Grown for its distinctive foliage, Strobilanthes dyerianus is a popular bedding and container plant. A problem in production is that over-wintered stock plants often flower. Once the plant becomes reproductive, stem elongation slows and floral buds arise from every node, rendering the plants useless for propagation. The objectives of this research were to examine the effectiveness of manipulating environmental factors and the application of ethephon on preventing floral bud initiation, as well as determine optimal nitrogen rate for stock plant culture. The first experiment was performed in a glass greenhouse and ran 11 weeks, utilizing 8 h, 10 h, 12 h and a 4 h night interruption photoperiod treatments to determine critical photoperiod. None of the photoperiod treatments were significant for inhibiting flowering and there was a positive correlation between plant size and flowering. A second experiment was performed in growth chambers to create three photoperiods (8 h, 12 h and 16 h) with two temperature regimes (24C day/ 21C night and 17C day/ 14C night) for a total of six treatments. Neither photoperiod nor temperature inhibited bud initiation, and there was no correlation between plant size and flowering. The third experiment examined potential use of ethephon to maintain vegetative plants. Six rates of ethephon (0, 150, 300, 450, 600 or 750 mg·Lˉ¹) were applied at three frequencies (weekly, biweekly and monthly) over an eleven week period. Floral initiation was not totally inhibited, but flowering was highly correlated to plant size. Additionally, plant growth response to nitrogen was examined to determine the optimal rate for stock plant production. Plants were treated with 0, 100, 200, 300 or 400 mg·Lˉ¹ N from a 15 N – 2.2 P – 12.4 K fertilizer at each irrigation for eight weeks. There were no differences among plant quality ratings for plants receiving 100, 200, 300 or 400 mg·Lˉ¹ N, and plants grown with 200 mg·Lˉ¹ N had the largest leaf area and shoot dry weight. / Master of Science

No description available.

No description available.

Recently designated as a bioenergy crop, Sorghum is rather unique as it can produce large quantities of cellulose or sugar which can be used to produce advanced biofuels or compounds. Sweet sorghum contains high levels of sugars and biomass sorghums consist primarily of ligno-cellulosic biomass. Improvement of both sorghum types is essential for maximizing production and conversion efficiency. Photoperiod sensitive sorghum is thought to maximize biomass production yet maturity influence on biomass production and composition is not fully understood. Utilizing sorghum for sugar production has increased efforts to develop sweet sorghums with sugar yields similar to sugarcane. Hybridization of these species has been investigated with, until recently, little success. Testing newly developed intergeneric hybrids and improvement of parents used in their creation will determine their feasibility and improve hybrid performance. Objectives of this research are multifaceted. First, analyze photoperiod sensitive sorghum in varying day length environments to determine maturity effects on plant phenotype, composition, and QTL detection. Second, analyze intergeneric sorghum × sugarcane hybrids to determine agronomic performance in relation to sugarcane. Lastly, introgress the iap allele into sweet sorghum females for use in intergeneric hybrid creation. Photoperiod sensitive sorghum RILs were evaluated in College Station and Weslaco, Texas and Puerto Rico which caused differential expression of plant maturity. Genetic control of trait expression was high for each location. Results indicate gradual induction of plant maturity increases detection of phenotypic QTL and detection of compositional QTL increases when maturity effects on plant phenotype are reduced. Intergeneric sorghum × sugarcane F_1 hybrids were compared to sugarcane in Weslaco, Texas in 2011. Each hybrid expressed agronomic traits similar or better than that of the sugarcane variety. High levels of repeatability and genetic influence on trait expression were observed. Overall performance of the sugarcane variety was better than any individual hybrid tested. Introgression of iap into sweet sorghum was successful and generated seventeen new sweet sorghum female genotypes possessing the allele. Only two genotypes exhibited higher brix readings and both were later maturing than Tx3361. Height and maturity of all developed genotypes varied and desirability of developed lines was similar to Tx3361.

Genetic improvement of a number of crops including soybean (Glycine max L. [Merr]) has been associated with stay-green. Research on stay green genes has focused primarily on genes involved with photosynthesis and chlorophyll degradation. The current study explores the impact of a group of developmental genes, known as the E gene series, on the rate of soybean leaf senescence. The objective of this experiment was to determine the role of E-genes in the control of leaf senescence in soybean. The experiment was conducted in a split-plot design with three replications. The main plots were two photoperiods imposed following R1; i) natural day length (Amb) and ii) incandescent day length extension of 3 hours (Amb+3). The split plots were five E-gene near-isogenic lines (NILs), planted on different dates to obtain synchronous flowering. Phenology, photosynthesis, normalized difference vegetative index (NDVI) and fluorescence measurements were taken including, dark adapted photosynthetic efficiency (Fv/Fm), electron transport rate (ETR), and leaf chlorophyll concentration (SPAD). Leaf tissues were also analyzed for gene expression patterns among Harosoy isolines. Yield parameters like dry matter accumulation, harvest index and grain yields were recorded. The leaf net photosynthesis was more closely related to ETR than to SPAD values, suggesting that visual observation of stay-green may not be as effective in evaluating functional senescence as measurement of ETR. Cultivars with the dominant E1 allele maintained functional photosynthesis for longer, such that full senescence was delayed by 10-15 days in these cultivars. This phenomenon was observed under both photoperiod treatments and irrespective of the genetic background (Clark and Harosoy) in which the alleles appeared. Maintenance of functional photosynthesis by the E1 dominant allele can be attributed to maintenance of high ETR, and Fv/Fm, as well as delayed decline in leaf chlorophyll concentrations. Expression of senescence related genes were delayed in the isoline which had delayed leaf senescence phenotype. Consistent with the effect on leaf senescence, the dominant alleles also reduced the rate of phenological development, such that R5 occurred later in genotypes with dominant alleles and under the Amb+3 treatment. Cultivars with the dominant E1 allele under extended photoperiod treatment accumulated more biomass and had decreased apparent harvest index which caused no change in grain yields. The dominant E allele may delay leaf senescence directly or indirectly, through its delay of reproductive development.

