Long‐term ammonium nutrition of Arabidopsis increases the extrachloroplastic NAD(P)H/NAD(P)+ ratio and mitochondrial reactive oxygen species level in leaves but does not impair photosynthetic capacity

Ammonium nutrition has been suggested to be associated with alterations in the oxidation‐reduction state of leaf cells. Herein, we show that ammonium nutrition in Arabidopsis thaliana increases leaf NAD(P)H/NAD(P)⁺ ratio, reactive oxygen species content and accumulation of biomolecules oxidized by free radicals. We used the method of rapid fractionation of protoplasts to analyse which cellular compartments were over‐reduced under ammonium supply and revealed that observed changes in NAD(P)H/NAD(P)⁺ ratio involved only the extrachloroplastic fraction. We also showed that ammonium nutrition changes mitochondrial electron transport chain activity, increasing mitochondrial reactive oxygen species production. Our results indicate that the functional impairment associated with ammonium nutrition is mainly associated with redox reactions outside the chloroplast.     

Effect of sex and bright coloration on survival and predator‐induced wing damage in an aposematic lantern fly with startle display

1. Aposematic coloration in prey promotes its survival by conspicuously advertising unpalatability to predators. Although classical examples of aposematic signals involve constant presentation of a signal at a distance, some animals suddenly display warning colours only when they are attacked. 2. Characteristics of body parts suddenly displayed, such as conspicuous coloration or eyespot pattern, may increase the survival of the prey by startling the predator, and/or by signalling unpalatability to the predators at the moment of attack. 3. The adaptive value of such colour patterns suddenly displayed by unpalatable prey has not been studied. We experimentally blackened the red patch in the conspicuous red–white–black hindwing pattern displayed by an unpalatable insect Lycorma delicatula White (Hemiptera: Fulgoridae) in response to predator's attack. 4. There was no evidence that the presence of the red patch increased prey survival over several weeks. We hypothesise that predators generalised from the red–white–black patches on the hindwings of unpalatable L. delicatula to any similar wing display as a signal of unpalatability. Because a higher proportion of males than females stay put at their resting sites, displaying their wings in response to repeated attacks by predators, wing damage was more frequent in males than in females. 5. To our knowledge, this is the first experimental test of an adaptive role of aposematic signals presented by unpalatable prey during sudden displays triggered by direct predatory attack.     

EFFECT OF BLUE AND YELLOW LIGHT DURING THE LATER DEVELOPMENTAL STAGES OF SPHAEROBOLUS

When fruiting cultures of Sphaerobolus are transferred from continuous light to darkness the discharge of global masses continues for 1 day but then stops for the next few days. Experiments are reported in which this darkness is interrupted after 24 hr by brief (0.5-2 hr) treatment with light of different wavelengths and of equated low intensity (ca. 100 lux). Interruption by blue (ca. 448 mμ) or by green (ca. 500 mμ) light has no effect, but treatment with yellow (ca. 585 mμ) or red (ca. 650-700 mμ) leads to substantial discharge 24 hr later. If, however, the yellow treatment is followed immediately with blue there is little or no discharge; but if the order of this treatment is reversed, a high level of discharge results. This is somewhat greater than that resulting from treatment with yellow light alone. If, following a yellow treatment there is an interval of several hours before a blue treatment, the blue has less effect in negating the action of the yellow light. It is shown that, although in the final light-sensitive stages in development of the sporophore before it opens, yellow and red light are stimulatory but blue and green are not; in the phototropic response of the mature sporophores blue light is effective and yellow is not.     

A new vitamin E analogue more active than alpha-tocopherol in the rat curative myopathy bioassay

Vitamin E owes its biological effects to its antioxidant activity. Kinetic and mechanistic studies on phenolic antioxidants in vitro have led us to design and synthesize all-rac-2,4,6,7-tetramethyl-2-(4',8',12'-trimethyltridecyl) -5-hydroxy-3,4-dihydrobenzofuran, 3. In the rat curative myopathy bioassay the acetate of this compound has 1.5-1.9 times the bioactivity of all-rac-alpha-tocopherol acetate. This represents the first time that a rationally designed synthetic 'vitamin' has been found to have more activity in vivo than the corresponding natural vitamin.