The influence of seed quality and pregermination treatment on cauliflower and cabbage transplant production and field growth

Seedling emergence and subsequent growth from untreated seeds and selected-germinated seeds which had been dried before sowing (low-moisture-content germinated (LMCG) seeds) were compared in cellular trays in a glasshouse and in the field following transplanting. Three seed lots of different quality of the same cultivar were used for cabbage and cauliflower. In all cases, seedling emergence was greater, earlier and more uniform from LMCG seed than that from untreated seeds. LMCG seed effectively eliminated the differences due to seed quality shown by untreated seeds at emergence suggesting an improvement in seed vigour as well as viability from the selection treatment. Higher quality seed and LMCG cauliflower seed led to larger curd weights and therefore an increase in marketable yield at harvest compared to that from lower quality seeds. However, differences in transplant uniformity due to seed quality and seed treatment had little impact of agronomic significance following transplanting.     

Levels of protein, RNA, DNA, glycogen and lipid during growth and development of Daphnia magna Straus (Crustacea: Cladocera)

1. Protein, RNA, DNA, glycogen and lipid content were determined in Daphnia magna on days 0, 2, 4, 6, 8 and 21 of growth and development. The composition of D. magna as percentage of reconstituted dry weight was similar to other zooplankton with the exception of DNA content, which was lower than values previously reported.
2. The relative content of protein, RNA, DNA and reconstituted dry weight changed during the 21-day growth period, and these changes were related to growth rate and total growth of D. magna . RNA:protein, RNA: reconstituted dry weight, and protein:RNA : DNA ratios were highly correlated to relative growth rate and total growth as measured by protein content or reconstituted dry weight.
3. Addition of progeny biomass to adult biomass increased correlations between biochemical ratios and absolute growth rate, but had little effect on relationships involving relative growth rate or total growth.
4. The relationship between biomolecule ratios and growth established for D. magna grown under optimal conditions was not successful in predicting growth of D. magna reared under crowded conditions.
5. These data indicate that variation in biochemical ratios among life, stages of D. magna may be used to predict growth of organisms grown under similar conditions, but may not be extended to other situations. It is suggested, however, that variation in biochemical ratios in a particular life stage of a zooplankton species may be related to the productivity for that species.     

The Effect of Temperature on Reproduction in FivePrimulaSpecies

Primula vulgarisHuds.,P. verisL.,P. frondosaJanka, and threepopulations ofP. farinosaL. were legitimately and illegitimatelypollinated, and the self-fertileP. scoticaselfed and cross-pollinatedand then subjected to uniform temperature conditions of 6, 15or 26 °C for 4 d before gynoecia were examined for pollengermination and pollen tube growth, or plants progressed toseed set at 15 °C, after which seeds were weighed, germinated,and seedlings grown on. The temperature responses of pollengermination and pollen tube growth were not always congruent,and varied between species, populations, and often between morphs(pin and thrum) in the distylous species. Nevertheless, optimaltemperature responses tended to be lower for vernal species(P. vulgarisandP. veris) and for subarcticP. scoticathan forlater flowering montane species. However, no relationship wasfound between pollen temperature response, and fertility. Thegreatest seed set occurred after legitimate pollination at 15°C in most cases; a flowering temperature of 26 °C tendedto impede seed set, except forP. scoticaand the low altitudepopulation ofP. farinosa. InP. veris, P. frondosaand the highaltitude population ofP. farinosa,some illegitimate pollen germinationand pollen tube growth occurred at 26 °C, but this did notlead to increased within-morph seed set in these self-incompatiblespecies at this relatively high temperature. Temperature atflowering frequently affected average seed weight, and inP.verisand two populations ofP. farinosathis attribute may havebeen influenced by seed number, the average seed weight of few-seededcapsules tending to be greater than for many-seeded capsules.A high seed weight might mitigate the disadvantageous effectsof low fecundity resulting from interactions with floweringtemperature. However, inP. vulgarisandP. scoticainteractionsbetween flowering temperature and seed weight may have other,undetermined, causes. The seed of four species germinated leastwell in standard conditions when set following a flowering temperatureof 6 °C, which tends to support the hypothesis that temperatureat flowering can affect seed physiology; in contrast the seedof the two upland populations ofP. farinosagerminated leastwell after flowering at 26 °C. We conclude that much morework is needed on interactions between temperature and reproductiveefficiency, but that preliminary indications suggest that aglobal increase in temperature at flowering might adverselyaffect the quantity and quality of seed set in some species.Copyright1998 Annals of Botany Company Distyly, pollen tube,Primula farinosa, Primula frondosa, Primula scotica, Primula veris, Primula vulgaris,reproduction, seed set, temperature.     

The effect of nutrients on adenine nucleotide levels and the adenylate energy charge ratio in Spartina alterniflora and Spartina patens

Abstract. The response of the adenylate energy charge (AEC) ratio and the adenine nucleotide pools to nutrients was studied in two perennial marsh plant species. Adenine nucleotide levels and the AEC ratio were measured in Spartina patens (Alton) Muhl. plants which were grown in the greenhouse at various nutrient levels as well as in Spartina alterniflora Loisel. transplants removed from the field but maintained in marsh soil amended with different nutrient supplements. In addition, adenine nucleotide concentrations were measured in both species in their natural environment and compared with that of the same species grown in the greenhouse with a complement of nutrients.
The addition of nutrients stimulated an increase in the individual and total adenylate pools and the AEC ratio. Low nutrient levels resulted in extremely reduced adenylate pools. The AEC ratio was significantly affected in some instances, but did not decrease proportionately with the adenine nucleotide level and was typically maintained at values above 0.60. The adenine nucleotide concentrations measured in the leaves of both species were significantly higher in greenhouse-grown plants compared to field plants, but the AEC ratios were not significantly different.
Because the AEC ratio in plants can be significantly affected by nutrient level. AEC response in field investigations should be planned with attention to the potential effect of dissimilar nutrient levels among study sites.