Field Trials of,Dichloro-Diphenyl-Trichloroethane (D.D.T.) Against the Raspberry Beetle (Byturus Tomentosus Fabr.)

Summary

Crops of early leek cv. Prelina were grown in four experiments at Wellesbourne and in Cornwall from 1995 to 1997. Treatments applied included time of sowing, plant raising temperature, transplant type and covering regime. There was no effect of plant raising temperature on marketable yield or on the percentage of flowering plants. It is suggested that with cv. Prelina it is particularly the conditions during early field growth that affect the ability to flower. Larger plants at transplanting, resulting from earlier sowing or the use of peat blocks, increased the percentage of flowering plants but effects of fleece cover were variable, depending upon how close temperatures were to the optimum for vernalization, which was shown to be close to 78C. It is suggested that rather than planting early, with subsequent air temperatures near to the optimum for vernalization, which will result in high levels of bolters, it would be better to delay transplanting. Plants can then be maintained at a raising temperature that is higher than the optimum for vernalization and transplanted when there is a strong probability of air temperatures being higher. Simple models have been developed to predict first, the rate of increase of leek diameter and secondly, the rate of flower stalk extension, so that it will be possible to predict when the crop will be large enough to harvest and when flowering stalks will become unacceptably long.     

Establishment and growth of the rhizome of Alstroemeria as affected by temperature and the root system

The effects of temperature and the root system on growth and establishment were assessed for rhizomes of three Alstroemeria cultivars.-The numbers of lateral rhizomes, aerial shoots and tubers produced by rhizome ‘splits’ were not significantly affected by increase in temperature in the range of 8 to 18°C. Significant increases in root system and rhizome dry weight were seen for cv. Butterfly and in aerial shoot dry weight for all three cultivars used. Increasing temperature significantly decreased the number of plants establishing from rhizome ‘splits’ obtained from plants grown in glasshouse soil. For maximum rhizome production a temperature of between 13 and 18°C was found to be required. A second experiment employing rhizome ‘splits’ from container-grown plants showed no effect of temperature on plant establishment. The presence or absence of the rootsystem on the ‘splits’ at planting was found to be important in plant establishment, with removal of the root system producing a significant decrease in the number of plants establishing. It is suggested that the rootsystem, and damage sustained by it prior to planting, are more important than temperature for the successful establishment of plants of Alstroemeria.     

Flowering,vegetative growth and mineral nutrition of pot chrysanthemums in sawdust and peat-life media

Plants of Chrysanthemum morifolium Ramat ‘Mountain Peak’, ‘Goldstar’ and ‘Cir Bronze’ were grown in sawdust, sawdust mixed with Ca(NO₃)₂ 7 weeks before planting and held at 20°C (unheated), or at 43°C (heated), and in a sphagnum-peat/vermiculite mix (peat-lite). C:N ratios for the sawdust media at planting were 265.9, 125.7 and 123.3, respectively. Plants grown in each medium received nutrient irrigation containing macro- and microelements, with N at 150, 200 or 250 mg l^?1.Days to full flower development, and flower diameter at harvest were not influenced by medium or irrigation N concentration. Plants grown in peat-lite produced the thickest and longest stems, although the stature of plants in all media was judged to be commercially acceptable. Plants grown in unheated sawdust pre-mixed with Ca(NO₃)₂ produced the thinnest and shortest stems.Leaf concentrations of N, P, K and Mg at harvest were highest in plants grown in peat-lite. Accumulation of Ca, B, Fe, Mn, Cu and Zn was more variable. With the exception of P, foliar nutrient concentrations in all plants were optimal or above published optimal ranges. The onset of flower senescence occurred an average of 1 day earlier in sawdust-grown plants.     

