Mineral nutrition in campos rupestres species Anna Abrahão, Rafael S. Oliveira, Caio G. Pereira, Hugo G. Cândido, Mariana C. de Campos, Hans Lambers
Campos rupestres • Mountaintop, grassy-shrubby, fire-prone vegetation mosaics • Rocky outcrops of quartzite, sandstone or ironstone • Sandy, stony and waterlogged grasslands (peat bogs). Photo: R.S. Oliveira
Silveira et al. (2015)
Photos A-C: R.S. Oliveira, D: A Silveira
0.78 % of the Brazilian territory
More than 5000 plant species
~15% of plant species in Brazil Silveira et al. (2015)
AM: A. Abrahão, EM: http://www.forestry.gov.uk/, cluster roots: Shane & Lambers (2007)
Lambers et al. (2008)
What are the nutrient-acquisition strategies along a P-availability gradient (mycorrhizas x other specializations)?
Campos rupestres over quartzite sands
P
Scrubland over oxisol
+P
• 10 most abundant species • Nutrient-acquisition strategies • Leaf nutrient concentrations
Peat-bog over OM-rich sands
++P
Resin P gradient
White sands
Gravel Cerrado (Scrubland)
Peat bogs
Bars are mean± SE (0-20 cm). Different letters indicate P < 0.05 in the post hoc Tukey test.
Leaf P concentrations Global average: 1.02 mg P g-1 leaf DW
White sands
Gravel Cerrado (Scrubland)
Peat bogs
N=10 species per site
N:P ratios
N=10 species per site
White sands
Gravel Cerrado (Scrubland)
Peat bogs
Mycorrhizal colonization x soil P
Root specializations
Conclusions • Low leaf P concentrations • Higher P than N limitation (high N:P ratios) • Very old Gondwanan lineages, for example, Eriocaulaceae and Velloziaceae that evolved (in situ) a wide range of root specializations to survive with P limitation.
How do these plants acquire P in such P-limited environments?
Shane & Lambers (2007)
Discocactus placentiformis
Sand-binding roots • What do they release? • Exudation for phosphorus acquisition? • Is the exudation pattern dependent on P supply? 0
50
10 μmol
l-1
of P
100
What do the roots release? Oxalic > malic > citric > lactic > succinic > fumaric > malonic acids
Is the total exudation dependent on P supply? Organic acid exudation decreases with P supply
Each circle represents a root tip, n = 5 plants per treatment, 3 roots tips per plant, χ2 = 4.2512; p = 0.0392
Conclusions • D. placentiformis presents a NEW root specialization
• Releases carboxylates in higher concentrations in low P supplies • Is nonmycorrhizal, despite being part of a mycorrhizal family • Functional convergence with other ancient landscapes (Cluster and dauciform roots)
Final conclusion • Species diversity is reflected in the diversity of nutrient-acquisition strategies
• Very low percentage of mycorrhizal colonization in the P-poorest vegetation types • Root specializations release carboxylates for P acquisition
Thank you!
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