Sex-related differences in growth and carbon allocation to defence in Populus tremula as explained by current plant defence theories.
Plant defence theories have recently evolved in such a way that not only the quantity but also the quality of mineral nutrients is expected to influence plant constitutive defence. Recently, an extended prediction derived from the protein competition model (PCM) suggested that nitrogen (N) limitation is more important for the production of phenolic compounds than phosphorus (P). We aimed at studying sexual differences in the patterns of carbon allocation to growth and constitutive defence in relation to N and P availability in Populus tremula L. seedlings. We compared the gender responses in photosynthesis, growth and whole-plant allocation to phenolic compounds at different combination levels of N and P, and studied how they are explained by the main plant defence theories. We found no sexual differences in phenolic concentrations, but interestingly, slow-growing females had higher leaf N concentration than did males, and genders differed in their allocation priority. There was a trade-off between growth and the production of flavonoid-derived phenylpropanoids on one hand, and between the production of salicylates and flavonoid-derived phenylpropanoids on the other. Under limited nutrient conditions, females prioritized mineral nutrient acquisition, flavonoid and condensed tannin (CT) production, while males invested more in above-ground biomass. Salicylate accumulation followed the growth differentiation balance hypothesis as low N mainly decreased the production of leaf and stem salicylate content while the combination of both low N and low P increased the amount of flavonoids and CTs allocated to leaves and to a lesser extent stems, which agrees with the PCM. We suggest that such a discrepancy in the responses of salicylates and flavonoid-derived CTs is linked to their clearly distinct biosynthetic origins and/or their metabolic costs.
Natural Products Research Laboratories, Department of Biology, University of Eastern Finland, P.O. Box 111, 80101 Joensuu, Finland tendry.randriamanana@uef.fi.
Tendry R
TR
Randriamanana
Natural Products Research Laboratories, Department of Biology, University of Eastern Finland, P.O. Box 111, 80101 Joensuu, Finland Department of Ecology and Natural Resource Management, Norwegian University of Life Sciences, Ås, Norway.
Line
L
Nybakken
Natural Products Research Laboratories, Department of Biology, University of Eastern Finland, P.O. Box 111, 80101 Joensuu, Finland.
Anu
A
Lavola
Department of Biosciences, University of Helsinki, Helsinki, Finland.
Pedro J
PJ
Aphalo
Natural Products Research Laboratories, Department of Biology, University of Eastern Finland, P.O. Box 111, 80101 Joensuu, Finland.
Katri
K
Nissinen
Natural Products Research Laboratories, Department of Biology, University of Eastern Finland, P.O. Box 111, 80101 Joensuu, Finland.
Riitta
R
Julkunen-Tiitto
D002244:Carbon / Q000378:metabolism*; D005387:Finland; D008903:Minerals / Q000378:metabolism; D009584:Nitrogen / Q000378:metabolism*; D010636:Phenols / Q000378:metabolism; D010758:Phosphorus / Q000378:metabolism*; D010788:Photosynthesis; D018515:Plant Leaves / Q000254:growth & development / Q000378:metabolism; D018520:Plant Shoots / Q000254:growth & development / Q000378:metabolism; D032107:Populus / Q000254:growth & development* / Q000378:metabolism*; D036226:Seedlings
D008903:Minerals; D010636:Phenols; D010758:Phosphorus; D002244:Carbon; D009584:Nitrogen
aspen; biomass; constitutive defence; dioecious; nitrogen; phenolics; phosphorus; photosynthesis; sexual dimorphism