A Method for Analysing Plant Architecture as it Relates to Fruit Quality Using Three-dimensional Computer Graphics

A method was developed for the spatial analysis of plant architectureas it relates to the within-plant variation in the physical,chemical, and postharvest characteristics of the fruit Computergraphics were used to reconstruct the architectural frameworkand spatial arrangement of the fruit in the canopy of kiwifruitvines (Actinidia deliciosa) trained on two different supportstructures An infra-red beam theodolite was used to obtain thespatial coordinates of the vines components The data files generatedby the theodolite were in turn used with software specificallywritten for the project (MAPIT—Microcomputer Aided PlantImaging Technology) to provide a 3-dimensional reconstructionof the original vines Each fruit was colour coded so that extremesin their attributes could be easily identified and accuratelylocated in the canopy of the vine Patterns were clearly discerniblefor both the pergola and T-bar trained vines The heavier fruitwere located at the apical ends of the canes, while greatersoluble solids concentrations were associated with the smallerfruit located closer to the cordon These patterns were consistentfor all of the vines examined The use of the theodolite coupledwith the computer graphics described in this paper providesa rapid and objective means of accurately describing plant architecture Computer graphics, plant architecture, spatial analysis, theodolite, three-dimensional analysis, fruit quality, Actinidia deliciosa, kiwifruit     

Effects of Water Stress on Fruit Quality Attributes of Kiwifruit

Four-year-old kiwifruit vines (Actinidia deliciosa(A. Chev.)C. F. Liang et A. R. Ferguson var.deliciosacv. Hayward) werestudied to determine response of the plant and effects on fruitquality when irrigation water was withheld either early or latein the growing season. The greatest effect on fruit growth occurredwhen water was withheld early in the season. Harvest weightof fruit from early-stressed vines was approx. 25% less thanthe weight of fruit on control vines. Early season water stressresulted in a transient increase in concentrations of solublecarbohydrates in both leaves and fruit. This was accompaniedby a reduction in stomatal conductance of the leaves. Starchlevels in leaves but not fruit were reduced by both stress treatments.Concentrations of sucrose at harvest in fruit from vines stressedlate in the season were markedly higher than in other fruit,and softness of the fruit was unaffected. These differenceswere maintained through the 12 weeks in cool storage after harvest.Withholding irrigation water to kiwifruit vines late in theseason may prove a useful management tool to manipulate somequality attributes of the fruit.Copyright 1998 Annals of BotanyCompany Kiwifruit;Actinidia deliciosa; water stress; fruit quality; soluble solids.     

Use of Interactive Computer Graphics for Simulation of Radiation Interception and Photosynthesis for Canopies of Kiwifruit Vines with Heterogeneous surface Shape and Leaf Area Distribution

A method incorporating interactive computer graphics to simulatespatially variable interception and canopy photosynthesis isdescribed. The method presents a graphical interface to a conventionalmodel of radiation interception and canopy photosynthesis. Includedis the capacity to consider a large number of positions withinthe canopy, thus providing a rapid and convenient representationof the dynamics of photosynthesis while also overcoming limitationsof one-dimensional models applied to complex plant canopies.The method was applied to examine spatial variability of photosynthesiswithin canopies of kiwifruit (Actinidia deliciosa) vines growingon two trellis types. The diurnal integral of simulated canopyphotosynthesis, assuming sunny conditions, for a vine trainedon a horizontal 'Pergola' trellis was 14% higher than that fora vine with similar leaf area distribution trained on a 'T-bar'trellis with inclined surfaces. Simulations of photosynthesisfor vines on a T-bar trellis, assuming spatially variable leafarea distributions as measured under filed conditions, indicateddisproportionate contributions from different regions of thecanopy. Canopy regions inclined to the east or the west wereusually the major sites for photosynthesis immediately aftersunrise and before sunset respectively, while regions near thecordon were the most important overall. For any day, the maximumsimulated photosynthetic rate generally declined with distancefrom the cordon and, at any distance from the cordon, increasedwith leaf index. For a vine with an average leaf area indexof 2·7, diurnal integrals of photosynthesis on a sunnyday in late summer ranged from 1·0 mol CO₂ m^-2 near thecordon to 0·5 mol CO₂ m^-2 at 1·5 m from the cordon.Within-canopy shading was more important on sunny days thanon cloudy days, while the spatial distribution of leaf areawas especially important on cloudy days. Comparison of simulationswith direct measurements of canopy photosynthesis indicatedthat a numerical integral of simulated photosynthesis, basedon a large number of canopy positions, provided a reasonableestimate of total canopy photosynthesis.Copyright 1993, 1999Academic Press Actinidia deliciosa, kiwifruit, interactive computer graphics, mathematical modelling, photosynthesis, radiation interception, spatial heterogeneity     

