Chemical aspects of heartwood formation

Summary A complete understanding of the processes underlying the transformation of sapwood into heartwood requires consideration of the chemical as well as other aspects of the change. A review of recent investigations into chemical topics is presented. There is a decrease in the storage materials from the outer and middle sapwood to the heartwood boundary, although there is one case where the reverse trend of sugar content was found and this may be a seasonal effect. The evidence presented shows that, in some species, some metabolic pathways operating at the sapwood-heartwood boundary differ from those in the sapwood. It is not known whether the reactions operating at the heartwood boundary include those previously operating in the sapwood or whether the new compounds are added to those already present. The composition of the heartwood extractives in a species is the same in different samles. Examples are given to show that the affected wood resulting from different forms of damage can be chemically different from normal heartwood. Consequently, the processes leading up to the death of the living cells can have a great influence on the composition of the extractives. Accordingly it is not only the constant composition of normal heartwood extractives that is under genetic control, but also the processes which initiate their formation. The intermediate zone and the factors which could initiate heartwood formation and control the amount of extractives formed, are considered. Evidence shows the extractives to be formed at the heartwood periphery from translocated carbohydrate, the amount of which is possibly under the control of growth-promoting hormones.

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Zusammenfassung Zum Gesamtverständnis des Vorganges der Umwandlung von Splintholz in Kernholz müssen sowohl chemische als auch andere Gesichtspunkte in Betracht gezogen werden. Es wird zunächst ein Überblick über die neuesten Untersuchungen mit chemischen Zielsetzungen gegeben. Man findet vom äußeren und mittleren Splintholz gegen die Kernholzgrenze hin eine Abnahme der Inhaltsstoffe, obwohl es auch einen Fall gibt, wo es sich mit dem Zuckergehalt genau umgekehrt verhält, was auf eine jahreszeitliche Gegebenheit zurückzuführen sein dürfte. Die gewonnenen Erkenntnisse weisen darauf hin, daß bei einigen Holzarten die Art und Weise des Stoffwechsels in der Nähe der Splint-/Kernholzgrenze von demjenigen im reinen Splintholz wesentlich abweicht. Es ist bisher nicht bekannt, ob die Prozesse, die an der Kernholzgrenze ablaufen, auch diejenigen Prozesse einschließen, die zuvor im Splintholz stattfanden oder ob die neugebildeten Bestandteile einfach zu den schon vorhandenen hinzutreten. Die Zusammensetzung der Inhaltsstoffe des Kernholzes einer Holzart bleibt dieselbe innerhalb verschiedener Proben. Es werden Beispiele dafür aufgeführt, daß Holz mit Verletzungen, die das Ergebnis verschiedener Formen von Beschädigung sind, sich chemiseh vom normalen Kernholz unterscheidet. Infolgedessen kann der Vorgang, der schließlich zum Absterben lebender Zellen führt, einen beträchtlichen Einfluß auf die Zusammensetzung der Inhaltsstoffe haben. Es ist ferner nicht nur die konstante Zusammensetzung der normalen Kernholz-Inhaltsstoffe, die einer genetischen Steuerung unterliegt, sondern auch der Vorgang, durch welchen ihre Entstehung eingeleitet wird. Die Zwischenzone und jene Faktoren, welche die Kernholzbildung einleiten und die Menge der gebildeten Inhaltsstoffe steuern, werden erörtert. Das Ergebnis zeigt, daß die Inhaltsstoffe an der äußeren Hartholzgrenze aus umgelagerten Kohlenhydraten geformt werden. Ihre Menge wird möglicherweise von wuchsfördernden Hormonen gesteuert.

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The paper was prepared for the Symposium Heartwood Formation and its Influence on Utilisation at the XIV. IUFRO Congress Section 41, Munich, September 1967.     

