Study On The Differences Of Photosynthesis And Peroxidation System In The Green And White Tissues Of Ananas Comosus Var.Bracteatus

Ananas comosus var.bracteatus as an important ornamental plant,its leaf mosaic characteristics are obvious.It is a good material for studying the mosaic mechanism of leaf color.In this paper,the whole leaves were used for determining Pn,Cond,chlorophyll fluorescence parameters,and the leaf cross sections were observed by ordinary microscope and laser scanning confocal microscope,describing their photosynthesis characteristic;The characteristics of the opening and closing of the stomata were observed and the contents of chlorophyll,key enzyme activity of the photosynthesis,the content of malic acid,the content of soluble sugar and starch,the content of antioxidants,the activity of the key enzymes of the ascorbic acid-glutathione cycle,the activity of other antioxidant enzymes and the active oxygen content of the two tissues were measured.And malondialdehyde content,describe the specific differences between green tissue and white tissue of chimeric leaves,and analyze how white tissue grow normally.The main results are as follows:?1?The diurnal changes of net photosynthetic rate of the chimeric leaf in summer and spring basically follow the typical characteristics of CAM plants,while the net photosynthetic rate at night is high and positive,and the net photosynthetic rate gradually decreases to negative in the daytime.The stomatal conductance of nocturnal stomata was also significantly higher than that of daytime stomatal conductance.The green and white tissues of the chimeric leaves were observed at different time points in the day,and the stomata were all kidney shaped,and the 2 guard cells were arranged symmetrically,and there were no auxiliary cells around them.The stomata of the two kinds of tissue were all open at 9:00 a.m.,and closed at12:00 a.m.,and open at 21:00,and to coincide with the stomatal opening and closing characteristics of the CAM plants.The diurnal variation of malic acid content and the diurnal variation of soluble sugar and starch content of the two tissues showed an opposite trend.Therefore,it is found that the chimeric chimeric seedlings are CAM plants.?2?The net photosynthetic rate of MGr leaves and MWh leaves in spring was compared.It was found that the net photosynthetic rate of 21:00-10:00MGr leaves and MWh leaves was positive.The peak of 21:00-2:00 two leaves appeared,and the peak value of MGr leaves was higher than that of MWh leaves.The net photosynthetic rate of 2:00-10:00MGr leaves and MWh leaves had no significant difference.The net photosynthetic rate of 10:00-21:00 two leaves was basically negative,and the leaf photosynthetic rate of MWh leaves fluctuated significantly at this stage.The daily variation trend of stomatal conductance of the two types of leaves is generally consistent,and stomatal conductance is also close.Stomatal conductance remained high at 21:00 PM to 10:00 am,while stomatal conductance was low in the morning and evening.The trend of this change is in accordance with the daily change trend of net photosynthetic rate.It is also consistent with the characteristics of stomatal opening during daytime light intensity of CAM plants and the opening of stomata at night light.?3?The non-optical quenching coefficient?qN?of MWh leaves is significantly higher than that of MGr leaves;there is no significant difference between the two leaves of the effective photochemical quantum efficiency?Fv'/Fm'?and photochemical quenching coefficient?qP?;the maximum photochemical quantum efficiency?Fv/Fm?,the actual photochemical efficiency of PSII,the apparent electron transfer rate?ETR?that of MGr leaves were significantly higher than MWh leaves.The results show that the PSII photochemical reaction ability of MWh blade is weak and the electron transfer rate is low,but it can dissipate the excess light energy in time and protect the light reaction center.It is also indicated that the increase of white tissue in the chimed leaves will cause the light chemical reaction of the leaves to be weakened,the light catching efficiency is reduced,the electron transfer rate is slower,and the absorption of light energy is more used in the heat dissipation.?4?The contents of total chlorophyll,chlorophyll a,chlorophyll b and carotenoid in white tissues were significantly lower than those of green tissue,only 0.038mg/g,0.015mg/g,0.023mg/g and 0.0055mg/g,and the content