Effects Of Girdling Circle On Photosynthesis And Translocation And Distribution Of ～(14)C-assimilates In Phellodendron Chinense Schneid. Var. Glabriusculum

With the two years old of P. chinense Schneid. var.glabriusculum as the experimentalMaterial, and the study processes in teaching farm and atomic agriculture practicelaboratory in Sichuan Agriculture University. Content: (1) Using the Li-6400photosynthesis system to measure the photosynthetic characteristic of P. chinense Schneid.var. glabriusculum's diurnal change of Pn,Cond,Ci,Tr and photosynthetic rate; explorethe photosynthetic characteristic; explore the impact of Bark regeneration on Tr,Pn,φ_PO,φ_P',q_P; (2) Use isotope tracer technique to do ¹⁴C-tracer about the P. chinenseSchneid. var. glabriusculum's photosynthate and to probe the impact of girdling circle on P.chinense Schneid. var. glabriusculum assimilator's translocation and distribution.The main results of the research are as follows:(1)Through measuring the P. chinense Schneid. var. glabriusculum'sphotosynthesis,transpiration and diurnal change, as the results: its leaves' netphotosynthetic rate and diurnal change showed one peak curve at the late. growing stagewith no midday depression, and the peak value, 26μmol.m^-2.s^-1,appeared at about 10o'clock; the Tr and Pn had the same variety trend, the peak value, 9.5mol.m^-2s^-1, appearedat 11 o'clock; the diurnal change between leaves' Cond and Pn showed positive correlation,a parallel variety trend; the Ci showed "U" curve which was higher in morning andevening and was lower at noon; the diurnal change of it's WUE was maximum at 10o'clock in the morning, which was 3.6μmolCO₂.mmol^-1H₂O, and the daily average valuewas 2.17μmolCO₂.mmol^-1H₂O; leaves' SUE was maximum at 8 o'clock in the morningand at 3 o'clock in the afternoon, it was 3.12mmolCO₂/mol photons and 3.44mmolCO₂/mol photons and the daily average value was 2.171mmolCO₂/mol photons; thephotosynthetic rate showed that it's LCP was 29μmol.m^-2.s^-1, LSP was 1491μmol.m^-2s^-1,and R_d was 1.8614μmol.m^-2.s^-1.The primary study indicated that it was C₃ plant.(2)Through studying the impact of bark regeneration on P. chinense Schneid.var.glabriusculum's gas exchange and chlorophyll fluorescence, the results: after girdlingcircle for 15 days, the photosynthesis obviously descended, and it reached the minimum3.75±1.24μmol.m^-2.s^-1at the 15th day, then the photosynthesis recovered rapidly, and itreached the maximum 10.87±1.201.24μmol.m^-2.s^-1 at the 20th day which had no obviousdifferences with the 1st after girdling circle; the impact of girdling circle on transpirationwas also obvious, Tr was 5.89±0.37 mol.m^-2.s^-1 before girdling circle and was 2.69±0.31mol.m^-2.s^-1after one day of girdling circle; when it was the 15th day after girdling circle, thetranspiration was 3.85±0.82 mol.m^-2.s^-1 which was obviously higher than it was in the firstday and the fifth day after girdling circle and the transpiration recovered to normal level in the 20th day; during the process of bark regeneration,φ_PO had no obvious differencesexcept it was obviously low in the 15th day; the variety trend ofφ_P^'after girdling circle wasthe same as Pn, which obviously descended in the 15 days after girdling circle and thenincreased in the following 5 days; qP decreased after girdling circle and it got the minimum0.67±0.05 mol.m^-2.s^-1 in the 15th day, and in the 20th day qP andφ_P^'grew higher than thatwere in the 15th day which was coincidence with the result of photosynthesis measure;after girdling circle photosynthetic and chlorophyll fluorescence parameter got theminimum around the 15th day and recovered around 20th day. Girdling circle not only cutcarbohydrate's transport from branches and leaves to root system but also degraded thetranspiration obviously, which broke the water balance of plant. The reason forphotosynthesis decreasing after girdling circle was not that girdling circle destroyedphotosystems construction but that photosynthate feedback suppressed the procedure ofphotosynthesis. Once the transport function recovered, this kind of suppression would beremoved and then photosynthesis and transpiration also recovered rapidly.(3)The ¹⁴C-assimilates transport rate in phloem of the normal two years old P.chinense Schneid. var.glabriusculum was 43.2～57.5cm/h, and the average rate was50.2cm/h,which indicated that the assimilates of the normal two years old P. chinenseSchneid. var.glabriusculum, whose height wasl.5 to 1.8 m, could be transported to the rootafter 3 to 4 hours.(4)After P. chinense Schneid. var.glabriusculum experienced girdling circle, thetransport path at phloem which ¹⁴C-assimilates went down through was blocked up. But itwould clear out when the new phloem organization formed. In the new phloemorganization, I found ¹⁴C-assimilates in the 11th day and ¹⁴C-assimilates in the place belowthe cut in the 15th day, which showed that when the new phloem grew well, the transportfunction of ¹⁴C-assimilates at phloem also recovered.(5)The distribution of assimilates in leaves' different parts of P. chinense Schneid.var.glabriusculum's canopy without barked: middle leaves＞top leaves＞lower leaves, andthis status kept stable for 1 to 15 days; and the barked one was: top leaves＞middleleaves＞lower leaves and the status also kept for 1 to 15 days.(6)After labeling in the non-barked I found ¹⁴C-assimilates both in bark and in root inthe former 15 days. The content of ¹⁴C-assimilates in bark and root were 11.3% and 9.1%respectively in the 1st day, then they were basically similar which showed thatphotosynthesis steadily went through phloem to root system. The barked tree with 20 cmlength bark peeled could be found ¹⁴C-assimilates only in girdling circle upward bark inthe former 11 days, and I didn't find it in the new bark or in the root which indicated thatthe path of ¹⁴C-assimilates went through new phloem and roots was blocked up after phloem of stem was peeled; the ¹⁴C-assimilates appeared in the new phloem and roots inthe 15th day showed the conducting tissue of new phloem connected the girdling circleupward and downward barks ,and the transport function recovered.(7)The variety curve of ¹⁴C-assimilates content in girdling circle upward bark was"S", assimilates got the maximum after barked in the 2nd day and went down to theminimum in the 11th day then continually went up to the level as well as it was in the 1stday; there was no ¹⁴C-assimilates in the bark below the peeled cut in the former 11 days,but it was higher than it in the bark up the peeled cut and lower than it was in phloem inthe 15th day which didn't arrive at the average level of it in the bark without peeled.