Hydraulic conductivity in roots of ponderosa pine infected with black-stain (Leptographium wageneri) or annosus (Heterobasidion annosum) root disease

Roots from healthy and diseased mature ponderosa pine, Pinus ponderosa Laws., trees were excavated from a site near Burns, Oregon. The diseased trees were infected with black-stain root disease, Leptographium wageneri Kendrick, or annosus root disease, Heterobasidion annosum (Fr.) Bref., or both. Axial hydraulic conductivity of the roots was measured under a positive head pressure of 5 kPa, and the conducting area was stained with safranin dye to determine specific conductivity (k(s)). In diseased roots, only 8-12% of the cross-sectional xylem area conducted water. Resin-soaked xylem completely restricted water transport and accounted for 13-16% of the loss in conducting area. In roots with black-stain root disease, 17% of the loss in conducting area was associated with unstained xylem, possibly resulting from occlusions or embolisms. Based on the entire cross-sectional area of infected roots, the k(s) of roots infected with black-stain root disease was 4.6% of that for healthy roots, whereas the k(s) of roots infected with annosus root disease was 2.6% of that for healthy roots. Although these low values were partly the result of the presence of a large number of diseased roots (72%) with no conducting xylem, the k(s) of functional xylem of diseased roots was only 33% of that for healthy roots. The low k(s) values of functional xylem in diseased roots may be caused by fungus induced occlusions preceding cavitation and embolism of tracheids. The k(s) of disease-free roots from diseased trees was only 70% of that for healthy roots from healthy trees. The disease-free roots had the same mean tracheid diameter and tissue density as the healthy roots, suggesting that the lower k(s) in disease-free roots of diseased trees may also have been caused by partial xylary occlusions.     

Mitteilung von Beobachtungen bei Untersuchungen über die Einwirkung der neuen Kontaktinsektizide auf Wachsmotten und Seidenraupen

Ohne Zusammenfassung     

Die Johannisbrotmotte,Myelois ceratoniae Zell. als Schädling an Apfelsinen

Ohne Zusammenfassung     

A new ent-kaurane diterpenoid from Croton tonkinensis leaves

A new ent-kaurane diterpenoid (1) was isolated from the leaves of Croton tonkinensis. The structure of 1 was determined as ent-7beta-hydroxy-15-oxokaur-16-en-18-ol from spectroscopic methods.     

Farmers participation and socio-economic effects of a watershed management programme in Central Java (Solo river basin,Wiroko watershed)

A self-help watershed management project in the densely populated areas of Central Java, Indonesia, is discussed in terms of its achievements to combine activities to improve the physical, the social and the economic environment. Without simultaneous, well-planned action on these three essential components the project's improvements cannot be sustained by the farmers. It was found that activities such as tree planting and maintenance, construction of soil erosion control structures and training in agroforestry-type intensification techniques for land cultivation serve as a focus to induce farmers to participate. Participation can be sustained in spite of initial decreasing net income if increases in land productivity based on agroforestry practices together with appropriate training programmes organize and motivate the farmers. In future watershed management programmes more emphasis may be placed on the rural development planning aspects of e.g. agroforestry techniques, and on rural community organization.This paper is based on a M.Sc. research study conducted by the first author under the supervision of the second author at the Rural Development Planning Programme of the Division of Human Settlements Development, A.I.T., Bangkok. The first author is indebted to FAO and the Canadian International Development Agency for scholarship and research grants and to his employer, the Solo Watershed Development Centre of the Indonesian Government. The second author acknowledges his secondment by the Belgian Development Co-operation Administration, Brussels. Comments of the research committee members, Prof. Dr. H. Dias and J. Piper on the research project and of anonymous referees on the paper are gratefully acknowledged. However, the responsibility for the views presented here lies solely with the authors.