Document: CAR-3-29-5

Seasonal variation in maximum photosynthetic rates of Alliaria petiolata.

MYERS, C.V.* and R.C.ANDERSON

Illinois State University, Normal, Illinois 61790 USA ¹

Abstract:
We propose that Alliaria petiolata an invasive, exotic plant attains a competitive advantage over native understory plant species by actively growing and achieving high maximum rates of photosynthesis in early spring when the majority of native understory species are still dormant. The rates of photosynthesis for a population of Alliaria petiolata were measured in summer, fall, and early and late spring using the LI-COR 6400 infared gas analyzer. Measurements of native understory cover were made at 3-4 week intervals from early April to late May. In Early spring (March 24) before substantial native understory development occurred, the maximum rate of photosynthesis was 8.2 ⁺ 1.1 mols m^-2s^-1. The maximum photosynthetic rate increased to 17.8 0.6 on 6 April and then declined during May, being 8.8 0.3 and 4.7 0.4 on May 3 and 24, respectively. Maximum photosynthetic rates were negatively correlated with understory cover from the early April sample through May (r = 0.999, P = 0.0057). The ability of Alliaria petiolata to achieve maximum rates of photosynthesis before the active growth of native understory species appears to provide it with a competitive advantage, which may contribute to its successful spread and eventual domination of a forest understory.

Keywords: _Alliaria petiolata_, exotic plants, maximum photosynthetic rate, understory plants

This abstract is being presented at: 1:45 PM in session:
Oral Session #10: Light Relations in Plants.