The demand for local sustainably grown produce and flowers has increased (Low et al., 2015), and stimulated a growing interest in high tunnel production. The goal of this research project was to evaluate the production of cut flowers in high tunnel structures and in the field in the Northern Great Plains (NGP) region. The NGP offers unique climatic and environmental challenges based on its continental climate. Specialty cut flower cultivars Karma Irene and Chocolate dahlia (Dahlia x hybrida), Potomac White and Rocket Mix snapdragon (Antirrhinum majus), and Mariachi Misty Blue, Echo Blue and ABC2 lisianthus (Eustoma grandiflorum) were planted in both field and high tunnel environments at two soil temperature setpoints in the NGP to determine which of the selected crops are best suited for cut flower production. Our results indicate higher yields and more consistent quality in the high tunnel; however, the field was suitable for all species investigated.

Master of Science / Department of Horticulture, Forestry, and Recreation Resources / Jason Griffin / The Midwest and southern Great Plains regions of the United States are known for historic and severe droughts. However, short-term recurring drought events are more common and can limit tree survival in landscape and production settings. The pressure of environmental stress combined with numerous diseases and pests are decimating existing Pinus L. spp. (pine) plantings and driving the effort to identify alternative species. Four species of conifer were grown in a pine bark substrate and subjected to recurring moderate to severe drought in a controlled environment glass greenhouse as well as field planted to observe root and shoot growth during the initial 12 months after transplant. The species utilized were Abies nordmanniana (nordmann fir), Cupressus arizonica (Arizona cypress), Picea engelmannii (engelmann spruce), and Thuja x ‘Green Giant’ (‘Green Giant’ arborvitae). Results indicate that C. arizonica exhibited extraordinary growth after establishment and was able to maintain growth and photosynthesis following several drought cycles. Thuja x ‘Green Giant’ exhibited significant increase in root and shoot growth after transplant. Under conditions of moderate and severe drought, only minimal reductions in height and shoot dry weight were observed while root growth and photosynthesis were unchanged. Abies nordmanniana experienced minimal increases in root and shoot growth throughout the growing season and was unaffected by drought. In contrast, P. engelmannii had only modest increases in root dry weight after transplant, while shoot growth was non-existent. Under conditions of severe drought, photosynthesis was reduced. Cupressus arizonica, a known drought tolerant species, with its ability to establish quickly and endure drought may have an advantage when establishing in harsh climates such as the Midwest and southern Great Plains. Thuja x ‘Green Giant’ is known to be a rapid grower, however, it established slowly during the current study and may require additional time before resuming rapid growth and maximum drought tolerance. Slow establishing species such as A. nordmanniana and P. engelmannii may require greater attention to season of planting to coincide with rapid root growth. However, P. engelmannii may not be a suitable choice for the Midwest due to the inability to maintain photosynthesis during periods of drought.

Com os objetivos de (i) caracterizar o acúmulo de massa de matéria seca da parte aérea do desenvolvimento relativo em dois ambientes de cultivo (casa-de-vegetação e campo); e (ii) quantificar a massa de matéria seca relativa de folha nos dois ambientes de cultivo, foram conduzidos sete experimentos no Departamento de Fitotecnia da Universidade Federal de Santa Maria, Rio Grande do Sul, (latitude: 29º42 Sul, longitude: 53º42 Oeste, altitude: 95 m), com a cultura de alface, variedade cultivada Regina, nos dois ambientes de cultivo, em cinco épocas (primavera [1 experimento], verão [3], verão/outono [1], outono [1] e inverno [1]). Em função do critério utilizado (valor mínimo de massa de matéria verde de referência da parte comercializável para se proceder a colheita foi 200 g por planta), houve diferença de duração do ciclo (número de dias entre o transplante e a colheita) nos dois ambientes de cultivo (casa-de-vegetação e campo), pois o acúmulo de massa de matéria seca da parte aérea (g.planta-1) foi igual em todas as épocas de cultivo, mas a duração do ciclo foi sempre inferior na casa-de-vegetação. Em função dos resultados obtidos, pode-se concluir que: (i) as curvas de caracterização do acúmulo de massa de matéria seca (Ms) da parte aérea em função do desenvolvimento relativo (Dr) da cultura de alface foram estatisticamente utilizáveis para todas as estações estudadas em casa-de-vegetação e campo; e (ii) o órgão com maior produção de massa de matéria seca foi a folha. O percentual da matéria seca produzida destinada às folhas ficou entre 73,5% e 93,5% para casa-de-vegetação e entre 56,8 e 91,5% para o campo. / With the purposes of (i) characterizing the accumulation of dry mass according to the relative development in two environments of cultivation (plastic greenhouse and field); and (ii) quantifying the relative leaf dry mass in these environments, seven experiments were carried out at Crop Science Department of the Federal University of Santa Maria, State of Rio Grande do Sul, (latitude: 29º42 South, longitude: 53º42 West, altitude: 95 meters), with the lettuce crop, cultivar \'Regina\', in five seasons (spring [1 experiment], summer [3], summer/autumn [1], autumn [1] and winter [1]). According to the used criterion (minimum value of the reference fresh mass of the marketable part to make the harvest was 200 g per plant), there was difference in cycle duration (number of days between the transplanting and harvesting) in two environments (plastic greenhouse and field), because the dry matter accumulation (g.plant-1) was equal in all seasons, but the cycle duration was always lower in plastic greenhouse. According to the results, we can conclude that: (i) the dry matter accumulation characterizing curves, as function of the relative development of lettuce crop, were statistically usable for all studied seasons for greenhouse and field; and (ii) the organ with higher dry matter production was the leaf. The percentage of leaf dry matter was between 73.5% and 93.5% for plastic greenhouse, and between 56.8 and 91.5% for the field.

