Acacia holosericea A. Cunn. Ex G. Don (Velvet Leaf Wattle, Family Mimosaceae) is indigenous to Australia and holds promise as a novel cut foliage crop due to its silvery green silky phyllodes. Insufficient water uptake, possibly due to low stem hydraulic conductivity (Kh), is potentially responsible for early wilting and desiccation of phyllodes and limiting vase life. This study aimed to characterize the anatomy of stem xylem conduits and determine cation (K+ and Ca2+) mediated stem Kh. Differential localization of Ca2+ in xylem vessels and the effects of KCl and CaCl2 salts as cation contributors in vase solutions were also evaluated for their effects on cut foliage longevity. Anatomical characteristics of stem xylem conduits were studied using light, scanning electron microscopy (SEM), and transmission electron microscopy (TEM). Tracheids and vessels with simple perforation plates were the principal water conducting cells. SEM and TEM revealed bordered vestured intervessel pits in xylem conduits. Vestures were branched and coralloid-like structures. Xylem conduit lengths were assessed by ink perfusion. The majority of conduits (89%) were short (1 to 5 cm), and only ~ 2% were long (15 to 16 cm). Mean conduit diameter was 77 ± 0.9 µm, with 29% of conduits in the range 70 to 80 µm. Effects of S-carvone (0, 0.318, and 0.636 mM), a monoterpene inhibitor of wound-healing enzyme inhibitor found in caraway (Carum carvi) and dill (Anethum graveoleus) seeds, on several native Australian, non-proteaceous cut flower and foliage species including A. holosericea (Mimosaceae), Baeckea frutescens (Myrtaceae), Chamelaucium uncinatum cv. ‘Mullering Brook’ (Myrtaceae), and the non-native Chrysanthemum sp. cv. ‘Dark Splendid Reagan’ (Asteraceae) were examined. As comparator treatments regular recutting of stem ends and use of standard tap water (STW: 0.7 mM CaCl2, 1.5 mM NaHCO3, and 0.05 mM CuSO4 in vases) were tested. S-Carvone treatments significantly (P≤0.05) extended the vase life of B. frutescens and C. uncinatum, constituting the first report of positive S-carvone effects on the vase life of Myrtaceous species. S-Carvone at 0.318 and 0.636 mM did not have antibacterial effects against Bacillus cereus (the main vase solution microbe) either in vitro or in the vase solution. Regular recutting of stem ends consistently improved all vase life parameters [viz. relative fresh weight (RFW), solution uptake, and vase life] in the three native species examined. STW had a positive effect on RFW and solution uptake only for A. holosericea cut foliage. Effects of di- and monovalent cations (Ca2+ as CaCl2 and K+ as KCl) on stem Kh of cut stem segments were studied. Abundance of Ca2+ on pit membranes versus xylem lumen wall surfaces was investigated using a novel low vacuum (LV) SEM plus energy dispersive X-ray (EDX) microanalysis technique. Both salts (0.1, 1, 10, and 100 mM KCl or CaCl2) did not significantly increase stem Kh compared to the corresponding deionised (DI) water controls (experiment 1). Highest increase in Kh was with KCl and CaCl2 at 10 and 1 mM, respectively. Increases in Kh with 100 mM KCl and CaCl2 were significant over DI water (experiment 2) for long (10 and 20 cm) and short (2 and 5 cm) stem segments, respectively. Increases in Kh of 1.2- and 2.4-fold for 100 mM KCl over DI water were found with increasing stem length from 2 to 20 cm. Kh decreased as stem segment length increased from 5 to 20 cm. However, contrasting results were found with 100 mM CaCl2, where ΔKh was larger in shorter (2 cm) than longer (20 cm) segments. To prevent dislocation of ions and distortion damage to the specimens, stem pieces were first LV freeze-dried, and then carbon-coated, viewed under SEM, and analysed for elemental composition and distribution by EDX. However, the method could not identify specific calcium peaks in xylem vessels perhaps because background signals were too high, and tissue topography interfered with signal detection. Effects of KCl and CaCl2 on vase life were also tested. RFW, solution uptake, and vase life were higher with 10 mM KCl and CaCl2 in the vase solution than with 0, 1, and 100 mM. STW had a significant (P≤0.05) positive effect on RFW and solution uptake rate when tested against deionised water, 10 mM KCl and 10 mM CaCl2. Different combinations of 0.05 mM CuSO4, 10 mM CaCl2, and 10 mM KCl were also tested as vase solutions. A significant positive effect on RFW and vase life was obtained with CuSO4 alone, CaCl2 alone, and CuSO4 plus KCl. Only CuSO4 and CaCl2 gave a significant positive effect on solution uptake rate. None of the eight treatments tested showed a consistent effect on stomatal conductance or stem Kh. Overall, the research revealed that tracheids and vessels with simple perforation plates and bordered vestured intervessel pits are the principal water conducting cells in A. holosericea. LV-SEM-EDX technique was unable to assess the spatial distribution of Ca2+ on xylem vessels, but this was the first attempt to apply this technique. Also, this is the first report on the extension of vase life of B. frutescens and C. uncinatum (Myrtaceous species) using S-carvone. In vase solutions, 0.05 mM CuSO4, 10 mM KCl plus 0.05 mM CuSO4 and 10 mM CaCl2 should have positive influences on the water balance of A. holosericea cut foliage stems.

