Predation is an important ecological process that shapes life-history traits, community dynamics, and species coexistence and therefore has been suggested to explain many patterns in avian ecology. Although many studies have reported spatial, temporal, or interspecific patterns in nest predation, relatively few studies have been designed to identify the specific mechanism(s) that underlie these patterns. I examined mechanisms underlying the risk of nest predation in birds by (1) reviewing nine of the most commonly cited hypotheses to explain spatial, temporal, and interspecific variation in the risk of nest predation, (2) conducting a comparative analysis of the nest-concealment hypothesis to examine which methodological issues, extrinsic factors, and species traits influence whether or not foliage density affects the risk of nest predation, and (3) testing six mechanistic hypotheses to determine the underlying cause(s) of intra-seasonal decreases in the risk of nest predation.Many of the hypotheses invoked to explain spatial, temporal, and interspecific variation in the risk of nest predation lack clearly defined mechanisms. I suggest that future studies explicitly define the mechanism and assumption(s) of each hypothesis prior to implementing empirical tests.I found that the discrepancy in results among past studies that have examined the nest-concealment hypothesis was due to interspecific differences in a variety of intrinsic and extrinsic factors that affect nest predation but have previously been ignored. The effects of nest concealment on nest placement and probability of nest predation vary among species and this variation is predictable based on the bird's morphological traits and characteristics of the ecosystem.Increased risk of nest predation early in the breeding season appears to be due, in part, to foliage phenology and spatial and temporal changes in predator behavior. The risk of nest predation was negatively associated with foliage density early, but not late, in the breeding season. Supplemental food provided to nest predators resulted in a numerical response by nest predators, increasing the risk of nest predation at nests located near feeders. I show that intra-seasonal changes in environmental features and predator behavior affect patterns of nest predation, which can influence timing of breeding.

Mercury (Hg) research in Ontario has centered on aquatic environments since fish can be a significant source of methylmercury for humans. Interactions between terrestrial and aquatic environments in regards to the Hg cycle have received less attention. This study focuses on the role of trees as a source and/or sink of Hg to the environment and the ap- plicability of deciduous trees as biomonitors for Hg. Leaf, bark and wood core samples were taken from a variety of deciduous species including Acer spp. (sugar, silver and red maple), Quercus spp. (red oak), Populus spp. (eastern cottonwood), and Salix spp. (willow) mainly from the Dorset and Kingston, ON regions. Examination of seasonal variation of Hg concentrations ([Hg]) in leaves indicated that average autumn leaf Hg ranged from 17– 45 ng/g and differed significantly among species. Leaf [Hg] increased with the growing season and roughly corresponded to regional atmospheric [Hg]. Microspatial trends in leaf [Hg], such as position on a branch, may increase variability. Tree cores from contami- nated and reference sites in the Kingston area showed that although dendrochronological techniques are not appropriate for estimating historical atmospheric Hg, they are useful for estimating the total Hg burden of a single tree. Populus and Salix, had the greatest bark and wood [Hg] with maximums reaching 18 ng/g. This was significantly higher than more inland trees such as Quercus and Acer, with maximum values of 7 and 1.2 ng/g for bark and wood [Hg]. Individual, average sized trees in this study contained a total of 0.4–2.6 mg of Hg. This study will provide forest and watershed managers with a better understanding of the importance of trees in the Hg cycle and the contribution of leaf and wood Hg to litterfall and waterbodies in southern Ontario. / Thesis (Master, Biology) -- Queen's University, 2007-12-18 23:48:21.97

During 1966 and 1967, a range plant clipping study was conducted at two locations in central Utah's Ephraim Canyon. It was found that extreme clipping treatment resulted in a significant increase in soil moisture due to a presumed decrease in transpiration during 1967. At the lower location, 7,100 feet elevation, a difference of 5.4 inches over a 5 foot soil profile was noted between the extreme and control clipping treatments in 1967. At the upper location, 10,000 feet in elevation, a savings of 3.6 inches soil moisture was observed over the 5 foot soil profile in 1967. Other clipping intensities also showed water savings in terms of reduced depletion values over the control plots, although these differences were not in all cases statistically significant.