Com os objetivos de (i) caracterizar o acúmulo de massa de matéria seca da parte aérea do desenvolvimento relativo em dois ambientes de cultivo (casa-de-vegetação e campo); e (ii) quantificar a massa de matéria seca relativa de folha nos dois ambientes de cultivo, foram conduzidos sete experimentos no Departamento de Fitotecnia da Universidade Federal de Santa Maria, Rio Grande do Sul, (latitude: 29º42 Sul, longitude: 53º42 Oeste, altitude: 95 m), com a cultura de alface, variedade cultivada Regina, nos dois ambientes de cultivo, em cinco épocas (primavera [1 experimento], verão [3], verão/outono [1], outono [1] e inverno [1]). Em função do critério utilizado (valor mínimo de massa de matéria verde de referência da parte comercializável para se proceder a colheita foi 200 g por planta), houve diferença de duração do ciclo (número de dias entre o transplante e a colheita) nos dois ambientes de cultivo (casa-de-vegetação e campo), pois o acúmulo de massa de matéria seca da parte aérea (g.planta-1) foi igual em todas as épocas de cultivo, mas a duração do ciclo foi sempre inferior na casa-de-vegetação. Em função dos resultados obtidos, pode-se concluir que: (i) as curvas de caracterização do acúmulo de massa de matéria seca (Ms) da parte aérea em função do desenvolvimento relativo (Dr) da cultura de alface foram estatisticamente utilizáveis para todas as estações estudadas em casa-de-vegetação e campo; e (ii) o órgão com maior produção de massa de matéria seca foi a folha. O percentual da matéria seca produzida destinada às folhas ficou entre 73,5% e 93,5% para casa-de-vegetação e entre 56,8 e 91,5% para o campo. / With the purposes of (i) characterizing the accumulation of dry mass according to the relative development in two environments of cultivation (plastic greenhouse and field); and (ii) quantifying the relative leaf dry mass in these environments, seven experiments were carried out at Crop Science Department of the Federal University of Santa Maria, State of Rio Grande do Sul, (latitude: 29º42 South, longitude: 53º42 West, altitude: 95 meters), with the lettuce crop, cultivar \'Regina\', in five seasons (spring [1 experiment], summer [3], summer/autumn [1], autumn [1] and winter [1]). According to the used criterion (minimum value of the reference fresh mass of the marketable part to make the harvest was 200 g per plant), there was difference in cycle duration (number of days between the transplanting and harvesting) in two environments (plastic greenhouse and field), because the dry matter accumulation (g.plant-1) was equal in all seasons, but the cycle duration was always lower in plastic greenhouse. According to the results, we can conclude that: (i) the dry matter accumulation characterizing curves, as function of the relative development of lettuce crop, were statistically usable for all studied seasons for greenhouse and field; and (ii) the organ with higher dry matter production was the leaf. The percentage of leaf dry matter was between 73.5% and 93.5% for plastic greenhouse, and between 56.8 and 91.5% for the field.