ALBERT

Notes: Abstract The developmental history, longevity and fecundity ofPteroptrix smithi (Compere) are described and discussed. Both sexes develop as primary parasites ofChrysomphalus aonidum (L.). Developmental duration at 26°C averages 25 days and the average fecundity at this temperature is 26.5 eggs for unmated and 21.4 eggs for mated females. Under laboratory conditions 50–80% of the eggs are laid during the first few days of adult life. Longevity of females ranges from a maximum of 44 days at 20°C to a minimum of 15 days at 32°C. Male longevity does not differ significantly.

Notes: Abstract The parasitePteroptrix smithi (Compere) prefers to oviposit in hosts (Chrysomphalus aonidum L.) that are at least 5 weeks old. Parasitization of two week old hosts is possible, but only few parasites reach maturity, and the developmental duration is lengthened by about one third. The sex ratio with both large and small hosts was usually 1∶2, whereas the average number of emerging parasites varied from 1.9 for 2 week old hosts to 3–4 for 5 week old ones. Non-ovipositing scales that are attacked by the parasite will fail to reproduce and ovipositing ones will only produce part of their potential progeny. Other externally observable changes in the young parasitized host include the formation of a thinner scale cover that differs in coloration and size from the normal one.

Notes: Summary By using N15-labelled calcium nitrate and ammonium sulphate, the uptake of ammonia and nitrate by young Jonathan/MM104 apple trees grown in a glasshouse in water culture was determined. A batch of 4 trees was exposed to the appropriate tracer for seven days and then sampled. This procedure was repeated at 4 weekly intervals during a 12-month period. The results show that the uptake by apple trees of either ammonia or nitrate is continuous throughout the year with a relative high peak (expressed in µg N/100 mg dry weight) in December (summer period) and low values during August-September (winter period). The total uptake in the whole tree was steady for December to June inclusive and decreased from July, with the lowest uptake during August-September period. The young trees, previously receiving nitrogen as ammonium plus nitrate (1: 7), absorbed both ions in nearly equivalent amounts, except for the winter period when the uptake of ammonia was in excess of that for nitrate. This difference in uptake of both ions probably results from a lower activity of the enzymic nitrate reducing system during the time of low temperature. Low activity of the nitrate reductase enzyme results also in a restricted uptake of nitrate by apple trees previously receiving only ammonia nitrogen. A detailed analysis of total nitrogen content showed the lowest nitrogen values (0.77%) in February, near the end of the second growth period of the first year. From then on, the total nitrogen percentage of the apple trees steadily increased to reach a peak of 1.57% N during the flush of early spring growth of the second year. Leaves, fruit, soft twig growth, blossoms and roots had the highest N levels at this time. The total nitrogen percentage of the whole tree then gradually decreased. The established distribution pattern of absorbed nitrogen from both N15-labelled compounds showed that the relatively highest incorporation of absorbed nitrogen from both sources was in newly grown tissues during early spring growth flush of the second year, indicating the importance of currently absorbed nitrogen for early spring growth. With the increase in rate of growth in the later period, the value of the nitrogen stored within the apple trees became evident.

Notes: Summary Three slow-release nitrogen fertilizers — medium- and coarse-sized granules of IBDU (isobutylidene diurea) and formalized casein — were applied before sowing or transplanting to Sitka sprucePicea sitchensis, and their effects on growth compared with that on plots not given N or given four topdressings of ‘Nitro-Chalk’ (the source of N used in practice). The comparisons were made at two sites: a very sandy podsol and a sandy loam with better nutrient retention. The experiments with seedlings were continued for four years, those with transplants for three, and the same treatments were applied to the same plots each year. Responses to ‘Nitro-Chalk’ were large, especially during wet seasons. Formalized casein was always as effective as ‘Nitro-Chalk’ for transplants. IBDU (especially the coarse fraction) was almost as good as formalized casein for transplants at both sites and equalled it for seedlings on the sandy loam. For seedlings on the sandy podsol, both particle sizes of IBDU became steadily less effective in succeeding years, and no satisfactory reason can be offered for this decline.