Seasonal Accumulation of Starch by Components of the Kiwifruit Vine

The accumulation of starch by various components of 6-year-oldkiwifruit vines (Actinidia deliciosa var dehciosa cv Hayward)was recorded over one season Twenty vines were harvested periodicallythroughout the year and separated into perennial components(fibrous roots, structural roots, stump, stem, cordon, laterals)and current season's growth (shoots, leaves, and fruit) The concentration of starch in the fibrous roots followed asinusoidal trend Minimum concentrations occurred 98 d afterbudbreak, while the maximum concentrations occurred 182 d laterCorresponding times in the structural roots were approximately42 d earlier In the above-ground perennial components, elevatedconcentrations of starch in the cordon, fruiting wood and barkof the stem were evident at budbreak and fruit harvest (approx220 d later) In the case of the stem, concentrations were greatestat fruit harvest Because the biomass of the perennial componentswas found to be relatively constant throughout the year, starchconcentrations and contents were directly proportional in thesetissues For current season's growth, peak concentrations and contentsin leaves and shoots were observed at fruitset and fruit harvest,respectively For fruit, starch increased continuously untilharvest Approximately 30% of the total starch content accumulated inthe perennial components by leaf abscission was lost duringwinter and early summer Quantitative losses were greatest forthe roots Regeneration of the starch pools in the perennialcomponents of the vine occurred from midseason until leaf abscissionAt the same time, approximately five times more starch was accumulatedby the current season's growth, in particular the fruit, thanby the perennial components As a result of the difference inthe rate of accumulation, the starch content of the currentseason's growth increased from less than 10% midseason to nearly60% of the total starch content of the vine by fruit harvest The results were discussed in relation to the carbon economyof the kiwifruit vine, and compared with seasonal trends instarch concentrations found for other deciduous crops Actinidia deliciosa, kiwifruit, seasonal changes, starch content, whole plant     

Ice-nucleation on kiwifruit

Ice-nucleating capability of the kiwifruit vine, Actinidia deliciosa, was examined. Pseudomonas viridiflava, present as an epiphyte on the vine, was an effective icenucleating agent. The presence of other sources of ice nuclei on the surface of the vines, leaves and fruit, which could not be inhibited by anti-bacterial agents, was also demonstrated.     

Water Use of Kiwifruit Vines and Apple Trees by the Heat-Pulse Technique

Green, S. R. and Clothier, B. E. 1988. Water use of kiwifruitvines and apple trees by the heat-pulse technique.–J.exp. Bot. 39: 115–123. The compensation heat-pulse method has been used to measuresap velocities in the stem of kiwifruit vines (Actinidia deliciosa)and apple trees (Malus sylvestris x Red Delicious). Becauseof the high flow rates typical in kiwifruit vines, we were unableto measure heat-pulse velocity using standard probe spacings.We increased the spacing between sensors with the downstreamsensor 20 mm and the upstream sensor 5-0 mm respectively fromthe heater probe. Corrections for flow blockage by the probeswere re-calculated at this new spacing for our 2-0 mm-diameterheater and teflon temperature probes following the procedureof Swanson and Whitfield (1981) Sap flux through the stem was found from heat-pulse velocitiesat four radial depths in the stem. Fluxes measured using theheat-pulse technique were compared with water uptake from appletrees and kiwifruit vines that had been cut-off at the baseand the butt placed in a container of water. Heat-pulse measurementswere also compared with known flow rates through stem-sectionsof kiwifruit vine in the laboratory. In apple the heat-pulsemeasurements agreed with independent flux measurements in excisionexperiments. In kiwifruit the independently measured fluxeswere consistently 1.6 times larger than the fluxes measuredwith the heat-pulse method. Possible reasons for this anomalousresult in kiwifruit vines are discussed     