Post-Harvest Studies on Autumn-Drilled Bulb Onions. The Effect of Harvest Date,Conditioning Treatments and Field Drying on Skin Quality and on Storage Performance

Overwintered onion cvs Express Yellow and Senshyu Semi-globe Yellow were harvested at 80% foliar fall-over (early June) and two and four weeks later, in 1975 and 1976. Plants were conditioned for one (1975) or two weeks (1976) at 20°C, 70% RH or 30°C,60% RH or field dried, and then stored at ambient temperature. Measurements of fresh weight loss during the first six weeks after harvest in 1976 indicated that drying was slow and was incomplete after 14 days conditioning at 30°C. Skin staining and splitting generally increased with delay in harvest date. Skin colour improved with delay in harvest date and with conditioning at 20°C. Wastage due to both rotting and sprouting during storage was generally lower when plants from the first two harvest dates were conditioned at 30°C. These bulbs are likely to be useful for long-term storage as total wastage levels of only 20% were reached in both cultivars after 3-5 months storage. Good field drying of the bulbs could not be consistently obtained and consequently storage performance was more variable than for bulbs conditioned at 20 °C and 30 °C before storage.     

The effect of day and night temperatures on the growth,development and yield of glasshouse cucumbers

The responses of January-sown cucumber cvs Farbio and Sandra to day and night temperature during the early post-planting stage (late February to mid-April) were examined in a glasshouse experiment. Three day temperatures (15°, 20° and 25°C) were combined factorially with three night temperatures (10°, 15° and 20°C). Comparisons were also made between two temperature regimes (21°C day: 19°C night and 24°C day: 17°C night) applied during the pre-planting stage (late January to late February) and between two mainstem cropping methods (restriction or retention of mainstem fruits). In the pre-planting stage the 24°C day: 17°C night temperature combination produced plants which were taller, heavier and leafier than those grown at 21°C day: 19°C night. During the first 12 weeks of harvesting the larger plants produced significantly more fruit and higher gross monetary returns than did their smaller counterparts. The difference then diminished and after 20 weeks of harvesting plants from the two pre-planting temperature treatments had produced similar weights of marketable fruit of equivalent value. In the early post-planting period increases in total leaf area and stem length were closely correlated with 24-h mean temperature. Earliness (first harvest) and total weight of fruit after four weeks of harvesting were also linearly related to mean post-planting temperature. Raising the 24-h mean air temperature (within the range 15.2° to 22.6°C) by 1°C during the early post-planting stage increased early (4 week) yield by 0.82 kg m^-2 and total (20 week) yield by 1.17 kg m^-2. There was no effect of day/night temperature amplitude. After 20 weeks of harvest, gross monetary returns and profitability were generally highest when mean temperature in the early post-planting period was high and fell progressively with reduced mean temperature. Restricting stem fruits to oné per leaf node produced no significant difference in either the yield or quality of fruit from plants of any of the temperature treatments. The results are discussed from physiological and practical viewpoints and a cost-benefit comparison of temperature treatments is presented.     

An analysis of the growth of forced tulips. 1. Changes in plant fresh and dry weights during growth at two temperatures

Changes in the fresh and dry weights of the component parts of plants of tulip cv. ‘Apeldoorn’ were followed in bulbs kept at low and high temperatures (9 and 18°C respectively) from the time of completion of flower differentiation until anthesis.There were marked differences between shoot dry weights at the two temperatures. At 9°C the stem, leaves and flower grew exponentially throughout the whole period, but at 18°C the specific growth rate of the stem and leaves declined throughout the period of the experiment. At 9°C the proportion of total dry weight in shoots and daughter bulbs was higher than at 18°C, and the proportion in the mother bulb was correspondingly smaller.At both temperatures the $\text{fresh weight}\text{dry weight}$ ratios of the mother bulb, shoot and daughter bulbs declined during dry storage, the decline being greater at 9°C. After planting, the ratio for all plant parts increased at 9°C, but scarcely changed at 18°C.These results are discussed in relation to dormancy, to the low-temperature requirement for successful and rapid flowering and to flower quality.     