A model to predict the daily green leaf area index (GLAI) for corn has been developed for Indiana conditions. Using daily maximum and minimum temperatures the GLAI was predicted for the vegetative stage, reproductive and grain filling stage, and the leaf senescing stage of corn. Predictions of GLAI for corn can be made on a daily basis from the day corn is planted until it is harvested for grain. The GLAI model was tested under Virginia conditions using green leaf area measurements collected from corn plants grown on Davidson silty clay loam, Davidson silty clay, and Mayodan sandy loam soils in the Piedmont region of the State. Maximum and minimum temperature data were also collected at the three sites. Measurements were made for two growing seasons using corn hybrid Pioneer 3369A, three plant population densities and two irrigation schedules. Short duration temperature data were also collected to compare with the daily maximum and minimum temperature data for the Mayodan site. Also a combination of soil temperature at 10 cm depth and air temperatures were used for the temperature functions accumulated from date of planting at the Mayodan site. Results of this study show that the predicted and measured GLAI values compare favorably under irrigated conditions on the Davidson soil. The results were not as favorable on the irrigated corn on the Mayodan soil. When the corn is subjected to severe moisture stress on either soil, GLAI cannot be predicted with this model. Short duration temperature data resulted in a better prediction of GLAI on the Mayodan soil. When applying nitrogen fertilizer to the corn through the irrigation system through the grain filling stage, the measured GLAI values compared favorably with the predicted GLAI values. However, the application of nitrogen and sulfur fertilizer together resulted in GLAI being maintained above that predicted for a longer period of time during the grain filling stage before its decline. / Ph. D.

Thesis (MScAgric)--University of Stellenbosch, 2005. / ENGLISH ABSTRACT: Quality of certain Leucospermum and Leucadendron cultivars after approximately 21 days shipping has been reported to be substandard due to ‘drying out’ of leaves and, in the case of Leucadendrons, involucral leaves. The nature of the symptoms of this ‘drying out’ and the conditions under which they form, viz. long exposures to low temperatures, has led us to hypothesize that these are symptoms of chilling injury (CI). Chilling injury, as far as we are aware, has not been documented on Leucospermums or Leucadendrons. Typical CI symptomology is discussed and shown for Leucospermum ‘Gold Dust’, ‘High Gold’ and ‘Succession’ and for Leucadendron ‘Chameleon’, ‘Laurel Yellow’ and ‘Safari Sunset’. The nature of CI symptoms for Leucospermums and Leucadendrons was generally membranous breakdown that manifested in some cases as a ‘water soaked’ appearance which, at a more advanced stage, was generally visible as ‘dried out’ patches on the leaves. In the case of the Leucadendrons CI was also visible on the immature involucral leaves which are more sensitive to chilling conditions than mature leaves. Dark discoloration of especially immature involucral leaves is also a symptom of CI. As water uptake of shoots with chilling injury is hindered the styles of the Leucospermums wilt. As can be expected, the lower the temperature below the threshold temperature and the longer the exposure the more severe the symptoms. CI was recorded on cut flower shoots of Leucospermum ‘Gold Dust’, ‘High Gold’, ‘Rigoletto’, ‘Succession’ and ‘Vlam’ after 21 and 24 days storage at 1ºC. After 24 days storage the chilling injury was more severe than after 21 days storage in most cases. Each cultivar was pulsed with 5 ml per stem of a 2% (w/v) sugar solution of either lactulose, sucrose, glucose, fructose or mannose before storage. After storage, CI was recorded on day 0, 3, 7 and 10 of the vase phase. Of the cultivars tested ‘Vlam’ and especially ‘Rigoletto’ were more prone to chilling injury development. ‘High Gold’ and ‘Vlam’ shoots were pulsed with 0 (control), 1.5, 3 or 4% (w/v) solutions of either mannose