The Conservation of Sea Turtles: Practices and Problems

The various techniques in common use for conservation and restorationof depleted sea turtle populations are reviewed, namely: banninginternational commerce; operating artificial hatcheries, bothin the natural beach environment and in styrofoam and othertypes of incubators; "head-starting" of hatchlings in captivity;protection of nesting females by means of beach patrols; andtranslocation of eggs or hatchlings to distant areas from whichturtles have been extirpated or to which it is desired to introducenew colonies. The difficulties of monitoring the results ofall of these techniques are discussed, and potential dangersor disadvantages of each approach are reviewed. It is concludedthat, until unequivocal data become available, turtle conservationistsshould continue to pursue common sense or logically sound restorationprograms, but should constantly re-evaluate their actions inthe light of the latest available knowledge and modify or desistfrom current approaches as necessary.     

Stratigraphical classification and all that

Quantitative treatment of the geological sciences must remain limited; there continues to be need for a language of words. This is keenly felt in stratigraphy, where the practising geologist is dismayed by the effusions of the stratigraphical philosophers. The situation, in so far as it appears to remain in some ways obscure or troublesome, is briefly reviewed in terms of lithostratigraphy. biostratigraphy. and chronostratigraphy. A revised version of a controversial diagram is presented, in which the role of the boundary stratotype as anchor point is believed to be clarified. Finally a synthesis is attempted of relationships between the various stratigraphical procedures and the provision of dates in years through the parallel discipline of geochronometry.     

Phase Change in Hedera helix: Induction of the Mature to Juvenile Phase Change by Gibberellin A3

A sensitive and reproducible method to obtain GA₃ induced morphological reversion of mature Hedera helix to the juvenile form has been developed. Dose response experiments indicate that GA₃ stimulates reversion over a 50–100 fold range with a half maximal response at approximately 0.5 μg GA₃ per plant. The individual characteristics involved in phase change revert to the juvenile form in a sequential manner as GA₃ dose is increased. Variations in light intensity from 1.2–3.6 × 10⁴ lux and temperature from 15 to 26°C do not affect this hormonal response. Other growth regulators including indoleacetic acid, kinetin, abscisic acid and (2-chloroethyl)phosphonic acid (Ethephon) are inactive but other gibberellins (GA₁ and a mixture of A₄–A₇) are active in stimulating reversion. Therefore, the response is specific for gibberellins as a class of hormones but non-specific for a particular form of gibberellin. The significance of this response in relation to juvenility in woody plants is discussed.     

Stomatal Response to Humidity and Lanthanum

Lanthanum fed to the base of excised leaves of Sesamum indicum L. and Helianthus annuus L. was used as a tracer to investigate by electron microscopy the path of water in the apoplast of leaves. The generally random distribution of lanthanum in cell walls provided no support for the hypothesis that cuticular transpiration may be greater for guard cells than for adjacent epidermal cells. Occasionally, accumulations of lanthanum were observed in anticlinal walls of epidermal cells and at the outer surface of the plasma membrane but lanthanum was not observed in the symplast. The influx of ⁸⁶Rb to excised roots of sesame and sunflower was inhibited during incubation with 0.5 mM lanthanum or calcium for 15 or for 180 min. Stomata of sunflower partially closed when 2.5 mM lanthanum was supplied to the base of excised shoots in a potometer, whereas this treatment had little effect on stomatal conductance of sesame shoots maintained in a constant environment. Supplying 2.5 mM lanthanum to the base of sesame shoots strongly inhibited stomatal opening response to increase in ambient humidity but had little effect on stomatal opening response to light. It was concluded that stomatal opening response to increased humidity may be dependent upon some process, such as ion influx, that is inhibited by lanthanum, and that opening response to humidity may differ in mechanism from stomatal opening response to increased irradiance.