Photosynthetic Responses to Light in an Understory Herb, Aster Acuminatus

Abstract

Previous studies of the understory herb, Aster acuminatus, have shown that variation among natural patches in ramet growth, reproduction and population dynamics reflects environmentally induced responses to differences in patch light regimes. This set of experiments was undertaken to determine if photosynthetic responses to variation in light could provide a physiological explanation for the observed differences among patches. Ramets were raised in pots under different light regimes in either the field or growth chambers and then were taken to the lab for analyses of photosynthetic light responses. Ramets acclimated to the light conditions they experienced. Low‐light plants had lower maximum photosynthetic rates, light saturation points and light compensation points compared to high‐light plants. These differences were more pronounced for growth chamber‐grown plants than for those from the field. Differences between ramets grown in deep shade and partial sun in the field were greatest early in the season and then became less as photosynthetic rates for all plants declined. Photosynthetic rates were strongly correlated with leaf nitrogen level, and there was no evidence that nitrogen was any more limiting for one treatment compared to others. These results demonstrate a physiological basis for patch differences in growth, reproduction and dynamics.

Photosynthetic adaptation and acclimation to exploit seasonal periods of direct irradiance in three temperate, deciduous‐forest herbs

“…Similar upregulation of photosynthetic capacity after canopy leaf drop in the autumn has been reported for Pachysandra terminalis (Yoshie & Kawano 1986) and Hexastylis arifolia (Skillman et al 1996). However, the potential for leaf acclimation from summer to autumn is by no means the rule for evergreen and semi-evergreen herbs of temperate deciduous forests (Landhausser et al 1997;Oberhuber & Bauer 1991;Pitelka & Curtis 1986;Tissue et al 1995).…”

The response of the pseudoannual species Trientalis europaea L. to forest gap dynamics in a near-natural spruce forest

“…For instance, A. acuminatus only produced flowers at high light intensities. At deeply shaded sites A. acuminatus ramets survived but they were much smaller and never flowered compared to bright sites (Pitelka and Curtis, 1986). However, T. europaea seems to perform best at intermediate position along the light gradient.…”

The effect of light on the growth and reproduction of Floerkea proserpinacoides

“…Most of the spring ephemeral herbs such as Erythronium americanum, Claytonia caroliniana, Dicentra cucullaria and Allium tricoccum are perennials ; these plants grow clonally and are able to accumulate reserves in below ground structures. Such traits enable these plants to persist on the forest floor for relatively long periods when PPFR is below the compensation point, little or no growth is possible and conditions are unfavourable for reproduction by seed (Tamm, 1972 ;Anderson & Loucks, 1973 ;Schemske et al, 1978 ;Pitelka et al, 1980 ;Pitelka & Curtis, 1986 ;Grandtner & Gervais, 1990 ;Packham et al, 1992 ;Nault & Gagnon, 1993).…”