Effects Of Aluminum Stress And AMF Infection On Growth And Photosynthesis Of Cinnamomum Camphora L. Seedlings

Camphor tree (Cinnamomum camphora L.) is well-known for the camphor and camphor wood oil that are important industrial and pharmic materials, and it is also a good tree species for planting vegetation. Growth characteristic, absorb of Nitrogen and Phosphorus elements, phytohormones of different organs, and characteristic of photosynthesis were systemic studied by using the acidic Aluminum solutions to irrigate and the arbuscular mycorrhiza fungus (AMF) to infect the camphor tree seedlings planted in pots. The main purpose of this study was to examine the effects of AMF inoculation on the photosynthesis of camphor tree seedlings exposed to Al. The main results are as follows:1. The effects of AMF infection on growth of camphor tree seedlings were greater. Inoculation with AMF increased the lengths, volumes and surface areas of roots of camphor tree seedlings; decreased the specific root lengths and root/shoot ratios of camphor tree seedlings; increased the heights and ground diameters of camphor tree seedlings; increased the leaf numbers, lengths, widths, areas, leaf stalk lengths and specific leaf areas of camphor tree seedlings; increased the relative growth rates of roots, stem, leaf and whole plant of camphor tree seedlings. Similarly, inoculation with AMF increased the biomass of root, stem, leaf and whole plant of camphor tree seedlings; however, inoculation with AMF had no effects on allocation ratio of biomass to organs of camphor tree seedlings. As far as Al stress were concerned, inoculation with AMF could alleviate the inhibition caused by Al toxicity to the morphology and biomass index of camphor tree seedlings under control (Al=0mM), Mild Al stress (Al=0.5mM) and moderate Al stress (Al=8mM), but not severe Al stress (Al=15mM).2. AMF infection also affected the N and P contents of camphor tree seedlings. Inoculation with AMF increased the P contents of root, stem and leaf and N contents of leaf of camphor tree seedlings. Mycorrhiza increased the cytokinin (ZR) contents of leaf, auxin contents (IAA) and ZR contents of roots, reduced the abscisic acid (ABA) contents of root and leaf. As far as Al stress were concerned, inoculation with AMF could alleviate the inhibition caused by Al toxicity to the nutrient elements contents and phytohormones contents of camphor tree seedlings under control (Al=0mM), and Mild Al stress (Al=0.5mM), but not severe Al stress (Al=15mM). Although the AM fungal consortium confer Al resistance on the nutrient elements contents and phytohormones contents to camphor tree seedlings under moderate Al stress (Al=8mM), it was not significant.3. So far as the photosynthesis of camphor tree seedlings infected by AMF, Inoculation with AMF did not increase the chlorophyll a, chlorophyll b, chlorophyll a+b and carotenoid contents, and also change the chlorophyll a/b ratio significantly. The parameters of AQ curve of leaf of camphor tree seedlings, such as Maximum assimilation rate at light saturation (Amax), apparent quantum efficiency (AQE), Dark respiration rate (Rday), Light saturation point (LSP), Light compensation point (LCP) and convexity (k), were not affected by AMF infection. Similarly, The parameters of ACi curve of leaf of camphor tree seedlings, such as Assimilation of CO₂ saturation (Asat), Carboxylation efficiency (CE), Dark respiration rate (Rday), CO₂ compensation point (CCP), Maximum carboxylation velocity of Rubisco (Vcmax), Maximum rate of electron transport (Jmax), Triose phosphate utilization rate (TPU) and Jmax/Vcmax, were not affected by AMF infection.Inoculation with AMF did not significantly affect the Net photosynthesis rate (Pn), Stomatal conductance (Gs), Intercellular CO2 concentration (Ci), Transpiration rate (Tr) and Stomatal limitation (Ls) of leaf of camphor tree seedlings. Inoculation with AMF did not significantly affect the Light use efficiency (LUE), Water use efficiency (WUE), Photosynthetic N use efficiency (PNUE) and Photosynthetic P use efficiency (PPUE). Inoculation with AMF did not significantly affect the Area-based net photosynthesis rate Pn(area), however, inoculation with AMF did affected the Mass-based net photosynthesis rate per mass Pn(mass) and net photosynthesis rate of whole plant. As far as Al stress were concerned, inoculation with AMF could alleviate the inhibition caused by Al toxicity to parameters of photosynthesis of camphor tree seedlings under control (Al=0mM), and Mild Al stress (Al=0.5mM), but not severe Al stress (Al=15mM). Although the AM fungal consortium confer Al resistance on the parameters of photosynthesis to camphor tree seedlings under moderate Al stress (Al=8mM), it was not significant.4. AMF infection did not change the respiration rate of roots of camphor tree seedlings, whereas, Al stress inhibited the respiration rate of roots of camphor tree seedlings.5. As far as the photosynthesis of camphor tree seedlings infected by AMF, Inoculation with AMF did not change the basic parameters of chlorophyll fluorescence of leaf of camphor tree seedlings, for example, Initial fluorescence intensity (Fo), Maximal fluorescence intensity (Fm), Minimal fluorescence in the light (Fo), Maximal fluorescence in the light (Fm') and Steady state fluorescence (Fs); Inoculation with AMF also did not change the parameters that can indicate the photochemical efficiency of PS II of chlorophyll fluorescence of leaf of camphor tree seedlings, for example, Maximal photochemical efficiency of PS II (Fv/Fm), Potential activity of PS II (Fv/Fo), Photochemical efficiency of PSII (Fv'/Fm'), Actual photochemical efficiency of PSII (Φ_psII), Linear electron transport rate (ETR); Similarly, inoculation with AMF did not change the parameters of quenching of chlorophyll fluorescence of leaf of camphor tree seedlings, for example, Photochemical quenching of chlorophyll fluorescence (qP), Non-photochemical quenching of variable chlorophyll fluorescence (qn) and Non-photochemical quenching (NPQ). Furthermore, inoculation with AMF did not change the parameters of allocation pattern of excitation energy absorbed in the PS II antennae of leaf of camphor tree seedlings, for example, PS II Photochemistry (P), Thermal dissipation (D) and excess excitation (E). As far as Al stress were concerned, inoculation with AMF could alleviate the inhibition caused by Al toxicity to parameters of chlorophyll fluorescence of camphor tree seedlings under control (Al=0mM), and Mild Al stress (Al=0.5mM), but not severe Al stress (Al=15mM). Although the AM fungal consortium confer Al resistance on the parameters of chlorophyll fluorescence to camphor tree seedlings under moderate Al stress (Al=8mM), it was not significant.