Leaf production and curd initiation of winter cauliflower in response to temperature

Summary

In experiments in 1994 and 1995 a range of transplanting dates and thermal crop covering treatments were used to produce different environmental conditions for the growth of two Roscoff cauliflower selections ‘December/January’ and ‘March’. In 1994 non-covered plants of ‘March’ initiated on average 19 d later and with 19 leaves more than ‘December/January’. In the two seasons, covering the crops gave delays in curd initiation of up to 93 d, depending on planting date, and increased the number of leaves produced by up to 50 compared with non-covered crops. Leaf production was best described by an accumulated effective day-degree scale using day-degrees <17°C for ‘December/ January’ and day-degrees <16°C for ‘March’. This shows that both light and temperature are concerned with controlling leaf production. During the juvenile phase of growth, apex diameters expanded linearly with temperature up to a diameter of about 0.2 mm. After this there was a different response to temperature suggesting that a phase change had occurred at an apex diameter of 0.2 mm. When this occurred numbers of leaves ranged from 23 to 28. Vernalization appeared to occur most rapidly in ‘December/January’ between 12 and 16°C with an optimum at about 14°C while in ‘March’ the optimum appeared to be slightly lower than this. Any increase in time spent at temperatures in excess of 16°C delayed curd initiation.     

The Field Performance of Cold-Stored Strawberry Runners in South-East England

After 4-5 months’ storage at 30° F. (-1° C.), runners of Redgauntlet and Cambridge Favourite strawberries established well when planted in June or July. In contrast to freshly lifted runners, stored plants runnered fairly freely in the year of planting and grew with an erect habit. In the year after planting, plant habit was normal but more stolons were produced early in the season.

Deblossoming cold-stored runners after planting, though not necessary for satisfactory establishment, increased the subsequent yield. Cold-stored runners planted in late July and deblossomed in August cropped well in the following year, the total crop and in particular the yield of large fruit (> ? in. diameter) being similar in amount to that from fresh runners planted in early August. The weight of early fruit harvested from Redgauntlet was appreciably greater from cold-stored than from early-planted fresh runners, but stored runners of Cambridge Favourite showed no gain in earliness. It is concluded that stored runners may satisfactorily be used as a substitute for fresh ones to obtain the recognized advantages of early planting.

Cold-stored Redgauntlet runners planted in June ripened a small crop of fruit in August. Reducing the inter-plant spacing from 18 in. to 9 in. doubled the initial yield and also increased the total amount of fruit harvested in the two succeeding years without lessening the quantity of large fruit.     

Flowering performance and yield of established and recent strawberry cultivars (Fragaria × ananassa) as affected by raising temperature and photoperiod

Plants of six strawberry cultivars were raised under controlled conditions and tested for flowering and yield potential. Short days (SD) at intermediate temperatures for 4 weeks in August induced profuse flowering in subsequent long days (LD) in all cultivars except the late-flowering ‘Malwina’. LD conditions induced flowering only in ‘Nobel’, which has an everbearing parent. ‘Nobel’ and ‘Saga’ exhibited broad temperature adaptation for SD floral induction, which was generally reduced or suppressed at 9 and 27°C. After autumn planting, all cultivars flowered most abundantly in plants raised in SD and intermediate temperatures. Flowering was earliest in ‘Nobel’ and ‘Rumba’. Plants that did not reach floral commitment after 4 weeks in SD continued and completed induction under subsequent natural SD conditions after planting in the field, demonstrating the capability of fractional induction. Berry yield varied in parallel with flowering in the field and was always higher in plants raised under SD conditions. The traditional cultivars ‘Florence’ and ‘Sonata’ out-yielded the more recent cultivars. Some cultivars lost more than two thirds of their initiated flowers during the winter with obvious consequences for their yields. With proper raising management, acceptable yields were obtained after autumn planting even in a cool Nordic climate.     