Seasonal Dynamics of Biomass and Mineral Nutrient Partitioning in Mature Kiwifruit Vines

The accumulation of dry matter plus macro- and micronutnentsby various components of 6-year-old, field-grown kiwifruit vines(Actinidia deliciosa var deliciosa cv Hayward) was recordedover one season Twenty vines were harvested periodically throughoutthe year and separated into perennial components (roots <20 mm diameter, structural roots, stump, stem, cordon, one-year-oldfruiting wood) and current season's growth (non-fruiting shoots,laterals on fruiting wood, leaves and fruit) There was minimalseasonal variation (CVs < 7%) in biomass change in perennialcomponents of the vine Concentrations in these components eitherfluctuated about a constant value, or indicated a strong seasonaldependence Changes in biomass and nutnent concentrations incurrent season's growth, however, were very regular Prior tobudbreak, below-ground components contained between 48 and 81% of the total content of each element Roots < 20 mm diametercontained more total nutrient than any other perennial componentof the vine during the season, with the exception of Zn andCu, which were concentrated in the cordon There was consistentaccumulation of each nutrient from budbreak until harvest Ratesof greatest uptake occurred in the month following budbreak,or in the 3 weeks after anthesis Between dormancy and harvest,whole-vine contents increased for all nutrients Increases inFe, Mg, P, S and Zn ranged from 21 % (Zn) to 88% (Mg), and inB, Ca, Cl, Cu, K, N and Mn from 109% (Cu) to 302% (Cl) Despitethe large requirements of the current season's growth, net changesin the seasonal content of perennial components were relativelysmall Copper, Mg, P, N and Cl were the elements in which perennialreserves were utilized to the greatest extent to meet transientdeficits between nutnent demand for the current season’sgrowth, and that recently taken up from soil Generally, reserves utilized during the period of vegetativegrowth were replaced by harvest-time These observations, basedon application of a single fertiliser dressing before budbreak,suggest the vine maintains satisfactory fertility without theneed for late-season or post-harvest applications of fertiliserto supplement nutrient reserves, as occurs with some other fruitingcrops Actinidia deliciosa, kiwifruit, mineral nutrition, seasonal accumulation, whole-plant harvesting     

Sex expression in fruiting male vines of kiwifruit

Summary In three canes on each of five fruiting male kiwifruit vines (A. deliciosa var. deliciosa (A. Chev) Liang and Ferguson), staminate and bisexual flowers were interspersed, so that staminate, bisexual and mixed inflorescences were found. Further variation in inflorescence composition resulted from the abortion of flower buds prior to anthesis. These two sources of variation, in combination, resulted in 19 inflorescence patterns, which varied substantially in frequency among and within vines. Some tendencies were determined. In particular, most of the inflorescences had retained their terminal flower, whereas just over half had retained one or both primary lateral flowers, and in two-thirds of the inflorescences retaining a terminal flower, this was bisexual. The five vines ranged in bisexual flower frequency from 40% to 70%. Phenotypic Gender (P) estimates are given for each vine, based on the frequencies of staminate and bisexual flowers from three canes per vine. Flower development, lability in sex expression and the use of P estimates as part of a selection index in breeding for hermaphrodite kiwifruit cultivars are discussed.     

