title: Effects of foliar potassium concentration on morphology, ultrastructure and polyamine concentrations of Scots pine needles.
abstract: We examined the effects of three foliar potassium concentrations (high, intermediate and low) on the morphology, ultrastructure and polyamine concentrations of current-year and 1- and 2-year-old needles of 30-year-old Scots pine (Pinus sylvestris L.) trees. Foliar K concentration had only a slight effect on needle morphology. The sclerenchyma cell walls were thinner, the xylem area was larger, and the resin ducts were smaller in needles with a low K concentration than in needles with a high or intermediate K concentration. In addition, the bundle sheath cells were collapsed in needles having a low K concentration. The secondary growth of phloem tissue and the mesophyll area were greater in needles with a high or intermediate K concentration than in needles with a low K concentration, possibly indicating greater production of photoassimilates in these trees. At the ultrastructural level, mesophyll cells with enlarged central vacuoles and small vacuoles containing electron-dense material were common in needles having a low K concentration. Enlargement of the central vacuole coincided with an exponential increase in putrescine concentration in needles with a low K concentration, suggesting that the central vacuole may function as a storage site for putrescine.
authors.affiliation: University of Oulu, Department of Biology, Botany, P.O. Box 333, FIN-90571 Oulu, Finland.
authors.forename: A
authors.initials: A
authors.lastname: Jokela
authors.forename: T
authors.initials: T
authors.lastname: Sarjala
authors.forename: S
authors.initials: S
authors.lastname: Kaunisto
authors.forename: S
authors.initials: S
authors.lastname: Huttunen