Submitted by LIVEA MARIA GOMES (livea_pitti@hotmail.com) on 2016-02-02T12:14:18Z No. of bitstreams: 1 Dissertação Lívea M Gomes final com ficha (3).pdf: 1791851 bytes, checksum: eeb7f3ff7c0cffdcdb1eeb86397ed634 (MD5) / Approved for entry into archive by Sandra Manzano de Almeida (smanzano@marilia.unesp.br) on 2016-02-02T13:24:27Z (GMT) No. of bitstreams: 1 gomes_lm_me_bot.pdf: 1791851 bytes, checksum: eeb7f3ff7c0cffdcdb1eeb86397ed634 (MD5) / Made available in DSpace on 2016-02-02T13:24:27Z (GMT). No. of bitstreams: 1 gomes_lm_me_bot.pdf: 1791851 bytes, checksum: eeb7f3ff7c0cffdcdb1eeb86397ed634 (MD5) Previous issue date: 2015-12-11 / Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) / O objetivo do presente estudo foi avaliar os efeitos do aumento do nível de triptofano na dieta de leitões desmamados submetidos a diferentes programas de luz. Foram utilizados 72 leitões desmamados aos 21 dias de idade (peso inicial de 6,6+ 2,33 kg). O delineamento experimental foi o de blocos casualisados com 24 dias de duração em esquema fatorial 2 x 2 (PL: 12 ou 23h de luz/dia e dois NT digestível: 2,6 ou 5,2 g de L-Trp / kg de ração pré-inicial 1 (0-14 dias) e de 2,4 ou 4,8 g de L-Trp / kg na dieta pré-inicial 2 (15-24 dias), com 6 repetições e 3 animais por parcela. Foram avaliados o desempenho, glicemia, perfil plasmático do cortisol e comportamento dos animais. A glicose no sangue foi determinada nos dias 0 e 24, e o cortisol nos dias 0 e 8. O comportamento foi observado nos dias 2, 9, 16 e 23. Não houve interação entre PL e NT sobre desempenho e glicose. Nos períodos de 0-14 e 0-24 dias, os tratamentos não influenciaram o ganho diário de peso, consumo diário de ração e glicose no sangue, enquanto que a conversão alimentar melhorou (P<0,05) apenas no período de 0-14 dias para os animais que receberam 12 horas de luz/dia. Os tratamentos não influenciaram a frequência do comportamento “em movimento”, entretanto houve interação entre PL e NT para o cortisol plasmático, frequência dos comportamentos “ócio” e “alimentar”. Leitões que receberam o maior NT apresentaram menor nível de cortisol plasmático (P<0,05), menor comportamento “alimentar” (P<0,05) e maior comportamento “ócio” (P<0,05) em relação aos animais que receberam NT normal quando submetidos ao PL de 23 horas de luz/dia. O uso de PL de 23h de luz/dia não é indicado, entretanto, quando este manejo for adotado o maior nível de triptofano na dieta é recomendado. / The objective of the present study was to avaluate the effects of light programs (LP) and tryptophan levels (TL) in the diet on performance, blood glucose, plasma profile of cortisol and behavior. A total of 72 piglets weaned at 21 days of age (starting weight 2.33 kg 6,6±) was used. The experimental design was randomized blocks with 24 days duration in a factorial 2 x 2 (LP 12 or 23h light / day and two digestible TL: 2.6 or 5.2 g of L-Trp / kg diet on pre-starter 1 (0-14 days) and 2.4 or 4.8 g of L-Trp / kg diet on prestarter 2 (15-24 days), with 6 repetitions and 3 animals per pen. Glucose blood was determined on d 0 and 24, and cortisol on d 0 and 8. The behavior was observed on d 2, 9, 16 and 23. No effects of PL and NT interaction were observed on performance and blood glucose. In periods of 0- 14 and 0-24 days, the treatments did not influence the daily weight gain, daily feed intake and blood glucose, while feed conversion improved (P <0.05) only in the period of 0-14 days for piglets receiving PL 12h light / day. Treatments did not influence the frequency of “moving” behavior, however there was interaction between PL and NT for plasma cortisol, frequency of “feeding” and “lying” behavior. Piglets that received high NT had lower plasma cortisol level (P <0.05), lower “feeding” behavior (P <0 .05) and increased “lying” behavior (P <0.05) compared to animals that received normal NT when subjected to PL 23 hours light / day. The PL 23h light / day isn’t indicated for piglets, but when this happen, highest tryptophan level in the diet is recommended.