Estimation of the Annual Cost of Kiwifruit Vine Growth and Maintenance

Elemental analysis (for carbon, hydrogen, nitrogen and sulphur)and ash data for kiwifruit [Actinidia deliciosa (A. Chev.) C.F. Liang et A. R. Ferguson var. deliciosa cv. Hayward] stems,leaves and fine roots were used to calculate the specific costs(kg carbohydrate kg^-1 dry matter) of organ synthesis with ammoniacalnitrogen supply. Those costs ranged between 1·19 and1·35 for stems and 1·19 and 1·27 for leaves.The mean annual specific cost for fine roots was 1·17.Seasonal vine growth costs were calculated by multiplying thespecific costs by biomass data for a typical vine. Total costof synthesis was 57·2 kg carbohydrate per vine year^-1,taking fine root turnover as three times per season. Nitratenitrogen supply increased that cost by 6·6% to 61·0kg carbohydrate per vine year^-1. Fruit growth accounted forthe largest proportion of synthetic costs. Vine growth respiration(expressed in terms of carbohydrate equivalents) accounted forapproximately 11·5% of the total cost of synthesis. Maintenancerespiration was estimated to be 5·28, 8·44, 1·90,8·62 and 13·3 kg carbohydrate per organ year^-1for stems, leaves, fruit, above-ground perennial componentsand roots, respectively. Total annual cost of growth and maintenancefor a mature vine was 94·7 and 98·5 kg carbohydrateper vine year^-1 with ammoniacal and nitrate nitrogen supply,respectively. Both values are similar to an estimate of vinephotosynthesis. Maintenance respiration accounted for approximately40% of the total annual cost of vine growth, regardless of theform of nitrogen supplied. Peak carbohydrate demand was duringthe period from 60 to 160 d after budbreak.Copyright 1995, 1999Academic Press Actinidia deliciosa, kiwifruit, carbon economy, growth respiration, maintenance respiration     

Gender variation in Actinidia deliciosa,the kiwifruit

Summary Flower and fruit characters were measured in ten female, five male and five fruiting male selections of A. deliciosa var deliciosa (A. Chev) Liang and Ferguson. Flowers from female vines had functional pistils, which contained many ovules. Stamens appeared to be fully developed but produced only empty pollen grains. Flowers from male vines had functional stamens that produced high percentages of pollen grains with stainable cytoplasmic contents. Pistils did not contain ovules and were generally small with vestigial styles. Fruiting male vines had both staminate and bisexual flowers. Staminate flowers were similar to those found on strictly male vines. Bisexual flowers produced ovules and stainable pollen. Pistils were smaller than in pistillate flowers. Although the three flower sexes differed in style length, ovary dimensions and ovules per carpel, staminate and bisexual flowers were similar in number of flowers per inflorescence, stamen filament length, pollen stainability, inflorescence rachis length and carpel number, and differed from pistillate flowers in these characters. The three flower sexes had similar sepal and petal numbers. The fruit of fruiting males were considerably smaller than those of females. Low ovule number appears to be the major factor limiting fruit size in the fruiting males studied. Prospects for developing hermaphroditic kiwifruit cultivars through breeding are discussed.     

Growth and Compositional Changes in Kiwifruit Berries from Three Californian Locations

Kiwifruit [Actinidia deliciosa (A. Chev.) C. F. Liang et A.R. Ferguson var. deliciosa cv. Hayward] berries were sampledfrom three Californian locations, two sites in the central valley(near Davis and Fresno), the other on the coast (near Watsonville).Samples were analyzed for nitrogen, lipid, starch, soluble sugars,organic acids and ash, at regular intervals from flowering untilharvest. The results of the analyses of the fruit from the twocentral valley sites were similar, but markedly different fromthose from the cooler coastal site Sugar/acid ratios were consistentlyhigher in fruit from the coast than the central valley. Thismay prove a useful refinement to the current maturity index. Actinidia deliciosa (A. Chev.) C. F. Liang et A. R. Ferguson var. deliciosa cv. Haywood, kiwifruit, fruit growth, fruit composition, seasonal changes     

Magnesium deficiency of kiwifruit (Actinidia deliciosa)

