Bendolassi, J. A.

Godoy, Rodolfo

Santos, Patricia M.

English

University of Kentucky

University of Kentucky UKnowledge International Grassland Congress Proceedings 21st International Grassland Congress / 8th International Rangeland Congress Free Amino Acids Content and Nitrogen Mobilization in Panicum maximum Patricia M. Santos EMBRAPA, Brazil J. A. Bendolassi Centro de Energia Nuclear na Agricultura, Brazil Rodolfo Godoy EMBRAPA, Brazil 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/21/2-1/50 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. 　 Multifunctional Grasslands in a Changing World 　 Volume Ⅰ 　 瞯 ]345　 瞯Grasslands/Rangelands Resources and Ecology ——— Soil Quality and Plant NutritionFree amino acids content and nitrogen mobilization in PanicummaximumP .M . Santos2 , J .A . Bendolassi 3 , R . Godoy 21 Funded by International Foundation f or Science‐IFS2 Embrapa Pecu ria Sudeste , CP 339 , 13560‐970‐S o Carlos‐SP , Braz il . E‐mail : p atricia＠ cp pse .embrapa .br ,3 Centro de Energia Nuclear na A gricultura ,CENA /USP , CP 96 , 13400‐970‐Piracicaba , SP , Braz il .Key words : １５ N , organic reserves , tropical grassIntroduction １５ N‐tracer techniques cannot be used accurately in the field to quantify N mobilisation due to problems of equallyand uniformly labelling all the different soil N pools with １５N . In remaining tissues of grasses following defoliation , protein isdegraded to amino acids through the action of protease enzymes ; the amino acids being subsequently transported to leafmeristems to support grow th . Potentially therefore , amino acids concentrations could be used as a surrogate for N mobilisationdetermination in the field . A greenhouse experiment involving １５ N techniques was used to test the hypothesis that , followingdefoliation of P . max imum , a correlation exists between the N mobilised from leaves and the amino acids concentration of thesetissues .Material and methods P . max imum �Tanzania�plants were cultivated in pots filled with fine sand . The position of the pots inthe greenhouse was randomised in replicate blocks . Plants were cut to ３０ cm ３３ days after seeding . Three replicate pots wereharvested immediately after cutting ( day zero ) and １ , ２ , ３ , ５ , ７ , １４ and ２１ days thereafter . Concurrent with the first harvest ,all nutrient solution was washed from the remaining pots that were than watered with a nutrient solution enriched with １５ N . Atharvest ,�young leaves" ( two youngest expanded leaves at the time of the first harvest ) were separated and weighted . Totalfree amino acids content was determined following reaction with ninidrine and OPA derivatives amino acid were detected asdescribed by Jarret et al . ( １９８６ ) . The total N and １５N concentrations were determined using a continuous flow massspectrometer . The difference between the total and labelled nitrogen content ( unlabelled nitrogen ) was assumed to be thenitrogen present within the plants at the time of the first harvest .Results and discussion Unlabelled N content of young leaves decreased from １ .５３ ± ０ .０６ to ０ .６１ ± ０ .０１ on the first seven daysafter defoliation and unlabelled N mobilisation rate was highest just af ter defoliation ( decrease of ０ ,５１ mg/ plant of unlabelled Nbetween day zero and day １) . There was also an increase of amino acids concentration in young leaves of Tanzania" just afterdefoliation , which was higher two days after defoliation (２００ .８ nmol/mL ; Figure １) . The increase of the amino acids contentat the same time as unlabelled N mobilisation increases may be related to protein degradation through the action of proteaseenzymes and subsequent transport of amino acids to meristems to support grow th . Aspartic acid , glutamic acid , asparagine ,glutamine , glicine , threonine , tyrosine and leucine ＋ isoleucine represented more than ９０％ of free amino acids in young leavesof Tanzania . Although the most important �transportable" amino acids ( aspartic acid , glutamic acid , asparagine andglutamine) represented around ５０％ of free amino acids , its concentration did not follow any pattern throughout harvests .Figure 1 Free amino acids concentration ( nmol /mL ) on young leaves o fP . maximum .Means o f three rep licates ± s .e .Conclusion There is a correlation between free amino acids content and N mobilisation on�young leaves" of P . max imum afterdefoliation .ReferenceJarret , H .W . ; Coosky , K .D . ; Wllis , T . et al . , １９８６ . The separation of o‐phthalaldehyde derivatives of amino acids byreverse‐phase chromatography on octylsilica column . A naly tical Biochemistry , １５３ , １８９‐１９８ .250 :3' f i 200 l i .=. 150 "' "C·o 1 oo "' 0 C: ·E 50 <( I 0+-----~----~----~----~----~ 0 5 10 15 20 25 Days after defoliation 

Free Amino Acids Content and Nitrogen Mobilization in \u3cem\u3ePanicum maximum\u3c/em\u3e

https://uknowledge.uky.edu/cgi/viewcontent.cgi?article=2512&amp;context=igc

Free Amino Acids Content and Nitrogen Mobilization in \u3cem\u3ePanicum maximum\u3c/em\u3e

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