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    Growth analysis and plant hormone studies in apple (Malus sylvestris Mill.) : a thesis submitted in partial fulfilment of the requirements for the degree of Doctor of Philosophy
    (Massey University, 1975) Park, Heung Sub
    Previous data on gravitational effects on shoot growth and flowering have been inconsistent. Attempts have been made to investigate shoot growth and flowering on shoots with a 3/8 phyllotaxis in 90 cm and 150 cm laterals. These were bent at different times to the horizontal or to a pendulous position in apple varieties Red Delicious and Granny Smith on MM 106 rootstocks grown under a semi-intensive system on a commercial orchard in the major apple growing area of Hastings. The four treatments comprised: horizontal or pendulous bending during the dormant period, at petal fall, second cover stage and with normal vertical laterals as controls. Horizontal bending increased total shoot growth and flowering relative to the vertical controls in the 90 cm treatment in both varieties. There seemed to be a tendency to decrease total shoot growth when the time of bending was later in the season and no differences in flowering occurred among the horizontal bending treatment. On the other hand shoot growth was relatively constant in all treatments in the 150 cm treatment. A very significant increase in flowering, however, was found in the petel fall pendulous bending. In the dormant period pendulous bending there was a slight effect on the flower promotion relative to the verticals. The production of laterals and flower buds was always more pronounced on the upper side of the bent shoots, with an intermediate on the flanks, and greatly inhibited effects on the lower side, indicating a steep linear relationship from the lower to the upper during the dormant period treatment in all experiments. Generally, the percentages of shoot growth and flower production were increased from the dormant period bending to the petal fall, second cover and to the vertical control. The greatest increase in shoot length and increased percentage of flowering in all experiments were found in the apical whorl zone, and these further decreased from the, 1st to the 2nd, and to the 3rd whorl; this was the case for shoot growth and flowering in the first whorl was not increased due to the inherent properties in Red Delicious. The shoot growth and flowering at the different whorls in 150 cm length laterals bent pendulously in Red Delicious showed a quadratic relationship due to the longer shoots in the apical and the arch position on the shoot when bent at the 5th whorl in all treatments. But at the 5th whorl flowering was reduced considerably, because of substantial lateral growth. In order to describe the growth relationship between shoot volume and total leaf area an index based on the ratio of vegetative and reproductive responses was established e.g. vegetative 10.83 and reproductive 19.80-24.40. The relationship of shoot growth and flowering are discussed in terms of a hormone balance theory. Plant hormone studies In order to establish a ratio of different plant hormones for an understanding of physiological phenomena, appropriate extraction procedures are required for especially apple leaves which are rich in phenolic compounds and other inhibitors. Therefore extraction procedures and purification were examined using 14C-IAA and 3H-zeatin. Loss of 14C-IAA during extraction procedures was due to a high pH in the aqueous phase during solvent partitioning. The final recovery of 14C-IAA was 3.8% at pH 8.0 and 81.1% at pH 2.5 through solvent partition and column chromatography. 14C-IAA was chromatographed on a silica gel-celite column and a Sephadex LH-20 column, giving 80 recovery in 30 ml elution volume around the main peak and 90% recovery in 20 ml elution volume around the main peak respectively. Nearly 100% recovery from a Sephadex G-10 column was obtained. 50-57% recovery of 14C-IAA wes obtained in cellulose thin layer chromatography at the Rf of IAA, and no loss of 14C-IAA occurred during 3 days storage in a dark cabinet. The partition coefficient of 3H-zeatin at pH 8.3 was 13.12 with ethyl acetate and 0.488 with n-butanol; at pH 2.5, 108-89 with ethyl acetate and 16.73 with n-butanol. Backwashing can recover 3H-zeatin from ethyl acetate phase which was partitioned at pH 2.5. 80% recovery of 3H-zeatin in the first 1,000 ml was obtained from Sephadex G-10 and Dowex 50 W x 8. 88.6% recovery of 3H-zeatin could be obtained in a 20 ml peak using Sephadex LH-20 eluted with 95% EtOH containing 0.001 M HCl. The behaviour of 3H-zeatin was studied in paper chromatography and cellulose, DEAE cellulose and silica gel, thin layer chromatography, about 82-60% of 3H-zeatin the Rf of 3H-zeatin being recovered. Four series of plant hormones were determined from apple leaves by ethyl acetate partitioning, Sephadex G-10 column, silica gelcelite column and cellulose thin layer chromatography of acidic fractions containing auxin-, gibberellin-, and ABA-like substances, and by butanol partitioning, Sephadex G-10, Sephadex LH-20, and'DEAE cellulose thin layer chromatography for cytokinin-like substances from basic fractions. Possibly two kinds of auxin-like substances were found and possibly GA9, GA4, GA5, GA1, or GA3, and GA8-like substances were eluted from a silica gel-celite adsorption column. Several groups of cytokinin-like substances were obtained from Sephadex LH-20 column chromatography, possibly zeatin, zeatin-riboside and other cytokinins were found in apple leaves. Based on the estimation of each plant hormone from thin layer chromatography, a relative plant hormone index was established, i.e., Relative Auxin Activity Index, Relative Inhibitor Activity Index, Relative Gibberellin Activity Index, and Relative Cytokinin Activity Index, representing 6.59, 1.04, 2.64, and 8.16 respectively, the hormone giving the highest ratio being considered the dominant hormonal factor at that stage of development. GLC techniques were also studied for plant hormone analysis, using 3% OV-1 and NAA, IAA, TPA, GA1, GA3, GA4, GA5, GA7, GA9, GA13 and ABA markers to establish retention times and detector response at the 2.5 ng level. N.O.-bis(trimethylsilyl)trifluoroacetamide (BSTFA) together with Trimethylchlorosilane (TMCS) silyl reagents produced the best peak heights for IAA, IPA, GA3 and GA1 but reduced the ABA peak by half and the GA9 peak by 20%.