Magnesium deficiency was associated with large yield reductions in a five-year-old commercial kiwifruit (Actinidia deliciosa) orchard. The effect on yield resulted primarily from a reduction in fruit numbers, there being no difference in mean fruit weight between fruit harvested from affected and unaffected vines. Magnesium deficiency had no deleterious effect on postharvest storage characteristics of fruit stored at 0.5–1°C for 18 weeks; fruit from deficient vines were firmer but had slightly lower soluble solids than fruit from control vines. Although deficiency symptoms were first observed on the basal leaves of the non-fruiting shoots mid season, indications of the impending deficiency could be established very early in the season using foliar analysis. Magnesium concentrations in youngest fully expanded leaves (YFEL) on the affected vines were less than 2.0 g kg⁻¹ DM four weeks after budbreak and remained below this value for the rest of the season; concentrations in YFEL on unaffected vines did not decrease below this value and gradually increased after fruitset to 4.5 g kg⁻¹ DM at harvest. To avert potential production losses, it is suggested that soluble magnesium fertilizers (containing at least 200 kg ha⁻¹ Mg) should be broadcast early in the season if foliar magnesium concentrations less than 2.0 gkg⁻¹ DM are measured four–six weeks after budbreak.     

Comparison of Four Methods Calculating the Seasonal Pattern of Plant Growth Efficiency of a Kiwifruit Berry

Four methods of determining the substrate requirements for synthesisof a kiwifruit [Actinidia deliciosa (A. Chev.) C. F. Liang etA. R. Ferguson var. deliciosa cv. Hayward] berry were comparedusing data derived from common kiwifruit berry samples collectedfrom anthesis to fruit maturity. The four methods were basedon fruit proximal analysis, elemental analysis, heats of combustion,or tissue carbon content. All methods gave similar patternsof seasonal costs and values of final cost to the plant (mean1.21 g glucose g^–1 season^–1) but there was lessagreement for growth respiration (mean 0.147 g glucose g^–1season^–1). This is the first time that a continuous recordof growth cost over the course of development has been presented,and the trends in seasonal cost reflect the uptake into andsynthesis of the different biochemical constituents in the fruit.The differences between the results of each method reflect theunderlying assumptions used in their development. It appearsfrom this work that the method of McDermitt and Loomis (1981),utilizing elemental analyses, is most preferred. Actinidia deliciosa (A. Chev.) C. F. Liang et A. R. Ferguson var deliciosa cv Haywood, kiwifruit, true growth yield, plant growth efficiency, production value, glucose value, bioenergetic cost     

Seasonal Variation of Nitrogenous Compounds in Components of the Kiwifruit Vine

Free amino acids in 6-year-old kiwifruit vines [Actinidia deliciosa(A. Chev.) C. F. Liang et A. R. Ferguson] were measured overthe course of 1 year using components obtained from whole-vineharvests. Tissues examined from the perennial structure consistedof the wood and cortex of structural roots, wood and bark ofstem, leader and 1-year-old fruiting canes. Free acids in theannual growth (fine roots, flowers, fruit, leaves and non-fruitingshoots) were also measured. The range of amino acids extracted indicated that kiwifruitconforms to a conventional pattern of nitrogen metabolism. Acidspresent in greatest concentration depended on tissue type andsampling time. In perennial components and fine roots, arginineand glutamine were the predominant species, followed by gamma-aminobutyrate,aspartate, glutamate, alanine and valine. Generally, maximumconcentrations of all free acids were measured in a 10-weekperiod around budbreak. These same acids, plus asparagine, serineand threonine, were also prevalent in annual growth. In leaves,flowers and non-fruiting shoots, concentrations were greatestin the young tissue and declined with age. By contrast, concentrationsof arginine, asparagine and glutamine in fruit peaked approximately10 weeks after anthesis, subsequent to the cell division phaseof growth. During the year, free arginine averaged 44, 48 and 58 % of thetotal N in the fine roots, and the cortex and wood of structuralroots, respectively (the quantity of total N and amino-N inother components of the structural framework was much less thanthat in root tissue). Arginine was the principal N-containingspecies measured in xylem sap vacuum-extracted from 1-year-oldcanes over winter. During the period of vegetative growth, however,glutamine and nitrate were the principal N-transport forms present.The study highlights the importance of the fine root systemas the primary location of nitrogenous reserves in this plantand identifies arginine as the dominant N-storage form. Actinidia deliciosa (A. Chev.) C. F. Liang et A. R. Ferguson, amino acid composition, kiwifruit, nitrogen, whole-plant harvesting     

