Oecologia (2003) 134:167–175 DOI 10.1007/s00442-002-1102-6 ECOPHYSIOLOGY Vivien P. Thomson · Saul A. Cunningham · Marilyn C. Ball · Adrienne B. Nicotra Compensation for herbivory by Cucumis sativus through increased photosynthetic capacity and efficiency Received: 19 February 2002 / Accepted: 19 September 2002 / Published online: 23 November 2002  Springer-Verlag 2002 Abstract Herbivory is an important selective pressure in the life history of most plant species, as it usually results in reduced plant fitness. In some situations, however, plants are able to compensate for the resources lost to herbivory and do not suffer any reduction in growth or reproduction after attack. We examined the ability of Lebanese cucumber (Cucumis sativus) to compensate for both pre-flowering and during-flowering foliar herbivory through increased photosynthetic efficiency and capacity. Plants that were damaged before flowering were able to compensate, in terms of vegetative biomass and fruit production for up to 80% leaf area loss. Plants that were damaged during the flowering period were less able to compensate and fruit production declined with increasing herbivory. Damaged plants had higher photosynthetic efficiency and capacity, and dissipated less light energy as heat. Herbivore-damaged plants may be induced to use a greater proportion of the absorbed light energy for photosynthesis as a result of altered carbohydrate source-sink relationships. Keywords Chlorophyll fluorescence · Plant–animal interactions · Source-sink dynamics · Light use efficiency · Photosynthesis Introduction For most plants, loss of leaf tissue to herbivores is a constant feature of the environment (Cyr and Pace 1993). Herbivory results in resource reduction through a loss of nutrients and/or photosynthetic area, often leading to a reduction in plant fitness. However, within the last 30 years, increasing evidence has indicated that many plants are able to compensate for lost tissue by replacing it through rapid growth (McNaughton 1983). In this study, we examined the ability of Lebanese Cucumber (Cucumis sativus) to compensate for foliar herbivory by the brown garden snail (Helix aspersa). Compensatory ability, defined as the difference in fitness between herbivore damaged and undamaged individuals of the same genotype (Belski 1986), varies widely across plant species. For example, Piper arieanum suffered a reduction in growth and reproduction with only 10% leaf loss (Marquis 1984), whereas Abutilon theo- phrasti fully compensated for 75% defoliation under certain conditions (Mabry and Wayne 1997). The degree of compensation depends on the plant species, amount of leaf lost, mode of herbivore damage, environmental conditions and the timing of the herbivory event (Maschinski and Whitham 1989; Simons and Johnston 1999). Plants are more likely to compensate if the damage occurs early in the growing season, before the reproduc- tive phase has started (Maschinski and Whitham 1989; Lehtila and Syrjänen 1995; ScarrØ et al. 1996; Lennarts- son et al. 1998). Proposed mechanisms for compensation include increased photosynthetic rate (Dyer et al. 1991; Houle and Simard 1996; Meyer 1998), increased growth rate (Danckwerts 1993; Oba et al. 2000), increased branching or tillering after the release from apical dominance (ScarrØ et al. 1996; Sacchi and Connor 1999; Simons and Johnston 1999; Lortie and Aarssen 2000), high pre-herbivory levels of stored carbon (Hochwender et al. 2000) and the ability to reallocate those stored resources (Caldwell et al. 1981; Mabry and Wayne 1997), alteration of the external light environment (J¼remo et al. 1996; Mabry and Wayne 1997), and higher reproductive efficiency through increased percentage of fruit set (Mabry and Wayne 1997). The capacity for a plant to compensate for herbivory depends on carbohydrate source-sink dynamics. Net sources of carbohydrates include mature photosynthesis- V.P. Thomson ( ) ) · A.B. Nicotra Botany and Zoology, Australian National University, Canberra, ACT 0200, Australia Fax: +61-2-98508245 S.A. Cunningham CSIRO Entomology, GPO Box 1700, Canberra, ACT 2601, Australia M.C. Ball Research School of Biological Sciences, Australian National University, Canberra, ACT 0200, Australia