Search Results

You are looking at 1 - 3 of 3 items for

  • Author or Editor: Michelle Wirthensohn x
Clear All Modify Search
Free access

Michelle G. Wirthensohn, Margaret Sedgley and Renate Ehmer

Optimum pruning height for cut foliage production was investigated for 3-year-old trees of Eucalyptus globulus Labill. Trees cut at a height of 1.0 m above ground level had most stems resprouting from the trunk, but a pruning height of 0.5 m produced the longest stems. Postharvest trials were conducted to assess the vase life of cut stems, and the effect of pulsing and simulated transportation on vase life. Holding solutions containing 1% or 2% sucrose and 8-HQC at 200 mg·L–1 significantly increased vase life of E. globulus and E. cinerea F. Muell. ex Benth. over the control, but pulsing E. cinerea in 1%, 5%, or 10% sucrose plus 8-HQC for 2 hours at 24 °C or 24 hours at 3 °C had no effect. In simulated transport trials, pulsing overnight in 1% or 5% sucrose plus 8-HQC at 3 °C followed by 1 week dry storage at 3 °C had no effect on the vase life of cut stems of E. sideroxylon Cunn. ex Wools., E. platypus Hook., E. spathulata Hook., E. cladocalyx F. Muell. E. platypus, or E. spathulata E. sargentii Maiden, but a 5% sucrose pulse plus 8-HQC significantly increased the vase life of E. spathulata E. platypus. A long pulse at low temperature (24 hours/3 °C) followed by 1 week dry storage was more effective than a short pulse at high temperature (2 hours/24 °C) for E. albida Maiden & Blakely stems and no sucrose was more effective than 1% or 5%. Thus, a pruning height of 0.5 or 1.0 m was optimum for cut foliage production of E. globulus, and a 2% sucrose holding solution extended vase life. There was no advantage of sucrose pulsing to extend vase life, or to improve vase life following dry storage, except for the hybrid E. spathulata E. platypus. Chemical name used: 8-hydroxyquinoline citrate (8-HQC).

Free access

Vahid Rahimi Eichi, Stephen D. Tyerman and Michelle G. Wirthensohn

Instantaneous water use efficiency (WUEi) is a measure made at the leaf scale, which can be used as a criterion for estimating WUE in breeding programs. To study the WUEi in different almond (Prunus dulcis) genotypes, we measured stomatal conductance (g S), assimilation rate (A), transpiration, internal concentration of CO2 (C i), and leaf hydraulic conductance normalized to leaf area in five mixed crosses of almond trees. For all measured parameters we observed the most significant differences between ‘Johnston’ × ‘Lauranne’ and ‘Nonpareil’ × ‘Lauranne’. Nevertheless, ‘Carmel’ × ‘Tarraco’ showed the highest WUEi among the five crosses. The significant correlations among g S, A, and C i indicated that A was probably limited by both stomatal and non-stomatal parameters that might be affected by genotype variations. In another experiment, we selected three cultivars of a new set of almond cultivars (Nonpareil, Carmel, and Masbovera) in four replicates for measuring g S at field capacity. Meanwhile, using a cryo-scanning electron microscopic (SEM) method, we prepared some images from the internal structures of leaves collected from the same cultivars of almond trees. Results showed that ‘Masbovera’ leaves, in which post-venous hydraulic distance (Dm) was higher compared with ‘Carmel’ and ‘Nonpareil’, represented significantly lower values of g S rather than the two other cultivars. Comparing mesophyll anatomy and g S between these cultivars demonstrated that Dm and the density of mesophyll cells might indirectly affect g S in almond leaves. In conclusion, our study demonstrated that water relations, WUEi, and leaf anatomy in almond trees differed among genotypes.