Current issue: 54(5)
Under compilation: 55(1)
Two-year-old containerized Scots pine (Pinus sylvestris L.) seedlings, raised under different fertilization and watering regimes, were subjected to feeding preference tests with pine weevils (Hylobius abietis L.) in a bioassay. In the tests carried out with pairs of seedlings, the weevil preferred water-stressed seedlings to well-watered ones. In the case of well-watered seedlings, the weevil caused significantly more damage to NPK-fertilized seedlings than those given pure PK fertilization, or no fertilization at all. It is apparent that PK fertilization reduces, and water stress increases seedling susceptibility to weevil damage. The results support findings from field trials that water stress (planting shock) predisposes seedlings to weevil damage. Weevil resistance is discussed with respect to fertilization and water stress as determinants of seedling quality.
The PDF includes an abstract in Finnish.
Genetic variation in the physiological characteristics and biomass accumulation of Acacia mangium Willd. was studied in both field and laboratory conditions. Variation in the growth characteristics, foliar nutrient concentration, phyllode anatomy and stomatal frequency was analysed in 16 different origins under field conditions in Central Thailand. Family variation and heritability of growth and flowering frequency were calculated using 20 open-pollinated families at the age of 28 months. The effect of environmental factors on diameter growth in different provenances is also discussed.
Under laboratory conditions, such physiological characteristics as transpiration rate, leaf conductance and leaf water potential were measured at varying soil moisture conditions. The responses of photosynthesis, photorespiration and dark respiration as well as the CO2 compensation point to temperature and irradiance were also investigated. All physiological characteristics indicated differences among provenances. An attempt was made to relate the results obtained in the laboratory to the growth performance in the field. Recommendations on provenance selection for the planting of A. mangium in Thailand are also given.
The PDF includes a summary in Finnish.
The net photosynthetic rate per unit of foliage was studied in two-year old cuttings of Norway spruce (Picea abies (L.) H. Karst.), representing four clones, at varying temperature and soil moisture. The CO2 compensation point (Γ), photorespiration, dark respiration, and water balance were also investigated. All these characteristics indicated differences among the clones. A correlation between CO2 exchange and transpiration suggested that stomatal control determined at least a part of this variation during a favourable water balance. An inverse relationship existed between Γ and net photosynthetic rate, and the same curvilinear model explained this variation in unstressed as well as stressed plants at a given temperature. An increase in Γ seems to be a normal result of water stress, particularly at high temperature, indicating an increase in mesophyll resistance to CO2 diffusion. This result was in agreement with calculated values of mesophyll resistance. It also supported our earlier conclusions about the significance of mesophyll resistance during water stress.