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    Fresh and processed apple products : vacuum infiltration, texture and quality : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Plant Science at Massey University
    (Massey University, 1997) Newman, Suzie Marie; Newman, Suzie Marie
    Apple slice texture and quality is affected by a diverse array of preharvest, postharvest and processing factors. The study described in this thesis had two primary objectives: 1) to investigate factors that influence the effectiveness of the vacuum infiltration process and thereby identify ways to enhance infiltration in difficult-to-infiltrate fruit. 2) to ascertain the effects of a range of pre- and post- harvest factors including cultivar, temperature, edible surface coatings and calcium treatments on fresh and processed apple texture and quality. Vacuum infiltration is used to replace the 8-36% of tissue volume made up by occluded gases in the commercial production of solid-pack canned apple slices. This removal: reduces textural degradation caused by thermal expansion of these gases; prevents can corrosion and off-flavour development caused by residual oxygen; and ensures that relative density of the tissue is increased sufficiently to achieve prescribed can fill weights. Vacuum infiltration is often incomplete for fruit produced in cold growing seasons and also with immature fruit. In this study, level of infiltration achieved in apple slices was affected by pre-condition of the tissue (eg. maturity, porosity, whole fruit density) and by variables that relate directly to the vacuum infiltration process (eg. vacuum time, absorption time, solution temperature). Infiltration was enhanced in fruit taken from later harvests and in fruit pre-stored for a short period at 20 °C. Key aspects of the vacuum infiltration process were investigated and the relationships between vacuum time, absorption time, and slice relative density were characterised. Reduced vacuum levels were detrimental to liquid impregnation. To maximise infiltration in 'Braeburn' fruit required: high vacuum levels (preferably > 95 kPa), vacuum times of approx 2 min, and absorption times > 6 min. Infiltration was enhanced by heating the infiltrating solution. The texture and quality of solid-pack canned apple slices is to a large extent determined by the quality of the raw product. 'Braeburn', 'Fuji' and 'Granny Smith' apples varied quite markedly in terms of textural quality, storage potential, tolerance of ambient temperatures and ultimately in their response to processing. In general, fresh and processed apple texture declined with increasing fresh fruit storage temperature and duration. Application of edible surface coatings enhanced texture and reduced free-juice content of canned slices. The level of benefit achieved varied considerably with cultivar and storage temperature and, to a more limited extent, grower line and coating concentration. Calcium application during the pre- or post-harvest phases had little effect on processed slice texture, but in some cases free-juice volume was reduced. The interrelationships between the variables under study are discussed and a conceptual model presented that describes the effects of key postharvest variables on fresh and processed fruit texture.
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    Postharvest apple softening : effects of at-harvest and post-harvest factors : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Plant Science at Massey University, Palmerston North, New Zealand
    (Massey University, 2001) Johnston, Jason William
    'Cox's Orange Pippin' (COP) and 'Royal Gala' (RG) are rapid softening apple cultivars. This makes it difficult for growers to meet minimum firmness standards in the marketplace. Research was undertaken to characterise softening curves of COP and RG in relation to different at- and post-harvest factors, and to compare these cultivars with the slower softening cultivars 'Granny Smith' (GS) and 'Pacific RoseTM' (PR). Regular measurement of firmness during low-temperature storage showed that the postharvest softening curve for all cultivars was triphasic with an initial slow softening phase (I), followed by a phase of more rapid softening (II), and then a final slow softening phase (III). Phase I largely determined the fruit market life for firmness, as fruit with a short phase I had less market life than fruit with a longer first phase. Phase I of RG and COP was lengthened by harvesting fruit at an earlier rather than later maturity, by rapidly cooling fruit after harvest to 0.5-3°C, and by placing fruit in controlled atmospheres (CA). Rate of phase II softening was not affected by harvest maturity, but decreased as storage temperature was reduced from 22 to 0°C, and was reduced in CA relative to air. A modified Arrenhius equation described softening rates of COP and RG at different temperatures, where softening rate increased from 0°C to a maximum at 22°C, and then decreased through 35°C. In contrast, this equation could not describe softening rates of PR and GS at different temperatures, as both cultivars softened slowly at similar rates from 0-12°C, and phase II did not occur at 20-35°C. Prior cold or ethylene treatment induced phase II softening at 20°C for GS, but not PR. Internal ethylene concentration (IEC) may have a role in regulating onset of phase II softening in RG and COP at 0-35°C, while for GS and PR fruit sensitivity to ethylene may have a more important regulatory role than IEC. A prototype model was developed for estimating loss of RG and COP firmness through the postharvest handling chain. This model has potential to improve commercial management of the "soft fruit" problem in the marketplace.