Browsing by Author "Chen, Jianyu"

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    The physiology and control of re-greening in spathes of Zantedeschia : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Plant Physiology at Massey University, Palmerston North, New Zealand
    (Massey University, 2011) Chen, Jianyu
    Spathe re-greening is a primary determinant limiting postharvest quality of Zantedeschia Spreng. as a cut flower, pot- or landscape-plant. A treatment that can be utilised by growers to delay re-greening offers potential to improve the postharvest quality and provide a marketing advantage. To achieve this, and develop an understanding of the physiological mechanism of re-greening, this project investigated the changes in colour, levels and types of pigment, and differentiation of plastids in spathe tissue durng re-greening; and how this process was controlled by various factors including fructification, light and various plant hormones (e.g. cytokinin and gibberellin). In the hybrid ‘Best Gold’, spathe re-greening was initiated within three days after horticultural harvest-maturity and, within two weeks the whole abaxial surface of the spathe had re-greened. During this period, the adaxial surface did not re-green and remained yellow in colour. The change in colour of the abaxial surface primarily resulted from the accumulation of chlorophyll within the subepidermal layers, as reflected by a strong correlation between the colour coordinate hue angle (Hº) and total chlorophyll content in that surface (r = 0.98). Monitoring Hº can therefore, be used to evaluate the degree of re-greening for ‘Best Gold’ without chlorophyll analysis. The content of carotenoid (in particular lutein which was predominant) was comparatively steady during re-greening. From an ultrastructural perspective, spathe re-greening was characterized by redifferentiation of chloroplasts from chromoplasts, as compared with de novo synthesis of chloroplasts from proplastids. The redifferentiation of chloroplasts involved thylakoid reformation through multiple mechanisms. In addition to de novo synthesis of thylakoid by invaginations of the inner-envelope membrane, it is likely that the thylakoids were either derived from primary thylakoids or plastoglobuli present in mature chromoplasts. The occurrence of re-greening in the spathe of both Zantedeschia aethiopica and ‘Best Gold’ following the removal of the spadix prior to pollination, contradicted the hypothesis that re-greening was induced by fructification (Pais and Neves, 1982- 1983). Further to this, the occurrence of re-greening in the spathe of ‘Best Gold’ with a spadix naturally devoid of female flowers, and the re-greening of pigmented leaves devoid of any true flower parts, also contradicted this hypothesis. The current findings therefore, indicate that fructification is not necessarily a prerequisite for induction of re-greening. In absence of light, no chlorophyll accumulated in spathe tissue of ‘Best Gold’, but the initial redifferentiation of chloroplasts from chromoplasts, as characterized by the formation of double-membrane lamella, was noted. Without light however, redifferentiation of chloroplasts was not completed. These suggest spathe re-greening requires light for the process to complete, but the onset of re-greening can be induced in darkness. The application of 6-benzylaminopurine (BAP) stimulated re-greening in spathe tissue by enhancing accumulation of carotenoid and chlorophyll, and also stacking of grana. But the response to BAP was dependent on the presence/absence of light, the stage of re-greening, and which surface, i.e. abaxial or adaxial. In contrast, the application of gibberellin (GA3) retarded formation of double-membrane lamella, and thus delayed the onset of re-greening. Hence, a synergistic effect of BAP and GA3 in delaying the onset of re-greening was likely to be a result of co-regulation between BAP-stimulated accumulation of carotenoid and GA3-stimulated retardation of chloroplast redifferentiation. By integrating both light and hormonal factors, several methods were tested on the actual horticultural commodity, i.e. flowers (peduncle, spathe and spadix) of ‘Best Gold’, so as to evaluate their efficacy in delaying re-greening. Pulsing flowers in darkness at 5 ºC for 24-h in a solution containing both GA3 and BAP, was the most effective treatment in postponing re-greening, resulting in a seven-day delay in regreening of the spathe.
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    Variety comparison and modelling flowering of Limonium perezii (Stapf) Hubb. x Limonium sinuatum (L.) Mill. 'LSLP4' : a thesis presented in partial fulfilment of the requirements for the degree of Masters in Horticultural Science, Massey University, Palmerston North, New Zealand
    (Massey University, 2005) Chen, Jianyu
    A series of new inter-specific hybrids have been derived between L. perezii and L. sinuatum. One of the selections 'LSLP4' offers potential as a cut flower. Precise knowledge on quality, yield and timing of these selections, as well as scheduling 'LSLP4' accurately in commercial production were required. To address these needs, this project comprised both a variety trial and an experiment to model the time to flower. Plants of 'LSLP4', 'LSLP5' (a sibling of 'LSLP4'), L. perezii and L. sinuatum derived from tissue culture were grown in a temperature-controlled (daily mean temperature around 20°C) greenhouse and long-day photoperiod. With the exception of the inferior wing characteristic, the yield, timing, and quality as well as the consistency of yield and quality of 'LSLP4' were intermediate or superior to L. sinuatum and L. perezii. The potential of 'LSLP5' as a cut flower could not be assessed due to its failure to flower during the variety trial. To develop a predictive model for time to flower of 'LSLP4', 7 sequential plantings were conducted from autumn through to late spring, utilizing one of two light regimes (50% shaded and no-shade). This resulted in 11 treatments of average daily light integral (DLI). Duration from transplanting to first visible flower bud (DTV) was correlated with average DLI, with the response being saturated above 15 mol.m-2.d-1. This relationship between DTV and average DLI is the foundation of a pre-planting predictive model for 'LSLP4'. DTV was also correlated with leaf number accumulation rate (LNAR) and ground cover index increase rate (GCIR). The combination of average DLI and LNAR together as predictors of DTV improved the r² of the model over that using DLI alone from 88% to 92%, which subsequently formed the basis of a 'post-planting' predictive model. It was recommended that growers of 'LSLP4' for cut flowers use the 'pre-planting' model to schedule planting dates and predict flowering time according to historical DLI data. Once planting occurs, and actual DLI and LNAR are collected, the prediction of DTV can be refined by the post-planting model.