Phalaenopsis efficiently acclimate to highlight environment through orchid mycorrhization 菌根化有助於蝴蝶蘭適應高光環境 Ming-Chih Lee ( 李明治 ), Doris C.N. Chang ( 張喜寧 ), Chun-Wei Wu ( 吳俊偉 ), Ying-Tung Wang ( 王寅東 ) and Yu-Sen Chang ( 張育 森 )* 2014 光合作用與植物生理研討會 NATIONALTAIWANUNIVERSITY

2 Background Phalaenopsis: 1.Epiphytic 2.CAM metabolism 3.Establish a symbiotic relationship with fungi NATIONAL TAIWANUNIVERSITY

3 Light intensity: 1.Saturating PPF: μmol∙m -2 ∙s -1 (Lee and Guo, 2012) 2.Photoinhibition: >200 μmol∙m -2 ∙s -1 PPF (Baker, 2008) 3.Commercial cultivation: μmol∙m -2 ∙s -1 (Chen and Wang, 1996). NATIONAL TAIWANUNIVERSITY

4 How plants cope with highlight ? 1.Photoacclimation 2.Photoprotection 3.Photorepair (Ragni et al., 2008) NATIONAL TAIWANUNIVERSITY

5 Photoacclimation: Plant modulates and optimizes its photosynthetic performance according to the light environment. NATIONAL TAIWANUNIVERSITY

6 Photoprotection: Plant prevents or minimizes light energy from inducing photodamage. NATIONAL TAIWANUNIVERSITY

7 Photorepair : Plant degrades and de novo synthesizes the damaged D1 protein. NATIONAL TAIWANUNIVERSITY

8 Hypothesis NATIONAL TAIWANUNIVERSITY Orchid mycorrhization Photosynthetic Performance Highlight growing ? ? ? ? ? ? ?

9 Objectives To evaluate the OM effects on the growth of HL-Phalaenopsis, and to elucidate the photochemical mechanisms involved in photoacclimation to photoinhibitory irradiance. NATIONAL TAIWANUNIVERSITY

10 Materials & Methods Plant materials: 1.Five-month-old Phalaenopsis amabilis ‘KC1410’ were cultivated in 12-cm diameter pots filled with the processed bark of Pinus radiata for 6 months. 2.20N-8.7P-16.6K Peters solution at 0.5 g∙L -1 was provided once every two weeks. NATIONAL TAIWANUNIVERSITY

11 Greenhouse conditions: μmol∙m -2 ∙s -1 (due to cloudiness) about 40% of the prevailing solar radiation. 2.Air temperature was controlled at 28/22°C (day/night) by a pad and fan cooling system. NATIONAL TAIWANUNIVERSITY

12 Orchid mycorrhization: 1.Ceratobasidium sp. (AG-A, binucleates) inoculum were prepared using peat and potato-dextro solution. 2.7 plants in a treatment, and totally 2 experimental repeats were conducted in this study. NATIONAL TAIWANUNIVERSITY

13 Measurements: 1.Open flow gas exchange system (LI-6400) 2.Multi-Channel Chlorophyll Fluorometer (MONI-PAM) 3.Spectrometer HandySpec Field (tec5) NATIONAL TAIWANUNIVERSITY

14 LI-6400: CO 2 uptake rate was measured from 10 p.m. to 12 a.m.. NATIONAL TAIWANUNIVERSITY

15 MONI-PAM: 1.1st acropetal fully expanded leaf. 2.The fluorescence measurements (Fv/Fm, ETR, ФPSII, qP, and the NPQ) were made on the 30 min dark-adapted plants during Phase III of CAM photosynthesis (2 p.m.) using rapid light curve (RLC). NATIONAL TAIWANUNIVERSITY

16 tec5: 1.Assess growth quality and photosynthesis using equations: (1)NDVI computed as (R800 – R600) / (R800 + R600) (Rouse et al., 1974) (2)PRI computed as (R531 – R570) / (R531 + R570) (Peñuelas et al., 1995). NATIONAL TAIWANUNIVERSITY

