A 3-min pulse of 11CO2 was fed to leaves of various plant species to allow us to compare the patterns of movement of 11C translocate over 90 min. Three groups of profiles were found. (1) In Helianthus, Nymphoides, Tropaeolum, Ipomoea, and Fraxinus, a mass flow passed successive detectors, rising steadily over a 90-min period. (2) In Zea and Triticum, the mass flow remained at a peak for 5–10 min and fell steadily thereafter. (3) In Picea and Pinus, no obvious mass-flow pattern was detected in 90 min but rather a series of waves or packets. In every case, the activity opposite certain positions accumulated faster than others, suggesting that points of local buildup of translocate occur along a stem or petiole.By using high activity 11CO2 counting times of 5 s or 1 s, and the five-point mean technique of analysis of data, we have been able to detect aberrations in the tracer profile opposite each detector. These aberrations are due in part to the movement of tracer at different speeds in parallel veins, in part to the superposition of reverse flow of tracer, and in part to apparent discontinuities of flow or small waves of tracer. We conclude that some pulsatory sucrose loading mechanism is possible in the leaves, but a nonsteady-state translocatory mechanism is also possible. We have developed techniques for detecting the points of time of the onset of mass flow and the method of following small peaks of tracer activity past successive detectors. Waves of translocate moved at 0.2 cm min−1 in pine and spruce and 0.5–10 cm min−1 in ash and the angiosperms. Some synchrony of flow causes activity reinforcement or interference to occur in transient fashion.

Latania scale insect is a pest of global significance affecting kiwifruit. The sessile insect (life stage: settled crawler—mature adult) is covered with a waxy cap that protects it from topical pesticides, so increasingly, a selection of resistant cultivars and application of elicitors are being used in pest control. Thus far, the application of a salicylic acid (SA) phytohormone pathway elicitor, acibenzolar-S-methyl (ASM), has been shown to reduce insect development (as indicated by cap size) on one kiwifruit cultivar (‘Hayward’). To investigate how cultivar-associated resistance is affected by the ability to respond to different elicitors, we measured phytohormones (by LCMS) and gene expression (by qPCR and NanoString) on latania scale-tolerant ‘Hort16A’ and susceptible ‘Hayward’ kiwifruit over two seasons. Potted plants in the presence/absence of settled latania scales were treated with ASM (0.2 g/L) or methyl jasmonate (MeJA, 0.05% v/v), representing elicitors of the SA and JA signalling pathways, respectively. ‘Hort16A’ cultivar resistance to latania scale was associated with elevated expression of SA and SA-related defence genes (PR1 and two PR2 family genes) in the ASM treatment. MeJA treatments did not significantly affect insect development in ‘Hayward’ (latania scale did not survive on ‘Hort16A’) and did not correlate with phytohormone and gene expression measurements in either cultivar. ‘Hayward’ had greater concentrations than ‘Hort16A’ of inert storage forms of both SA and JA across all treatments. This information contributes to the selection of tolerant cultivars and the effective use of elicitors for control of latania scale in kiwifruit.

No abstract

Consumer acceptance of fruit is determined by size, flavour and ripeness. In this study we investigated how altering the carbohydrate supply to Actinidia chinensis var. chinensis ‘Zesy002′ kiwifruit altered the balance between growth and accumulation of metabolites. Canes were phloem girdled and fruit thinned to a leaf-to-fruit ratio (L:F) of either 2 (Low carbohydrate) or 6 (High carbohydrate) at either 38 (Early) or 86 (Late) days after anthesis (DAA) and compared with ungirdled control canes with a L:F of 3. Fruit growth, metabolite accumulation, cytokinin concentrations and maturation were monitored and the sensory attributes of ripe fruit were assessed. The final weight of Early-High and Late-High carbohydrate fruit was 38% and 16% greater compared with control fruit. High carbohydrate fruit had increased starch,soluble sugar and cytokinin concentrations and fruit began to mature earlier and those with a Low carbohydrate had decreased concentrations and matured later compared with control fruit. Control fruit were described by consumers as more acidic and under-ripe compared with those from Early-High carbohydrate canes, but as sweeter than those from Low carbohydrate canes. This study showed that carbohydrate supply can have a major impact on the growth, sugar accumulation and maturity of ‘Zesy002′ fruit sinks.

No abstract