The Nene Branta sandvicensis Recovery Initiative: research against extinction

Since 1960, about 2150 Hawaiian Geese or Nene Branta sandvicensis were reintroduced in Hawaii to supplement the remaining wild population of about 30 birds. These geese were released mostly in high mountain sanctuaries. These sites became unsuitable during prolonged drought and the few surviving birds were those which had moved away from the release sites. The geese that survived had moved to, or were released near, agricultural pasture land. About 600 Nene are currently living in the wild; numbers are declining on the island of Hawaii, stable on Maui and increasing on Kauai. Management priorities include enhancement of grasslands, predator control and maximizing genetic diversity. To enable the species to recover, management will probably have to be large scale, intensive and prolonged. Further released captive-bred or translocated Nene should have access to enhanced habitats after predators have been controlled.     

The evolution of hymenopteran wings: the importance of size

The allometric relationships between body size and several aspects of wing morphology in the insect order Hymenoptera were investigated using multivariate morphometric techniques. The study focused primarily on wing allometry in five monophyletic genera of bees ( Perdila, Halictus, Ceratina, Trigona and Apis ), but the patterns of size-related evolutionary change found within each of these genera are also found to exist in numerous other hymenopteran taxa. Increased body size in hymenopteran lineages is correlated with the following changes in wing morphology: (1) decreased relative stigma area, (2) distal extension of wing vein elements, (3) increased aspect ratio and (4) proximal shift in the centroid of wing area. The reverse is true for decreased size. The widespread allometric trends most likely result from adaptive change in wing morphology due to size-related changes in the physical properties impinging on the organism–principally the quality and magnitude of drag. The fact that similar wing morphologies among distantly related species can result from similarity in body size has important implications for the study of hymenopteran phylogeny, especially at lower taxonomic levels and when a high proportion of wing characters are employed.     

The pale brown allele in Cepaea nemoralis

The pale brown colour morph in Cepaea nemoralis appears to be determined by an allele at the C (colour) locus ( C ^{P B}). Pale brown is dominant to yellow, codominant with pink and recessive to dark brown. It is linked to the B locus (which controls the presence or absence of banding on the shell), but not to the U locus, which determines whether there is one band or five. In segregations of pale brown and yellow there is a significant deficiency of pale brown, suggesting that there are differences in viability between the morphs.     

Inter-organ Synergism and the Control of Chlorophyll Accumulation in Sunflower (Helianthus annuus) Cotyledons

Prior to illumination, the embryonic axis of sunflower seedlingsmakes a contribution to the cotyledons which enables them togreen more rapidly when subsequently irradiated with white light.The contributions made to this stimulation by the hypocotylhook, hypocotyl, and roots have been investigated. Greeningin sunflower cotyledons reaches an optimum rate when they are6 d old. The developing embryonic axis not only promotes theattainment of this optimum rate but also aids in the maintenanceof this optimum rate as the cotyledons continue to age. Thisstimulatory effect appears to arise primarily from the rootsand can be duplicated by the exogenous application of benzyladenine. In contrast to previous reports we find that the hypocotyl hookplays no role in the control of greening when present duringillumination.     

Effects of Atmospheric Saturation Deficit on the Stomatal Conductance of Pearl Millet (Pennisetum typhoides S. and H.) and Groundnut (Arachis hypogaea L.)

Experiments were carried out to investigate the influence ofatmospheric saturation deficit on the stomatal conductancesof millet and groundnut plants grown in undisturbed soil incontrolled environment glasshouses. Environmental conditionsduring growth were maintained close to those experienced inthe semi-arid tropics. The results demonstrated that the stomatal conductances of well-wateredplants of both species were affected strongly by changes insaturation deficit. The response was stronger at higher irradianceswhen variations in saturation deficit between 1.5 and 3.0 kPacaused 3–4-fold changes in leaf conductance. However,the stomatal response was greatly reduced or absent in unirrigatedplants in which stomatal conductances were reduced. Reduction of the transpiring leaf area by covering some of theleaves increased the leaf conductances of the remaining leavesand partially restored the stomatal response to saturation deficitin unirrigated plants. Leaf conductance was sensitive to thetranspiring area per plant and declined as the transpiring areaincreased. However, the reduction in mean leaf conductance wasinsufficient to prevent an increase in canopy conductance owingto the increased transpiring area: The results are compared to earlier field data for millet, andthe possible origin of the stomatal response is discussed.     

A Quantitative Study of the Resistances to Transpirational Water Movement in Sunflower (Helianthus annuus L.)

Hydroponic sunflower plants were used in a quantitative studyof the relationship between total plant and leaf resistancesto transpirational water movement and transpiration rate. Theresults demonstrate that both resistances are flux-dependentand decline 5–6-fold during a comparable increase in transpiration.The resistance of excised leaves including the petiole was approximatelyhalf the total plant resistance. Subsequent analyses of the water potential gradients and transpirationalfluxes in whole plants permitted calculation of the magnitudeof the partial resistances imposed by roots, stem, petiole,and leaf. The root and leaf resistances were approximately 50%and 30% of the total resistance respectively. Stem and petiolarresistances were relatively small and both influenced watermovement to the upper leaves similarly. The values obtainedare compared with previous published results obtained usingdiverse experimental techniques.     

Requirement of Ethylene for Growth of Callus and Somatic Embryogenesis in Medicago sativa L.

The role of ethylene in the growth of callus and somatic embryogenesisin Medicago sativa was examined. The application of 2,5-norbornadiene,a competitive inhibitor of ethylene action, during a 10 d inductionperiod to medium containing 2,4-D and kinetin inhibited thegrowth of callus but did not affect somatic embryogenesis, nordid it affect ethylene production during the induction stage.The exposure of tissue, incubated on differentiation medium,without hormones, to an atmosphere of 2,5-norbornadiene, inhibitedboth growth and embryo maturation and stimulated pigmentation.The inhibition of embryo maturation was observed even in thepresence of norbornadiene at a concentration which did not affectgrowth of tissue. It is suggested that the action of endogenous ethylene is necessaryfor the growth of the callus and embryo maturation. Key words: Medicago sativa, ethylene, callus growth, somatic embryogenesis     

Effects of Low Concentration of Ozone, Singly, and in Combination with Sulphur Dioxide on Net Photosynthesis Rates of Vicia faba L.

Net photosynthesis rates (P_N) of Viciafaba plants were measuredin chambers containing either clean air or air containing between50 and 300 parts 10^–9 ozone (O₃) with or without 40 parts10^{– 9} SO₂. Exposure to O₃ concentrations greater than 50 parts 10^–9 for periods of 4 h resulted in reductions in PN with greaterreductions at higher concentrations. After exposure ceased,recovery of pre-exposure PN depended on O₃ concentration. Exposureto less than 90. 100 parts 10^{– 9} was followed by completerecovery after 20 h whereas 200-300 parts 10^{– 9} resultedin visible injury and irreversible depression of PN. The additionof 40 parts 10^{– 9} SO₂ to O₃ significantly decreased Psbut the effect of SO₂ declined with increasing O₃. The additionof SO₂ had no significant affect on recovery patterns. It is postulated that Vicia faba plants are able to toleratethe absorption of O, up to a threshold above which progressivedecreases in PN occur due to effects on photosynthetic processes.The slow and sometimes incompletely reversible effects of O₃on PN indicate cellular differences in the injury mechanismand repair capacity compared with the action of SO₂ alone. Lowconcentrations of O₃ with SO2 result in additive injury to PNsuggesting independent action of the pollutants, but the reductionin SO₂ action with increasing O₃ indicates a limit for potentialphysiological injury More the onset of visible injury.