The primary objective of this research was to identify practices by which specialty cut flower growers can extend the vase life of cut delphinium, sunflower, and dahlia. Experiments investigated the effects of nitrogen fertilization rate on delphinium 'Guardian Mix' and the effects of deficit irrigation on delphinium 'Guardian Blue.' 'Guardian Mix' plants produced marketable cut stems at nitrogen rates as low as 50 mg/L. Deficit irrigation did not change vase life, stomatal conductance, or transpiration rates of delphinium 'Guardian Blue.' Studies tested the effects of foliar calcium applications or benzyladenine application on sunflower 'Moulin Rouge' and 'Procut Lemon.' Calcium did not change the vase life, stomatal conductance, or transpiration rates of either sunflower cultivar. Benzyladenine applied as a preharvest spray or a postharvest dip did not alter vase life of sunflower 'Moulin Rouge' or 'Procut Lemon.' Transpiration rate and conductance rates of sunflowers significantly decreased in the first three days after harvest. In both sunflower experiments, vase life of 'Moulin Rouge' was shorter than vase life of 'Procut Lemon.' Benzyladenine was also applied to dahlia 'Park Princess' and 'Karma Yin Yang' cut flowers. Benzyladenine did not change dahlia vase life. Dahlia 'Park Princess,' 'Bride to Be,' 'Cherish,' and 'Lollipop' cut flowers were not sensitive to exogenous ethylene. Further experiments tested the effect of flower stage at harvest, vase water temperature, or preharvest fungicide application on dahlia 'Park Princess' and 'Karma Yin Yang' cut flowers. Vase life of 'Park Princess' flowers was extended when flowers were harvested before fully open, but 'Park Princess' flowers harvested at budbreak failed to open completely after harvest. 'Karma Yin Yang' cut flower vase life did not differ when flowers were harvested at different stages. Placing cut dahlias in hot vase water had varied effects, but did not extend vase life of either cultivar. Fungicide applications extended vase life of 'Park Princess' flowers. However, the use of fungicide is not necessary to prevent postharvest fungal infection in cut dahlias. The results of all experiments indicate that optimal handling practices vary between cut flower taxa and that factors determining cut flower vase life are complex. / Master of Science

This study was aimed at exploring data analysis techniques for generating accurate estimates of the loss in quality of fresh fruits, vegetables and cut flowers in chilled supply chains based on data from advanced sensors. It was motivated by the recent interest in the application of advanced sensors, by emerging concepts in quality controlled logistics, and by the desire to minimise quality losses during transport and storage of the produce. Cut roses were used in this work although the findings will also be applicable to other produce. The literature has reported that whilst temperature was considered to be the most critical post-harvest factor, others such as growing conditions could also be important in the senescence of cut roses. Kinetic modelling was the most commonly used modelling approach for shelf life predictions of foods and perishable produce, but not for estimating vase life (VL) of cut flowers, and so this was explored in this work along with multiple linear regression (MLR) and partial least squares (PLS). As the senescence of cut roses is not fully understood, kinetic modelling could not be implemented directly. Consequently, a novel technique, called Kinetic Linear System (KLS), was developed based on kinetic modelling principles. Simulation studies of shelf life predictions for tomatoes, mushrooms, seasoned soybean sprouts, cooked shrimps and other seafood products showed that the KLS models could effectively replace the kinetic ones. With respect to VL predictions KLS, PLS and MLR were investigated for data analysis from an in-house experiment with cut roses from Cookes Rose Farm (Jersey). The analysis concluded that when the initial and final VLs were available for model calibration, effective estimates of the post-harvest loss in VL of cut roses could be obtained using the post-harvest temperature. Otherwise, when the initial VLs were not available, such effective estimates could not be obtained. Moreover, pre-harvest conditions were shown to correlate with the VL loss but the correlation was too weak to produce or improve an effective estimate of the loss. The results showed that KLS performance was the best while PLS one could be acceptable; but MLR performance was not adequate. In another experiment, boxes of cut roses were transported from a Kenyan farm to a UK distribution centre. Using KLS and PLS techniques, the analysis showed that the growing temperature could be used to obtain effective estimates of the VLs at the farm, at the distribution centre and also the in-transit loss. Further, using post-harvest temperature would lead to a smaller error for the VL at the distribution centre and the VL loss. Nevertheless, the estimates of the VL loss may not be useful practically due to the excessive relative prediction error. Overall, although PLS had a slightly smaller prediction error, KLS worked effectively in many cases where PLS failed, it could handle constraints while PLS could not.In conclusion, KLS and PLS can be used to generate effective estimates of the post-harvest VL loss of cut roses based on post-harvest temperature stresses recorded by advanced sensors. However, the estimates may not be useful practically due to significant relative errors. Alternatively, pre-harvest temperature could be used although it may lead to slightly higher errors. Although PLS had slightly smaller errors KLS was more robust and flexible. Further work is recommended in the objective evaluations of product quality, alternative non-linear techniques and dynamic decision support system.