or fructose. The best control of CI for both cultivars was achieved with 1.5% (w/v) solution. Lower concentrations of mannose and fructose were tested on ‘High Gold’ shoots, with a 1% (w/v) solution giving the best control for both. At high concentrations signs of toxicity became evident directly after pulsing. ‘High Gold’ shoots were pulsed with 1% (w/v) solutions of mannose and fructose and sugar analyses were performed on shoots at different stages of storage and after 10 days in the vase. A slight increase in mannose and fructose was detectable in the stems of the shoots directly after pulsing but not in the leaves or the inflorescences. This is due to the low concentrations being used. The levels of all the carbohydrates decreased during the 21 days storage and more so during the vase phase of the flowering shoots. The fact that such low concentrations were effective in controlling chilling injury suggests that the sugars may have an effect other than on the osmotic potential. Cut ‘flower’ shoots of Leucadendron ‘Chameleon’, ‘Laurel Yellow’ and ‘Safari Sunset’ were stored for 14, 21 and 28 days, at 1º, 3º and 5ºC and CI development recorded during the subsequent 10 day vase phase. ‘Laurel Yellow’ and ‘Safari Sunset’ showed signs of chilling injury on the leaves after 28 days storage at 3ºC or lower and ‘Safari Sunset’ stored for 21 days developed chilling injury during the vase phase. Immature involucral leaves were more sensitive to chilling injury than leaves. CI increased with longer exposure times and lower storage temperatures for all three cultivars evaluated. ‘Chameleon’ was the most chilling tolerant of the cultivars up to 21 days. At 5ºC chilling injury was low irrespective of cold storage duration but longer exposures to 1º and 3ºC resulted in increased chilling injury development during the vase phase. All three cultivars were pulsed with 5 ml per stem of a 1% (w/v) solution of lactulose, sucrose, glucose, fructose or mannose and stored for 14, 21 and 28 days at 1ºC. The sugars reduced chilling injury on the leaves for ‘Safari Sunset’ when stored for 28 days and, to a lesser extent, in ‘Chameleon’. The sugars failed to reduce chilling injury of the involucral leaves of ‘Chameleon’ and ‘Laurel Yellow’ whereas there was some control especially after 28 days for ‘Safari Sunset’. In some cases the sugar pulse exacerbated chilling injury. Chilling injury generally increased rapidly after storage during the first three days in the vase and then at a lower rate for the next seven days. Leucadendron ‘Chameleon’, ‘Laurel Yellow’ and ‘Safari Sunset’ ‘cut flower’ shoots were pulsed with a 1% (w/v) glucose solution. Expressed on a dry weight basis, an increase in glucose concentration was not detected. The reduction in chilling injury of leaves by a sugar pulse is speculated, as for the Leucospermums, to be as a result of their presence in the apoplast and not the symplast and that their presence there protects the membranes against chilling conditions in some way. / AFRIKAANSE OPSOMMING: Die kwaliteit van sekere Leucospermum en Leucadendron kultivars na ongeveer 21 dae verskeping is waargeneem as substandaard as gevolg van die uitdroog van blare en, in die geval van Leucadendrons, die ‘involucral’ blare. Die aard van die simptome van hierdie uitdroging en die toestande waaronder dit plaasvind nl. lang periodes van blootstelling aan lae temperature, het ons tot die hipotese gebring dat hierdie simptome van koueskade is. Sover as wat ons bewus is, is koueskade nog nie gedokumenteer op Leucospermums of Leucadendrons nie. Tipiese koueskade simptomologie word bespreek en gewys vir Leucospermum ‘Gold Dust’, ‘High Gold’ en ‘Succession’ en vir Leucadendron ‘Chameleon’, ‘Laurel Yellow’ en ‘Safari Sunset’. Die koueskade simptome vir Leucospermums en Leucadendrons was oor die algemeen membraan afbraak wat ‘n water deurdrenkte voorkoms tot gevolg gehad het wat in ‘n meer gevorderde stadium sigbaar was as uitgedroogde kolle op die blare. In die geval van Leucadendrons was koueskade ook sigbaar op die onvolwasse ‘involucral’ blare wat meer sensitief is vir koue toestande as volwasse