James G. Carew

The control of the annual growth cycle in raspberry.

Summary The Brassicaceae (syn. Cruciferae) is an economically important botanical family providing a diverse range of foliar, root and seed crops for both human and domesticated animal consumption. However, in common with other plant species the Brassicacae have been endowed with the capacity to synthesize a range of antinutritional compounds, the most important of which are the glucosinolates, S-methylcysteine sulfoxide, tannins and erucic acid. In this review the adverse and possible beneficial effects of the inclusion of these compounds in human and animal diets are reviewed together with their chemistry, biosynthesis and methods for their analysis.

The effect of chilling and post-chilling temperatures on growth and flowering of sweet cherry (Prunus avium L.).

Summary The effects of chilling duration (0-1440 h) and post-chilling temperatures (9°C, 19°C and 25°C) on flowering and vegetative growth were examined in Prunus avium L. cv. Stella. Increased chilling caused an increase in the number of branches, leaf fresh and dry weights and reduced the time to bud break. Flower size and pedicel length also increased with increasing chilling duration. However, vegetative growth and flower size and pedicel length tended to decrease with an increase in post-chilling temperature. The proportion of fruit set was greater after longer chilling durations whilst higher post-chilling temperature reduced the proportion of fruit set.

Far-red light filtering by plastic film, greenhouse-cladding materials: effects on growth and flowering in Petunia and Impatiens

Summary Photoselective plastic films with low transmission to far-red (FR) light (700–800 nm) are now available so that plants grown in greenhouses clad with such plastics exhibit reduced stem extension and, consequently, plant height. Here we compare the action of three FR-absorbing polythene films on extension growth of Petunia (Petunia hybrida) cv. ‘Express Blue’ and Impatiens walleriana cv. ‘Accent Deep Pink’ with plants grown under a control polythene film (standard UVI/EVA film). Half of the plants under the control film were treated with a chemical plant growth regulator (PGR; diaminozide, B-Nine) and half were sprayed with water alone. Possible negative effects of such film plastics on flowering, and on fresh and dry weight accumulation, were also quantified. Plants were harvested destructively when all plants in each treatment had reached the first open flower stage. In Petunia, plant height was reduced by all three FR-filtering films and by PGR-treatment. The FR-filtering films giving the highest R:FR ratios also reduced plant height in Impatiens. Leaf number, leaf area and total dry weight in both species were greatest in the controls and smallest under films with the lowest PAR transmission. The film giving the highest R:FR ratio and PAR transmission also produced the most compact Petunia plants; while the film with the lowest PAR transmission produced the least compact plants in both species. There was no significant effect of treatments on time to first flower in Impatiens. However, Petunia plants under low PAR transmission films took longer to flower. Plastic films which filter out FR light to increase the R:FR ratio, combined with high PAR transmission, can therefore be used as an alternative to conventional PGRs.

Chill unit models for the sweet cherry cvs Stella, Sunburst and Summit

Summary Bud break of one year old cut shoots of sweet cherry cvs Stella, Summit and Sunburst was recorded to quantify the effect of chilling on dormancy release. Chilling was applied in the dark at constant temperatures of ‒1.2°C, 3.8°C, 6.8°C, 9.4°C, 11.9°C and 15.4°C (± 0.5°C) for 0,168, 336, 504, 672, 840, 1008, 1176 and 1334 h. Multiple regression analysis showed that at temperatures of ‒1.2°C, 3.8°C, 6.8°C, 9.4°C the proportion of bud break increased through successive chilling durations, up to approximately 1000 h of chilling. However, chilling for more than this duration reduced the percentage bud break. The control treatment (no chilling), chilling for 168 h and chilling at average temperatures of 11.9°C or 15.4°C did not break dormancy. The data collected were used to develop a chill unit model which predicted that chilling temperatures of 3.2°C, 3.2°C and 3.7°C were optimum for cvs Stella, Summit and Sunburst respectively. The chilling requirements for these cultivars were estimated to be saturated after 1131,1081 and 1214 hours respectively.