Studies were conducted to better understand the effect of temperature, photoperiod, cultural practices, and growth regulators on the hardening and dehardening of peach tree wood. Greenhouses were constructed to control temperatures to which peach trees were exposed. It was noted that hardening and dehardening usually followed the temperature fluctuation fairly closely. However, trees exposed to temperatures above 60 F (15. 6 C) became hardy to 0 F (-17. 8 C). A photoperiodic response in regard to an increase or decrease in hardiness was not definitely observed in peach wood. Extended photoperiod did not produce any significant effect on hardiness. Defoliation, bloom date, and fruit set were all the same as the controls. The cultural practices of fall pruning and heavy late summer fertilization with nitrogen did not result in a change in the hardiness level of the trees when compared with the controls. Likewise gibberellic acid spray had no effect. Defoliation produced serious physiological damage when done in mid-August, while defoliation in mid-September was not nearly so damaging, Defoliated trees were less hardy than the controls until mid winter.

Flower forcing to meet holiday market can increase the value of potted flowering plants. This study was to investigate the effects of chilling and post-chilling photoperiod treatments on flowering of banana shrub and the effects of water stress, daminozide, chlormequat, and ethephon on flowering of bougainvillea. Experiments were conducted at R.R. Foil Plant Science Research Center and MSU Dorman Greenhouse at Mississippi State University (MSU), Mississippi State, MS. Results from banana shrub experiment indicated that 8-week chilling at 8 ºC was necessary for banana shrub to break bud dormancy and a tank mix of daminozide and chlormequat was able to increase the number of flower buds on banana shrub. Results from bougainvillea experiment indicated that water stress, daminozide, and chlormequat enhanced flowering. In conclusion, this study provided fundamental information to future research on flower forcing of banana shrub and bougainvillea.

Yes / Life in a seasonally variable environment has evolved to interpret the time of year through day length (photoperiod) which is translated into a neurochemical signal. In mammals, the pars tuberalis is a key site where seasonal time signal (melatonin) interfaces and relays photoperiodic information to the hypothalamus via thyrotropin. Recent work has elucidated a potential circannual clock in ‘calendar cells’ of the pars tuberalis. In the hypothalamus, tanycytes are an integral part of the hypothalamic network. Previous studies show the importance of local synthesis of thyroid hormone and retinoic acid in tanycytes. Recently novel downstream neuroendocrine signals, e.g. VGF, FGF21 and chemerin, were identified to govern seasonally appropriate phenotype. Additionally, the hypothalamic-pituitary-growth axis has been implicated in seasonally bodyweight and torpor regulation. Here, we will focus on the endocrine drivers of photoperiod response and highlight novel downstream effects on bodyweight and growth focusing on recent findings from seasonal rodent studies.

Master of Science / Department of Agronomy / Scott A. Staggenborg / Current demand for ethanol production is stressing feedstock production. Previous research has shown sweet sorghum and photoperiod sensitive sorghum [Sorghum bicolor (L.) Moench] as viable feedstocks which may supplement or replace current feedstocks. Studies were conducted at two dryland locations in north central and northeast Kansas in 2008 and 2009 to determine the effects of cultivar, nitrogen fertilizer rate, plant density, and harvest date on sweet sorghum juice and biomass yields. The cultivar study indicated the cultivar ‘M81E’ generally had the greatest yield. Other cultivars were not well suited for this region. No significant results were found in the nitrogen rate trial, indicating sweet sorghum may be insensitive to nitrogen fertilizer applications. The plant density trial results indicated that sweet sorghum possess a great ability to compensate for plant spacing. No differences were found in juice yields across densities, and the only difference found in total dry biomass was at the highest plant density. Results from the harvest date study indicate that sweet sorghum harvest should be delayed until at least the grain soft dough stage and can be continued for at least 10 days after a killing freeze without a yield penalty. Delaying harvest allowed for an increase in total dry matter and fermentable carbohydrates without a decrease in juice yield. Two studies were conducted at two dryland locations in northcentral and northeast Kansas in 2008 and 2009 to determine the effects of plant density on photoperiod sensitive sorghum yields, with an additional study to determine the effects of winter weathering. Photoperiod sensitive sorghum was found to be similarly insensitive to plant density, with few differences found in total dry biomass yield. Yields were found to decrease significantly due to winter weathering. A final study was conducted to examine a variety of sorghums as biofuel feedstocks. Photoperiod sensitive sorghum yielded the greatest in 2008 while sweet sorghum yielded less. In 2009, sweet and photoperiod sensitive sorghum yielded less than the cultivar TAMUXH08001. Sweet sorghum yields are generally the greatest with ‘M81E’ and when harvested after soft dough. Yields of both sorghums are occasionally influenced by plant density.