No abstract

We studied water content, H 2 O 2 content, antioxidant enzymes activities of different organs and root activity in potato cv. Desiree pretreated with NO under water-stress. It was found that the bound water content in root and root activity was significantly increased by treating NO before water-stress. Pretreatment with NO decreased the H 2 O 2 content and raised activities of CAT and GR significantly in roots under water-stress. The results suggested that NO might enhance the resistance to water-stress in potato.

Being an important garden plant, Dianthus chinensis ower has a great variety of colors and color patterns. Chalcone synthase (CHS) is the key enzyme in the anthocyanin biosynthetic pathway. Although CHS genes have been isolated and characterized in ornamental plants, the CHS gene is still unknown in D. chinensis. In our study, three CHS genes, DchCHS1 (KX893854), DchCHS2 (MK404175) and DchCHS3 (MK416198) were isolated in D. chinensis. Their deduced amino acid sequences show high homology with the known CHS sequences in Caryophyllaceae. The phylogenetic tree suggests that the DchCHS1 and the DchCHS3 have a close relation with the known CHS sequences in Caryophyllaceae and the DchCHS2 is different from them. The DchCHSs were characterized by the Tobacco Rattle Virus (TRV)based virus-induced gene silencing (VIGS) system. We obtained white or pale purple owers in the DchCHS1-silenced owers and reducing purple owers in the DchCHS2-silenced and the DchCHS3silenced owers. The anthocyanin content and the transcript level of the silenced DchCHS were signi cantly reduced in accordance with the silencing phenotypes. The DchCHSs showed different expression patterns during oral bud developments, among ower colors and in organs. Their expression levels in the purple ower were greatly higher than those in the white ower. Compared with DchCHS2 and DchCHS3, DchCHS1 was abundantly expressed at each oral bud stage, in each ower color and in the ower organ. In conclusion, the three DchCHSs are all involved in the anthocyanin synthesis and the ower coloration, and DchCHS1 probably plays a major role in D. chinensis owers.

Microtubers are valuable tools to be used in the researches of potato. Among the factors sucrose is the most critical stimulus for potato microtuber production in vitro. The aim of our study was to define whether only sucrose was enough to induce the tuber and how it impacted on physiological responses in potato in vitro. Among sucrose concentrations chosen 80 and 100g/l sucrose could induce maximum tubers in three cultivars of Solanum tuberosum L., Atlantic, Desiree and 851 in vitro at 22 o C under 16-h photoperiod. Meanwhile tuber induction percentage showed no difference in MS with 80 and 100g/l sucrose among 0, 16 and 24-h photoperiod and cuttings with no nodes induced no tubers in cv. Atlantic. Therefore, 80 or 100g/l of exogenous sucrose concentrations and cuttings with node were essential to in vitro tuber induction in potato. The endogenous sucrose content and acid invertase in induced cuttings were higher than corresponding tubers and dramatically increased with the increase of sucrose concentration in MS. Starch content was completely opposite to endogenous sucrose content and decreased with the increase of sucrose concentration in MS. Sucrose synthase (Susy) and sucrose phosphate synthase (SPS) accumulated only in tubers, but no significant differences of Susy and SPS were between 80g/l and 100g/l sucrose. In conclusion, high levels of exogenous sucrose resulted in a dramatic high gradient of endogenous sucrose content between inducing cuttings and the corresponding tubers, which was beneficial to trigger differential activity expression of sugar metabolizing enzymes and to accumulate starch in tubers in vitro.

Dianthus chinensis L. is a salt-tolerant ornamental plant. Root is the first and critical part of plant to encounter soli salinity. In order to elucidate H 2 O 2 impact on root morphology and mitochondrial permeability transition as well as activities of antioxidant enzymes in root of Dianthus chinensis L., we treated seedling with H 2 O 2 and DMTU under NaCl. The results revealed that change of H 2 O 2 level under NaCl would negatively influence the root growth, as well as lower the value of mitochodrial membrane absorbance at 540 nm and the ratio of Cyt c/a. Meanwhile, SOD and POD under NaCl plus H 2 O 2 and NaCl plus DMTU were far lower than those under NaCl alone.