| Chrysanthemum (Chrysanthemum morifolium Tzvel), a perennial plant of Composite, is one of the Ten Traditional Chinese Famous Flowers and of four important cut flowers all over the world, which is widely used as pot plant, cut flower and ground- covers, and plays an important role in flower producing. A horticultural practice of grafting chrysanthemum by using Artemisia has been reported, however, how a grafted chrysanthemum tolerates abiotic stress and the mechanisms involved in abiotic stress tolerance remained unknown. Chrysanthemum is not photoperiod inductive and floral inductive unless the plant is at a certain physiological development stage. But few knowledge of the floral initiation in popular cut chrysanthemum cultivars has been disclosed yet. Moreover, nutrition need of chrysanthemum remained to be further studied for a better mineral elements supply during producing practice. In present study, the effects of grafting on the heat tolerance and salt tolerance were investigated in grafted chrysanthemums using two Artemisia species as stocks. On the other hand, effects of the developmental stages and different levels and ratios of nitrogen, phosphorus and potassium on the growth and development as well as cut flower quality were monitored in chrysanthemum’Jinba’. The results are as follows.1、Grafted chrysanthemums were generated by using Artemisia lactiflora and Artemisia annua as root stocks, and chrysanthemum’Zaoyihong’and’Qiuyi’as cions. Growth and development index, photosynthetic parameters, mineral element contents, chlorophyll content, water content, soluble sugar and protein content, GA and ABA content, antioxidant enzyme activities and root ability were compared between the cuttings plants chrysanthemum and their grafted ones. The results showed that graft improved the growth of chrysanthemum, in grafted chrysanthemums, plant height, canopy diameter and leaf area were better than those in cuttings plants. The fresh weight and dry weight in the leaf, stem, root and inflorescence are improved in the grafted chrysanthemums. The root/canopy rate was higher than that in cuttings plants, whereas, number of inflorescence per plant of grafted chrysanthemum few changed. There is no significant difference in the content of chlorophyll a, while content of chlorophyll b is higher than cuttings plants. The values of Chla/b and Chl(a+b)/Caretonoids are lower than those in cuttings plants. The photosynthesis saturation point in grafted plants except the grafted plants generated from ’Yidalihong’-A.is higher than those in cuttings plants. Whereas photosynthesis compensation point in cuttings is higher than those in grafted plants. There is no significant difference in apparent quantum yield between cuttings and grafted plants.Net photosynthetic diurnal integral value, diurnal net photosynthetic rate (Pn) and transpiration rate in grafted plants are higher than those in cuttings plants, while intercellular CO2 concentration, stomatal conductance(Gs) remained unaffected by grafting. Nitrogen, phosphor, K+, Ca2+, Mg2+, Cl- and Na+ are higher or equal to those in cuttings plants. Water content in grafted plants is lower than those in cuttings plants, contents of soluble sugar and protein don’t change significantly. GA and ABA contents in cuttings plants both are higher than those in grafted ones, however, IAA content is lower in grafted plants. ABA/GA ratio is higher in grafted plants than in cuttings plants. Root activity in grafted plants is significantly higher compared with cuttings ones during either vegetative or flowering stages, and decline in root ability is lower in grafted seedlings than in cuttings ones during late stage. In conclusion, grafting improved the growth and development, enhanced the photosynthesis, content of mineral elements and root ability.2、Using Artemisia lactiflora and Artemisia annua as root stocks, grafted chrysanthemum were created. The membrane permeability, O2·- production rate, and activities of superoxide dismutase (SOD), peroxidase (POD), catalase (CAT), ascrobate peroxidase (APX) and contents of soluble protein in leaves of the cuttings plants and grafted plants of chrysanthemum were studied under heat stress. The results showed that grafted plants had lower membrane permeability and O2·-production rate, while SOD, CAT and APX activities and soluble protein contents were higher compared with those in the cutting plants. However, there was no significant difference in O2·- production rate and activities of antioxidant enzymes between the grafted plants with different root stocks. The leaf curiling, wilting, yellowing were alleviated in grafted plants than those in cutting plants under heat stress. It suggested that grafting could improve the heat tolerance of chrysanthemum.3、Grafted chrysanthemums were generated by using Artemisia lactiflora and Artemisia annua