The effects of seed production techniques on seed characteristics, seedling growth and crop performance of crisp lettuce

Seed crops of crisp lettuce were produced in three years with and without gibberellin 4 plus 7 (GA₄₊₇) application to the young seedlings. The effects on seed and seedling characters and field performance of harvesting seed at different times, either by shaking out mature seed or by ‘windrow’ harvests, were assessed. Differences between treatments in seed and seedling characters within any one year were relatively small although those treatments producing large seed gave large seedlings and those giving uniform seed gave uniform seedlings. There were no important effects of seed production treatments on field characters in any one year. However, when different years of seed production were compared directly there was a large effect of year of production on seedling establishment and the size and uniformity of seedlings. Application of GA₄₊₇ resulted in heavier and more uniform seedlings in two of the three years. The results suggest that major differences between commercial seedlots occur as a result of differences in the environment rather than in the technique of seed production.     

Some effects of temperature during seed development on carrot (Daucus carota) seed growth and quality

The growth and development of carrot seeds cv. Chantenay Red-cored Royal Chantenay at day/night temperatures of 20/10°C, 25/15°C and 30/20°C and subsequent seed performance were examined in 1984 and 1985. An increase in temperature from 20/10°C to 30/20°C reduced mean weight per seed by 20% in 1984 and by 13% in 1985. There were no effects of temperature on endosperm + embryo weight, or on endosperm cell number but the weight of pericarp decreased with an increase in temperature. Seeds grown at the highest temperature had the largest embryos and the highest nitrogen, DNA and rRNA content; they germinated and emerged earlier, and gave higher percentage seedling emergence than those grown at the lowest temperature. There were no effects of temperature during seed growth on the rate of imbibition of water by seeds during the germination process.     

The incidence of gangrene of potatoes caused by Photna exigua in relation to handling and storage

Damage to potatoes during harvesting and grading increases the incidence of gangrene. Among the factors involved, the condition of the soil and the type of damage caused by the implements may be of importance. Gangrene is most evident in tubers which have been stored cold or moved when cold; warmer storage at some stage usually reduces its incidence and severity. Seasonal incidence is not directly related to rainfall but is determined by factors affecting ripening and destruction of haulm, moisture status of soils at harvest, susceptibility to damage, and exposure during storage and in transit.     

Rm Differences in Leaf Malate Dehydrogenases of Flax (Linum usitatissimum) Genotrophs: Apparent Developmental Effects

Fieldes, M. A. and Gray, T. J. 1988. R_m differences in leafmalate dehydrogenases of flax (linum usitatissimum) genotrophs:apparent developmental effects.—J. exp. Bot. 39: 499–509. Malate dehydrogenase (MDH) isozyme relative mobility (R_m) wasexamined in leaf extracts of Durrant's large (L) and small (S)flax genotrophs. Within both L and S there were differencesin R_m between leaves sampled from different positions down themain stem and between leaves sampled from plants of differentages. For leaves sampled from plants which were at the onsetof flowering, the R_m differences from the apex to the base ofthe stem showed similar trends in L and S. However, the neteffect of the trend for L was a linear increase in R_m from apexto base, which did not occur in S. The changes in R_m which occurredin apical leaves as the plants aged were also different in Land S; R_mdecreased in L and increased in S during the growthperiod just prior to flowering. The possible relationship betweenthese differences in the changes in MDH R_m within L and S, previouslyreported differences in the changes in peroxidase (PER) isozymeR_m and the morphological/developmental differences between Land S is discussed. In addition, the experimentation demonstratedthat ‘negative’ bands detected in MDH-stained gelsunder certain staining conditions appear to correspond to PERisozymes and effectively mean that PER and MDH isozyme R_m'scan be obtained from the same electrophoretic gels. Key words: Malate dehydrogenase, peroxidase, relative mobility, flax     

Evaluation of trichothecene and nontrichothecene mycotoxins produced byFusarium in soybeans

Each of 12 cultures ofFusarium, comprising four species, isolated from moldy soybeans suspected of being involved in illness of wild geese, were grown separately in autoclaved moist rice, in autoclaved moist soybeans, and in surface sterilized-disinfected soybeans, assayed for various mycotoxins, and fed to rats. Four additional cultures that produced known toxins on rice were also grown on soybeans as controls. All isolates, except one ofF moniliforme, grown in rice resulted in weight loss of rats, and that one resulted in weight gain; 12 of the isolates caused death. One isolate ofF poae grown in soybeans caused death when consumed by rats, but none of the other 15 resulted in weight loss or overt injury. Much larger amounts of zearalenone, deoxynivalenol (DON), T-2 toxin, neosolaniol, T-2 tetraol, wortmannin, and moniliformin were produced by the cultures on rice than on soybeans, but more HT-2 toxin was produced by one isolate ofF poae grown on soybeans than when grown on rice. Soybeans appear to be a poor substrate for elaboration of most of the toxins produced by the isolates tested.