Yield Nutritional value Protein contentPlant defence: cyanogenic glycosideAvailability
Below ground, : soil microbial associations MODEL FOR OTHER CYANOGENIC PLANTSsubterranean clover is the most important annual pasture legume sown in southern Australia. It originated in the Mediterranean region, parts of western Europe, southern England and Ireland.Subterranean clover (sub clover) was accidentally brought to Australia in hay, straw and pasture seed, probably as early as the 1830s, and was spread along transport routes, in stock camps and on town commons throughout southern Australia.The potential of sub clover to provide nutritious feed for livestock and improve soil fertility
Ever since I did this work I’ve been wondering what the impact would be on crop plants.
To investigate relationships between cyanogenesis in T. repens and nutrient supplyIs allocation of N to chemical defence affected by relative availability N and P?How this that affected by microbial associationsIs there a trade off between defence & growth?How is cyanogen concentration likely to change under future climate changes & eCO2? AgFACE elevated CO2 study, Horsham
Does this translate into higher HCN levels?
27 vs. 36% (+/- 3) Mycorrhizae colonisation: 54 vs. 59 % (+/- 5) ns?
Haven’t yet measured total N and other nutrients – expect CN per protein will be higher as in this study given sufficient nutrientsConsistent with this pot study – higher CN: protein at eCO2. This study also shows that importance of nutrient supply. These plants has rhizobium but were not inoculated mycrorrhizae.Effect only detected when P was added/sufficient.So here N – no difference with soil N because able to fix N, take up N to compensate for low soil N.
IN order to understand importance of N and phosphorus and whether the source of N and P (i.e. whether from soil microbes) impacts on HCN content,Q…..N from rhizobium compensates for less soil N and plants can continue to synthesis cyanogenic glycosidesAs before under low N , rhizobium compensated i.e. low N plants actually had higher plant NBUT low P plants had lower PO4- mycorrhizae were unable to compensate.N treatment had no effect on HCN, but P treatment did.
Available nitrogen is reallocated to cyanide in plants grown at elevated CO2ANDNitrogen (and Cyanogenesis) is dependent on soil microbesTHEN
Nutrient supply, below ground processes and elevated CO2 change the nutritional quality of cyanogenic clover Trifolium repens - Ros Gleadow
CCRSPI Feb 2011Plant themeNutrient supply, below groundprocesses and elevated CO2 changethe nutritional quality of cyanogenicclover Trifolium repensRos GleadowSiobhan Isherwood, Tim Cavagnaro, SamanSeneweera, Rebecca Miller,
2/20Factors affecting food security Production •Yield •Area •Agronomy Change in precipitation Availability Nutrition •Distribution •Safety •Cost •Value •Wealth Change in temperature IPCC WG1
3/20How will climate change affect nutritional value?1. Yield 2. Nutritional value 3. Availability
4/20 Why clover? 1. Interesting roots VAM Legume – N fixing Mycorrhizae – P uptakeAccess to nutrients may facilitate positive response to CO2
5/20Why clover? 2. Cyanogenic glycosides HOCH2 O CH3 O CH3 HO CN Linamarin (valine) Lotaustralin (isoleucine) OH Chewing releases -glucosidase glucose (detonator) HCN Binds to cytochrome oxidase + ketone Gleadow& Woodrow 2002, J Chem Ecol, 28, 1297.
6/20Why clover?3. Model for other important cyanogenic crops Forage sorghum Cassava/Manioc Photo: Peter Stuart, Pac Seeds, Qld Photo: Julie Cliff, UEM, Moz 5-10% of all plants cyanogenic Gleadow, Conn et al, 2008 Phytochem, 69: 1870 60% crop plants (some parts) Jones 1998 Phytochem 47: 155; Miller et al. 2006 Ann Bot 97: 1017.
7/20IF Less protein required for photosynthesis at high CO2THEN resources may be diverted to defence 120 Is “excess” N used to Rubisco (% of control) 100 synthesise cyanide? 80 60 Rubisco 40 Other Cyanide 20 0 350 700 CO2 ppm Gleadow and Woodrow 1999, Plants in Action – Leaf protein, Rice available www.plantsci.org.au/publications/
8/20More Nitrogen allocated to cyanide at high-CO2 Sugar gums Natimuk Road, Horsham 20 ~400 ppm CO2 ~ 800 ppm CO2 CN-N per N % E A 10 E A 0 Low Nitrogen High NitrogenGleadow et al. 1998, Plant Cell Environ, 12:21
9/20CO2 effects on cyanogenesis in clover Siobhan Isherwood• FACE• Pot trials (ANU) CassavaFACE• Nutrient trials –N, P, microbes
11/20Cyanide in clover trending higher at 550 ppm 1000Cyanide mg/g dry wt 800 600 400 200 380 ppm 550 ppm • Is leaf protein lower? • Nodulation rates: 6% higher significant?? • Mycorrhizae colonisation: 5% higher ns?
12/20ANU study: More cyanide relative protein atelevated CO2…ONLY with +P 370 ppm 12 700 ppm 10 Cyanide : protein 8 6 4 2 0 -N-P -N+P +N+PGleadow et al. 2009 J Chem. Ecol 35, 476Edwards & Evans 2005 Global Change Biol.11, 1968
13/20 Nutrient cyanogenesis trials 1.2 1.0 CN-N/N% 0.8 0.6 0.4 0.2 0.0 HP:HN HP:LN LP:HN LP:LN Nutrient Treatment • N15/N14 isotopes – P improved N fixation High P: 0.125g/kg – Fixed N used to make HCN Low P: 0.025g/kg High N: 8mM Low N: 2mMIsherwood, 2010 HONS THESIS
14/20Conclusion: nutritional value IS affected by eCO2 • Leaf composition – Less leaf protein – Increased cyanide, relative to protein – Increase tannins, phenolics • Soil environment is crucial • Microbes important in nutrient acquisition …How will elevated CO2 affect these symbioses??? VIEWPOINT: Cavagnaro, Gleadow, Miller (2011) Functional Plant Biology 38, 87–96
15/20 Monash Cyanogenesis GroupCollaborators Cecilia Blomstedt Tim CavagnaroUniversity of Copenhagen Rebecca Miller Birger Møller Kirsten Jørgensen, Morten Møldrup Alan Neale John HamillRSB (ANU) Anna Burns John Evans, Stephanie McCaffrey Natalie O’Donnell Howard Bradbury, Bill Foley Cara Griffiths Sam FromholdPacific Seeds Melissa Bain Peter Stuart, Wayne Chesser Siobhan IsherwoodMozambique/South Africa Kiara O’Gorman Julie Cliff UEM Anabela Zacarias, IIAM FUNDING Simon Adams (Monash) ARC Linkage AusAIDUniversity of Melbourne Finkel Foundation Saman Sereweena (AGFACE) Ian Woodrow, Jennifer Fox Monash University CasstechDPI: AGFACE Pacific Seeds