Studies On The Micromorphology Characteristics And The Photosypthetic Physiological Feature And Drought Tolerance Of Nine Species Of Asplenium

Taking nine species of Asplenium distributing in Yunnan, China (A. dimorphum X diforme, A. prolongatum, A. normale, A. griffithianum, A. ensiforme, A. laciniatum, A. indicum, A. tenuifolium and A. yunnanense) as materials, the morphological characteristics of nine species of Asplenium were observed and compared, and drought tolerance under the artificial conditions of six species of Asplenium and the photosynthetic physiological feature of five species of Asplenium were studied.(1)Nine species of the Asplenium of leaf epidermal cells are most irregular wavy and anticlinal walls (about8species), in addition to A. laciniatum it s regular strip and anticlinal walls are approximate straight; their stomatal apparatus distributing in upper epidermis, the aspect ratio is stable in interspecies and the ratio not more than0.2, all stomatal type mainly include anomocytic type, coaxillocytic type, polocytic type, and the stomata density are significant difference; the characters of leaves stalk cross section of nine species of Asplenium in the comparison, xylem vascular bundle are oval single column siphonostele in six species of Asplenium, the rest of oval double column siphonostele, distributed back to crescent; there are obvious tracheary element in vascular bundle, secondary wall thickening of different degree of lignification for example, pitted, scalariform and thread, the diameter of the tubular molecules are smaller around14.6～30.8μm, most of these tubular molecular belongs to a new definition of tracheid. All the evidence suggests that divide the nine species of Asplenium in Asplenience, Asplenium, sect. Asplenium, is more reasonable.(2)Through the study of the water characteristics in six species of Asplenium, bound water and free water content and its ratio of six species of Asplenium varied in the order:A. laciniatum>A. prolongatum>A. dimorphum X diforme>A. ensiforme>A. indicum>A. tenuifolium. The water potential of six species of Asplenium was different with sequence of A. tenuifolium>A. indicum>A. dimorphum X diforme>A. ensiforme>A. prolongatum>A. laciniatum. It is concluded that the drought resistance of six species of Asplenium are as follows:A. laciniatum>A. prolongatum>A. dimorphum×diforme>A. ensiforme>A. indicum>A. tenuifolium.(3)According to the changes of physiological and biochemical parameters under drought stress for six species of Asplenium, the conclusions drawn that:the leaf water content of six species of Asplenium decreased, and the content of chlorophyll unchanged, and the MDA content and the relative electric conductivity and the soluble sugar content persistently increased, while the activities of POD, the content of proline showed:first and decreased afterwards by the increase extent of drought stress.(4)According to the changes in physiological and biochemical parameters, the drought-tolerance ability of six species of Asplenium under drought stress condition has been evaluated with subordinate function method. The results are as following:A. laciniatum>A. prolongatum>A. dimorphum X diforme>A. ensiforme>A. indicum>A. tenuifolium.(5) By compared the light response curve characteristics, showed that Pn of six species of Asplenium was:A. dimorphum X diforme> A. prolongatum> A. yunnanense>A. griffithianum>A. normale, the Cond and the Tr was:A. griffithianum>A. dimorphum X diforme>A. yunnanense>A. prolongatum>A. normale. While the Ci in changes300μmol·m-2·s-1between400μmol·m-2·s-1, no significant difference in interspecies.(6) The chlorophyll fluorescence parameters in six species of Asplenium were determined under field conditions. The results showed that Fo, Fm, Fv, Fv/Fm, ETR, qP, qN of the difference is significant. The electron transport rate (ETR), photo-chemical quenching coefficient (qP) in the leaf were much higher in A. yunanense than in A. dimorphum X diforme, A. prolongatum, A. griffithianum, A. normale. These results indicated that A. yunnanense has higher the quantum yield of PS Ⅱ electron transport and the efficiency of primary conversion of light energy of PS Ⅱ. And the non-photochemical quenching coefficient (qN) in the leaf were much higher in A. griffithianum and A. dimorphum X diforme than in A. prolongatum, A. normale, A. yunnanense. The result showed that A. griffithianum and A. dimorphum X diforme has significant resistance under the light damage.