Facility for studying the effects of elevated carbon dioxide concentration and increased temperature on crops

The requirements for the experimental study of the effects of global climate change conditions on plants are outlined. A semi-controlled plant growth facility is described which allows the study of elevated CO2 and temperature, and their interaction on the growth of plants under radiation and temperature conditions similar to the field. During an experiment on winter wheat (cv. Mercia), which ran from December 1990 through to August 1991, the facility maintained mean daytime CO2 concentrations of 363 and 692 cm3 m-3 for targets of 350 and 700 cm3 m-3 respectively. Temperatures were set to follow outside ambient or outside ambient +4-degrees-C, and hourly means were within 0.5-degrees-C of the target for 92% of the time for target temperatures greater than 6-degrees-C. Total photosynthetically active radiation incident on the crop (solar radiation supplemented by artifical light with natural photoperiod) was 2% greater than the total measured outside over the same period

Wheat Grain and Forage Yields are Affected by Planting and Harvest Dates in the Central Great Plains

Although grazing of winter wheat (Triticum aestivum L.) is a common practice in the southern Great Plains, little is known about the efficacy of wheat as a dual-purpose crop in the Nebraska Panhandle. The objective of this study was to evaluate the effects of establishment and harvest times on forage and grain production of wheat cultivars adapted to the region. Six cultivars were planted at four dates (very early, recommended early, recommended late, and very late) in each of 3 yr. Forage samples were taken from a previously non-harvested area late in the fall, at jointing, and at the boot stage. Grain yield at maturity was measured from each forage harvest treatment and from a full-season unharvested control. In 2 of 3 yr, grain yield was reduced an average of 25% compared with the full-season check when plants were harvested for forage at the joint stage. No grain was produced when forage was removed at the boot stage. Forage removal during the fall averaged 1300 kg ha-1 dry matter and resulted in insignificant losses in grain yield. While most of the fall growth was too low to the ground for clipping, it could provide high- value supplemental grazing on account of the high crude protein (310 g kg-1) and in vitro organic matter digestibility (800 g kg-1) levels. Spring grazing in this region is limited to the time prior to jointing if market conditions favor grain production

Emissão do afilho do coleóptilo em genótipos de aveia e em diferentes condições de estresses e manejo Coleoptile tiller development in genotypes of oat and in different stress conditions and management

A seleção de plantas de cereais de inverno com o desenvolvimento do afilho do coleóptilo poderá se tornar uma estratégia importante para se aumentar o número de grãos por unidade de área. Esse modelo de planta poderá, assim, contribuir para o aumento de rendimento de grãos. Nesse sentido, o objetivo deste trabalho foi estudar o impacto do comportamento de genótipos de aveia e de tipos de manejo sobre o desenvolvimento e crescimento de plantas dessa espécie com ênfase para o afilho do coleóptilo. Foram implantados quatro ensaios em telado para avaliar: genótipos de aveia com diferentes capacidades de afilhamento, impacto do corte das folhas do colmo principal das plantas, influência do peso da semente e influência da profundidade de semeadura. Mediram-se o desenvolvimento foliar, a emissão de afilhos e o peso da matéria seca das plantas e dos afilhos. O trabalho mostrou que os genótipos de aveia avaliados apresentaram baixo potencial de afilhamento, principalmente do afilho do coleóptilo. Danos causados à primeira folha do colmo principal, bem como a maior profundidade de semeadura reduziram o crescimento e desenvolvimento das plantas. O peso da semente não afetou essas características.<br>Plant selection of small grain species for coleoptile tiller development might become an important strategy for increasing the number of grains per unit of area and, consequently, crop yield. With this concern, the objective of this work was to study different genotypes and management practices regarding the coleoptile tiller. Four trials were established to evaluate different oat genotypes regarding their tillering capacities, as well as the impact of cutting of leaves of the main stem, and the influence of seed weight and seeding depth on tillering. Leaf and tiller development and dry weight of plants and tillers were measured in all trials. All genotypes presented low tillering potential, especially for the coleoptile tiller. The cut of the primary leaf of main stem, as well as the deeper seeding depth reduced both growth and development of plants. The seed weight did not affect these traits

Carbon dioxide exchange in leaves of Spartina anglica Hubbard

The gas-exchange method has been used to measure net carbon dioxide assimilation at different temperatures and irradiances in leaves of salt-treated and untreated plants of Spartina anglica. The results together with those of the CO2 compensation point and leaf anatomical data clearly indicate that Spartina anglica is a high photosynthetic capacity plant. At high temperatures and irradiances leaves of the salt-treated plants were able to maintain net photosynthesis, in contrast to the behaviour of leaves of untreated plants. The ecological significance of these results is discussed