Gas Exchange in Populus maximowiczii in Relation to Potassium and Phosphorus Nutrition

1990

S. 675-679

4 Abb., 2 Tab., 22 Lit. Ang.

Unselbständiges Werk

200050409

Cuttings of Populus maximowiczii Henry were grown in half-strength Hoagland nutrient solution with varying levels of K (0, 0.3 and 3 mM) and P (0, 0.05 and 0.5 mM). The effects of K and P deficiency on gas exchange and biomass of the plants was investigated. The absence of K markedly suppressed plant growth and reduced biomass of the roots more than that of the shoots. The 0.3 mM k and zero K (0 mM) treatments produced a significant increase in stomatal resistance and a decrease in net photosynthesis rate and RuBP carboxylase activity. The transpiration rate in all treatments was closely correlated with stomatal resistance (r = 0.94). The CO2 compensation point increased with K supply. Biomass accumulation at 0.05 mM P was equal to that of the control, but was greatly reduced in the zero P treatment where the growth of shoots was much more affected than that of the roots. In the 0.05 mM P treatment stomatal resistance also increased. There was, however, a lower correlation between stomatal resistance and transpiration rate. Net photosynthesis and RuBP carboxylase activity markedly declined with the zero P treatment but not in the treatment with 0.05 mM P. The data show that K and P deficiency affect gas exchange and growth of poplar in different ways. Their influence on gas exchange and growth of the plants is discussed.