PARENT SESSION
Oral Session # 64: Plant Ecology V: Physiology and Function II.
Presiding: G North
Thursday, August 7. 8:00 AM to 11:30 AM, SITCC Meeting Room 102.
Gas exchange and water use efficiency of glandular and non-glandular trichome types in Datura wrightii (Solanaceae).
Smith, James*,1, Hare, J Daniel1, 1 University of California - Riverside, Riverside, CA
ABSTRACT- The maintenance of a trichome dimorphism in Datura wrightii in light of the apparent fitness cost of producing glandular trichomes suggests that there could be one or more trait-associated life history characteristics that are beneficial. Sticky plants (glandular) occur more frequently than velvety plants (non-glandular when mature) in populations located in more mesic habitats. This suggests that water use and availability may play an important part in determining the relative distribution of sticky and velvety plants. Leaf hairs have been shown in other species to significantly reduce absorbed solar radiation, temperature, transpiration rate (E), and photosynthetic CO2 assimilation rate (A). Gas exchange parameters of sticky and velvety plants grown in a common garden were measured during midday on several dates in late summer and early fall of 2002. Water use efficiency (WUE; A/E) was 11.2% higher on average in sticky plants, however there was an interaction between type and date. On hot, sunny days there was no difference in WUE, but on cooler, less sunny days WUE was up to 25.0% higher in sticky plants. This difference in WUE cannot be attributed to stomatal conductance or E, which did not differ significantly between types; rather, it appears to be due to fluctuations in A, which varied up to 22.1% higher in sticky plants than in velvety plants. Higher WUE in sticky plants at lower temperature and light intensity is most likely due to physiological or anatomical differences associated with trichome type rather than any direct effect (shading/evaporation) of the trichomes themselves. In relatively mesic habitats with lower temperatures and less intense solar radiation, sticky plants may have a physiological advantage that could translate into more rapid growth and competitive ability.
Key words: cost of resistance , Datura wrightii, trichomes, ecophysiology