17 Results NATIONAL TAIWANUNIVERSITY

18 NATIONAL TAIWANUNIVERSITY Figure 1. Phalaenopsis amabilis ‘KC1410’ plants grown under highlight environment with (OM) and without Ceratobasidium sp. (NM) inoculation. Scale bar represents 10 cm. OM plants have longer leaves that result in greater leaf span under highlight environment

19 NATIONAL TAIWANUNIVERSITY Table 1. Mycorrhizal effects on the growth characteristics, biomass, and dry matter partitioning of Phalaenopsis plantlets grown under highlight for 6 months. NM: non-mycorrhizal control; OM: orchid mycorrhizal treatment; FW: fresh weight; DW: dry weight. Water content: (FW − DW)/FW. OM colonization enhances plant size and biomass of HL-Phalaenopsis

20 NATIONAL TAIWANUNIVERSITY Figure 2. Carbon dioxide (CO 2 ) uptake rate measured in the late evening (10 p.m.) 6months after highlight cultivation of non-mycorrhizal (NM) and mycorrhizal (OM) orchids (Phalaenopsis amabilis ‘KC1410’).***p ≤ OM leaves achieve higher rate of CO 2 uptake than the NM plants at the night time

21 NATIONAL TAIWANUNIVERSITY Figure 3. The maximum quantum yield of PSII photochemistry (Fv/Fm) measured with PAM fluorometer on dark-adapted samples of mycorrhizal (OM) and non-mycorrhizal (NM) Phalaenopsis during light- recovery experiment. OM plants have higher photoacclimation capabilities than NM plants under HL environments

22 NATIONAL TAIWANUNIVERSITY Figure 4. Analysis of light dependent changes in PSII operating efficiency (ФPSII) in an intact leaf of Phalaenopsis amabilis ‘KC1410’ with (OM) or without (NM) mycorrhization grown under highlight environment. Higher ФPSII sustained during photoinhibition demonstrates an higher carbon assimilation efficiency in OM plants

23 NATIONAL TAIWANUNIVERSITY Figure 5. Analysis of light dependent changes in electron transport rate (ETR) in an intact leaf of Phalaenopsis amabilis ‘KC1410’ with (OM) or without (NM) mycorrhization grown under highlight environment.

24 NATIONAL TAIWANUNIVERSITY Figure 6. Analysis of light dependent changes in photochemical quenching (qP) and non-photochemical quenching (NPQ) in an intact leaf of Phalaenopsis amabilis ‘KC1410’ with (OM) or without (NM) mycorrhization grown under highlight environment. The sustained lower NPQ and higher qP indicate the efficient photoprotection capability and radiation use efficiency in OM plants.

25 NATIONAL TAIWANUNIVERSITY Figure 7. Assessing photoprotection capacity with evaluation of photochemical reflectance index (PRI) in an intact leaf of Phalaenopsis amabilis ‘KC1410’ with (OM) or without (NM) mycorrhization grown under highlight environment. Higher PRI represents higher photoprotection and photosynthetic performance in OM plants.

26 Conclusions The improved photosynthetic performance & radiation use efficiency in PSII are probably the acclimation mechanism of OM plants to efficiently respond to highlight. NATIONAL TAIWANUNIVERSITY

27 Conclusions The OM-mediated higher photosynthetic performance & radiation use efficiency is most evident around 800~1000 μmol∙m - 2 ∙s -1 PPF, which is close to the irradiance during cultivation, thus indicates photoacclimation. NATIONAL TAIWANUNIVERSITY

28 Conclusions 28 Photoinhibition Excessive Light Growth Orchid Mycorrhization NATIONAL TAIWANUNIVERSITY Photoacclimation ФPSII, ETR, qP, NPQ, PRI

29 NATIONAL TAIWANUNIVERSITY Members of YSC Laboratory Department of Horticulture & Landscape Architecture Yu-Sen Chang Professor Tel: (02) # 206 Fax: (02) Ming-Chih Lee Ph.D student Tel: (02) # 302

30 Thank you for your attention !