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Subject: search.filters.subject.Pine cones

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    Morphological and physiological changes in developing Pinus radiata D. Don seed and the effects of early cone collection and post-harvest treatment on seed quality : a thesis presented in partial fulfilment of the requirements for the degree of Master of Agricultural Science in Seed Technology at Massey University
    (Massey University, 1987) Rimbawanto, Anto
    Morphological and physiological changes in developing Pinus radiata D. Don seed and the effects of early cone collection and post-harvest treatment on seed quality Anto Rimbawanto This study aimed to characterise the sequence of cone and seed development, investigate morphological and physiological changes occurring during artificial ripening and assess the potential of artificial ripening in commercial practice. In general, the results show that cone and seed development of Pinus radiata exhibit a pattern similar to other coniferous species, but seed development and the acquisition of germinability proceed at a rate much faster than the maturation of the cone itself. Seed germinability is attained in June when cone dry weight and size are at maximum; cone colour and specific gravity changes occur much later, thus lessening the effectiveness of these two parameters as indices of maturity. Therefore, a cone with a green colour and high specific gravity does not necessarily contain poorly germinable seeds. The aquisition of germination capacity is closely associated with the level of moisture within the seed. The seed requires a low level of moisture to switch on the germination programme. A moisture level of between 20 - 25% is suggested as the 'required' level. The seed needs to remain at this critical moisture level for a period of time to allow the developing seed to complete the process of switching. The more developed the embryo and megagametophyte, the better the germination performance. Immature seeds collected in March are not capable of germinating despite desiccation during artificial ripening. Artificial ripening of P. radiata seed for three weeks substantially improves the germinability of early collected seeds (April and May). For the late collected seeds (June onwards) artificial ripening has little scope to improve it since initial germination was high. Although further storage has little effect on the final germination, it reduces the speed of germination indicating a process of deterioration. During artificial ripening, no further development of embryo and megagametophyte of the early collected seed is observed nor are there any increases in dry weight. Moreover, the main protein complement of the seeds remains proportionally the same irrespective of time of collections and artificial ripening. These suggest that artificial ripening of P. radiata seed is a maturation process rather than a developmental one. The practical implications of these findings are potentially good. Brown cone colour is no longer a pre-requisite indicator to commence cone harvesting. Infact cone collection as early as autumn/winter is justifiable provided that the cones are allowed to dehydrate at a temperature not exceeding 20°C for at least six weeks, or until the specific gravity drops below 1.00 because at this point seed extraction can be successfully done by the kilning method. Cone storage for more than nine weeks would not be advisable since the seed will begin to deteriorate owing to unfavourable storage conditions. At this stage seed should be extracted from the cones and stored separately at 5°C.
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    Male cone development in Pinus radiata : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Plant Biology at Massey University, Palmerston North, New Zealand
    (Massey University, 1995) Wang, Yunqiu; Wang, Yunqiu
    Light microscopy and transmission electron microscopy were used to investigate the morphological, anatomical changes and the timing of these changes during male cone development of Pinus radiata growing in the central part of the North Island, New Zealand. The timing of developmental events, including the initiation of the male cone primordia, the onset of meiosis of pollen mother cells and the formation of pollen grains were recorded. Their relationship with environmental factors in comparison with pine species growing in the Northern Hemisphere was discussed. Some significant morphological aspects of male cone buds, microsporophylls and structural/ultrastructural changes of microsporangia, tapetal cells and pollen mother cells during the meiotic processes in particular, were reported in the morphological and anatomical study. In correlation with these structural/ultrastructrual changes, the soluble protein content, banding patterns of the total soluble protein, banding patterns of four isoenzymes during male cone development were studied by SDS-PAGE and isoelectric focusing techniques. Seven soluble protein species were detected by SDS-PAGE closely related to the different developmental stages of the male cone, and one of them with a molecular mass of 20.5 KD in particular was found to be a potential male cone tissue specific gene expression product. Acid phosphatase, esterase, malate dehydrogenase and peroxidase were studied during male cone development, using isoelectric focusing methodology. Variations in banding patterns of the enzyme activity and number of isoforms of each enzyme in relation to the different developmental stages of the male cone were revealed. A number of isoforms of these four isoenzymes were found to be unique to specific developmental stages. A search for floral-specific genes controlling floral developmental events was attempted. MADS-box DNA sequences belonging to a homeotic gene family controlling floral development in higher plants are reported for the first time in the genus Pinus in this study. The MADS box gene AGAMOUS from Arabidopsis thaliana was used as a probe to hybridise with genomic DNA of P. radiata. The tentative evidence of hybridisations was obtained in Southern blots, suggesting the possible existence of MADS box related DNA sequences in P. radiata. PCR technique was subsequently used to clone these sequences from genomic DNA of radiata pine to confirm the result obtained from Southern blot study. PCR with two degenerate primers targeted to highly conserved regions within the MADS- box resulted in the amplification of a 78 bp DNA sequence. These PCR amplified pine DNA sequences were subcloned in M13 and were sequenced by the dideoxy protocol. The analysis of these DNA sequence data and the amino acid sequences deduced from these DNA sequences showed that these DNA sequences can be divided into three groups, probably belonging to three MADS-box genes of Pinus radiata. Two DNA sequence groups are most likely to be the conserved regions of pine MADS-box genes, controlling the late steps of "floral" development which are homologous to class C genes determining the identity of male floral parts (stamens) and female parts (carpels) in angiosperms. One DNA sequence group is speculated to be the conserved region of pine MADS-box gene controlling the earlier steps of floral development, analogous to class B genes controlling petal and stamen development in angiosperms