Document: CHA-3-35-35

Microclimate affects stress protein expression.

KNIGHT, C.A.* and D.D.ACKERLY

Stanford University, Stanford, CA 94305-5020 USA ¹

Abstract:
The chloroplast low molecular weight heat shock protein (cLMW HSP) has been implicated in the protection of photosystem II during and after severe temperature stress, yet little evidence exists that plants growing in the field actually express cLMW HSPs in response to naturally occurring environmental stress. Here we show not only that plants growing in the field use the cLMW HSP response, but that cLMW HSP expression is correlated with the microclimate in which plants are growing, and that cLMW HSP expression tracks changes in average air temperature throughout the season. Weekly leaf collections for three Ceanothus cuneatus individuals growing on exposed south facing slopes and three individuals of the same species growing on relatively cooler north facing slopes were conducted at Jasper Ridge Biological Preserve in the Northern California chaparral. Plants growing on south facing slopes expressed cLMW HSPs more frequently and intensely than did plants growing on the north facing slopes. Chloroplast LMW HSP expression in the plants growing on south facing slopes was also correlated with extreme maximum air temperature events during the summer months, and absent during an unseasonably cool period during late July and early August. Because C. cuneatus is co-dominant on south facing slopes in the Jasper Ridge chaparral and less abundant on north facing slopes, we conclude that cLMW HSP expression is a frequent occurrence in areas where C. cuneatus is most abundant and not just limited to the edges of the species distribution.

Keywords: Chaparral, Heat Shock Protein, Ceanothus, Microclimate

This abstract is being presented at: 9:15 AM in session:
Oral Session #1: Plant Carbon Allocation.