100 mg L-1 had no significant effect on natural flowering. A double application of aviglycine at 500 mg L-1 first applied on 9 Nov. reduced flowering from 95.0% in the control to 51.3% when evaluated on 25 Feb. 2002. In the 2002-03 production season, triple applications of aviglycine applied at 20-day intervals beginning on 10 Nov. 2002 significantly reduced natural flowering when evaluated on 28 Mar. 2003. There was 95.8% flowering in the control, 64.6% with 250 and 375 mg L-1 aviglycine, and 50% with 500 mg L-1 aviglycine. Aviglycine has the potential to partially control precocious flowering of pineapple, which will reduce crop losses associated with such flowering.

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A plastochron index was established for four commercial cultivars of Phalaenopsis: Phalaenopsis 'Taisuco Carol' x (Doritaenopsis 'New Cinderella' x P. 'Isaribi') (Taiwan Sugar Corp., code No. S88-41); Phalaenopsis 'Taisuco Swan' x (P. 'Casablanca Dream' x (P. 'Hohoemi' x P. 'Grace Palm')) (code No. S88-89); Doritaenopsis 'I-Hsin Dreamer' x Phalaenopsis 'Taisuco Harmonylip' (code No. S88-104), and Phalaenopsis aphrodite. The plastochron was based on a 20-mm reference leaf length. Semilogarithmical plots of ln-transformed leaf lengths versus time and linear regression analysis were used to evaluate three criteria of the plastochron index. The results showed that leaves 3-9 of Phalaenopsis aphrodite and leaves 3-8 of the other cultivars grow exponentially (r2 values between 0.90 and 0.97). Therefore, leaves that fulfilled all three criteria for the plastochron index were leaves 3-5 of No. S88-41, leaves 3-4 of No. S88-89, leaves 5-6 of No. S88-104, and leaves 4-5 of Phalaenopsis aphrodite. However the plastochron index can not be used for the slow-growing Phalaenopsis, because two successive leaves could not be measured simultaneously during the exponential phase of leaf development. The average relative growth rate of 0.43 mm/week for Phalaenopsis aphrodite was significantly lower than that of the other three cultivars (0.52 mm/week); plastochron duration also showed significant variation among the four cultivars (P value = 0.0269). In addition, the linear relationship (r2 = 0.97-0.99) of the plastochron index plotted versus time indicates that the intervals between initiation of successive leaves was equal for each of four cultivars. Thus, for these cultivars of Phalaenopsis, leaves that emerge before the reproductive phase can not be fully assessed by the plastochron index

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