The influence of macromolecular substances on reduction of vascular water conductance and photosynthetic processes in lucerne
1995
Plhak, F. (Masarykova Univ., Brno (Czech Republic). Prirodovedecka Fakulta)
Increasing reduction of water conductance caused by dextran macromolecules with mol. weight of 75, 500, 2 000 and 5 000-20 000 kDa was evoked in detached lucerne shoots exposed during 7 h at 560 micromol s-1m-2 PPFD. Plant wilting connected with stem and leaf bending occurred after exposure to larger molecules above 5 000 kDa, while smaller ones caused leaf desiccation without organ bending. An increase in water saturation deficit in leaf blades was accompanied by a decrease in chlorophyll content and photosystem 2 activity as well as by lowering photosynthetic dry matter, total nonstructural saccharides and especially structural substances increments. The results confirmed that macromolecular substances produced by pathogens and released into xylem vessels interfere with water conductance, and can at sufficient concentrations be the main cause of deleterious processes in plants.
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