He, Shubin

Liu, Guoli

Yang, Huimin

Zhang, Zhilong

English

University of Kentucky

University of Kentucky UKnowledge International Grassland Congress Proceedings 21st International Grassland Congress / 8th International Rangeland Congress Responses of Photosynthetic Rate of Lucerne and the Mechanisms under Cutting at Different Water Availabilities Shubin He Lanzhou University, China Huimin Yang Lanzhou University, China Guoli Liu Lanzhou University, China Zhilong Zhang Lanzhou University, China Follow this and additional works at: https://uknowledge.uky.edu/igc  Part of the Plant Sciences Commons, and the Soil Science Commons This document is available at https://uknowledge.uky.edu/igc/21/1-4/49 The 21st International Grassland Congress / 8th International Rangeland Congress took place in Hohhot, China from June 29 through July 5, 2008. Proceedings edited by Organizing Committee of 2008 IGC/IRC Conference Published by Guangdong People's Publishing House This Event is brought to you for free and open access by the Plant and Soil Sciences at UKnowledge. It has been accepted for inclusion in International Grassland Congress Proceedings by an authorized administrator of UKnowledge. For more information, please contact UKnowledge@lsv.uky.edu. 瞯 ]198　 瞯 　 Multifunctional Grasslands in a Changing World 　 Volume Ⅰ 　Grasslands/Rangelands Resources and Ecology ——— Ecology of Grasslands/RangelandsResponses of photosynthetic rate of lucerne and the mechanisms under cutting at different wateravailabilitiesShubin He , H uimin Y ang 倡 ,Guoli L iu , Zhilong ZhangCollege o f Pastoral A griculture Science and Technology , L anz hou University , L anz hou ７３００２０ , China . 倡 Correspondingauthor . E‐mail :huimyang＠ lz u .edu .cnKey words : forage cutting , photosynthesis , regrow th , stomatal characterIntroduction The regrow th after cutting ( defoliating ) is essential to the utilization of forage and grassland . After forage cutting ,the residue has to change its original function to adapt new situation . Some clue showed that photosynthetic rate ( Pn) of theaboveground part would increase after cutting and would keep higher for a longer period ( Nowak and Caldwell , １９８４ ; vonCaemmerer and Farquhar , １９８４) . That might be resulted from the change of light illumination . However , Pn change shortlyafter cutting was still not clear and the mechanisms under cutting stimulus awaited further exploitation .Materials and methods Local Lucerne variety ( Medicago sativ a cv . Xinjiangdaye) was chosen as the experimental material . Onegroup of materials was kept ７０％ field water capacity ( FWC ) and another was ３５％ FWC . On a clear day , plant Pn andstomatal conductance ( gs) were measured every two hours using LI‐６４００ after forage cutting . Proline and antioxidases werealso measured ５ , １０ and ３０ h after cutting .Results and discussions Higher Pn was observed in the residue with cutting , especially ５ h after cutting . Accordingly , greater gswas also measured under cutting treatment . Furthermore , proline content and the activities of SOD ( superoxidase ) , POD( peroxidase) and CAT ( catalase ) were greater under cutting than without cutting ５ h after cutting . Greater gs promisedenough CO２ supply , thus resulting in higher Pn . The enhanced antioxidases would efficiently clean out free radicals resultingfrom cutting stimulus and more proline would help to maintain cell osmotic potential , thus maintain cell normal function ,including guard cell/ stomatal function . Additionally , more water supplies ( i .e . ７０％ FWC) could keep plant more sensitive andefficient in response to cutting stimulus . CAT was found very significant responding to cutting , suggesting that it may play akey role in this stimulus‐response signaling . Further investigation concerning regrowing mechanisms is now conducted .Acknowledgement This work was supported by the grants from ９７３ Program of China (２００７CB１０６８０４ and ２００７CB１０８９０１) .ReferencesNowak , R . S . , Caldwell , M . M . , ( １９８４ ) . A test of compensatory photosynthesis in the field : implications for herbivorytolerance . Oecologia ６l , ３１１‐３１８ .von Caemmerer , S . , Farquhar , G .D . , (１９８４) . Effects of partial defoliation , changes of irradiance during grow th , short‐termwater stress and grow th at enhanced p( CO２ ) on the photosynthetic capacity of leaves of Phaseolus vulgaris L . Planta １６０ ,３２０‐３２９ .14 ---❖-- A ---o- B ---½--- C ---❖-- D 2 -2 7:00 9:00 11:00 13 :00 15:00 17:00 19:00 Time (o'clock) 0.3 ---❖-- A --o-B ---½--- C --o-D :f 0.2 " _,,, 0 " I 0.1 w bI) 0 7:00 9:00 11:00 13:00 15:00 17:00 19:00 Time (o'clock) 

Responses of Photosynthetic Rate of Lucerne and the Mechanisms under Cutting at Different Water Availabilities

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Responses of Photosynthetic Rate of Lucerne and the Mechanisms under Cutting at Different Water Availabilities

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