Browsing by Subject "Plant growth"
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Item The effects of extracellular ATP on growth in Arabidopsis thaliana(2007-08) Butterfield, Timothy Scott; Roux, Stanley J.Exciting contributions to the field of plant biology have challenged traditional views of and modes of signaling molecule action and activities. In addition to startling and widely touted discoveries such as F-box protein auxin receptors and endomembrane ethylene receptors, evidence has accumulated indicating that ATP may possess a non-canonical function external to the plant cell as a signaling agent. Recent publications have detailed the presence of extracellular ATP at the growing end of root tips, extracellular ATP-induce fluxes in cytosolic calcium, and the effects of extracellular ATP upon root growth and pollen tube elongation. Within these pages, I present evidence for concentration-dependent effects of extracellular ATP upon etiolated hypocotyl elongation and gene expression changes. These findings prompted us to measure the ATP concentration in wound serum of WT and mutant plants that produce an NTDPase, or apyrase (atAPYOE) protein in greater abundance than WT, and we found that the ATP concentration in wound serum derived from the atAPYOE mutants is lower than WT. I also report that apyrase protein levels decrease following exposure to red light, that it is present on the plasma membrane, and the active site likely faces the extracellular matrix. Finally, I describe my attempts to directly label a putative ATP-receptor protein predicted to reside on the external face of the plasma membrane. I have labeled a small number of plasma membrane proteins using a photoactive, radioactive ATP-derivative. As described more fully in the text, the predicted sequence of the labeled proteins was generated using mass-spec fingerprinting. In sum, I present novel data that contributes to our understanding of how plants and the plant cell perceive and respond to the external environment.Item Growth and consumer evaluation of Cucumis sativus L. cultivated in controlled environments(2008-12) Crosby, Leah C.; Peffley, Ellen B.Cucumber is a commonly consumed vegetable that is growing in popularity. Recently, there has been an increase in cucumber cultivation in controlled environments. The overall objectives of this research were to (1) identify a cucumber cultivar for optimal growth in a controlled environment, (2) investigate the effects of elevated CO2 on fruit production and plant growth, and (3) evaluate consumer perception of cucumber. Ten Cucumis sativus L. cultivars were hydroponically, greenhouse-grown in a randomized block design to evaluate fruit production and plant growth. Of the cultivars screened, the gynoecious, parthenocarpic cultivars produced the most fruit; of which, the cultivar ‘Rocky’ was chosen as the elite cultivar for optimal growth in a controlled environment. ‘Rocky’ was chosen for evaluation in the growth chamber trials because it is a quick-growing cultivar that yields a heavy, concentrated fruit set, a relatively high harvest index, a low disease incidence, and is aesthetically pleasing. The elite cultivar ‘Rocky’ was grown at 400 and 2000 ppm CO2 to evaluate fruit production and plant growth. Plants grown at 2000 ppm CO2 had an increase in vegetative and reproductive growth when compared to plants grown at 400 ppm CO2. As part of an outreach program, Texas Tech University horticulture students participated in a Hydroponic Cucumber Lab in which they were able take care of cucumber plants and taste the cucumbers they grew. In order to evaluate consumer perception of cucumber, the horticulture students were administered a survey, consisting of a pre- and post-test, which asked students demographic questions and questions about their cucumber eating habits in general. A majority of the students indicated they liked cucumbers and the post-test showed that the student’s perception of cucumber had changed. Sensory panels were conducted to evaluate appearance and taste perception of cucumber. Two cultivars were evaluated: ‘Rocky’ and ‘Socrates’. Students indicated they liked the appearance of ‘Socrates’ more than ‘Rocky’. ‘Socrates’ looks more like a traditional slicer sold in supermarkets; ‘Rocky’ is a non-traditional pickler that is harvested at a shorter length and has a smooth yellowish skin. Overall, students indicated they liked the taste of ‘Rocky’ and ‘Socrates’.Item Knowing them by knocking them out : initial studies to characterize Arabidopsis annexin gene family function(s)(2007-05) Cantero-Garcia, Maria Araceli, 1967-; Roux, Stanley J.Annexins are a multigene family in most plant species and are suggested to play a role in wide variety of essential cellular processes. Analysis of paralogous blocks within the genome of Arabidopsis showed that AnnAt6 was a duplicated gene from AnnAt1 and AnnAt2. The motif analysis of the promoters of these three annexins indicated some putative functional redundancy but also agreed with the model that duplicated genes functionally diverge over time and undergo functional specialization that can principally be observed in their regulatory regions. This in silico analysis contributes important information which can be used to guide phenotypic analysis of mutants. The use of quantitative real time reverse transcription PCR (quantitative real time RT-PCR) to assess differential expression of annexins in different tissues from 5.5 day-old etiolated seedlings showed a trend of major expression of annexins in root and hypocotyl tissues compared to cotyledon tissue. This result supports previous data about the participation of annexins during growth and development. The light-dependent regulation of annexin gene expression was also examined using etiolated seedlings under red and far-red light conditions by quantitative real time RT-PCR. Red light treatment significantly altered transcript levels in hypocotyls and cotyledons for AnnAt5 and AnnAt6, respectively, and this early up-regulation was reversible by far-red light, implicating phytochrome as the receptor mediating this response. In order to begin testing the hypothesis that plant annexins have individual functions, over thirty annexin putative T-DNA insertional lines were obtained and screened. After a screen of these mutants, further work was focused on fourteen lines for which annexin insertion sites were confirmed. For AnnAt1 through AnnAt5 at least two allelic lines and for AnnAt6 and AnnAt7 one allelic line has been confirmed by PCR. For some of them the absence of mRNA was determined by RT-PCR which confirms that they are true knockouts. These annexin T-DNA insertion lines will allow for future phenotypic characterization and likely provide valuable information regarding individual functions of Arabidopsis annexins.