blare. Donker verkleuring van veral onvolwasse ‘involucral’ blare is ook ‘n simptoom van koueskade. Aangesien wateropname van stele met koueskade verhinder word, verwelk die ‘styles’ van die Leucospermums. Soos verwag kan word hoe laer die temperature onder die drempel temperatuur en hoe langer die blootstelling, hoe meer ernstig die simptome. Koueskade is aangeteken op gesnyde blomstele van Leucospermum ‘Gold Dust’, ‘High Gold’, ‘Rigoletto’, ‘Succession’ en ‘Vlam’ na 21 en 24 dae opberging by 1°C. Na 24 dae opberging was die koueskade meer ernstig as na 21 dae opberging in meeste gevalle. Elke kultivar het 5ml per steel van ‘n 2% (g/v) suiker oplossing van laktolose, sucrose, glucose, fruktose of mannose voor opberging opgeneem. Na opberging is koueskade aangeteken op dag 0, 3, 7 en 10. Van die kultivars wat getoets is, was ‘Vlam’ en veral ‘Rigoletto’ meer geneig tot koueskade ontwikkeling. ‘High Gold’ en ‘Vlam’ stele is geplaas in oplossings van 0 (kontrole), 1.5, 3 of 4 % (g/v) oplossings van mannose of fruktose. Die beste beheer van koueskade vir beide kultivars is deur die 1.5 (g/v) oplossing behaal. Laer konsentrasies van mannose en fruktose is getoets op ‘High Gold’ stele met ‘n 1% (g/v) mannose oplossing wat die beste beheer gegee het. Met hoë konsentrasies het tekens van toksisiteit sigbaar geword direk na opneem van die oplossing. ‘High Gold’ stele is geplaas in 1% (g/v) oplossings van mannose of fruktose en suiker analises is uitgevoer op stele by verskillende stadiums van opberging en na 10 dae in die vaas. ‘n Effense toename in mannose en fruktose is waargeneem in die stele van die blomme direk na opname van die oplossing, maar nie in die blare of die blomme nie. Dit is as gevolg van die lae konsentrasies wat gebruik is. Die vlakke van al die koolhidrate het afgeneem gedurende die 21 dae opberging en nog meer so gedurende die vaas periode van die blommende stele. Die feit dat sulke lae konsentrasies effektief is in die beheer van koueskade dui daarop dat die suikers ‘n effek het anders as op die osmotiese potensiaal. Snyblomme van Leucadendron ‘Chameleon’, ‘Laurel Yellow’ en ‘Safari Sunset’ is opgeberg vir 14, 21 en 28 dae, by 1º, 3º en 5°C en koueskade ontwikkeling is aangeteken gedurende die opvolgende 10 dae vaas periode. ‘Laurel Yellow’ en ‘Safari Sunset’ het tekens gewys van koueskade op die blare na 28 dae opberging by 3°C of laer en ‘Safari Sunset’ opgeberg vir 21 dae het koueskade ontwikkel gedurende die vaas periode. Onvolwasse ‘involucral’ blare was meer sensitief vir koueskade as die blare. Koueskade het toegeneem met langer blootstellingstye en laer opbergins temperature vir al drie kultivars geëvalueer. ‘Chameleon’ was die mees koueverdraagsaam van die drie kultivars tot op 21 dae. By 5°C was laag ongeag van die koue opberging tydperk, maar langer blootstellings aan 1º en 3°C het gelei tot toename in koueskade ontwikkeling gedurende die vaas periode. Al drie kultivars is voorsien met 5ml per steel van ‘n 1% (g/v) oplossing van lactulose, sucrose, glucose, fruktose of mannose en opgeberg vir 14, 21 en 28 dae by 1°C. Die suikers het koueskade verminder op die blare van ‘Safari Sunset’ wanneer opgeberg vir 28 dae en, tot ‘n mindere mate, in ‘Chameleon’. Die suikers het egter nie koueskade verminder van die ‘involucral’ blare van ‘Chameleon’ en ‘Laurel Yellow’ nie, waar daar egter wel in ‘n mate beheer was veral na 28 dae vir ‘Safari Sunset’. In sommige gevalle het die voorsiening van suiker die koueskade vererger. Koueskade het oor die algemeen vinnig toegeneem na opberging gedurende die eerste drie dae in die vaas en dan teen ‘n laer tempo vir die volgende sewe dae. Leucadendron ‘Chameleon’, ‘Laurel Yellow’ en ‘Safari Sunset’ snyblom stele is voorsien van ‘n 1% (g/v) glukose oplossing. Uitgedruk op ‘n droëmassa basis is ‘n toename in glukose konsentrasie nie waargeneem nie. Die afname in koueskade van blare deur die voorsiening van ‘n suiker oplossing is gespekuleer vir die Leucospermums, om ‘n resultaat te wees van hulle teenwoordigheid in die apoplas en nie die simplas nie, en dat die teenwoordigheid daar die membrane op ‘n manier beskerm teen koue toestande.