of chlorophyll b in white tissues was more than that of chlorophyll a.This may be yellowish white with the white tissue of the chimeric leaves,and the chlorophyll b is yellowish green,indicating that the white tissue may absorb more light energy through a relatively large number of chlorophyll b.The section sections of chimeric leaves showed that there was almost no chloroplast distribution in the white tissue,but there were large amounts of chloroplasts distributed in green tissue.?5?The diurnal variation of the key enzyme activities of the two tissues basically followed the changes of CAM plant enzyme activities,but abnormal fluctuations occurred at certain time points.Comparing the activities of the two tissues,it was found that the activity of phosphoric acid pyruvate carboxylase?PEPC?in white tissue at night was significantly lower than that of green tissue,while the activity of malate dehydrogenase?NADP-MDH?was significantly higher than that of green tissue;the activity of white tissue malate?NADP-ME?in daytime and-1,5-two phosphate carboxylase?Rubisco?The carboxylation activity was significantly higher than that of green tissue,and pyruvate phosphate double kinase?PPDK?activity was not significantly different from that of green tissue.In general,the ability to synthesize malic acid,decarboxylation and immobilized decarboxylation of the white tissues are stronger than those of green tissue,except for the ability of the white tissue to fix the CO₂ in the atmosphere than the green tissue.This may be because white tissues capture light energy,low electron transfer rate,and weak photosynthetic capacity in light reactions,but it can provide CO₂ for green tissue to promote photosynthesis in green tissues.?6?The content of malic acid in the two tissues showed a tendency to decrease in the daytime at night,and the content of soluble sugar showed a tendency to decrease in the daytime at night,but there was an abnormal fluctuation in some time points,but the fluctuation of malic acid and soluble sugar and starch was in the opposite direction,and it was consistent with the activity fluctuation of the key enzymes used for light cooperation.In general,the soluble sugar content of white tissue was significantly lower than that of green tissue,and starch content was significantly higher than that of green tissue.The white tissue is the storage tissue of the leaves,and the photosynthetic products of the green tissue are exported to the white tissue and stored in the form of starch to promote the photosynthesis of the green tissue.?7?The content of alpha tocopherol,reductive ascorbic acid?AsA?and reduced glutathione?GSH?in the non-enzymatic antioxidant system of white tissue was significantly higher than that in green tissue.The white tissue ascorbic acid-glutathione cycle?AsA-GSH?helps to regenerate AsA and GSH substances-oxidative type ascorbic acid?DHA?,oxidized glutathione?GSSG?,and enzymes that catalyze AsA and GSH regenerative reactions-dehydrogenate ascorbate reductase?DHAR?and mono dehydrogenate ascorbate reductase?MDHAR?.The activity of glutathione reductase?GR?was higher than that of green tissue,which was consistent with the results of white tissue AsA and GSH content significantly higher than that of green tissue.The activity of ascorbic acid peroxidase?APX?,superoxide dismutase?SOD?,catalase?CAT?and peroxidase?POD?in the antioxidant system of white tissue was also significantly higher than that in green tissue.White tissue may balance the production and elimination of peroxide by strengthening the AsA-GSH cycle and enzymatic antioxidant system to avoid damage to tissues.?8?The content of white tissue superoxide anion?O₂^-?was significantly lower than that of green tissue,while the content of H₂O₂ was slightly higher than that of green tissue,and the content of malondialdehyde in white tissue was lower than that of green tissue.Two the contents of reactive oxygen species and malondialdehyde in the tissue were at a low level and were not subjected to oxidative stress.It is considered that the O₂^-of white tissue is more disproportionate to H₂O₂ by high active SOD enzyme,and a large number of H₂O₂ are also higher content of alpha tocopherol,reduced type ascorbic acid?AsA?,reduced glutathione?GSH?and higher active superoxide dismutase?SOD?,catalase?CAT?and peroxidase?POD?,ascorbic acid.The elimination of peroxidase?APX?can make H₂O₂ at a low level.White tissue is not in oxidative stress state in chimeric leaves.