plants-12-01186.pdf

Citation:Wang,X.-Q.;Zeng,Z.-L.;Shi,Z.-M.;Wang,J.-H.;Huang,W.Variation in Photosynthetic Efficiencyunder Fluctuating Light betweenRose Cultivars and its Potential forImproving Dynamic Photosynthesis.Plants 2023,12,1186.https:/doi.org/10.3390/plants12051186Academic Editors:Lorenzo Ferroniand Marek ZivcakReceived:31 January 2023Revised:9 February 2023Accepted:21 February 2023Published:6 March 2023Copyright:2023 by the authors.Licensee MDPI,Basel,Switzerland.This article is an open access articledistributedunderthetermsandconditions of the Creative CommonsAttribution(CC BY)license(https:/creativecommons.org/licenses/by/4.0/).plantsArticleVariation in Photosynthetic Efficiency under Fluctuating Lightbetween Rose Cultivars and its Potential for ImprovingDynamic PhotosynthesisXiao-Qian Wang1,2,Zhi-Lan Zeng2,3,Zi-Ming Shi4,Ji-Hua Wang4and Wei Huang2,*1School of Life Sciences,Northwest University,Xian 710069,China2Kunming Institute of Botany,Chinese Academy of Sciences,Kunming 650201,China3University of Chinese Academy of Sciences,Beijing 100049,China4Flower Research Institute of Yunnan Academy of Agricultural Sciences,Kunming 650205,China*Correspondence:These authors contributed equally to this work.Abstract:Photosynthetic efficiency under both steady-state and fluctuating light can significantlyaffect plant growth under naturally fluctuating light conditions.However,the difference in photo-synthetic performance between different rose genotypes is little known.This study compared thephotosynthetic performance under steady-state and fluctuating light in two modern rose cultivars(Rose hybrida),“Orange Reeva”and“Gelato”,and an old Chinese rose plant Rosa chinensis cultivar,“Slaters crimson China”.The light and CO2response curves indicated that they showed similarphotosynthetic capacity under steady state.The light-saturated steady-state photosynthesis inthese three rose genotypes was mainly limited by biochemistry(60%)rather than diffusionalconductance.Under fluctuating light conditions(alternated between 100 and 1500mol photonsm2m1every 5 min),stomatal conductance gradually decreased in these three rose genotypes,while mesophyll conductance(gm)was maintained stable in Orange Reeva and Gelato but de-creased by 23%in R.chinensis,resulting in a stronger loss of CO2assimilation under high-lightphases in R.chinensis(25%)than in Orange Reeva and Gelato(13%).As a result,the variation inphotosynthetic efficiency under fluctuating light among rose cultivars was tightly related to gm.These results highlight the importance of gmin dynamic photosynthesis and provide new traitsfor improving photosynthetic efficiency in rose cultivars.Keywords:chlorophyll fluorescence;CO2assimilation;mesophyll conductance;photosyntheticlimitation;stomatal conductance1.IntroductionPlants use photosynthesis to convert light energy into stable chemical energy by photo-synthetic electron transport and the Calvin-Benson cycle.Plants with high photosyntheticefficiency usually have relatively fast growth rate and high levels of biomass and pro-ductivity.The light-saturated photosynthetic capacity under steady state is thought tobe the critical determinant of plant growth.For example,the higher steady-state photo-synthetic capacity in C4plants facilitates their higher productivity than C3plants underoptimal conditions 1,2.Photosynthesis can be limited by CO2diffusional conductanceand biochemical factors 3.Stomatal conductance(gs)and mesophyll conductance(gm)to-gether determine the CO2diffusion from air into chloroplast and thus influence chloroplastCO2concentration 48.Biochemical factors represent the capacity for the Calvin-Bensoncycle and photosynthetic electron flow.High values of gsand gmare the prerequisitesof high CO2assimilation rate(AN)in plants grown under high nitrogen condition andhigh light 6,8.Generally,photosynthetic capacity in angiosperms is mainly limited bybiochemical factors and gmrather than gswhen measured under favorite conditions 5,9.Plants 2023,12,1186.https:/doi.org/10.3390/plants12051186https:/ 2023,12,11862 of 15However,gmimposes the major limitation on ANin sclerophyllous oaks 10,Rhododendronspecies 11 and Orchid species 12.Therefore,the major limiting factor of ANmightlargely differ between species.Modern rose is one of the most important fresh cut flowersall over the world,owing to its high values in ornamental,food and material industry.However,the major limiting factor of light-saturated ANunder steady state in modern rosecultivars is not well known.In nature,leaves usually experience fluctuating light due to cloud,wind,andshading from other leaves 13,14.In addition to steady-state photosynthetic capacity,dynamic photosynthesis under fluctuating light significantly affects plant growth andbiomass 1519.Upon transitioning from low to high light,net CO2assimilation rate(AN)gradually increases,but the time required to fulfill light induction largely differsamong different plants and cultivars 9,16,18,2022.For example,C3plants n