| "Blunt with blossom" is a common disorder in cucumber (Cucumis sativus L.) production happening in the seedlings, vegetative and productive growth stages, decreasing its commercial value by 20-50%. But the role that involved in the cucumber "blunt with blossom" is still unknown.By light microscopy (LM), transmission electron microscopy (TEM) and scanning electron microscopy (SEM) procedures we studied the morphological, anatomical and cytological characteristics of the shoot tops in "blunt with blossom" cucumber (BBC) by comparing it with normal cucumber (NC). The investigation showed that there were significantly changes in BBC young leaves. The leaf area significantly reduced and leaf number obviuosly decreased in BBC, but the angle of leaf blade was more than that of the NC for the upper epidermis of the young leaves in the BBC was larger than those of the NC. The stoma density of the BBC young leaves increased, but most of the stoma closed, which may inhibit the photosynthesis. The anatomy analysis revealed that the number of palisade cell and spongy cell layers did not change, but the thickness of the leaf blade, and palisade and spongy tissue in BBC were all markedly less than those of NC. Meanwhile, the inner layer palisade cells of BBC leaves were more isodiametric with large air spaces between them, suggesting reduced cell-to-cell adhesion. The starch granules in the chloroplast of the palisade and spongy cell in the BBC spread leaves were also obviously larger than those in the NC spread leaves. Moreover, the membrane of the chloroplast, vacuole and nuclear envelope dissolved partly, and the osmiophilic granules that denote the decomposition accumulated in the chloroplast of BBC.Comparing with NC, there were also markedly differences in BBC young stem. The internode number and length, and the stem diameter were significantly decreased in BBC for the reduction of the cell length and width. The number of vascular bundles, the number of vessels with secondary cell wall in the vascular bundles and the cell wall thickness of collenchyma all increased in BBC.Except for the changes in leaf and stem, more important differences happened in the SAM after the cucumber "blunt with blossom". First, the volume of the SAM, the number of peripheral primordia reduced. Despite there were differentiated primordia around the SAM,sthey formed a cluster because of the repression of the cell elongation. Second, the SAM cells in BBC were highly vacuolated, as well as plastid, nuclear and vacuole membranes all partially degenerated. In addition, no clear endoplasmic reticulum and less divisive cells in the SAM cells of BBC have been observed. All the results indicated the reduction of the SAM dividing ability and the senescence of the BBC.By mRNA differential display technology, RACE method, DNA and RNA gel-blot analysis, we obtained 6 positive differential expression cDNA fragments between NC and BBC. Two of them are homologous to the chloroplast ATPase subunit III and arginine decarboxylase (ADC) respectively, and four others are unknown fragments.In the followed experiments, we isolated the whole sequence of the cucumber chloroplast ATPase subunit III and ADC by RACE precedures, renamed them as CuATP and CuADC, both have been registered in GenBank, which numbers are AY274821and AY274822. The whole CuATP cDNA sequence of is 755bp, including 382bp 5 ' untranslated region, 127bp 3 ' untraslated region and 243 bp coding region. The whole CuADC cDNA sequence is 2875bp, including 580bp 5 ' untranslated region, 144bp 3 ' untraslated region and 215-lbp coding region.Gel-blot analysis of DNA indicated that there is one copy CuATP in cucumber. Gel-blot analysis of RNA isolated from cucumber leaf, root, stem and flower showed that the abundance of CuATP mRNA was low or no in root, moderate in stem and flower, and higher in leaves. The expression of CuATP in different species seedlings is not the same and is all affected by many kinds of stress conditions such as drought, salinity, cold, heat and ethylene. In BB...
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