The effect of thermal environment,planting date and crown size on growth,development and yield of Fragaria × ananassa Duch. cv. Elsanta

Summary

The effects of environmental conditions, planting date and crown size on the timing, intensity and duration of cropping in the strawberry Fragaria × ananassa cv. Elsanta were investigated. Temperature was positively correlated with the rate of progress to fruiting whereas crown size had no effect. The first fruit reached harvest maturity after an estimated 891 day-degrees had elapsed above a base temperature of 2.9°C for waiting bed plants and 831 day-degrees above a base temperature of 2.4°C for cold stored plants. Temperature was negatively correlated with total yield, berry number and average berry weight for both waiting bed and cold stored plants of different crown sizes. Yield, berry number and average berry weight were positively correlated with crown size. The effect of temperature on the yield components appeared to be due to its effect on vegetative growth of the plants: canopy development was more limited at warmer temperatures. These results can be used to generate models to predict the effect of growth environment on cropping in strawberry.     

Root damage affects nitrogen uptake and growth of young Fuji/M.26 apple trees

Summary

Effects of root damage during the transplant process on growth and nitrogen (N) uptake were studied with one-year-old bench-grafted Malus domestica Borkh ‘Fuji’ on M.26 rootstock apple nursery plants. Plants were potted after grafting and grown outside for one season. At the end of the season uniform trees were selected and randomly divided into four groups. One group of plants were moved into a 2°C cold room with soil and container intact (IR Treatment). Plants in other groups were removed from pots and stored as bareroot in the same cold room for three months. In the spring, bareroot plants were either: (1) transplanted with about 10% of the root system damaged during transplant (TP Treatment and Control-CK); or (2) root pruned by 25% (by volume) prior to transplant (RP treatment). Five trees from each treatment received 1 g of ¹⁵NH₄¹⁵NO₃ at 12, 41 and 76 d after repotting. Control (CK) trees received no N. Trees were harvested 10 d after each N application, and plant growth and total N and ¹⁵N content of different tissues were determined. Root pruning reduced plant total biomass and root biomass at the first two harvests, but the plants from the RP treatment had highest total plant biomass and root biomass at the third harvest. There was no significant difference in the new stem and leaf growth among IR, RP and CK treatments at harvests but the TP treatment reduced new shoot biomass. Plants with intact roots (IR) had the higher total N content while control plants (CK) had the lowest. Root pruning reduced ¹⁵N uptake rate at the first two harvests but promoted it at the third harvest. Our results suggest that plant growth and nutrient uptake was suppressed by root pruning/damage during transplanting only in the early season, and the negative effects on growth and N uptake were offset later in the season by compensative root regeneration.     

鲜干兼用辣椒新品种‘赣丰辣线101’

‘赣丰辣线101’是鲜干兼用型辣椒一代杂种。生长势中等,株型紧凑,早熟,从定植至采收青椒约45d。果实羊角形,味辛辣,青熟果深绿色,生物学成熟果鲜红色;果实纵径19.5cm,横径1.4cm,肉厚0.1cm,平均单果质量15.1g,维生素C含量1.25mg·g-1,干物质含量12.0%。鲜椒产量30.0～37.5t·hm-2,干椒产量4.6t·hm-2以上。抗病耐热,适于长江流域地区春季早熟栽培。     

Long-day control of flowering in everbearing strawberries

Summary

Photoperiod and temperature control of flowering in a number of perpetual-flowering or everbearing strawberry cultivars of widely varying pedigree has been studied in controlled environments. Flower bud initiation in the cultivars ‘Flamenco’, ‘Ridder’, ‘Rita’ and ‘Rondo’ was significantly advanced by long-day (LD) conditions at temperatures of 15°C and 21ºC; while, at 27ºC, flowering took place under LD conditions only. Some plants of the seed-propagated F₁-hybrid ‘Elan’, raised at 21°C, also flowered under short-day (SD) conditions at 27°C, but reverted to the vegetative state after a few weeks when maintained under these conditions. When vegetative plants growing in SD at 27°C were transferred to LD conditions at the same temperature, they consistently initiated flower buds and started flowering after about 4 weeks. At such a high temperature, flowering could thus be turned on and off by switching between SD and LD conditions. This applied to all the cultivars studied. Also the cultivar ‘Everest’, which was tested only at 21°C, produced similar results. Night interruption for 2 h was effective in bringing about the LD response. At 9°C, flowering was substantially delayed, especially in ‘Flamenco’ and, at this temperature, flowering was unaffected by photoperiod. Runner formation was generally promoted by high temperature and SD conditions, but the photoperiodic effect varied between experiments. We conclude that everbearing strawberry cultivars, in general, whether of the older European-type or the modern Californian-type originating from crosses with selections of Fragaria virginiana ssp. glauca, are qualitative (obligatory) LD plants at high temperature (27°C), and quantitative LD plants at intermediate temperatures. Only at temperatures below 10°C are these cultivars day-neutral.     

