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Photosynthetic responses of field-grown Pinus radiata trees to artificial and aphid-induced defoliation


Eyles, A and Smith, D and Pinkard, EA and Smith, I and Corkrey, R and Elms, S and Beadle, C and Mohammed, C, Photosynthetic responses of field-grown Pinus radiata trees to artificial and aphid-induced defoliation, Tree Physiology: An International Botanical Journal, 31, (6) pp. 592-603. ISSN 0829-318X (2011) [Refereed Article]

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Copyright 2011 Oxford University Press

DOI: doi:10.1093/treephys/tpr046


The phloem-feeding aphid Essigella californica represents a potential threat to the productivity of Pinus radiata plantations in south-eastern Australia. Five- and nine-year-old field trials were used to characterize the effects of artificial and natural aphid-induced (E. californica) defoliation, respectively, on shoot photosynthesis and growth. Photosynthetic capacity (Amax) was significantly greater following a 25% (D25) (13.8 ýmol m−2 s−1) and a 50% (D50) (15.9 ýmol m−2 s−1) single-event uppercrown artificial defoliation, 3 weeks after defoliation than in undefoliated control trees (12.9 ýmol m−2 s−1). This response was consistently observed for up to 11 weeks after the defoliation event; by Week 16, there was no difference in Amax between control and defoliated trees. In the D50 treatment, this increased Amax was not sufficient to fully compensate for the foliage loss as evidenced by the reduced diameter increment (by 15%) in defoliated trees 36 weeks after defoliation. In contrast, diameter increment of trees in the D25 treatment was unaffected by defoliation. The Amax of trees experiencing upper-crown defoliation by natural and repeated E. californica infestations varied, depending on host genotype. Despite clear differences in defoliation levels between resistant and susceptible genotypes (17 vs. 35% of tree crown defoliated, respectively), growth of susceptible genotypes was not significantly different from that of resistant genotypes. The observed increases in Amax in the lower crown of the canopy following attack suggested that susceptible genotypes were able to partly compensate for the loss of foliage by compensatory photosynthesis. The capacity of P. radiata to regulate photosynthesis in response to natural aphid-induced defoliation provides evidence that the impact of E. californica attack on stem growth will be less than expected, at least for up to 35% defoliation.

Item Details

Item Type:Refereed Article
Research Division:Agricultural, Veterinary and Food Sciences
Research Group:Forestry sciences
Research Field:Forest health and pathology
Objective Division:Plant Production and Plant Primary Products
Objective Group:Forestry
Objective Field:Softwood plantations
UTAS Author:Eyles, A (Dr Alieta Eyles)
UTAS Author:Pinkard, EA (Dr Elizabeth Pinkard)
UTAS Author:Corkrey, R (Dr Ross Corkrey)
UTAS Author:Beadle, C (Dr Christopher Beadle)
UTAS Author:Mohammed, C (Professor Caroline Mohammed)
ID Code:64240
Year Published:2011
Web of Science® Times Cited:34
Deposited By:Agricultural Science
Deposited On:2010-07-08
Last Modified:2017-11-08

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