Study On Resources Of Hydrangea L. In Hunan Province And Characteristics Of Aluminum Tolerance

Hydrangea is an important ornamental plant, which has high medicinal value. There also is an important taxonomic significance for its central position in the evolution of Hydrangeoideae.Hunan province is one of the distribution centers of Hydrangea as well as a province suffering serious aluminum toxicity. Hydrangea macrophylla is an Al-tolerant species, and showed a strong Al-tolerance and Al-accumulation ability. This paper studied Al-tolerance characteristics and physiological response of Hydrangea under Al-toxicity stress by collecting and investigated the resources of Hydrangea in Hunan province. The purpose of the study is to select a strong Al-tolerant species or varieties, and provide a theoretical basis practice comment for revealing plant Al-tolerance mechanisms, preventing and remeding Al-toxicity. Up to now, there was few report about Hydrangea Al-tolerance characteristics.This paper studied the resource and Al-tolerance characteristic of Hydrangea. The results are as follows:1. An investigation on typical natural community, species and quantity of Hydrangea resources in Hunan Province was conducted by randomly set up a number of observation points in Nanyue Mountain Scenic Spots, Badagong Mountain National Nature Reserve and Dawei Mountain National Forest Park. The result showed that there were 15 species and 3 varieties in Hunan Province, account for 39.1%of total Hydrangea resources in China.2. To explore relationship between phylogenetic and the character of trichome and stomatal apparatus of leaves of some species of Hydrangea, the leaves surface was observed by using the optical microscope and scanning electron microscope. The result showed that stomatal density and stomatal apparatus shape among four species were differenct. The stomatal shape of H. macrophylla, H.strigosa, and H. paniculata's stomatal were elongated oval, while H.villosa was oval. The stomatal density of H.villosa was the biggest (819.43/mm2), and the smallest one was H. paniculata(286.05/mm2), which may be related to the resistance and growth. Trichome modality differences were shown in the length, width, density and shape, etc., and its trichome appendage had obvious difference in appearance. H.strigosa's trichome was long and narrow linear form, and trichome appendage were hill-like protuberances; H. villosa's trichome was flaky, adjunct for the papilla-like protuberances; H. paniculata's trichome was cylindrical cone, adjunct for the stellate protrusions; H. macrophylla had no obvious trichome, adjunct for granular material.The highlighting differences from the observed morphological characteristics of stomatal apparatus and trichome and the changing of appendage shape on trichome supported the classification published in《Chinese tree species》for the genus Hydrangea.3. The optimal SRAP system in Hydrangea was established with single factor's experimental design for 25μL:10×PCR Buffer2.5μL, template DNA 30ng, Mg2+1.6mmol/L, dNTPs0.6 mmol/L, Taq enzyme3.5U, primer 0.2μmol/L. Fourteen out of 110 pairs of primer combinations were selected,233 SRAP bands were generated in 19 materials of Hydrangea, of which 232 were polymorphic, polymorphism rate is 99.7%.The genetic similarity coefficient based on Nei&Li of 19 materials of Hydrangea were analyzed, most of which had far genetic distance, and were classified into four groups at the GS(0.43and 0.27). Group 1 included H.umbellata; Group 2 included the other 7 cultivated species besides No.18; Group3 included No.18 and H.strigosa, H.strigosa var, H.longipes, H.rosthornii, H.strigosa var, H.villosa, H.glabripes, H.lingii; Group4 included H. hypoglauca and H. panciulata. The result of cluster analysis based on SRAP showed that the 19 materials of Hydrangea can be divided into 3 series, namely, Ser.Petalanthae, including H.umbellata and No12,13,14,15,16,17,19; Ser. Piptopetalae, including No 18 and H.strigosa, H.strigosa var, H.longipes, H.rosthornii, H.strigosa var, H.villosa, H.glabripes, H.lingii; Ser. Heteromallae, including H. hypoglauca and H. panciulata.4. The photosynthetic characteristics was studied. The result showed that chlorophyll and carotenoid content of several Hydrangea gradually increased first and then gradually decreased when the Al3+concentration increased. It was suggested that low concentration of aluminum (≦0.15mmol·L-1) was conducive to the accumulation of chlorophyll and carotenoids of Hydrangea, and played a positive role on photosynthesis. Net photosynthetic rate (Pn) and intercellular CO2 concentration (Ci) of several Hydrangea increased first with the increase of Al3+concentration, and then gradually declined, while the saturated vapor pressure (VpdL), by contrast, showed tendency to ascend first and then descend, Aluminum stress had little effect on Tair (leaves room temperature) and Tleaf (leaf temperature) of several Hydrangea. The ability of Al-tolerance was H.villosa.>H.strigosa>H.paniculata>H.macrophylla by Subordinate Function (SF).5. Aluminum absorption characteristics of Hydrangea were studied on the three aspects of aluminum absorption rate, absorption capacity and increase extent. The results showed that the absorption rate of Al in the four materials of H.macrophylla,Hstrigosa,H.villosa and H.paniculata was related with Al3+concentration as a linear equation in one variable, and the correlation coefficient was over 0.95, which didn't match the Michaelis-Menten enzymatic kinetic equations. Therefore, we concluded that Al absorption of four Hydrangea were passive absorption. Continuously cultivated for some time in 0.10 mmol.L"1 solution of Al3+,the aluminum absorption rate of H.macrophylla,H.strigosa,H.villosa and H.paniculata descended with time, while the absorption capacity increased and increase extent descended. The increase extent was relatively large in the 0～4h, and after 4h the absorption of aluminum gradually saturated.6. Physiological characteristics of H.macrophylla changed a lot under Al3+stress, with the increase of stress, the soluble sugar content in leaf tissue of 7 H.macrophylla had significantly increased. The proline content of H.macrophylla was very sensitive to Al3+stress, with the stress increased, it changed in a big range. There was a negative relationship between soluble protein content in leaf and Al3+stress, while injurious electrolyte leakage rate (IL) was positively correlated. The MDA content under aluminum stress increased as the stress increased, but the rate of increase varied by species.Along with the stress increase,SOD and POD activity of 7 varieties first increased and then decreased in the manner of a single peak curve.