The effects of low temperatures on the vegetative growth and flowering of the primocane fruiting raspberry ‘Autumn Bliss’

Summary The effects of low temperatures on subsequent vegetative growth and flowering in the raspberry ‘AutumnBliss’ were investigated. In the first experiment, a number of lifting dates were used to determine the seasonal pattern of dormancy and the effect of natural chilling on plant development. In the second, different durations of artificial chilling(0, 2, 4, 6, 8 and 10 weeks at 0˚C) were combined with two lifting dates to investigate the effect of natural and artificial chilling. In these experiments, plants which received little chilling grew slowly and failed to develop beyond short rosettes of leaves but as chilling increased, the rate of vegetative growth increased. This coincided with a decline in the time toflowering. These two responses, however, were distinct. In a third experiment, the effect of vernalization of actively growing canes was tested in an attempt to separate the effects of cold on time to flowering, and on the removalof dormancy. The plants responded significantly to cold treatment and flowering was advanced, indicating a distinct vernalizing effect

Effect of plant density and initial crown size on growth, development and yield in strawberry cultivars Elsanta and Bolero

Summary The effects of density (plant spacing) and initial plant size on vegetative growth, flowering and fruiting were studied in the strawberry cultivars Elsanta and Bolero in their first and second years of cropping. The influence of these factors on light use and dry-matter partitioning was investigated. The size of planting material in ‘Elsanta’ and ‘Bolero’ slightly affected plant growth and yield, but this effect was not consistent and radiation use efficiency (RUE) and harvest index were unaltered. Plant spacing did not significantly affect the early stages of crop growth, but was important in determining growth and yield later in the season, this effect being more significant in the second year of cropping. Plant growth and yield per plant increased as plant spacing increased from 20 to 30 cm in both ‘Elsanta’ and ‘Bolero’, but the highest harvest index and yield per square metre were obtained at the closest spacing. Increased plant spacing also resulted in a greater leaf area and leaf area index. However, light was used less efficiently resulting in a lower RUE and lower harvest index (HI).

Techniques for manipulation of the annual growth cycle in raspberry

I n the accompanying paper we described how the growth cycles of biennial and primocane fruiting raspberry cultivars are controlled by the environment, the genotype and cultural practices (Carew et al., 2000). For plants to fruit outside their normal season, these growth cycles need to be manipulated and optimized for fruit production at speci®c times of the year. Techniques to achieve this are discussed in this paper and areas are identi®ed which are less well understood and in need of further investigation. Raspberries can be produced under protection to exploit the high prices of an early or late season, fresh market crop; during week 21 in 1998 prices were as much as four times greater than during the main cropping season (week 26 onwards) (Figure 1). Despite this, it is estimated that in 1997, of the 1280 ha of raspberries grown in the UK, just 3% were protected (Janet Allen, ADAS, pers. comm.). A number of factors currently limit protected raspberry production. For example, for biennial cultivars poor and uneven bud break can result not only in a reduction in yield, but also in an irregular picking season (Jennings, 1988). In the autumn, when the prices are again high, primocane fruiting cultivars could be used to extend the season. However, this potential is often not realised because cropping is terminated by frosts. These and other associated problems with out-of-season raspberry production need to be addressed to guarantee productivity and pro®tability and to allow UK growers to compete with imports.

Misshapen Fruits in Strawberry

Abstract Misshapen fruit are a perennial problem in strawberry (Fragaria xananassaDuch.) production. The strawberry is an aggregate fruit originating from the receptacle of the flower. The true fruits, the achenes form from the carpels present on the surface of the receptacle. Fruit growth and shape are largely determined by the number and position of achenes on the receptacle; an uneven distribution or an insufficient number of fertilized ovaries will result in small, misshapen fruit. A number of factors contribute to the formation of misshapes, but most important seem to be genotype, flower position within the inflorescence and stamen and carpel viability. However, effects of the environment, pollination and nutrition must also be considered. In this review, we summarize information on the causes of misshapes, and discuss ways in which they could be overcome.

The Control of the Annual Growth Cycles of Six Temperate Fruit Crops

Abstract Temperate perennial fruit crops typically show a clearly defined cycle of growth through which they pass each year. In most, this cycle is completed over two years so that to understand how growth is controlled, both years must be considered. Some, however, complete a full cycle of growth within one year. The objective of this paper is to present the cycle of growth for four species: strawberry, raspberry, grape and apple. Each species behaves differently in detail but there are, nevertheless, some significant common features that provide opportunities for a greater understanding of underlying physiological mechanisms.