Impaired leaf CO2 diffusion mediates Cd-induced inhibition of photosynthesis in the Zn/Cd hyperaccumulator Picris divaricata.
Mechanisms of cadmium (Cd)-induced inhibition of photosynthesis in the Zn/Cd hyperaccumulator Picris divaricata were investigated using photosynthesis limitation analysis. P. divaricata seedlings were grown in nutrient solution containing 0, 5, 10, 25, 50, or 75 μM Cd for 2 weeks. Total limitations to photosynthesis (TL) increased from 0% at 5 μM Cd to 68.8% at 75 μM Cd. CO2 diffusional limitation (DL) made the largest contribution to TL, accounting for 93-98% of TL in the three highest Cd treatments, compared to just 2-7% of TL attributable to biochemical limitation (BL). Microscopic imaging revealed significantly decreased stomatal density and mesophyll thickness in the three highest Cd treatments. Chlorophyll fluorescence parameters related to photosynthetic biochemistry (Fv/Fm, NPQ, ΦPSII, and qP) were not significantly decreased by increased Cd supply. Our results suggest that increased DL in leaves is the main cause of Cd-induced inhibition of photosynthesis in P. divaricata, possibly due to suppressed function of mesophyll and stomata. Analysis of chlorophyll fluorescence showed that Cd supply had little effect on photochemistry parameters, suggesting that the PSII reaction centers are not a main target of Cd inhibition of photosynthesis in P. divaricata.
School of Environmental Science and Engineering, Sun Yat-Sen University, Guangzhou 510275, China.
Lu
L
Tang
Rong-Rong
RR
Ying
Dan
D
Jiang
Xiao-Wen
XW
Zeng
Jean-Louis
JL
Morel
Ye-Tao
YT
Tang
Rong-Liang
RL
Qiu
D000222:Adaptation, Physiological; D019659:Asteraceae / Q000187:drug effects* / Q000378:metabolism / Q000502:physiology; D002104:Cadmium / Q000009:adverse effects* / Q000378:metabolism; D002245:Carbon Dioxide / Q000378:metabolism*; D002734:Chlorophyll / Q000378:metabolism; D008027:Light; D010788:Photosynthesis / Q000187:drug effects*; D045332:Photosystem II Protein Complex / Q000378:metabolism; D018515:Plant Leaves / Q000033:anatomy & histology / Q000187:drug effects* / Q000378:metabolism / Q000502:physiology; D054046:Plant Stomata; D036226:Seedlings; D013312:Stress, Physiological; D015032:Zinc / Q000378:metabolism
D045332:Photosystem II Protein Complex; D002104:Cadmium; D002734:Chlorophyll; D002245:Carbon Dioxide; D015032:Zinc
2-morpholinoethanesulfonic acid; A(N); B(L), D(L), MC(L) and S(L); C(a) and C(i); CA; CO(2) mesophyll and stomatal conductances, respectively; Cadmium (Cd); Chlorophyll fluorescence; D; Diffusional limitation (D(L)); E; E(x); F(m); F(o); F(s); F(v)/F(m); MES; NPQ; P; PPFD; PSI and PSII; Photosynthesis; Picris divaricata; ROS; Stomata; V(c,max); biochemical conductance, CO(2) diffusional conductance, mesophyll conductance and stomatal limitations, respectively; carbonic anhydrase; effective quantum yield of photochemical energy conversion in actinic light; efficiency of open PSII centers; fraction of absorbed light defines excess energy; g(m) and g(s); in vivo maximum rate of Rubisco carboxylation; light fraction used for PSII photochemistry; light fraction used for heat dissipation; maximal fluorescence yield under illumination; maximum fluorescence yield; maximum quantum efficiency of PSII primary photochemistry; minimal fluorescence yield; minimal fluorescence yield under illumination; net photosynthetic rate; non-photochemical quenching; photochemical quenching efficient; photosynthetic photon flux density; photosystem I and photosystem II, respectively; q(P); reactive oxygen species; reference atmospheric and intercellular CO(2) concentrations; steady-state fluorescence; transpiration rate; Φ(PSII)