Response of the chrysanthemum to soil heating

Chrysanthemum plants were exposed to 16°C day-temperature, 11°C night-temperature, 13°C soil-temperature, to be indicated as 16/11/13°C, or to 16/11/25°C, 20/16/18°C, or 20/16/25°C, first long day, then short day, (long day = 12-h light period with 3-h night break; short day = 12-h light period) from planting to harvest in controlled environments to study the effects of soil heating on growth and flowering. There were significant, but not substantial, effects of soil heating on leaf area, percent soluble carbohydrate, flower bud diameter, days to visible bud and some other parameters. Two winter cultivars responded similarly, while 2 summer cultivars differed in flowering-response to soil heating. An experiment was also conducted using 16/11/25°C day/night/soil temperatures during long days, short days or throughout the complete growth cycle, with 16/11/13°C day/night/soil temperatures at other times. Soil heating during long days resulted in the highest quality flowers. Soil heating during short days or throughout the growth period resulted in most rapid flowering but decreased flower quality.     

Leatheriness and mealiness of peaches in relation to fruit maturity and storage temperature

Summary

`Huangjin' peaches (Prunus persica Batsch) were harvested at commercial harvest time (commercial) and 20 d before (early) or after (later) commercial harvest. Fruit from each harvest were stored at three temperature regimes (0, 5 and 10°C) at 95% r.h. After four weeks of storage at 0 or 5°C, early harvested fruit developed more leatheriness but less mealiness and later harvested fruit did not develop leatheriness but developed more mealiness comparedwith fruit from commercial harvest. Overall, fruit stored at 5°C developed more mealiness but less leatheriness than fruitat 0°C for the same period of storage. When stored at 10°C for two weeks, after which fruit were senescent, fruit did not develop any leatheriness or mealiness regardless of harvest times. Fruit with leatheriness were firmer (>30 N) thanjuicy or mealy fruit (<10 N) after the same period of cold storage and 4 d at 20°C. Mealy fruit were as soft as juicy fruit. 1-Aminocyclopropane-1-carboxylate oxidase (ACO) activity, 1-aminocyclopropane-1-carboxylic acid (ACC) content, and polygalacturonase (PG) and galactosidase (GAL) activities were lower, and insoluble pectin content was higher in leathery fruit than that in juicy or mealy fruit. ACO, PG and GAL activity, ACC, and insoluble pectin content were similar between mealy and juicy fruit.     

Effect of temperature on dormancy in strawberry

Early in autumn, at the end of September or at the beginning of October, strawberry plants of the cultivars ‘Glasa’ and ‘Tioga’ were transferred from outdoors to separate phytotron glasshouses at constant temperatures of 10° and 14°C. In November a number of these plants were chilled at 3°C for 0 to 4 weeks and subsequently forced; the rest remained at 10° and 14°C until June.The plants kept at 10°C and subsequently chilled and forced, grew faster and more vigorously than those pretreated at 14°C. The 14° plants showed more pronounced growth differences resulting from the length of the chilling treatments than did the 10° plants. Those remaining continuously at 10° developed vigorously from March onwards, while those at 14°C retained their flat appearance into June. These results showed that a continuous temperature as high as 10°C was still able to break dormancy in the strawberry plants, while 14°C was ineffective.     

