Effects of Leaf Removal on Reproductions vs. Belowground Storage in Trillium Grandiflorum

We investigated the joint and separate effects of partial defoliation and pollination on components of reproduction and rhizome carbohydrate reserves in Trillium grandiflorum, a perennial spring ephemeral frequently abundant in the herbaceous understory of deciduous forests in eastern North America. To disrupt annual net production maximally, defoliation treatments were applied during flowering just as the year's flush of leaves matured. Natural pollination limited seed set in one year but not another at our study site near Montreal, Quebec; it is likely that year—to—year variation in pollinator availability is the norm. Removal of leaf or floral bract tissues did not affect mean seed set, but leaf removal did reduce allocation of biomass and nonstructural carbohydrates to rhizomes. As the level of defoliation increased, the correlation between reproduction and storage within plants became increasingly negative. Although the mean seasonal leaf conductance of partially defoliated plants was greater than that of intact plants, any compensatory increases in photosynthesis that may have occurred were apparently insufficient to prevent the reduced allocation to belowground storage. The allocation of resources to current reproduction at the expense of survival and future reproduction possibly reflects the selective effects of unpredictable availability of pollinators for this spring ephemeral.