Control of intracellular glutathione and its effect on ultraviolet radiation-induced K+ efflux in cultured rose cells

Abstract Modification of the ‘intracellular concentration of reduced glutathione’ (IC-GSH) affected the response of cultured rose cells (Rosa damascena) to ultraviolet radiation (UV)-induced leakage of K⁺. High IC-GSH induced by incubation of cells in 10 mol m^?3 GSH (IC-GSH increased linearly with time from 20 to about 600 μmol g^?1 in 61.2 ks) caused cells to become significantly less sensitive to UV. Low IC-GSH induced by treatment with 1 mol m^?3 buthionine sulphoximine (BSO) plus 1 mol m^?3 diethylmaleate (DEM) (IC-GSH decreased from 20 to about 3 μg g^?1 in 61.2 ks) reduced, rather than increased, the UV-sensitivity of the cells. However, treatment with DEM also induced a large transient K⁺ leakage; and treatment with BSO induced a slight leakage. The K⁺ leaked was recovered by 3.24 ks. Following K⁺ recovery, the DEM-treated cells showed almost complete insensitivity to UV, and BSO-treated cells showed a slightly reduced sensitivity to UV. These results are in agreement with our previous findings that other treatments (heat, cycloheximide, UV), which also cause a transient leakage of K⁺, also reduce the induction of K⁺ leakage by a subsequent UV treatment. We conclude that high IC-GSH may play a role in protecting plant cells from UV-induced K⁺ leakage. Increased UV-sensitivity with low ICGSH was not observed, we believe, because of the transient K⁺ leakage, though the mechanism of reduced sensitivity to UV induced by transient leakage of K⁺ is not known at this time. Treatment with UV did not reduce the IC-GSH, showing that this is not the mechanism by which UV induces K⁺ leakage.     

Three new species of Coniopteryx from Singapore (Plannipennia: Coniopterygidae)

Both sexes of two new species of Coniopteryx, and the male of a third, are described from Singapore rain-forest. Notes on their morphology include an account of internal reproductive structures in the female. The vertical distribution of the species is recorded.     

Water Flow Across the Sieve-Tube Boundary: Estimating Turgor and Some Implications for Phloem Loading and Unloading. II. Phloem in the Stem

Confirming a previous analysis by Lang (1974), it is concludedthat in tree trunks, phloem turgor and turgor gradients maybe estimated from osmotic pressure and osmotic-pressure gradients,respectively. The present analysis is an improvement becauseit is based on observed osmotic-pressure gradients rather thansupposed turgor gradients, and allowance is made for sucroseunloading and gradients of external water potential. It is concludedthat the rate of sucrose unloading in tree trunks must be lessthan 50 nmol m^–2 S m^–1. In small plants, higherrates of unloading (100 nmol m m^–2 S m^–1) and steeperconcentration gradients will lead to larger errors, but turgorpressures can still be estimated with acceptable accuracy. Oneshould be more cautious when considering turgor gradients insmall plants, although it seems likely that reasonable estimateswill still be obtained. Assuming plasmodesmatal transport throughan unconstricted cytoplasmic annulus, it is concluded that thesieve elements and their associated cells will sustain verysimilar turgor and osmotic pressures. Convection and diffusioncan both contribute significantly to plasmodesmatal sucroseunloading. Similarly, the plasmodesmatal volume flux will reflecta combination of pressure flow and osmosis. Water fluxes acrossthe sieve element plasmalemma and through the plasmodesmatacan be in opposite directions. It may be possible to assessthe extent of hydraulic coupling between the sieve elementsand their associated cells from studies of phloem water relations Phloem, turgor, osmotic pressure, plasmodesmata, phloem unloading, Munch hypothesis     

SPERM HARVESTING AND POSTMORTEM FATHERHOOD

The motives and consequences of harvesting sperm from brain dead males for the purpose of effecting post mortem fatherhood are examined. I argue that sperm harvesting and post mortem fatherhood raise no harms of a magnitude that would justify forbidding the practice outright. Dead men are not obviously harmed by the practice; children need not be harmed by this kind of birth; and the practice enlarges rather than diminishes the reproductive choices of surviving partners. Certain ethical and legal issues nevertheless require attention. As a matter of consistency with other harvesting protocols, there ought to be a mechanism for respecting the wishes of men who when alive do not wish to become fathers post mortem. Mechanisms governing entitlement to harvest and use sperm will also be required. I note that the law is unlikely to recognize the paternity of children born from harvested sperm, though there may be reasons to recognize that paternity in some instances.