Uptake of 15N by Kiwifruit Vines from Applications of Nitrogen Fertilizer Prior to Budbreak

Mature field-grown kiwifruit vines (Actinidia deliciosa var.deliciosa cv. Hayward) were fertilized with ¹⁵N-labelled fertilizer(ammonium sulphate, 10 atom % ¹⁵N, 50 kgN ha^-1) to investigatethe timing of uptake of fertilizer nitrogen (N) and its availabilityfor new season's growth. Treatments were applied on four occasions,representing 2, 6, 10 and 14 weeks prior to budbreak. Samplesof root, stem, cordon, fruiting cane, vacuum-extracted xylemsap, and new season's growth were collected at fortnightly intervalfrom early winter until 2 months after budbreak. Two weeks after application of each treatment, ¹⁵N equivalentto an average of 7% of the applied label was recovered in rootmaterial. Although label was taken up by roots, there was nomovement of ¹⁵N within the plant until about 1 month prior tobudbreak when it was measured in the stem and cordon. Fertilizernitrogen was not detected at the distal end of fruiting canes,and in new season's growth until 3-4 weeks after budbreak. Beforebudbreak, all nitrogen in the xylem sap was in amino forms.Nitrate appeared 4 weeks after budbreak, and although more enrichedwith ¹⁵N than the amino nitrogen, accounted for only 19% ofthe label. Eight weeks after budbreak, nitrate nitrogen accountedfor 57% of the label. There were no major treatment effects of ¹⁵N on vines in eitherspring or at harvest, although enrichments in fruit and leavesfrom the earliest treatment tended to be less at the end ofthe season than those from the later applications.Copyright1993, 1999 Academic Press Actinidia deliciosa, kiwifruit, nitrogen, ¹⁵N, nutrient uptake     

Sensitivity of Floral Shoot Growth, Fruit Set and Early Fruit Size inActinidia deliciosato Local Carbon Supply

The sensitivity of pre-anthesis shoot growth, fruit set andearly fruit size in kiwifruit [Actinidia deliciosa(A. Chev.)C. F. Liang et A. R. Ferguson] to cane girdling and defoliationtreatments was tested, and the results discussed in terms ofshoot carbon balance. The nature and degree of responses obtainedwas dependent on the time of application. When treatments wereapplied soon after budbreak, defoliation initially reduced growth,whereas increasingly severe girdling treatments induced responsesprogressing from stimulation to severe impairment of growthand photosynthetic capability. Similar treatments imposed laterin shoot development produced qualitatively different results.The development of floral tissues on the shoot is shown to besensitive to shoot carbon status during a period close to anthesis,and the significance of this result in relation to fruit heterogeneityat maturity is discussed.Copyright 1998 Annals of Botany Company Actinidia deliciosa, kiwifruit, shoot growth, fruit variability, fruit set, reserves.     

Bacterial blight of kiwifruit

Bacterial blight of kiwifruit (Actinidia deliciosa) is caused by Pseudomonas viridiflava. Symptoms are rot of floral buds and flowers, and spots on leaves. Buds and flowers nearest the ground are most likely to be affected. Isolations made from healthy buds, flowers and leaves suggest that the pathogen is an epiphyte on vines throughout the year. Disease incidence fluctuates between seasons, and varies between orchards. A relationship between disease incidence and rainfall in spring is indicated.     

