Browsing by Subject "Phytochrome"
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Item A theoretical analysis of the phototransformation of phytochrome(Texas Tech University, 1981-05) Kwak, Young-wooNot availableItem Aspects of vegetative and reproductive physiology of dwarf Pharbitis nil(Texas Tech University, 1979-12) Simmons, Harold AddrickDevelopmental and growth responses resulting from differences in the status of the endogenous rhythm, phytochrome, and gibberellin (GA). were analyzed in Pharbitis nil. The effects of these three components on floral induction, floral development, stem elongation and leaf expansion were assayed independently to determine if the action of each regulatory component is the same or different in growth and development processes. The status of the endogenous rhythm and/or phytochrome was effected by application of specific photoperiodic treatments known to influence these two components differently. In order to assay effects of both a change in phytochrome status and light perception during a light sensitive phase of the endogenous rhythm, responses were analyzed following exposure of plants to a diurnal (24 hour) short day with a light break at the eighth hour of darkness. In order to show the developmental regulation resulting only from light impingement on the endogenous rhythm, responses were analyzed following exposure of plants to a bidiurnal (48 hour) short day with a light break at the eighth hour of darkness. This light break is followed by a long dark period of sufficient length to allow phytochrome to become innocuous in reference to flowering. The influence of GA status was evaluated for each of the photoperiodic conditions above. The effects of GA were studied by comparing the growth and development of a GA deficient dwarf (strain Kidachi), to that of the dwarf treated with exogenous GA.,, and to that of a normal strain (Violet) which contains abundant endogenous GA. Normal and dwarf Pharbitis exposed to diurnal long days and diurnal short days with a light break remained vegetative due to combined inhibition imposed by the phytochrome status and light impingement during the photophobe (light sensitive) phase of the endogenous rhythm. However, plants exposed to diurnal light break cycles exhibited development of axillary buds which did not occur in plants subjected to diurnal long days. Application of GAo caused increased stem elongation, increased leaf area, and axillary bud development of plants exposed to diurnal long days or diurnal light break cycles. Both normal and dwarf Pharbitis subjected to diurnal or bidiurnal short days were induced to flower. Shoot apex analysis of dwarf plants exposed to bidiurnal short days revealed subapical elongation and development of axillary buds, characteristics found only on GA-treated plants from other photoperiods. Both exogenous and endogenous GA increased flowering, stem elongation, and leaf area of plants treated with diurnal or bidiurnal short days. Applied GA^ was sufficient to overcome the stem growth deficiency of the dwarf; however, flower production of the dwarf strain equaled that of the normal only if it received the extended dark period of a bidiurnal short day in conjunction with applied GA-. Therefore, the extended dark period must facilitate synthesis and/or utilization of some factor which enhances flowering. Pharbitis exposed to bidiurnal short days with a light break were induced to flower; however, the level of flowering was repressed compared to plants that received short day treatments. The length of darkness following the light break was sufficient for phytochrome reversion; therefore, the repression of flowering was due to light effect during a light sensitive phase of the endogenous rhythm. GA^ applied in conjunction with bidiurnal light break cycles increased flowering, stem elongation, and leaf area, but had no effect on the size or shape of developing floral primordia. These data show that the effects of the endogenous rhythm, phytochrome status, and GA, may be analyzed separately and in combination, and that these components affect development of Pharbitis nil in different ways.Item Comparative Genomics of Gossypium spp. through GBS and Candidate Genes ? Delving into the Controlling Factors behind Photoperiodic Flowering(2013-08-09) Young, Carla Jo LoganCotton has been a world-wide economic staple in textiles and oil production. There has been a concerted effort for cotton improvement to increase yield and quality to compete with non-natural man-made fibers. Unfortunately, cultivated cotton has limited genetic diversity; therefore finding new marketable traits within cultivated cotton has reached a plateau. To alleviate this problem, traditional breeding programs have been attempting to incorporate practical traits from wild relatives into cultivated lines. This incorporation has presented a new problem: uncultivated cotton hampered by photoperiodism. Traditionally, due to differing floral times, wild and cultivated cotton species were unable to be bred together in many commercial production areas world-wide. This worldwide breeding problem has inhibited new trait incorporation. Before favorable traits from undomesticated cotton could be integrated into cultivated elite lines using marker-assisted selection breeding, the markers associated with photoperiod independence needed to be discovered. In order to increase information about this debilitating trait, we set out to identify informative markers associated with photoperiodism. This study was segmented into four areas. First, we reviewed the history of cotton to highlight current problems in production. Next, we explored cotton?s floral development through a study of floral transition candidate genes. The third area was an in-depth analysis of Phytochrome C (previously linked to photoperiod independence in other crops). In the final area of study, we used Genotype-By-Sequencing (GBS), in a segregating population, was used to determine photoperiod independence associated with single nucleotide polymorphisms (SNPs). In short, this research reported SNP differences in thirty-eight candidate gene homologs within the flowering time network, including photoreceptors, light dependent transcripts, circadian clock regulators, and floral integrators. Also, our research linked other discrete SNP differences, in addition to those contained within candidate genes, to photoperiodicity within cotton. In conclusion, the SNP markers that our study found may be used in future marker assisted selection (MAS) breeding schemas to incorporate desirable traits into elite lines without the introgression of photoperiod sensitivity.Item Item Conformational changes in phytochrome induced by the chromophore phototransformation(Texas Tech University, 1987-05) Chai, Young GyuNot availableItem Excited states of photomorphogenic and visual receptors: phytochrome and retinylic chromophores(Texas Tech University, 1977-12) Chae, QuaeNot availableItem Hydrodynamic properties and molecular topography of phytochrome(Texas Tech University, 1983-05) Sarkar, Hemanta KumarNot availableItem Isolation and circular dichroic spectra of large phytochrome(Texas Tech University, 1978-05) Gardner, Jack DavidNOT AVAILABLEItem Molecular differences between the physiologically active (Pfr) and inactive (Pr) forms of phytochrome(Texas Tech University, 1983-05) Hahn, Tae-ryongNot availableItem Molecular Topography and Binding Properties of Phytochrome and Other Related Tetrapyrrolic Proteins(Texas Tech University, 1987-05) Singh, Bal RamNot Available.Item Physicochemical differences between the PR and PFR forms of phytochrome(Texas Tech University, 1987-12) Kwon, Tae-ikLight is one of the most important environmental factors that influences the life of plants. Plants utilize light energy to produce glucose through the process of photosynthesis for survival. In addition to the photosynthetic energy conversion process, plants respond developmentally to light in various ways. Phototropism and photomorphogenesis are typical examples of the response to light by plants. Phototropism is the phenomenon in which plants or plant organs bend toward light. By photomorphogenesis we refer to the light mediated changes in growth and differentiation of plants. Phototropism and photomorphogenesis involve specific regulatory photoreceptors for the perception of light signal. Although the photoreceptor for phototropism has not yet been identified, the photoreceptor for photomorphogenesis is relatively well characterized. The most important regulatory photoreceptor involved in photomorphogenesis is phytochrome. This photoreceptor plays a central role in controlling plant growth and development during every phase of the life cycle of plants. Some examples of the control include seed germination, stem elongation, plastidogenesis, biosynthesis of chlorophylls, carotenoids and anthocyanines, flowering, dormancy and senescence.Item Protein topography and binding properties of phytochrome(Texas Tech University, 1987-08) Choi, JungkapNot available