P. J. Salter

Studies on crop maturity in cauliflower: III. Effects of cold treatment and certain growth regulators on crop maturity characteristics and yield

SummaryStudies were made to determine the influence of cold treatment of transplants on the maturity characteristics of representative varieties of three groups of autumn cauliflower over a period of three years. Treatment variables included store temperatures of 2 °C and 5 °C, length of treatment from 0 to 4 weeks, different transplant ages, and selection for uniformity of the plants before treatment. In separate experiments the effects of chemical growth regulators on the maturity characteristics of the same varieties were also assessed.When the cold treatment was given at the optimum stage of growth, which varied with varieties, the crops matured much more uniformly than crops grown from untreated plants in all three years with the four varieties grown. A cold treatment of 2 weeks at 2 °C had the maximum effect in reducing the length of the harvest period on the majority of occasions. For example, in 1970 the harvest period was reduced from 24 days (control) to 4 days for Le Cerf ‘B’, from 26 to 7 days...

Analysis of the Growth and Yield of Overwintered Onions

SummaryThe growth of a number of onion cultivars sown on different dates during late summer in several years was assessed by regular sampling. The growth during the winter of five different winter-hardy cultivars was very similar, whereas that of Rijnsburger Bola, a cultivar normally sown in spring, was clearly slower. Sowing date was shown to affect final yield through its effect on overwintering size, which in turn influenced bulb size at harvest, the proportion of plants which bolted and the extent of winter losses. During the winter months the rate of leaf initiation appeared to be decreased to a lesser extent than the growth in dry weight, which itself was decreased less than growth in leaf area. The growth of the winter-hardy cultivars from all sowing dates and seasons was well summarized by a single linear relationship between the logarithm of plant dry weight and the accumulated day-degrees between 6° and 20°C from the day of seedling emergence. Using this relationship together with temperature re...

Studies on crop maturity in cauliflower: II. Effects of cultural factors on the maturity characteristics of a cauliflower crop

SummaryThe effects of six cultural treatments on (a), the time of 50% crop maturity and (b), the duration of the maturity period, were studied on representative varieties of three groups of autumn ...

The effects of plant density, spatial arrangement and sowing date on yield and head characteristics of a new form of broccoli

SummaryThree systematic fan designs were used at each of three sowings of a new form of terminal-headed broccoli, made in late March, early May and early July; two provided densities in the range 2-100 plants m-2 in 20 logarithmic intervals with fixed rectangularities of 1:1 and 6:1 respectively, and the third provided rectangularities between 1:1 and 6:1 at a constant density of 20 plants m-2. Individual heads were harvested when mature and the mean harvest dates for the three sowings were 25 June, 22 July and 29 September. Maximum fresh weight yields of trimmed heads were 2.16, 2.01 and 1.75 kg m-2 from sowings 1 to 3, and maximum yields were always obtained from the plots with a square (1:1) planting arrangement. The relationship between yield and density was generally asymptotic, yield being relatively insensitive to density above 20 plants m-2 but mean head size decreasing with increasing density. With all sowings the proportion of purple:green heads also decreased with increasing density. Yield, mat...

Further Studies on the Effects of Cold Treatment of Transplants on Crop Maturity Characteristics of Cauliflower

SummaryStudies were made to determine some of the factors which could modify the influence of a cold treatment of transplants on the maturity characteristics of three autumn cauliflower varieties. These included controllable experimental variables and uncontrollable environmental factors some of which were investigated by multiple regression techniques.Results from the four experiments indicated that while the cold treatment considerably shortened the harvest period of the majority of the crops grown, the magnitude of the response of individual crops was affected by the temperature conditions under which the plants were raised and also, on some occasions, by temperature conditions prevailing just after planting and at harvest. There were varietal differences in responsiveness to the cold treatments. Selection for uniformity of transplant growth stage did not increase the cold treatment effect. It is suggested that plant-to-plant variation in low temperature requirement for curd induction may be a factor c...

Hormonal Changes in the Stem Apex of the Cauliflower Plant in Relation to Curd Development

SummaryThe correlation between curd development and changes in endogenous hormones in the stem apex of cauliflower plants was investigated. In particular, plants raised normally were compared with equivalent plants given a 2-week cold treatment when 6 weeks old. Hormones were extracted and assayed from the two groups of plants from the time of seedling emergence until they were 10 weeks old. Hormone activity was high in the young seedlings but gradually decreased with age. Gibberellin activity increased in the apices after 6 weeks, with a further peak after 9 weeks, at which time the morphological changes associated with curd development were detected in a small proportion of the apices sampled from untreated plants. Both gibberellin peaks were enhanced by cold treatment. An increase in auxin activity was apparent in cold-treated plants, concurrent with the first gibberellin peak, but cytokinin activity was reduced by cold treatment. The physiological implications of these results are discussed.

Comparative Studies of Different Production Systems for Early Crops of Bulb Onions

SummarySeven experiments were carried out over a period of three years to compare 10 different systems of producing early crops of bulb onions during the period from June to August. The methods involved cultivars with daylength requirements for bulbing ranging from 11.5 to 16.0 h and the use of seed, transplants and sets, drilled and planted at different times of the year. For UK conditions, drilling the recently introduced, winter-hardy, intermediate daylength cultivars in late summer was the most reliable way of obtaining good yields of bulbs from early June to late July. Transplanting plants of the same cultivars raised in heat in the spring also gave high yields in July. The advantages and disadvantages of the various production systems are discussed and it is concluded that with the combined use of two or three of these methods of production together with storage facilities, a supply of onions can be maintained throughout the year.

The effects of plant spacing on the breeding of broccoli from an expanded genetic base

SummaryA population was constructed from a broad genetic base in order to breed new forms of green-heading broccoli and was selected and recombined over several generations. Sub-populations were selected from the F2, F3 and F4. Five sub-populations were grown at five spacings (15 × 15 to 75 × 75 cm) in a field experiment to assess both the effects of spacing on characters which would be the subject of further selection, and progress in the breeding programme. Most characters affecting quality were unaffected by spacing. Characters affecting yield showed linear and quadratic responses to spacing, emphasizing the importance of equal spacing between plants in selection plots. Some yield characters showed linear differences between the responses of sub-populations to spacing, showing that cultivars might be bred which were adapted to particular spacings. Genetic correlations between characters were generally advantageous. There were improvements in quality between the F2 and F4, but yield had decreased, proba...

A comparison of the effects of regular versus random within-row spacing on the yield and uniformity of size of spring-sown bulb onions.

SummaryExperiments on spring-sown bulb onions grown from seeds and from sets at densities near to the optimum for ware bulb production showed there was no advantage in terms of yield or uniformity of bulb size from having plants spaced regularly rather than at random within the rows.

The effects of cultural factors on yield and curd quality of autumn cauliflower

SummaryThe effects of six cultural treatments on (a) marketable yield, (b) percentage marketable plants and (c) percentage perfect quality curds produced, were studied on representative varieties of three groups of autumn cauliflower in experiments carried out over a period of five years. The treatments included a comparison of the use of graded and ungraded seed, transplanting and direct-drilling of the crop, different transplant ages, selection for uniformity at planting or thinning time, and plant density and nitrogen levels during the early seedling stage of growth.In general the yields and quality of drilled and transplanted crops were similar with all varieties each year and neither the use of graded seed nor the nitrogen treatments had any significant effect on yield or curd quality. Both increasing plant density in the seedbed and increasing age of transplant caused a reduction in yield on most occasions. The effects of the treatments on yield and quality are discussed in relation to their effects...