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An investigation was undertaken to examine responses of mangoes cv. Kensington Pride to irradiation treatment.Gamma irradiation of preclimacteric fruit increased fruit respiration immediately after treatment, delayed the time to attain the climacteric respiratory peak and reduced the magnitude of this peak rate. Fruit softening was unaffected whereas skin colour development was strongly inhibited by irradiation treatment. Inhibition of skin degreening was half-maximal at a dose of 200 Gy. Exposure to ethylene failed to reverse this inhibition. Less mature fruit were more strongly affected by irradiation treatment. Fruit which were partially ripe and in their climacteric rise at time of treatment were largely unaffected by irradiation. These results are discussed in terms of the utility of irradiation technology for commercial disinfestation.

The effects of added ammonium ion (10-1000 μM) on photosynthetic 14 CO 2 fixation by tissues slices from the mantle of tridacnid clams, by coral tips, and by isolated zooxanthellae from clam mantle were examined. Ammonium ions stimulated photosynthesis in tissue slices but not in freshly isolated zooxanthellae. When ammonium stimulated 14 CO 2 fixation by coral tips an increase in water-soluble labelled compounds, especially amino acids, was observed. Even though ammonium ions did not stimulate photosynthesis in isolated zooxanthellae from clam mantle, light stimulated ammonium uptake in these cells. Studies with 15 NH + 4 confirmed earlier observations (in zooxanthellae isolated from Hippopus ) of light-stimulated transfer of ammonium from the amido-N of glutamine to the amino-N of glutamate, glutamine and other amino acids. This observation, in isolated zooxanthellae and tissue slices, suggests that the glutamine synthase-glutamate synthetase pathway of ammonium incorporation is light-driven in these systems. The possible significance of these processes during ammonium recycling by symbiotic algae in marine animals is discussed.

The effects of gamma irradiation and disease control treatments on disease severity and post harvest quality of several mango cultivars were investigated.In mangoes cv. Kensington Pride, irradiation doses ranging from 300-1200 Gy reduced disease, but the level of control was not commercially acceptable. Hot benomyl immediately followed by irradiation provided effective control of anthracnose (Colletotrichum gloeosporioides) and stem end rot (Dothiorella dominicana) during short-term storage (15 days at 20°C). The effects of the two treatments were additive.Satisfactory disease control was achieved during long term controlled atmosphere storage when mangoes were treated with hot benomyl followed by prochloraz and then irradiated. Effects of fungicide treatment and irradiation were additive.Fungicide, or irradiation treatments alone, were unsatisfactory.Irradiation of cv. Kensington Pride at doses in excess of 600 Gy caused unacceptable surface damage (i.e. lenticel spotting, surface discolouration and retardation of degreening) which was particularly severe after long-term controlled atmosphere storage.In a separate short-term storage trial, several other mango cultivars were assessed. Hot benomyl followed by prochloraz controlled anthracnose on all cultivars and stem end rot on some. Irradiation at 600 Gy contributed only minor improvements to disease control. The severity of surface damage that developed following irradiation and fungicide treatment varied with cultivars.