Phenotypic And Photosynthetic Physiology Of Phyllostachys Edulis ’Mira’

Phyllostachys edulis ’Mira’ （P.edulis ’Mira’ ）belong to phyllostachys of gramineae is a rare and singular new variety,which is a high-quality ornamental plant in China.The culms,branches and leaves all have yellow longitudinal stripes,the lower part of the culms are tortoise-shaped,beautiful in shape,which has important economic,ecological and ornamental values.In this study,we investigated the phenotypic traits of P.edulis ’Mira’ ,including external morphology and internal anatomy,and then carried out photosynthetic physiology research,and compared the differences with P.edulis ’Kikko-chiku’ to reveal the unique phenotypic characters and photosynthetic physiological characteristics of P.edulis ’Mira’ .It aims to provide theoretical support for its introduction,breeding,and the same clums and leaves color variation mechanism and application development of P.edulis ’Mira’ ,so as to further cultivate or screen for the application of excellent ornamental bamboo species.The main results are as following:（1）The clum height of P.edulis ’Mira’ is 2.3～4.5 m,the DBH is 1.4～5 cm,the ground diameter is 3.4～8 cm,the number of variability is 7～25,the leaf length is 4～12 cm,and the leaf width is 0.6～1.6 cm,and the leaf dry matter content（LDMC）and specific leaf area（SLA）were0.5024 and 215.67,biomass was 0.54,respectively.Plant height,DBH,ground diameter and SLA,it was smaller than P.edulis ’Kikko-chiku’ ,indicating that the overall plant size was smaller than that of P.edulis ’Kikko-chiku’ .Through phenotypic investigation,the bamboo culm of P.edulis ’Mira’ has a unique pattern of tortoise nail pattern and yellow-green striped pattern,which is a rare and singular ornamental bamboo species for good garden observation of culms and leaves.（2）The ultrastructure of the leaf color variation showed that there were more chloroplasts in green leaf cells of P.edulis ’Kikko-chiku’ ,and the grana layer and stroma lamellae were abundant,while only part of mesophyll cells contained chloroplasts in the pale yellow areas of the leaves of P.edulis ’Mira’ .The chloroplasts in the subepidermal tissue cells of the green clums were more than the yellow clums,the grana layer and stroma lamellae are clearly visible.Only a few cells in subepidermal tissue cells of yellow clum contain chloroplasts and have no lamellar structure.Therefore,the clum and leaf color variation is related to whether there is a fully developed chloroplast and its quantity.（3）The photosynthetic fluorescence of P.edulis ’Mira’ :The light compensation point（LCP）were 7.54μmol·m^-2·s^-1,the light saturation point（LSP）were 1213.25μmol·m^-2·s^-1,the maximum net photosynthetic rate(P_nmax)were 9.19μmol·m^-2·s^-1,the rate of dark respiration（R_d）were 0.354,and their CO₂compensation（Γ）、saturated intercellular CO₂concentration(C_isat),photosynthetic capacity(A_max)and initial carboxylation efficiency（CE）were 79.39μmol·mol^-1、2283.39μmol·mol^-1、21.14μmol·m^-2·s^-1and 0.0579,respectively.The photosynthetic diurnal change showed a“afternoon-nap”phenomenon,and the daily change photosynthetic rate（Pn）average was 7.42μmol·m^-2·s^-1,the short-term CO₂concentration doubling can promote the photosynthetic rate under the gas exchange of P.edulis ’Mira’ and the photosynthetic rate under the diurnal change of photosynthesis.The maximum quantum yield（F_v/F_m）of chlorophyll fluorescence parameters of P.edulis ’Mira’ was 0.6671,and the actual photochemical efficiency（ФPSII）of PSII was 0.4013 and the maximum electron transpot rate(ETR_max)was 49.79.Compared with the local P.edulis ’Kikko-chiku’ ,the photosynthetic light response curves（Pn-PAR）,CO₂response curves,diurnal change of photosynthesis,photo-response curve and photosynthetic diurnal change under the CO₂doubling condition,chlorophyll fluorescence response curves and rapid light curves of P.edulis ’Mira’ were basically consistent with the change trend of P.edulis ’Kikko-chiku’ .and there was no significant difference in the key photosynthetic physiological parameters(P_nmax,A_max,F_v/F_m,PSII,ETR_max,etc.).The results showed that there was no significant difference in photosynthetic rate between P.edulis ’Mira’ and P.edulis ’Kikko-chiku’ ,and both had shade tolerance and adaptability to strong light.The main difference was that the energy dissipation of the PSII reaction center of P.edulis ’Mira’ leaves was mainly based on non-regulated energy dissipation.The energy dissipation of P.edulis ’Kikko-chiku’ leaves is dominated by regulated energy dissipation.