The Control of “ Whlptail ” in Broccoli and Cauliflower

2-Naphthyloxyacetic acid (BNOA), having a side-chain 2 carbon atoms long, is highly active in stimulating seedless fruit development in tomatoes. In this paper it is shown that progressive lengthening of the side-chain results in a series of compounds of which only those having an even number of carbon atoms in the side-chain are active. This is thought to be due to the fact that the even carbon compounds are broken down by oxidation in the plant to the active BNOA, whereas those with odd numbers of carbon atoms are broken down to the inactive β-naphthol. It is further shown that the introduction of a chlorine atom at position 3 in the naphthalene nucleus prevents this oxidation. When the side-chain exceeds 6 carbon atoms in length there is a rapid falling off in the activity of the active members of the series, which is probably due to the slower penetration of these long molecules into the cell.     

The effects of temperature and plant developmental stage on the occurrence of the curd quality defects “bracting” and “riciness” in cauliflower

Summary

Models to simulate the induction of the “bracting” and “riciness” defects in cauliflower were estimated from field experiments. Bracting, where small cauline leaves develop and penetrate the curd surface, is caused by high temperatures – a kind of de-vernalization. Riciness, on the other hand, where small flower buds develop on the curd surface, is caused by low temperatures, especially after a preceding period of high temperature – a kind of strong vernalization. Both bracting and riciness can be induced only at certain stages during plant development. Plots of cauliflower were given periods of different temperature treatments in the field by portable compartments with both cooling and heating units. The treatments were both constant high or low temperatures (24, 18, 13 and 8°C) in 10 d periods, and alternating high and low temperatures (23/23, 23/15, 23/10 and 23/5°C) in 7 d periods. The treatments were started both before and after curd induction. The incidences of bracting and riciness in harvested curds were recorded in 84 plots with different temperature regimes. These data were used to estimate the combined effect of plant development and temperature on quality defects. The responsive developmental stages in the plants were described by a parabolic function, which depends on the apex/curd diameter. The curd diameter with the highest risk of induction of bracting was estimated to be around 12 mm (range 1–23 mm). A combined model of the diameter function and the summation of daily average temperature with a base temperature of 15°C explained 66% of the variation in the data of observed bracting. The apex diameter with the highest risk of induction of riciness was estimated to be around 0.35 mm (range 0.2–0.5 mm). A combined model of sensitive apex diameter and the preceding temperatures (average daily temperature of 10 d), during a temperature drop (average minimum temperature of 10 d), and after (average daily temperature of 6 d) explained 71% of the variation in the data of observed riciness. These models may be used to set up test equipment and to test susceptibility of new cultivars in breeding programmes. On a farm level, the models may be used to forecast risk of quality defects in cauliflower production. Alternatively, the knowledge of how the combination of developmental stage and temperature scenario induce either bracting or riciness may be used to study flower induction by temperature.     

The effect of nitrogen fertilization and shading on the incidence of “colour spots” in sweet pepper (Capsicum annuum) fruit

SUMMARY

“Colour spots” (CS) in pepper fruit is a physiological disorder characteristic of some sweet pepper cultivars. The symptoms are yellowish spots on the outer surface of affected fruits. We investigated the effects of shading and nitrogen supply on the susceptibility of three sweet pepper cvs (Maor, Lady Bell and 899) to CS. The most susceptible was ‘Maor’. The incidence of CS was promoted by high N and shading. The fruits of all cultivars had lower nitrogen concentrations than the leaves but there were no significant differences in fruit N content between Maor and the CS-insensitive cultivars. The CS-affected areas of the pericarp tissue had higher calcium concentrations than unaffected tissue. Differences in magnesium or potassium concentrations in these spots were less pronounced. Scanning electron microscopy revealed that the affected pericarp cells contained crystals, presumably of calcium oxalate. Only in ‘Maor’ fruits was the oxalate concentration elevated by approximately nine-fold when the nitrogen supply to shaded plants was increased. We suggest that in the fruits of the sensitive cultivar, oxalic acid production is enhanced under high-nitrogen + shading conditions and causes the CS damage, possibly be chelating intracellular calcium.     

Studies in the Development of the Strawberry: III. Flower-Bud Initiation and Development in Large-Fruited Perpetual (“Remontant”) Strawberries

Summary

Four N application rates generated a range of tree N status as indicated by leaf N concentrations in six year old trees of `Mission' almond (Prunus dulcis (Mill.) D. A. Webb). Leaf N concentrations were related positively with concentrations of amino acids - especially asparagine and glutamine - in phloem and xylem saps. A pulse of 1.25 kg N per tree was applied to trees previously receiving 0, 78, 157 or 313 g N per tree, annually. Apparent uptake of soil N into above-ground tree parts was determined over a 39 d period. N uptake was determined as the difference in the products of tree biomass and tissue N concentrations before and after the N pulse. Tissue N concentrations increased signi®cantly in trees previously receiving the two lowest N application rates, whereas trees previously receiving the high N treatments were unresponsive. Tree N contents (0 g N per year, and also 78 g N per year treatments) increased slightly in response to the N pulse, although statistical differences were not observed due possibly to high variability in biomass among trees. At the same time, the amino acid concentrations in phloem exudate and xylem sap were highest in trees grown under the highest N fertilization regime. We suggest that the high amino acid concentrations in the phloem and xylem saps are indicative of a larger pool of amino N cycling throughout the vasculature of high N-status trees. Our data indicate an inverse relationship between tree N status, amino acid concentrations in xylem and phloem saps and capacity for soil N uptake in ®eld-grown trees. These results represent the ®rst ®eld data to correlate the concentration of amino acids circulating in the plant vasculature with soil N uptake. A functional relationship between the amino acid concentrations cycling within the tree and the regulation of soil N uptake has, however, not yet been established.     

“Not in their front yard” The opportunities and challenges of introducing perennial urban meadows: A local authority stakeholder perspective

The growing evidence base for the benefits for people and wildlife of nature-based solutions to managing urban green infrastructure lacks research investigating land manager perspectives on their implementation. To address this gap, we explored UK local authority manager perceptions of the challenges and opportunities of introducing perennial urban meadows to prioritise biodiversity and aesthetics. This was co-produced as an experiment in urban greenspaces with Luton Parks Service and Bedford Borough Council 2013–15. We conducted semi-structured interviews with the eight stakeholder managers involved to identify key factors impacting on the perceived feasibility of future urban meadow establishment in other areas. All managers identified three dominant factors (aesthetics and public reaction, locational context, and human resources and economic sustainability). Additional factors (local politics, communication, biodiversity and existing habitat and physical factors) varied in importance according to personal values and managerial role. Support for future meadow introduction and a desire to overcome the economic challenge of the disposal of meadow arisings were related to manager biocentricity. Managers were aware of changing public values leading to increasing acceptance of a messier urban aesthetic. They perceived perennial meadows as a realistic alternative to amenity mown grass that in specific contexts could increase local biodiversity and enhance aesthetics if implemented in consultation with the public and local councillors. Our findings have relevance for the wider implementation of such nature-based solutions to urban GI management: Changes in management practice such as the introduction of perennial meadows have significant political, strategic, economic and practical implications and cannot be viewed purely as a technical challenge.