Notes: Summary By using N15-labelled calcium nitrate and ammonium sulphate, the uptake of ammonia and nitrate by young Jonathan/MM104 apple trees grown in a glasshouse in water culture was determined. A batch of 4 trees was exposed to the appropriate tracer for seven days and then sampled. This procedure was repeated at 4 weekly intervals during a 12-month period. The results show that the uptake by apple trees of either ammonia or nitrate is continuous throughout the year with a relative high peak (expressed in µg N/100 mg dry weight) in December (summer period) and low values during August-September (winter period). The total uptake in the whole tree was steady for December to June inclusive and decreased from July, with the lowest uptake during August-September period. The young trees, previously receiving nitrogen as ammonium plus nitrate (1: 7), absorbed both ions in nearly equivalent amounts, except for the winter period when the uptake of ammonia was in excess of that for nitrate. This difference in uptake of both ions probably results from a lower activity of the enzymic nitrate reducing system during the time of low temperature. Low activity of the nitrate reductase enzyme results also in a restricted uptake of nitrate by apple trees previously receiving only ammonia nitrogen. A detailed analysis of total nitrogen content showed the lowest nitrogen values (0.77%) in February, near the end of the second growth period of the first year. From then on, the total nitrogen percentage of the apple trees steadily increased to reach a peak of 1.57% N during the flush of early spring growth of the second year. Leaves, fruit, soft twig growth, blossoms and roots had the highest N levels at this time. The total nitrogen percentage of the whole tree then gradually decreased. The established distribution pattern of absorbed nitrogen from both N15-labelled compounds showed that the relatively highest incorporation of absorbed nitrogen from both sources was in newly grown tissues during early spring growth flush of the second year, indicating the importance of currently absorbed nitrogen for early spring growth. With the increase in rate of growth in the later period, the value of the nitrogen stored within the apple trees became evident.

Notes: Summary A number of crosses were made between diploid and tetraploid Lolium perenne plants in order to determine the degree of cross compatibility between the two different ploidy levels. The range of hybridization undertaken involved diploidxdiploid, and tetraploid x tetraploid control crossings, diploid x tetraploid crosses, tetraploid x diploid crosses and mixed pollinations. The seed set, the germination capacity of resultant hybrid seeds, and the chromosome constitution of derived seedlings was determined. In addition attempts were made to culture 12 day-old hybrid embryos from the diploid x tetraploid and reciprocal crosses. The crossing results obtained indicated no barrier to fertilization between diploids and tetraploids, but the irregular and poor development of the seed accompanied by much reduced germination, indicated unsatisfactory endosperm establishment of large numbers of triploids, as confirmed by the result of culturing embryos dissected from 12-day old “seeds”. In preliminary studies undertaken to determine the extent to which diploid and tetraploid ryegrass varieties intercross when grown in close proximity for seed production, Griffiths and Pegler (1966) observed a very low incidence of triploids amongst the progenies of diploid plants exposed to the pollen of tetraploid plants and also amongst the progenies of tetraploid material exposed to the pollen of diploid plants. In these and subsequent studies it was noted that only a very small proportion of the so-called fully formed seeds derived from diploid x tetraploid crosses did actually germinate. When, in 1964, propagules of clones of S.24 perennial ryegrass, well separated from one another, were placed in drills of the tetraploid perennial ryegrass variety Reveille, the proportion of florets which formed caryopses, and of caryopses which germinated was as follows (Table 1). The data (Table 1) clearly indicate that a considerable proportion of the S.24 florets had been fertilized by 2n pollen and had formed caryopses, but most of these had proved to be defective. As noted in the previous studies, the frequency of triploid seedlings was low, thus suggesting incompatibility between the n and 2n gametes for the production of viable zygotes. Of the total progenies classed as tetraploids in the early seedling stage, 80% proved to be ryegrass x tall fescue F1 hybrids. These arose as a result of free crossing with

Notes: Summary Three slow-release nitrogen fertilizers — medium- and coarse-sized granules of IBDU (isobutylidene diurea) and formalized casein — were applied before sowing or transplanting to Sitka sprucePicea sitchensis, and their effects on growth compared with that on plots not given N or given four topdressings of ‘Nitro-Chalk’ (the source of N used in practice). The comparisons were made at two sites: a very sandy podsol and a sandy loam with better nutrient retention. The experiments with seedlings were continued for four years, those with transplants for three, and the same treatments were applied to the same plots each year. Responses to ‘Nitro-Chalk’ were large, especially during wet seasons. Formalized casein was always as effective as ‘Nitro-Chalk’ for transplants. IBDU (especially the coarse fraction) was almost as good as formalized casein for transplants at both sites and equalled it for seedlings on the sandy loam. For seedlings on the sandy podsol, both particle sizes of IBDU became steadily less effective in succeeding years, and no satisfactory reason can be offered for this decline.