Alterations of the resin canal system of <Emphasis Type="Italic">Pinus pinaster</Emphasis> seedlings after fertilization of a healthy and of a <Emphasis Type="Italic">Hylobius abietis</Emphasis> attacked stand |
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Authors: | Xoaquín Moreira Luis Sampedro Rafael Zas Alejandro Solla |
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Institution: | (1) Centro de Investigación Ambiental de Lourizán, Apdo. 127, 36080 Pontevedra, Spain;(2) Ingeniería Técnica Forestal, Universidad de Extremadura, Avenida Virgen del Puerto 2, 10600 Plasencia, Spain |
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Abstract: | Changes in resource availability and biotic and abiotic stress may alter the defensive mechanisms of pine trees. The effect
of fertilisation on the resin canal structure of Pinus pinaster seedlings established in two trials in NW Spain, one attacked by Hylobius abietis and the other non-attacked, was studied. The leaders of 50 plants were destructively sampled and the resin canal density,
the canal area and its relative conductive area in the phloem and xylem were assessed. Experimentally increased nutrient availability
significantly decreased resin canal density in the phloem of the seedlings in the two analysed trials, where unfertilised
seedlings presented up to 30% more resin canal density than the fertilised seedlings (mean value ± SEM = 0.32 ± 0.02 resin
canals mm−2 in the fertilised plants versus 0.45 ± 0.04 resin canals mm−2 in the control plants). Fertilisation had no effect on the resin canal system in the xylem, but significantly increased tracheid
size. Significant differences of resin canals among sites were observed mainly in the xylem; the resin canal density was 1.7-fold
greater in the attacked site than in the non-attacked site. The similar structure of phloem resin canals in both sites supports
that phloem resin canals are constitutive mechanisms of defence in P. pinaster, whereas xylem resin canals would be constitutive mechanisms but also inducible mechanisms of resistance following the attack
of pine weevils or bark beetles.
XM and LS equally contributed to this paper. |
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Keywords: | Herbivory Constitutive defence Induced defence Phloem Xylem Large pine weevil |
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