A Study on the Mode of Infection of Pinus sylvestris L. by Peridermium pint (Pers.) Lev.

Inoculations by Peridermium pini (Pers) Lev. aeciospores ofscalpel wounds 2 mm deep on current year's Pinus sylvestrisL. shoots gave more numerous infections than shallower wounds.Some lesions resulting from these infections developed pycnidialdroplets and a few also produced aecial blisters within thefirst year after infection. Infection of P. sylvestris by P.pini can take place by direct stomatal penetration. This wasobserved only inside the needle sheaths of trees with previousnatural infections and was not observed on healthy trees. Thehyphae that developed from these penetrations passed intercellularlythrough the mesophyll to the vascular tissue where they proliferated.     

Uptake of tritium-labeled norepinephrine in brain and other tissues of cat in vitro

Slices of cat cerebral cortex, heart, and spleen that have been incubated in media containing approximately 5 to 25 mmicrog of dl-norepinephrine-7H(8) per milliliter contain levels of isotopic amine greater than those in the medium. The effects of norepinephrine concentration, reserpine, and ouabain on the uptake suggest that the amine enters cells both by diffusion and by a concentrating miechanism that is saturated at low levels of norepinephrine. The drugs inhibit the latter.     

A Study of Some Factors of Resistance of Pinus sylvestris L. to Peridermium pint (Pers.) Lev.

External needle extracts from an infected and a healthyPinussylvestris L. did not adversely affect the germination of aeciosporesof Peridermium pini (Pers.) Lev.Internal extracts and juicesexpressed from needles and shoots showed a fungistatic effecton spores. The effect was more pronounced when extracts and juices werederived from needles of a healthy tree than from an infectedone. In the former case, the germ tubes were invariably deformed.The significance of these differences in relation to resistanceis discussed.     

Nutrient Changes in Peaty Gley Soils after Clearfelling of Sitka Spruce Stands

The roots of second-rotation Sitka spruce (Picea sitchensis(Bong.) Carr.) planted on peaty gley sites are restricted tothe old litter (LFH) layer and are dependent on its decompositionfor availability of nutrients. A series of these sites of increasingage from felling were sampled to estimate changes in the nutrientcapital of the LFH horizon over time at Kielder Forest, Northumberland.Previous stand histories were reconstructed from stump data.Geographical, climatic, soil and mensurational data suggestedthat the use of a time series was justified. Nutrient capital in the LFH horizon generally declined overa 5 year period after clearfelling from approximately 997, 51and 83 kg ha^–1 to 676, 30 and 31 kg ha^–1 of N, Pand K, respectively. However, N concentration increased overa 5 year period from 11 mg g^–1 to 14 mg g^–1, P concentrationremained constant at about 0.6 mg g^–1, and K concentrationdecreased from 1.0 mg g^–1 to 0.7 mg g^–1. Nutrientconcentrations and contents of the LFH horizon were higher underthe brash (slash) swathes that resulted from the use of organizedfelling techniques than under clear strips devoid of brash. The patterned input of nutrient capital in brash as a resultof organized felling was also determined. Brash containing 219,20 and 71 kg ha^–1 of N, Pand K, respectively, was systematicallydistributed at a rate of 491 ha^–1 over 66 per cent ofthe site after harvesting. The needles and small branch fractionscontained 71 per cent of the N and 80 per cent of the P andK present in the brash.     

Nutrient Leaching from the Litter Layer after Clearfelling of Sitka Spruce Stands on Peaty Gley Soils

The nutrient dynamics in the litter layer of former Sitka sprucestands were examined from 0 to 7 years after clearfelling usingzero-tension lysimeters on a time series of sites 0, 2 and 5years after felling. The loss of most nutrients monitored inleachate was independent of the time from clearfelling. However,54 per cent (43 kg ha^–1) of the 7-year net loss of potassiumwas leached out of the litter layer in the first year. Also,nitrate losses, although small, increased after 5 years. Leachinglosses of NH₄-N, PO₄-P, K, Ca and H⁺ exceeded precipitationinputs. However, leaching losses were less than precipitationinputs for NO₃-N, Na and Mg. Nutrient losses from under brashswathes were generally greater than from clear strips.