Photosynthetic electron transport in pitcher plants (Nepenthes mirabilis)

Pitcher plants (Nepenthes sp.) are insectivorous angiosperm plants with modified leaves known as pitchers best known as acting as traps for insects. Pitcher plants are typically found under boggy conditions under both forest cover and open areas with very poor nutrient status, particularly N-status. The pitchers have low photosynthetic activity. The Chl a content of the pitcher tissue of both Nepenthes mirabilis (green and red) varieties was very low. Chl b/a ratios of the green variety phyllodes (lamina) and pitchers were approximate to 0.24 to 0.29. In the red variety, the mature phyllodes had a Chl b/a ratio approximate to 0.28 but both the pitchers and the young phyllodes had Chl b/a ratios of nearly 0.5. Photosynthetic electron transport (ETR) was measured using PAM technology. Phyllodes of both varieties showed photoinhibition at supra-optimal irradiances [Nepenthes mirabilis (green variety), E-opt approximate to 200-250 mu mol photon m(-2) s(-1); red variety, E-opt approximate to 100-150 mu mol photon m(-2) s(-1)]. Pitchers had low optimum irradiances (E-opt approximate to 40-90 mu mol photon m(-2) s(-1)). Maximum ETR (ETRmax) of phyllodes of both varieties was low (ETRmax approximate to 50 mu mol e(-) g(-1) Chl a s(-1)); ETRmax was higher for pitchers on a Chl a basis (ETRmax approximate to 80-100 mu mol e(-) g(-1) Chl a s(-1)); a consequence of their low Chl a content on a surface area basis. ETRmax of cut disks of phyllodes did not respond strongly to incubation in NH4+, glutamate or aspartate as N-sources but did respond positively to added urea.

Automated summary

Pitcher plants, which are insectivorous plants, have modified leaves that act as traps for insects. They have low photosynthetic activity and are often found in nutrient-poor environments. The chlorophyll content in the pitchers is very low, resulting in reduced photosynthetic electron transport. The pitchers have low optimum irradiances and a higher ETRmax on a chlorophyll basis, indicating their adaptation to low light conditions.