The significance of anomalous extractives in heart-shakes in Dacrydium species

Summary Morphological and chemical examinations of the extractives of the tissues and shake contents of eight Dacrydium and one Podocarpus species have been made. The whitish deposits in heart-shakes are without exception mainly podocarpic acid (PCA). This compound occurs also in the tissue of samples but only when shakes are found nearby. Accordingly PCA is regarded as an anomalous extractive, synthesized in response to those conditions resulting in shake formation. In samples with shakes PCA is present in very small amounts at the sapwood-heartwood boundary and in one sample there were traces even in the innermost sapwood. It was notable that shakes containing deposits can arise in those Dacrydium species with coloured heartwood and with a known tendency for wetwood formation. On the other hand Dacrydium franklinii does not develop coloured heartwood or wetwood or shakes, and the lack of these features may have taxonomic significance.The third author expresses his gratitude to the Division of Building Research, CSIRO, Highett, Vic., for a visiting Fellowship during 1974.     

Acanthocephalan infection and sparganosis in a green tree snake (Dendrelaphis punctulata)

Acanthocephalan and spargana parasites were identified within a body wall mass during exploratory surgery in a wild green tree snake. Acanthocephalan parasites have not previously been reported in this species. Surgical excision, the treatment of choice, could not be achieved because of the extensive infiltration of the coelomic cavity.     

Can the arbuscular mycorrhizal fungus Glomus intraradices actively mobilize P from rock phosphates?

Plants colonized by arbuscular mycorrhizal (AM) fungi have been shown to respond positively to the application of insoluble forms of inorganic phosphorus (P) such as rock phosphates (RPs). The mechanism(s) underlying such responses remain(s) unknown and although it has been hypothesized, there is no experimental support for the production of chelating agents by AM fungal hyphae. Here we investigate whether AM fungi can solubilize P from RPs and transfer it to plant roots. Using root-organ cultures of Daucus carrota L. inoculated or not with Glomus intraradices Schenk & Smith and containing P from different RP sources, we predicted that: (1) roots inoculated with G. intraradices would take up more P than those uninoculated; that (2) the amount of P taken up by roots through G. intraradices would be positively correlated with the RP reactivity; and that (3) G. intraradices would have access to RP through localized alterations of pH and/or by the production of organic acid anions that may act as chelating agents. The RP reactivity was positively correlated with P uptake. However, mycorrhizal roots grew initially slower and did not respond differently to any P treatment than those uninoculated. There was no evidence of localized changes in pH in proximity of G. intraradices hyphae, indicating that responses to RP by mycorrhizal plants observed in previous studies do not appear to result from the release of H⁺ ions alone or in combination with organic acid anions.     

Probing the Local Effects of Magnetic Impurities on Superconductivity

The local effects of isolated magnetic adatoms on the electronic properties of the surface of a superconductor were studied with a low-temperature scanning tunneling microscope. Tunneling spectra obtained near magnetic adsorbates reveal the presence of excitations within the superconductor's energy gap that can be detected over a few atomic diameters around the impurity at the surface. These excitations are locally asymmetric with respect to tunneling of electrons and holes. A model calculation based on the Bogoliubov-de Gennes equations can be used to understand the details of the local tunneling spectra.     

Spontaneous formation of macroscopic chiral domains in a fluid smectic phase of achiral molecules

A smectic liquid-crystal phase made from achiral molecules with bent cores was found to have fluid layers that exhibit two spontaneous symmetry-breaking instabilities: polar molecular orientational ordering about the layer normal and molecular tilt. These instabilities combine to form a chiral layer structure with a handedness that depends on the sign of the tilt. The bulk states are either antiferroelectric-racemic, with the layer polar direction and handedness alternating in sign from layer to layer, or antiferroelectric-chiral, which is of uniform layer handedness. Both states exhibit an electric field-induced transition from antiferroelectric to ferroelectric.     

Organic Glasses: A New Class of Photorefractive Materials

The performance of amorphous organic photorefractive (PR) materials in applications such as optical data storage is generally limited by the concentration of active molecules (chromophores) that can be incorporated into the host without forming a crystalline material with poor optical quality. In polymeric PR systems described previously, performance has been limited by the necessity of devoting a large fraction of the material to inert polymer and plasticizing components in order to ensure compositional stability. A new class of organic PR materials composed of multifunctional glass-forming organic chromophores is described that have long-term stability and greatly improved PR properties.