Papillar integrity as an indicator of stigmatic receptivity in kiwifruit (Actinidia deliciosa)

Stigmatic receptivity is a major factor limiting fruit set inkiwifruit (Actinidia deliciosa). The aim of this work was toknow what determines the cessation of stigmatic receptivityin this species. Stigmatic receptivity has been analysed inkiwifruit through the capacity of the stigma to sustain pollengermination and has been related to stigmatic development anddegeneration.The stigma of kiwifruit flowers has a papillatesurface which from anthesis is covered with an abundant exudate.Papillae are unicellular and contain a number of phenolic deposits.During the lifetime of the flower these papillae gradually loseturgidity, while stigmatic secretion increases until 5 d afteranthesis when papillae start rupturing and the papillar contentis liberated into the germination medium. Stigmatic receptivityis high at anthesis and lasts for the next 4 d. However, itdrastically decreases 5 d after anthesis and it is nil 2 d later.The pattern of stigmatic receptivity closely fits that of papillarintegrity, indicating that stigmatic receptivity relies on thisintegrity. Since papillar integrity can easily be evaluatedin stigmatic arms, this criterion can be used as a quick methodto estimate stigmatic receptivity. Key words: Actinidia deliciosa, kiwifruit, stigma, receptivity, pollen     

Changes in Cell Wall Composition and Water-soluble Polysaccharides During Kiwifruit Development

Changes in both cell wall and water-soluble polysaccharide compositionduring the growth of kiwifruits [Actinidia deliciosa (A. chev.) C. F. Liang and A. R. Ferguson var. deliciosa ‘Hayward’]were investigated. Cellulose was the major wall polysaccharide,with galactose and uronics the main non-cellulosic sugars. Muchsolubilization of cell wall pectic polysaccharides was detected.While wall-galactose solubilization started 3 months after anthesis,polyuronide degradation did not start until the fifth month,1 month prior to the harvest date. Parallel to these processes,a linear increase in water-soluble polysaccharides was detected.These mainly comprised galactose-rich polymers in the first3 months and little-branched polyuronides after the fifth month.Two different mechanisms for galactose and uronic acid solubilizationfrom kiwifruit cell walls during fruit development are proposed. Actinidia deliciosa ; cell wall; fruit growth; kiwifruit; water-soluble polysaccharides     

Temporal expression of effects of varying nitrogen supply on canopy growth, photosynthesis and fruit production for Actinidia deliciosa vines in the field

The effects of varying nitrogen supply on canopy leaf area, response of leaf net photosynthesis (A_n) to quantum flux density (Q), and fruit yields of kiwifruit vines (Actinidia deliciosa var. deliciosa) were examined in a two-year field experiment. Vines were grown with 0, 250 or 750 kg N ha^?1 year^?1. The responses to nitrogen supply were compared with responses to shade, to examine the impact of reduced carbon assimilation on canopy leaf area and fruit yields. Nitrogen supply did not affect significantly any of the measured variables during the first season of the experiment. In the second season, canopy leaf area was reduced significantly where nitrogen supply was limited. The quantum efficiency of photosynthesis (φ_q) increased from 0. 03 mol CO₂ mol^?1 Q soon after leaf emergence to more than 0. 05 mol CO₂ mol^?1 Q during the middle of the growing season. The quantum saturated rate of A_n (A_sat) also increased during the season, from 7–10 μmol CO₂ m^?2 s^?1 soon after leaf emergence, to 15–20 (μmol CO₂ m^?2 s^?1 during the middle of the growing season. φ_q and A_sat increased significantly with nitrogen supply at all measurement times during the second season. For vines with high nitrogen, fruit yields in both seasons were similar, averaging 3. 05 kg m^?2. Fruit yields in the second season were reduced significantly where nitrogen supply was limited, due to reduced fruit numbers. The relative effects of reduced leaf area and reduced leaf photosynthesis for carbon assimilation by nitrogen deficient vines were examined using a mathematical model of canopy photosynthesis for kiwifruit vines. Simulations of canopy photosynthesis indicated that effects on leaf area and on leaf photosynthesis were of similar importance in the overall effects of nitrogen deficiency on carbon assimilation. The effects of nitrogen supply on fruit numbers (i. e. flower development) preceded the measured effects on carbon assimilation, indicating that the nitrogen supply affected carbon partitioning to reserves in the first season.