Herbaceous peonies (Paeonia lactiflora Pall.) are common perennials used both in gardens and the landscape as well as for cut flowers. Peonies require a chilling period to break dormancy but not for flower bud differentiation. For all studies discussed in this dissertation, two peony cultivars, Sarah Bernhardt and Inspecteur Lavergne, small (3–5 eye) crowns from Holland were potted in 3.8-L pots in mid-November of 2017 and 2018. Our overall objective was to determine if we could manipulate chilling time, along with application of gibberellic acid (GA3) and growth retardants, to produce marketable containerized peonies from a small crown in a single season (November to May). We evaluated chilling, GA3 and a growth retardant (uniconazole; UNZ) under controlled chilling and greenhouse forcing conditions. All potted plants were held outdoors at Battlefield Farms (Rapidan, VA, 38˚ N) for 4 weeks [in 2017, 400 chilling units (CU) according to Fulton Chilling Model] or in a 10°C cooler for 5.5 weeks (in 2018, 400 CU) to root, then placed in a 5°C cooler for 3, 4 or 5 weeks (total 752, 869 or 986 CU). GA3 was applied as a 0 or 100 mg·L-1 drench at 250 ml/pot after the plants were moved into the Virginia Tech greenhouse (Blacksburg, VA, 37˚ N) for forcing. Uniconazole drenches were applied to each cultivar under each chilling treatment at 355 ml/pot at 0, 15, or 20 mg·L-1 at 7 days after the GA3 drench applications. Three weeks chilling at 5°C (752 CU total) provided sufficient chilling for 'Sarah Bernhardt' and 'Inspecteur Lavergne'. Application of GA3 reduced production time and resulted in a greater number of shoots, and, in three of the four studies, increased the number of flowering shoots in three of the four studies. Substrate drench application of 15 mg·L-1 UNZ prior to spring emergence reduced plant width moderately resulting in improved compactness of both cultivars. We evaluated the effects of plant growth retardants applied with different methods at different stages of production on the growth and development of containerized peony under nursery conditions. All potted plants were placed in an unheated coldframe at the Virginia Tech Urban Horticulture Center (Blacksburg, VA, 37˚ N) for one month after potting to promote rooting and then were moved outdoors to a gravel pad to receive natural chilling from November to February. In 2017–18, substrate drenches of UNZ at 0, 15, 30 or 45 mg·L-1 or paclobutrazol (PBZ) at 0, 30, 60 or 90 mg·L-1 at 237 mL/pot were applied about 4 weeks after potting for both cultivars in mid-December 2017. In 2018–19, fall drenches of uniconazole at 0, 15, 30 or 45 mg·L-1 at 237 mL/pot were applied about 4 weeks after potting in mid-December 2018, or spring sprenches of uniconazole were applied at 0, 15, 30 or 45 mg·L-1 at 840 mL·m-2 in March 2019 after 50% shoot emergence for each cultivar. Plant growth retardant applications had little effect on plant growth of either cultivar, but treated plants were of a darker green color compared to the control plants. In addition, higher rates of uniconazole applied as a fall drench increased the number of flowering shoots of both cultivars and the percentage of plants flowering for 'Sarah Bernhardt' in the second season of the study where plants were more protected from spring freezes. Fall paclobutrazol drenches or spring uniconazole sprenches had little effect on flowering. To determine the best timing for spring GA3 applications under nursery conditions, we applied three models based on natural chilling accumulation. The models were a modified Fulton Chilling Model (FCM) for herbaceous peonies, Blackberry Chilling Model 5 (BCM5) for blackberry, or a visual development model (VDM) which was 10% of plants showing shoot emergence in the spring. We choose 1,000 CU for the first two chilling models as the chilling required to break dormancy and promote normal plant growth and flowering. All plants were held in an unheated coldframe at the Virginia Tech Urban Horticulture Center for one month after potting to promote rooting, then were moved outdoors to a gravel pad to receive natural chilling over the winter months. Drenches of 0 or 100 mg·L-1 GA3 were applied at 250 mL/pot to each cultivar under each chilling model when the specific conditions were met. Due to greater winter injury in the 2017–18 season, results varied by year. In the 2017–18 season, GA3 applied according to BCM5 reduce days to emergence for both cultivars and reduce the plant width of 'Inspecteur Lavergne', and later application according to BCM5 and VDM reduced plant length and diameter of 'Sarah Bernhardt'. Reductions in plant size may have been due to greater winter injury due to the earlier emergence of GA3 treated plants. In the 2018–19 season, earlier GA3 drench applications tended to reduce days to emergence for both cultivars and the FCM application