as root stocks, and chrysanthemum’Zaoyihong’ as cions. The difference between plant biomass, mineral element contents, chlorophyll content, photosynthetic parameters, leaf protective enzyme activities, MDA content and production rate of O2·-under NaCl stress were compared between the cuttings and grafted plants of chrysanthemum. The results showed that biomass of grafted chrysanthemums were better than those in cuttings plants, and decreased degree of biomass indexes was lower than those in cuttings plants obviously. Under NaCl stress, the K+, Ca2+ and Mg2+ contents in the leaf, stem and root of the grafted chrysanthemums (excepted the leaf of grafted seedlings by A.annua) were extremely significantly better than those in cuttings plants, furthermore decreased degree of those indexes in the grafted chrysanthemums was obviously lower than cuttings plants. It showed that relatively strong mineral absorptive capacity, moreover the ratios of K+/Na+, Ca2+/Na+ and Mg2+/Na+ of leaves and stems in grafted plants were significantly higher than those in cuttings plants. There was no significant difference between two grafted chrysanthemums. There was no significant difference between grafted chrysanthemums and cuttings plants under NaCl stress in terms of the contents of Chla, Chlb and Chl(a+b), but decreased degree reduced greatly in grafted chrysanthemum. Leaf net photosynthetic rate (Pn), transpiration rate (Tr) and stomatal conductance (Gs) also decreased greatly, while intercellular CO2 concentration improved slightly. All these indexes are significantly different between grafted and cuttings plants, and the degree of decrease/improvement of these indexes was obviously lower than that in cuttings plants. Free proline content and soluble sugar content of grafted seedlings were extremely significant higher than those of cuttings plants, respectively, soluble protein content was also higher but not significantly higher in grafted chrysanthemum. SOD, CAT and APX enzyme activities of the grafted chrysanthemums under NaCl stress were higher than those in cuttings plants, high and long lasting time improvement was observed; however the MDA content and producing velocity of superoxide anion were lower than those of cuttings plants, especially during late stages of NaCl treatment. In conclusion, grafted chrysanthemums exhibited a great salt tolerance, enhanced the photosynthesis, mineral element absorption, anti-oxygenase activity, osmotic adjustment under NaCl stress.4、Effects of growth age on short day induced flower bud differentiation and quality of cut Chrysanthemum were studied using cultivar’Seiun’and’Jinba’. Flower bud differentiation, flowering process and flower quality were investigated in short day treated cuttings which were at different ages by modulating cutting and planting date. The result were as follows, grow age has great effects on flower bud initiation of cut Chrysanthemum’Seiun’ and’Jinba’, the younger grow age is, the later the flower bud initiation is. For’Seiun’and’Jinba’that grow age was 0 day,18 days were essential from flower bud induction to bud initiation, which longer distinctly than 4 days.21 d and 28 d is the physiological mature age that is perceivable to flower bud differentiation inducing for ’Jinba’ and’Seiun’. Time of different grow age’Jinba’ plants from flower bud induction to bud initiation is 32-38 days, and 24-39days for’Seiun’. The younger grow age of the’Seiun’and’Jinba’ was, the longer time required from flower bud induction to bud initiation was, and the later of bloom time was. Grow age also has great effects on quality of cut chrysanthemum, the younger grow age was, the poor quality of flower’s was. To obtain the high quality cutting flower according with the standard for export, grow age must achieve 28 days for’Jinba’ and 35 days for’ Seiun’when begin flower bud initiation.5、To determine the effects of N,P,K nutrients on the growth and development of cut chrysanthemum’Jinba’ and obtain the optimum formula,experiment with orthogonal experimental design with three factors including N,P,K nutrients at three levels was conducted.The results indicated that under the condition of this experiment,N was the most important factor influencing the growth and development,and stem diameter,leaves area,flower diameter,length of petal,growth days of flower bud break, plant weight and length of root among three levels was significant (P<0.05). The effects of P on stem diameter, length of flower neck and growth days of flower bud broke was significant. The effects of K on length of flower neck, growth days of flower bud broke,leaves fresh mass and stem fresh mass was significant. The optimum fertilization level of N,P,K was N:P:K= 14.3:2.0:8.0 during vegetative growth stage and N:P:K=7.1:4.0:12.0 during reproduction stage. |
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