| Chrysanthemum,as one of the four cut flowers in the world,has long been loved by people all over the world,and occupies a large proportion in the cut flower market.There is a demand for chrysanthemum in all seasons of one year.The photoperiod phenomenon of photosensitive plant chrysanthemum is often used in production to induce its anti-season flowering.In order to explore the flowering effect of different photoperiods and its relationship with photosynthetic,growth and biochemical indexes,six photoperiod treatments were set up with'Hongmian'cut chrysanthemum as test materials,which were day/night 7h/17h(Ph7),8h/16h(Ph8),9h/15h(Ph9),10h/14h(Ph10),11h/13h(Ph11),and long-day(13?14h)treatment as control CK.The photosynthetic pigments,photosynthetic characteristics,growth indexes,biochemical indexes,development duration at different stages,and cut flower quality were measured.The distribution rates of dry matter in different organs at full blooming stages of different treatments were measured,and the prediction models for different development stages of chrysanthemum were constructed.The results showed that:(1)Chlorophyll a,chlorophyll b,and carotenoid content showed an overall upward trend with the extension of light time.The photosynthetic systems of chrysanthemum leaves treated with Ph7 and Ph8 were seriously damaged.Ph7,Ph8photosystem II oxygen release complex,photosystem I terminal electron acceptor library NADP~+reduction in the mid-term of the test slightly eased outside,the rest of the time were in an inhibited state,and photosynthetic capacity was also the worst.The photosynthetic system of chrysanthemum leaves treated with Ph10 was the most sensitive.Ph10 photosynthesis changed continuously with the sudden drop of energy connection between PSII photosynthetic units,and the PSII oxygen release complex was always inactive.The photosynthetic system of chrysanthemum leaves treated with Ph11 had the strongest stress resistance.Photosynthetic performance of Ph11 was stable,and the enhanced PSI and PSII activities maked photoelectron transport normally under the condition of inactivation of oxygen releasing complex.(2)The content of soluble sugar and protein in leaves showed a‘M'-shaped change trend with the advance of development stage,and the two peaks appeared at the flower bud differentiation stage and before flowering.Under long-day CK the plant height was large and strong,and the vegetative growth was the strongest.Ph7,Ph8 plant stem ratio increased,plant overgrowth height but stem slender,easy lodging,sucrose and soluble protein content minimum;Ph10 had the highest content of sucrose and soluble protein,and the growth of plants under Ph10 was dwarfing symmetrical and they had small plant height,thick stem and dense leaves.IAA,GA3 and ZT,ABA in the same development period had antagonistic effect,and Ph7,Ph8,Ph10 hormone fluctuations were the largest.In the budding stage,the content of ZT and ABA,which promoted flowers,were the highest in Ph10 and the lowest in Ph7,while the content of IAA and GA3,which inhibited flowers,were the lowest in Ph10 and the highest in Ph7.(3)The effect of photoperiod on flowering was mainly to affect the initiation of flower bud differentiation and the formation of flower buds to achieve the purpose of flowering regulation.Although the expansion process of lingual petals was also regulated by photoperiod,it did not play a decisive role in the advance of flowering.Ph7,Ph8 and long-day above 13h/d chrysanthemum flowering were seriously delayed.The cut flowers of Ph7 and Ph8 were small and few,and the anthocyanin content was low.The cut flower quality was the worst.Ph10 had the shortest budding time,only 35days,and the largest number of flowers per plant.Ph11 flowering later than Ph10,but flower diameter,flower fresh weight,anthocyanin content were higher.Ph9 florets showed abnormal flowers.The distribution rate of dry matter in leaves was Ph7>Ph8>Ph9>Ph10>Ph11>CK.With the shortening of light time,the physiological activities of chrysanthemum focused on promoting leaf growth.(4)Compared with the thermal effectiveness and PAR model,the physiological development time model was more accurate.The determination coefficient R~2 of the simulation equation between the simulated days of budding stage,bud breaking stage,petal formation stage,initial flowering stage and full blooming stage of chrysanthemum and the actual observed days were 0.91,0.85,0.81,0.86 and 0.87,respectively.The physiological development time required for Ph7,Ph8,Ph9,Ph10 and Ph11chrysanthemum from treatment to budding was 53.72 d,45.43 d,25.09 d,14.50 d and18.81 d,respectively.In conclusion,Ph7,Ph8 photosynthetic system damaged seriously,growth potential were weak,the latest flowering and wilting fast.Ph10 had the largest number of flowers per plant with fast full-bloom and not easy to wilt.Ph11 had strong photosynthetic capacity,good vegetative growth,high flower diameter,flower fresh weight and anthocyanin content,but its flowering period was later than Ph10.Therefore,the suitable photoperiod should be selected according to the different cultivation purposes. |
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