apsicum annuum leaves were sprayed with a suspension of 2,000 P. nicotianae zoospores, 2.5 mM BABA, or water (control) and incubated in a humidity chamber. After 48 h inoculated leaf tissue was excised and imaged using a stereo fluorescent microscope. Auto-fluorescent spots, less than 1 mM in diameter, were present on leaves inoculated with P. nicotianae or treated with BABA at the site of inoculation or treatment (Fig 2). No auto-fluorescence was visible outside of the inoculated or treatment area. Occasionally, small necrotic spots (< 1mm in diameter) developed at the site of inoculation with P. nicotianae or treatment with BABA (data not shown). Capsicum annuum plants were soil drenched with a zoospore suspension of P. nicotianae or P. capsici (100,000 zoospores per plant), 2.5 mM BABA or water, and photosynthetic rates were measured using a Licor 6400 portable photosynthesis system. At three days post inoculation or treatment, photosynthetic rates for plants treated with BABA and plants treated with P. nicotianae were approximately one third of the photosynthetic rate observed for the plants treated with water. In contrast, photosynthesis in plants inoculated with P. capsici was negligible (Fig 2).