Assessment of leaf and canopy chlorophyll content provides information on plant physiological status; it is related to nitrogen content and hence, photosynthesis process, net primary productivity and carbon budget. In this study, a method is developed for the retrieval of total chlorophyll content (Chlorophyll a+b) per unit leaf and per unit ground area based on improved vegetation structural parameters which are derived using multispectral multi-angle remote sensing data. Structural characteristics such as clumping and gaps within a canopy affect its solar radiation absorption and distribution and impact its reflected radiance acquired by a sensor. One of the main challenges for the remote sensing community is to accurately estimate vegetation structural parameters, which inevitably influence the retrieval of leaf chlorophyll content. Multi-angle optical measurements provide a means to characterize the anisotropy of surface reflectance, which has been shown to contain information on vegetation structural characteristics. Hyperspectral optical measurements, on the other hand, provide a fine spectral resolution at the red-edge, a narrow spectral range between the red and near infra-red spectra, which is particularly useful for retrieving chlorophyll content. This study explores a new refined measurement concept of combining multi-angle and hyperspectral remote sensing that employs hyperspectral signals only in the vertical (nadir) direction and multispectral measurements in two additional (off-nadir) directions within two spectral bands, red and near infra-red (NIR). The refinement has been proposed in order to reduce the redundancy of hyperspectral data at more than one angle and to better retrieve the three-dimensional vegetation structural information by choosing the two most useful angles of measurements. To illustrate that hyperspectral data acquired at multiple angles exhibit redundancy, a radiative transfer model was used to generate off-nadir hyperspectral reflectances. It has been successfully demonstrated that the off-nadir hyperspectral simulations could be closely reconstructed based on the nadir hyperspectral reflectance and off-nadir multi-spectral reflectance in the red and NIR bands. This is shown using the Compact High-resolution Imaging Spectrometer (CHRIS) and Compact Airborne Spectrographic Imager (CASI) data acquired over a forested area in the Sudbury region (Ontario, Canada). Through intensive validation using field data, it is demonstrated that the combination of reflectances at two angles, the hotspot and darkspot, through the Normalized Difference between Hotspot and Darkspot (NDHD) index has the strongest response to changes in vegetation clumping, an important structural component of canopy. Clumping index (Ω) and Leaf Area Index (LAI) maps are generated based on previous algorithms as well as empirical relationships developed in this study. To retrieve chlorophyll content, inversion of the 5-Scale model is performed by developing Look-Up Tables (LUTs) that are based on the improved structural characteristics developed using multi-angle data. The generated clumping index and LAI maps are used in the LUTs to estimate leaf reflectance. Inversion of the leaf reflectance model, PROSPECT, is further employed to estimate chlorophyll content per unit leaf area. The estimated leaf chlorophyll contents are in good agreement with field-measured values. The refined measurement concept of combining hyperspectral with multispectral multi-angle data provides the opportunity for simultaneous retrieval of vegetation structural and biochemical parameters.

abstract: Atmospheric deposition of iron (Fe) can limit primary productivity and carbon dioxide uptake in some marine ecosystems. Recent modeling studies suggest that biomass burning aerosols may contribute a significant amount of soluble Fe to the surface ocean. Existing studies of burn-induced trace element mobilization have often collected both entrained soil particles along with material from biomass burning, making it difficult to determine the actual source of aerosolized trace metals. In order to better constrain the importance of biomass versus entrained soil as a source of trace metals in burn aerosols, small-scale burn experiments were conducted using soil-free foliage representative of a variety of fire-impacted ecosystems. The resulting burn aerosols were collected in two stages (PM > 2.5 μm and PM < 2.5 μm) on cellulose filters using a high-volume air sampler equipped with an all-Teflon impactor. Unburned foliage and burn aerosols were analyzed for Fe and other trace metals using inductively coupled plasma mass spectrometry (ICP-MS). Results of this analysis show that less than 2% of Fe in plant biomass is likely mobilized as atmospheric aerosols during biomass burning events. The results of this study and estimates of annual global wildfire area were used to estimate the impact of biomass burning aerosols on total atmospheric Fe flux to the ocean. I estimate that foliage-derived Fe contributes 114 ± 57 Gg annually. Prior studies, which implicitly include both biomass and soil-derived Fe, concluded that biomass burning contributes approximately 690 Gg of Fe. Together, these studies suggest that fire-entrained soil particles contribute 83% (576 Gg) of Fe in biomass burning emissions, while plant derived iron only accounts for at most 17%. / Dissertation/Thesis / Masters Thesis Chemistry 2019

