Root traits governed by biological and environmental factors. Louise Comas

Transcription

1 Root traits governed by biological and environmental factors Louise Comas

2 Breeding for root traits: a new frontier Critical functions Functional traits still poorly understood Dynamic Don Tremain, Tree with roots Getty Collection High C costs

3 Talk outline Plant strategies belowground: root trait evolution Effects of plant management and environment on root dynamics & functioning (UC Davis walnut research & breeding program) (USDA corn & sunflower water deficit research )

4 Evolved plant strategies below ground What can we learn from natural selection? Root system structure Coarse roots (structural support, plumbing) Fine roots (physiologically active, ephemeral) (3 rd ) 2 nd 1 st order

5 Root morphology Seedling traits 300 (a) SRL (m g -1 ) SRL Fast > Slow (P<0.05) Mature tree traits SRL (mg -1 ) AN AS QR QA PV TC Aceraceae Fagaceae Pinaceae BL FG CO AN 80.0 QR QA 60.0 CG AS Fast-growing seedlings faster root proliferation more soil eplored 40.0 PV PS Fast Fast Slow Comas et al. 2002; Comas & Eissenstat 2004

6 SRL = m g -1 Consistency Inde = Unordered linear parsimony - Square-root reconstruction - Tree based on APGII 2003 Comas & Eissenstat 2009

7 Phylogenetic pattern Paleozoic Mesozoic Cenozoic Carboniferous Permian Triassic Jurassic Cretaceous Paleo-gene Cenozoic Neogene MY Comas et al 2012 IJPS

8 Evolution in root diameter 1.4 Paleozoic Mesozoic Cen. Diameter (mm) R 2 = 0.83 P < 0.05 Lower [CO2] Greater stom. density High leaf vein density Thinner roots = less corte for less impedance to water movement? Distance from each node to root of the tree (MY) Comas et al 2012 IJPS

9 Trade-offs between morphology & RLD Root length density (cm/cm 3 ) R 2 = 0.69 P < SRL (m/g) Comas et al 2012 IJPS, data from Withington et al 2006

10 Conclusions Within close relatives, longer SRL and thinner roots allow fast-growing species to eploit soil pockets more quickly (with higher costs but faster returns on these costs) Root morphology more hard-wired than physiology Evidence suggests that angiosperms evolved thinner roots with longer SRL, potentially to increase water uptake & transport, and out compete plants in upland habitats

11 Effects of plant management and environment on root dynamics & functioni NE US vineyards Juice grape production Lake Erie region, NY Soil: Chenango gravelly loam Training: high-wire bilateral cordon Minimal pruning to reduce costs and raise crop yield Vitis labruscana Bailey cv Concord Issues with alternatebearing vines

12 Questions Balanced growth theory - does irrigation compensate for root growth? Irrigated vs non-irrigated? Competing sinks - do roots compete with fruit for plant carbon? Minimal vs heavy pruning? Timing?

13 Conventional wisdom in grape Roots compete with fruit for plant carbon Root growth is bimodal - major root flush in spring with a smaller root flush in fall Mullins MG, Bouquet A. Williams LE Biology of the Grapevine.

14 Eperimental layout Block 1 Block 2 Block 4 Block 3 eperimental vines buffer vines root tubes 25-yr-old vines, treatments initiated in 1991 Completely randomized block design; 22 factorial eperimental unit = 5 vines plus 2 as buffer study duration = 4 years ( ) roots observed with minirhizotrons

15 Minirhizotrons Record images: every 2 wks (active vines) 1 per month (dormant)

16 Root production Average total root production (mm cm -2 yr -1 ) NI Irr NI Irr Dry years Wet years Comas et al New Phytologist

17 Root distribution in dry years Non-irrigated Irrigated (wet) * (dry) Depth (cm) ** ** 1999 (dry) (wet) Comas et al New Phytologist Mean fine root production (%)

18 Timing of root production Heav/NI Heav/Irr Min/NI Min/Irr (wet) New roots (mm cm -2 ) (dry) (dry) (wet) 0.02 Comas et al AJGWR 0.00 Mar Apr May Jun Jul Aug Sep Oct Nov

19 Root production rate Dry years Wet years Rate of root production (mm cm -2 d -1 ) Heav/NI Heav/Irr Min/NI Min/Irr bl bl v v bl v bl v 0.00 Ear Bud dev dev Flwr Frt set dev Frt Frt dev dev Frt Frt ripe ripe Sht Sht dorm dorm Bud dev Flwr dev Frt dev Frt ripe Sht dorm Ear dev Frt set Frt dev Frt ripe Sht dorm Vine phenology Comas et al New Phytologist

20 Root phenology & distribution Depth (cm) Mean fine root production (mm cm-2 d-1) Minimally pruned Heavily pruned Apr May Jun Jul Aug Sep Oct Apr May Jun Jul Aug Sep Oct Comas et al New Phytologist

21 Conclusions No evidence of C limitations on root growth Amount & timing of root growth is controlled by both plant and environment (canopy development & soil moisture)

22 Aging effects on root function Root boes Ephemeral fine roots 1mm

23 Root metabolism with age White roots (%) TTC reduction (A g -1 DW) (a) (b) % white % dark Plot 1 Zero Root age (weeks) Respiration TTC reduction Respiration (nmol O 2 g -1 DW s -1 ) Comas et al New Phytologist

24 Metabolic decline w/ pigmentation White Brown Black TTC reduction (A g -1 d.wt.) mm White Brow n Black Control Root pigmentation Jul 97 1 Nov Mar 98 Comas et al New Phytologist

25 Root functioning with age Other work has shown nutrient uptake capacity declines quickly with root age (P in apple, Bouma et al 2001; N in grape, Volder et al 2005); What about water uptake? Young roots have high C costs but greatest nutrient acquisition capacity Apples vs oranges (Eissenstat 1999) Other environmental factors, especially temperature effects on root growth & function?

26 Implications & future directions Some broad generalizations may hold (fast growth, drought adapted = long SRL, thin diameters) Compleity in root functioning demands in-depth knowledge of the system breeders are breeding for What root traits do plants need to sustain yields under different types of drought? Different strategies for different species?

27 Acknowledgements Grape Research David Eissenstat, PSU Root evolution Alan Lakso, Cornell Kevin Mueller, Univ Minnesota Laurie Anderson, Ohio Wesleyan Lyla Taylor, Univ of Sheffield Rick Dunst, Cornell Vineyard Lab Peter Midford, NESCent Hilary Callahan, Barnard/Columbia David Beerling, Univ of Sheffield Funding sources USDA/CSREES Eastern & Western Viticulture Consortium NSF IOS NESCent

28 Standing root A. White roots B. Brown roots C. Total roots populations veraison Heav/NI Heav/Irr Min/NI Min/Irr bloom veraison harvest (wet) veraison veraison harvest 1.2 Roots present (mm cm -2 ) veraison bloom bloom veraison harvest (dry) (dry) veraison bloom veraison harvest (wet) Comas et al New Phytologist Apr May Jun Jul Aug Sep Oct Nov Apr May Jun Jul Aug Sep Oct Nov Apr May Jun Jul Aug Sep Oct Nov