The Effect of Fruiting upon Transpiration Rate and Stomatal Opening in Apple Leaves

The uptake of water by apple trees (Malus × domestica‘Golden Delicious’) was measured in a pot experiment and was found to be much greater in apple trees carrying many fruits than in comparable specimens without fruits. The main reason seemed to be differences in the transpiration rates of the leaves. This was corroborated by microscopic investigations which showed a higher degree of stomatal opening in the fruiting trees. In some cases minor reductions in water uptake per tree were caused by reducing the supplies of potassium and nitrogen.     

14C-studies on Apple Trees. IX. Seasonal Changes in the Formation of Fruit Constituents and their Subsequent Conversions

The formation and subsequent conversions of ¹⁴C-labelled compounds were followed in fruits of Malus domestica cvs. Golden Delicious and Cox's Orange Pippin after labelling proximate leaves with ¹⁴CO₂ at different times during the growing season. A few hours after labelling of the leaves, the larger share of fruit ¹⁴C was detected in sorbitol. This share descreased rapidly except in the late autumn. When labelling about 1 July (c. 1 month after bloom), 40–60% of the fruit ¹⁴C was permanently fixed in the methanol and water insoluble fraction. 25% or more was primarily found in organic acids, but this declined during the season to a few per cent. When labelling at the end of July, the dominating feature was the establishment of a peak of temporarily insoluble ¹⁴C, returning back to the soluble form through October and November. This was particularly pronounced in‘Cox's Organe Pippin'. Labelling with ¹⁴C at the end of August and at the end of September yielded increasing amounts of ¹⁴C in sugars. The labelling of fructose predominated, but as the autumn progressed the amount of label in sucrose increased. This was due to a conversion from ¹⁴C-compounds of older origin as well as to a larger share of the imported assimilates turning into sucrose at this time of the year. During prolonged storage of harvested fruits at 3°C, ¹⁴C in fructose increased at the expense of ¹⁴C in sucrose.     

Gut passage effect of the introduced red‐whiskered bulbul (Pycnonotus jocosus) on germination of invasive plant species in Mauritius

In Mauritius, many of the worst invasive plant species have fleshy fruits and rely on animals for dispersal. The introduced red‐whiskered bulbul (Pycnonotus jocosus) feeds on many fleshy‐fruited species, and often moves from invaded and degraded habitats into higher quality native forests, thus potentially acting as a mediator of continued plant invasion into these areas. Furthermore, gut passage may influence seed germination. To investigate this, we fed fleshy fruits of two invasive plant species, Ligustrum robustum and Clidemia hirta, to red‐whiskered bulbuls. Gut passage times of seeds were recorded. Gut‐passed seeds were sown and their germination rate and germination success compared with that of hand‐cleaned seeds, as well as that of seeds in whole fruits. Gut passage and hand‐cleaning had significant positive effects on germination of both species. Gut‐passed seeds of both C. hirta and L. robustum germinated faster than hand‐cleaned seeds. However, for L. robustum, this was only true when compared with hand‐cleaned seeds with intact endocarp; when compared with hand‐cleaned seeds without endocarp, there was no difference. For overall germination success, there was a positive effect of gut passage for C. hirta, but not for L. robustum. For both C. hirta and L. robustum, no seeds in intact fruits geminated, suggesting that removal of pulp is essential for germination. Our results suggest that, first, the initial invasion of native forests in Mauritius may not have happened so rapidly without efficient avian seed dispersers like the red‐whiskered bulbul. Second, the bulbul is likely to be a major factor in the continued re‐invasion of C. hirta and L. robustum into weeded and restored conservation management areas.     

A set of microsatellite markers for an endangered arboreal marsupial,Leadbeater's possum

Leadbeater's possum is a small, cryptic nongliding petaurid, which is threatened by habitat loss due to the collapse of large hollow‐bearing trees and ongoing timber production in Victoria's central highlands. The recent decline of this species and the difficulties faced by researchers collecting field data has prompted the development of a suite of polymorphic microsatellite markers for application to the continuing conservation of the Leadbeater's possum.     

Mutual Exclusion of ATP,ADP and g-Strophanthin Binding to NaK-ATPase

THE (Na⁺+K⁺)-activated ATPase found in cell membrane fragments is for many reasons thought to be part of the active sodium pump system of cells. One of the arguments is that cardiac glycosides specifically inhibit the ATPase as well as the sodium pump^1–3. It has been proposed that the inhibition is due to an interaction between the glycosides and some phosphorylated form of the ATPase system^4–6.