Stress-induced changes in the emissions of volatiles from many economically-important plants have been demonstrated in studies over the past decade. Plants such as cotton and corn change both the composition and concentration of their emissions when subjected to wounding, herbivory and pathogen attack. Terpene-accumulating plants have been overlooked as potential objects of such studies although work on conifers has shown that species rich in constitutive defences can also exhibit induced responses. The aim of this study was to investigate whether terpene-accumulating plants respond to stress by altering their foliar emissions qualitatively and/or quantitatively. Species examined included Salvia officinalis (common sage), Melaleuca alternifolia (Australian tea tree) and Ocimum minimum (Bush basil). An experimental design was developed to eliminate factors such as leaf ontogeny that can affect the obtained results and complicate their interpretation. Small-scale solvent extraction and HS-SPME-based techniques were also developed; they enabled the quantitative determination of treatment-induced changes over periods ranging from 10 minutes to 6 months. Treatment of plants included mechanical wounding, herbivory, pathogen attack and chemical elicitation. Overall, statistically significant induced-changes were observed for both leaf-oil composition and concentration. The response of the different species used varied. O. minimum exhibited the greatest compositional changes whilst M. alternifolia was the only species for which oil-concentration changes were observed. The demonstrated changes were not as great as those reported in similar studies with non-terpene producing plants. The results indicate that the high metabolic costs associated with the production and storage of constitutive defences may be responsible for the limited induction of further defensive responses / Doctor of Philosophy (PhD)

Assessment of leaf and canopy chlorophyll content provides information on plant physiological status; it is related to nitrogen content and hence, photosynthesis process, net primary productivity and carbon budget. In this study, a method is developed for the retrieval of total chlorophyll content (Chlorophyll a+b) per unit leaf and per unit ground area based on improved vegetation structural parameters which are derived using multispectral multi-angle remote sensing data. Structural characteristics such as clumping and gaps within a canopy affect its solar radiation absorption and distribution and impact its reflected radiance acquired by a sensor. One of the main challenges for the remote sensing community is to accurately estimate vegetation structural parameters, which inevitably influence the retrieval of leaf chlorophyll content. Multi-angle optical measurements provide a means to characterize the anisotropy of surface reflectance, which has been shown to contain information on vegetation structural characteristics. Hyperspectral optical measurements, on the other hand, provide a fine spectral resolution at the red-edge, a narrow spectral range between the red and near infra-red spectra, which is particularly useful for retrieving chlorophyll content. This study explores a new refined measurement concept of combining multi-angle and hyperspectral remote sensing that employs hyperspectral signals only in the vertical (nadir) direction and multispectral measurements in two additional (off-nadir) directions within two spectral bands, red and near infra-red (NIR). The refinement has been proposed in order to reduce the redundancy of hyperspectral data at more than one angle and to better retrieve the three-dimensional vegetation structural information by choosing the two most useful angles of measurements. To illustrate that hyperspectral data acquired at multiple angles exhibit redundancy, a radiative transfer model was used to generate off-nadir hyperspectral reflectances. It has been successfully demonstrated that the off-nadir hyperspectral simulations could be closely reconstructed based on the nadir hyperspectral reflectance and off-nadir multi-spectral reflectance in the red and NIR bands. This is shown using the Compact High-resolution Imaging Spectrometer (CHRIS) and Compact Airborne Spectrographic Imager (CASI) data acquired over a forested area in the Sudbury region (Ontario, Canada). Through intensive validation using field data, it is demonstrated that the combination of reflectances at two angles, the hotspot and darkspot, through the Normalized Difference between Hotspot and Darkspot (NDHD) index has the strongest response to changes in vegetation clumping, an important structural component of canopy. Clumping index (Ω) and Leaf Area Index (LAI) maps are generated based on previous algorithms as well as empirical relationships developed in this study. To retrieve chlorophyll content, inversion of the 5-Scale model is performed by developing Look-Up Tables (LUTs) that are based on the improved structural characteristics developed using multi-angle data. The generated clumping index and LAI maps are used in the LUTs to estimate leaf reflectance. Inversion of the leaf reflectance model, PROSPECT, is further employed to estimate chlorophyll content per unit leaf area. The estimated leaf chlorophyll contents are in good agreement with field-measured values. The refined measurement concept of combining hyperspectral with multispectral multi-angle data provides the opportunity for simultaneous retrieval of vegetation structural and biochemical parameters.

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.