reduced days to bud for 'Inspecteur Lavergne', but GA3 drench applications had no effect on plant size. GA3 can be applied after chilling (1,000 CU) using a suitable chilling model such as FCM for peonies, or BCM5, or VDM, but GA3 had little effect on plant development under nursery conditions. We also evaluated GA3 effects on peony bud differentiation and development during controlled chilling and early forcing, as well as effects on growth and flowering. All potted plants were held in a 10°C cooler for 5.5 weeks (400 CU) to root, then placed in a 5°C cooler for 4 weeks (total 869 CU). GA3 was applied at 0 or 100 mg·L-1 pre-chilling or post-chilling as a 250 ml/pot drench. Bud differentiation and development of excised buds were evaluated using a stereomicroscope at potting, after rooting (before chilling), after 1, 2, 3 or 4 weeks of chilling, and at 5, 10 or 15 days after the beginning of forcing. All buds were removed from the sample plants, measured for bud length and diameter, and dissected under a stereomicroscope to assess differentiation stages. Root dry weights and crown dry weights were also determined after rooting, after chilling, and at 15 days of forcing. Ten plants of each treatment were grown in the Virginia Tech greenhouse after chilling until flowering. GA3 applications did not advance the bud development stage because most of buds were already in the reproductive stages before dormancy, but GA3 enhanced bud elongation during chilling and the early forcing period. Our findings suggest that GA3 applications can reduce the time to emergence and flowering, as well as increase the numbers of shoots and flowering shoots. GA3 applied right after rooting in, prior to the chilling period, or before greenhouse forcing, resulted in earlier emergence and flowering with higher quality plants. However, earlier applications, pre-chilling, tended to produce plants with more shoots. Overall, our experiments indicate that three weeks of chilling at 5°C (752 CU total) is a sufficient chilling regime for forcing 'Sarah Bernhardt' and 'Inspecteur Lavergne' peonies, and 1,000 CU of naturally accumulated chilling is sufficient for nursery production. GA3 applications can reduce the time to emergence and flowering, as well as increase the numbers of total shoots and flowering shoots. Timing of GA3 application is flexible; it can be applied right after rooting, before the chilling period, just before greenhouse forcing, or after shoots have begun to emerge. Plant growth retardant applications had a little effect on the growth of tested cultivars, but all plants treated with growth retardants are generally darker green in color. Additionally, growth retardant applications have some positive effects on flowering. / Doctor of Philosophy / Herbaceous peonies (Paeonia lactiflora Pall.) are common perennials used both in gardens and the landscape as well as for cut flowers. Peonies require a chilling period to break dormancy but not for flower bud differentiation. For all studies, two peony cultivars, Sarah Bernhardt and Inspecteur Lavergne, 3 to 5 eye small crowns from Holland were potted in 3.8-L pots in mid November of 2017 and 2018. Our overall objective was to determine if we could manipulate chilling time, along with application of gibberellic acid (GA3) and growth retardants, to produce marketable containerized peonies from a small crown in a single season (November to May). We evaluated chilling, GA3 and a growth retardant (uniconazole) under controlled chilling and greenhouse forcing conditions. We evaluated the effects of plant growth retardants (uniconazole or paclobutrazol) applied with different methods (fall drenches or spring sprenches) at different stages of production on the growth and development of containerized peony under nursery conditions. To determine the best timing for spring GA3 applications under nursery conditions, we applied three models based on natural chilling accumulation. We also evaluated GA3 effects on peony bud differentiation and development during controlled chilling and early forcing, as well as growth and flowering. Overall, 3 weeks chilling at 5°C [752 chilling units (CU) total] is a sufficient chilling regime for forcing 'Sarah Bernhardt' and 'Inspecteur Lavergne' peonies, and 1000 CU naturally accumulated chilling is sufficient for nursery production. GA3 applications can reduce the time to emergence and flowering, as well as increase the numbers of shoots and flowering shoots. Timing of GA3 application is flexible, it can be applied right after rooting, after the chilling period, or after shoots have begun to emerge. Plant growth retardant applications had little effect on plant growth of either cultivar, but all plants treated with growth retardants were darker green in color. Additionally, growth retardant applications had some positive effects on flowering.

