| In the course of the modernization production of flowers, because plugseedlings are adopt, the excessive growth of the flowers is a very seriousproblem. It is a kind of simple and convenient method with instant effect touse plant growth retardants (PGRs) to control the physiology growth offlowers. As to this, already there have been many studies done at home andabroad. But because of different horticultural equipments,environmentalcondition and cultural modes between areas, it is different that the results ofthe studies applies to China directly. So it is significant for improvement ofquality of plug seedlings and advance of industrialization of seedling to studythe physiological effects of PGRs on plug seedlings pertinently andsystematically.For this reason, this thesis selected Brassica (Brassica oleracea var.Acephala), Salvia (Salvia splendens Ker. -Gawl.), Petunia (Petunia hybridaVilm), marigold (Tagetes erecta L.) and maidenhair (Tagetes patula L.),several kinds of herbaceous flowers used widely, as test materials, studied theretardant effects of different concentration of daminozide (B9), chlormequat(CCC ) and paclobutrazol (PP333 ) , the three PGRs, and identified the bestconcentration and mixed proportion. The mechanism of dwarfing maidenhairusing paclobutrazol was investigated from several aspects such as shape,anatomies configuration, physiology, endogenous hormones and so on. Theresult shows:(1) The plug seedlings of Salvia are treated with chlormequat (CCC) ofdifferent concentrations by spraying. 0.02% CCC is optimal concentration.(2) The plug seedlings of Petunia are treated with B9, CCC and solutionmade up of B9 and CCC of different concentrations by spraying. Theireffective and safe concentrations are 1000~2500 mg/L B9, 0.05%~0.3% CCCand 1500 mg/L B9+0.3% CCC respectively. And their optimal concentrationsare 2500 mg/L B9, 0.3% CCC and 1500 mg/L B9+0.3% CCC respectively.Among the three optimal concentrations, effect of 1500 mg/L B9+0.3%CCCis the best and that of 0.3% CCC takes second place. But the price of 2500mg/L B9 is the lowest. When the concentration of CCC is beyond 1%, thephytotoxicity of CCC on the plants will happen. (3) The plug seedlings of marigold are treated with B9, CCC, solutionmade up of B9 and CCC, and PP333 of different concentrations by spraying.Their effective and safe concentrations are 1000~2500 mg/L B9, 0.1% ~0.3%CCC, 1000 mg/L B9+0.2%CCC and 10~60 mg/L PP333 respectively. Andtheir optimal concentrations are 2500 mg/L B9,0.3%CCC,1000 mg/L B9+0.2% CCC 和60 mg/L PP333 respectively. Among the four optimalconcentrations, effect of 60 mg/L PP333 is the best, that of 1000mg/L B9+0.2% CCC takes second place and that of 0.3%CCC takes third place. Morever,the price of 60 mg/L PP333 is the lowest. When the concentration of CCC isbeyond 1%, the phytotoxicity of CCC on the plants will happen. (4) The plug seedlings of maidenhair are treated with PP333 of differentconcentrations by spraying in different periods. Their effective and safeconcentrations are 10～30 mg/L in pre-emergence, 30 mg/L in the stage ofcotyledon, 10～60 mg/L in the stage of one pair of leaves and 15～60 mg/L inthe stage of two pairs of leaves. Among of them, the optimal treatment is 30mg/L in pre-emergence. As far as plant height is concerned, the earlier theplants are treated, the more observable the effect of PP333 is. The phytotoxicityof PP333 on the plants will happen when the concentration of PP333 is beyond60mg/L in the stage of pre-emergence and cotyledon, and beyond 120 mg/L inthe stage of one pair of leaves. The concentrations of PGRs mentioned previously can control the heightof the plants effectively and safely. They are effective in reducing the height ofthe plants, increasing the thickness of leaves, increasing the content ofchlorophyll, making the leaf color darker, and effectively improve theappreciative value of the flowers. The higher the concentrations of PGRs are,the more effective they are. (5) Spraying 30 mg/L PP333 in pre-emergence can decrease the content of... |
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