Study On The Characteristics Of Chlorophyll Fluorescence Of15Phalaenopsis Cultivars

RLCs, the relationship between light intensity request and leaf color and thecharacteristics of chlorophyll fluorescence induction and dark-relaxing of15Phalaenopsis cultivars were studied. The main results are as follows:1. Ik ranges from160.000to290.000μmol m^-2 s^-1among15cultivars. AndrETRmax increased with Ik rise for most cultivars. Ik calculated from RLCs can beused to estimate the light intensity request for most cultivars. But rETRmax showeddifferent trend with Ik for some cultivars causing by Abs and α of their leaves.Subdivided the light intensity request of cultivars, the leaves Abs of cultivars shouldbe studied.2. The leaf color of cultivars is significant different. The relationship among leafcolor, Ik and rETRmax is not simple linear, but cubic. Some cultivars would be fit forthe relationship between light intensity request and leaf color or flower color, but thiscouldn’t be fit for all. Therefore distinguishing the light intensity request of cultivarssimply by leaf or flower color is unscientific. Since the genetic background ofcommercial Phalaenopsis cultivars is complex. In order to figure out the relationshipbetween light intensity request and leaf or flower color, the genetic mechanism shouldbe studied first.3. Analyzed with RCLs, chlorophyll fluorescence combined with quenching, anddark relaxation, the photosynthetic capacity of different cultivars can be reflected bydata from chlorophyll fluorescence with quenching analysis and dark relaxation.Preliminary based on Y（II）, rETR and qP,15Phalaenopsis cultivars are divided intoHigh Photosynthetic Capacity Cultivar Group （HPCCG）, Medium PhotosyntheticCapacity Cultivar Group （MPCCG）, and Low Photosynthetic Capacity CultivarGroup （LPCCG）. Furthermore, comparing the trends and the steady-state values ofNPQ, Y（NO） and Y（NPQ） of the cultivars at the different light intensities, thecultivars are accurately divided into the following three categories:a. HPCCG：Phal. Lious Fantasy, Phal. amabilis, Phal. Taida Smile, Dtps.Fusheng Purple Velvet Mount, Phal. Join Star;b. MPCCG：Phal. Sogo Yukidian, Dtps. Sogo vivien ‘Sarah’, Dtps. FushengSweetParadise ‘Golden Leopard’, Dtps. Gu Keng Beauty, Dtps. Fuller’s Sunset, Dtps.Chain Xen Queen;c. LPCCG：Dtps. Jiuhbao Fairy, Dtps. Jiuhbao Red Rose, Dtps. Fuller’s Sunset ‘Golden Girl’, Dtps. Jiuhbao Coral.4. The laws of chlorophyll fluorescence parameters changing of the cultivars atthe different light intensities are summarized as follows:a. At low and medium light intensity, the steady-state values of Y（II）, rETR, andqP: HPCCG> MPCCG> LPCCG;b. At low and medium light intensity, the trends of NPQ, Y（NO） and Y（NPQ）:NPQ and Y（NPQ） are on the decline in most of HPCCG and MPCCG, but Y（NO）increases;c. At low light intensity, the steady-state values of NPQ and Y （NPQ）: HPCCG<MPCCG<LPCCG; Y（NO） showes oppositely;d. At high light intensity, the steady-state values of NPQ and Y （NPQ）:HPCCG> MPCCG> LPCCG; Y（NO） showes oppositely;e. At low light intensity, qE and qI of the cultivars: HPCCG<MPCCG<LPCCG;f. At high light intensity, qE of the cultivars: HPCCG> MPCCG> LPCCG; qIshowes oppositely.5. According to comparing the trends and the steady-state values of NPQ, Y（NO）and Y（NPQ） from chlorophyll fluorescence induction, and the NPQ components ofqE and qI from dark relaxation, the photosynthetic response mechanisms of15Phalaenopsis cultivars at high light stress are summarized as follows:The protection mechanism against high light stress of Phalaenopsis is the NPQmechanism related to the xanthophyll cycle and across the thylakoid membraneproton gradient, and heat dissipation mechanism related to xanthophyll cycle andacross the thylakoid membrane proton gradient is more effective. At low lightintensity (200μmol m^-2 s^-1), the higher photosynthetic capacity cultivars are moreinclined to deal with energy excess at low light intensity by passive fluorescence andheat dissipation, and it could be more effective utilization of the light energy absorbedby PS II for photosynthesis, and reduce energy loss. At low light, most of the cultivarsuse passive fluorescence and heat dissipation and NPQ way to deal with excess lightenergy, and the lower photosynthetic capacity cultivars prefer the NPQ way to dealwith excess light energy. Under high light stress, NPQ regulation ability of HPCS isnot yet saturated, it could still deal with excess light energy from light damage by theheat dissipation.