Early leaf harvest reduces yield but not protein concentration of cowpea seeds

Five greenhouse-grown cowpea [Vigna unguiculata (L.) Walp] cultivars were tested in a generalized random complete-block design to determine the effect of early leaf harvest on dry weight and protein concentration of plant parts at maturity. The most recent, fully expanded leaves on each branch from one group of plants were harvested at 5 and 7 weeks after planting. On the other groups of plants, no early leaf harvest was performed. Dry weight and protein concentration (dry weight basis) were determined for leaves, stems, and seeds at maturity and for leaves harvested early. Weight and protein concentration of seeds, leaves, and stems differed significantly between cultivars; protein concentration of leaves harvested at 5 or 7 weeks did not. Dry weight of leaves harvested at 5 vs. 7 weeks did not differ significantly, but leaf protein concentration was significantly higher at 5 weeks compared to 7 weeks. Across all cultivars, early leaf harvest had no significant effect on leaf or stem weight per plant at maturity. However, there was a significant decrease in seed weight when leaves were harvested early. Results suggest that even limited leaf harvest at 5 and 7 weeks has detrimental effects on yield, but not on protein concentration, of cowpea seeds harvested at maturity.     

The effects of daminozide and under-soil heating on the growth of radish under winter conditions

The growth of radish cultivars ‘Saxa’, ‘Saxerre’, ‘Serra’, ‘Istar’, ‘Cherrybelle’ and ‘Robino’ was compared at 7 and 12°C under winter glasshouse conditions. ‘Serra’ alone produced marketable storage roots by 63 days at 7°C, but root weight was no greater at 12 than at 7°C; only ‘Robino’ produced significantly larger roots at the higher temperature. Under-soil heating applied to ‘Cherrybelle’ and ‘Robino’ grown at an air temperature of 7°C increased root growth, particularly in ‘Cherrybelle’. Daminozide treatment at 7°C increased total and storage root weight and root:shoot ratio of both cultivars. At 12°C, the only significant effect of daminozide treatment was reduced shoot weight in ‘Robino’.     

Growth responses of some greenhouse plants to environment. II. The effect of soil temperature on Chrysanthemum morifolium Ramat

The effect of a wide range of soil temperatures (6–26°C) on growth and flowering of Chrysanthemum morifolium Ram. ‘Horim’ were studied at the favourable air temperature of 18°C. Shoot growth was severely reduced at soil temperatures below 10°C which may be explained by poor root growth, while flowering was enhanced by approximately 2 days compared to higher soil temperatures. Increasing the soil temperature to 18°C was beneficial. Further increase had no positive effect on growth. Measurements of net photosynthetic rates revealed no effect of lowering soil temperatures from 18 to 6°C.Mother plants grown at 18°C air temperature revealed no effect of soil temperatures ranging from 13 to 21°C on number and fresh weight of the cuttings. Neither did mother plants grown at the less favourable air temperatures of 12 or 15°C. Cutting production was, however, affected by air temperature.     

Flushing and Leaf Growth of Cacao Under Controlled Temperature Conditions

Young clonal cacao trees have been grown for nine months in controlled- environment rooms at 74° F.,80°F. or 86° F. (23·3° C., 26·7° C., or 30·0° C.), or at one of these temperatures during the day and another during the night.

No specific temperature requirements for leaf flushing, which occurred in all the treatments, were found. Flushing was considerably greater at the higher temperatures, partly as a result of the loss of apical dominance, and was especially sensitive to day temperature.

The number of expanded leaves per flush and mean area per leaf increased with a decrease in day or night temperature, as did the duration of the leaves on the trees. The biggest net leaf area increases were made by plants given a day at 80° F. and a night at either 80° F. or 74° F. A night temperature of 86° F. resulted in a rapid turn-over of small unhealthy leaves having a low chlorophyll content.

The gain in total plant dry weight was greatest at a night temperature of 74° F., smallest at a night temperature of 86° F., and the plants which maintained the greatest leaf areas also gained the most dry weight. Leaf dry weight per unit leaf area was greatest at the lowest temperatures, as was the ratio of total plant dry weight to leaf area. The ratio of leaf weight to plant weight showed a small but significant increase with increase in day temperature.