Made available in DSpace on 2016-12-08T16:44:45Z (GMT). No. of bitstreams: 1 PGPV13MA127.pdf: 511615 bytes, checksum: 8ea8d8706c74bcaf1ec6542c4f4ef048 (MD5) Previous issue date: 2013-07-25 / The lack of incentive to production, small crop area and low grain yield are the main factors to annual deficit in Brazilian wheat production. The production can be increased by the area and/or grain yield. The use of nitrogen in wheat can to increase grain yield, but the N excess associated to the weather (rain and wind) can lead the occurrence of lodging and negatively affect the yield and grain quality. Thus, the aim of this study was to evaluate the effects of nitrogen application during the grain filling, associated with the use of plant growth retardants on the characteristics of plant height, yield and industrial quality of wheat cultivar Mirante. The experiment was carried out under field conditions in the experimental area of the Santa Catarina State University - UDESC in Lages SC, in the 2011 and 2012 growing seasons. The experimental design was a randomized block with four replications. For plant height and yield were used two times of application of nitrogen (at vegetative and vegetative plus reproductive stages) associated with six- growth retardants. For industrial quality evaluations the nitrogen topdressing was used in two application times (at vegetative and vegetative plus reproductive stages) associated with etil-trinexapac retardant. In both experiments the retardants were applied in two doses (stages 31 and 32 first and second visible nodes in the main stem of the plant) plus the control. Treatments were: control (no retardant), mepiquat chloride (25 g a.i. ha-¹), chlorocoline chloride (25 g a.i. ha-¹), chlormequat chloride (25 g a.i. ha-¹), etil-trinexapac (100 g a.i. ha-¹), proexadione-Ca (110 g a.i. ha-¹) and ethephon (110 g a.i. ha-¹), which were applied by sprayer pressurized with CO2 at a rate equivalent to 200 L ha-¹. The use of growth retardant lead to shortest plant height, and the etil-trinexapac and proexadione-Ca were provided to lowest plant height. The use growth retardant plus nitrogen fertilization in the reproductive stage did not affect grain yield. The use of etil-trinexapac positively affected the tenacity, extensibility, extensibility and toughness over falling number. Applying N at reproductive stage of wheat led to an increase in sedimentation, extensibility, protein content, wet gluten, dry gluten and gluten strength in improving the industrial quality of wheat; however the magnitude of the response was dependent manner of the environmental conditions in each crop year / A falta de incentivo à produção, a pequena área cultivada e os baixos tetos produtivos são fatores que contribuem para o déficit anual na produção brasileira de trigo. O aumento da produção pode ser por aumento da área e/ou da produtividade de grãos. O uso de nitrogênio na cultura do trigo visa o aumento da produtividade, porém o excesso deste nutriente aliado ao clima (chuva e vento) pode favorecer a ocorrência de acamamento e diminuir o rendimento e a qualidade final dos grãos. Desta forma, o objetivo desse trabalho foi avaliar os efeitos da aplicação de nitrogênio em cobertura durante o estádio vegetativo e reprodutivo, associado ao uso prévio de redutores de crescimento sobre as características de altura de planta, produtividade e qualidade industrial do trigo, cultivar Mirante. O experimento foi conduzido em campo, na área experimental da Universidade do Estado de Santa Catarina - UDESC, em Lages SC, nos anos agrícolas 2011 e 2012. O delineamento experimental empregado foi o de blocos ao acaso, com quatro repetições. Para altura de plantas e produtividade foram utilizados dois diferentes momentos de aplicação de nitrogênio em cobertura (estádio vegetativo) e (estádio vegetativo+reprodutivo) associado ao uso prévio de seis redutores de crescimento. Para a qualidade industrial foi utilizado o nitrogênio em dois diferentes momentos de aplicação de nitrogênio em cobertura (estádio vegetativo) e (estádio vegetativo+reprodutivo) associado ao uso prévio do redutor de crescimento etil-trinexapac. Em ambos os experimento os redutores foram aplicados em duas doses (estádios 31 e 32 primeiro e segundo nós visíveis no colmo da planta) mais a testemunha. Os redutores utilizados foram: testemunha (sem redutor), cloreto de mepiquate (25 g i.a. ha-¹), cloreto de clormequate (25 g i.a. ha-¹), cloreto de clorocolina (25 g i.a. ha-¹), etil-trinexapac (100 g i.a. ha-¹), proexadione-Ca (110 g i.a. ha-¹) e o etefom (110 g i.a. ha-¹); os quais foram aplicados via pulverizador costal pressurizado com CO2, com uma vazão equivalente a 200 L ha-¹. O emprego dos redutores de crescimento reduziu a altura das plantas, sendo que o etil-trinexapac e o proexadione-Ca foram os que proporcionaram plantas de menor altura. O uso dos redutores de crescimento e da adubação nitrogenada no estádio vegetativo+reprodutivo não afetou o rendimento de grãos. O emprego do etil-trinexapac afetou positivamente a tenacidade, extensibilidade, relação tenacidade/extensibilidade e o número de queda. A aplicação de N na fase reprodutiva do trigo propiciou um aumento na extensibilidade, teor de proteína, glúten úmido, glúten seco e na força do glúten melhorando a qualidade industrial do trigo, entretanto a magnitude da resposta foi dependente do ano agrícola