Understanding how ornamentals will respond to the increasing level of CO2 in the atmosphere will aid future plant selection. In addition, understanding how rising levels of CO2 affect the potential of introduced ornamentals to become invasive weeds will be crucial to future management. This study was conducted to determine the effects of elevated CO2 on growth of two non-native plants commonly used as ornamentals in the southeastern U.S. Lantana (Lantana camara) and vinca (Catharanthus roseus) were grown at either 375μmol mol−1 (ambient) or 575μmol mol−1 (elevated) CO2 for four months in open top field chambers. Measurements of plant morphology, biomass, and plant tissue nitrogen were made for both species. Lantana growth was more responsive to elevated CO2 than was vinca. Lantana root and total plant dry weights were increased by 31 and 19%, respectively; in vinca, these values increased by only 9% each. Vinca root length was unaffected by CO2, however, it was increased by 46% in lantana. Elevated CO2 had no effect on flower dry weight for either species. This study suggests that rising atmospheric CO2 will have little impact on vinca as either an ornamental or as a potential invasive weed. Lantana's value as an ornamental may increase due to its abundant growth under elevated CO2. Lantana's greater root growth may also increase its drought tolerance, adding to its ornamental potential. However, the factors which may make it a more desirable ornamental under future higher CO2 conditions could also enhance its potential to become a serious invasive weed in the southeastern U.S.
To examine the relationship between fruit growth and sugar metabolism, gynoecious parthenocarpic cucumbers (Cucumis sativus L.) ‘Freedom House No. 3’ were grown in a glasshouse with different fruit load conditions, and starch grains in the mesocarp were observed microscopically and activities of sucrose-catalysing enzymes were measured in the fruit at node 15. Flower buds below node 9 and all lateral shoots were removed, but the plant was not pinched. Fruit load was changed as follows: (1) all flowers below node 15 were removed on the day of the anthesis of the flower at node 15; (2) all fruits below node 15 were removed 4 days after anthesis (DAA) of the fruit at node 15; (3) all fruits below node 15 were removed 8 DAA; and (4) all fruits on nodes 9–15 were allowed to grow. The growth of fruit at node 15 was suppressed by fruit load and resumed 4 days after the removal of fruits at the lower nodes. Starch grains disappeared 4 DAA in fruit load treatment and reappeared 4 days after the removal of fruits at the lower nodes. The activities of sucrose-catalysing enzymes, especially acid invertase, were suppressed by heavy fruit load and increased 4 days after the removal of the fruit load. These results suggested that the existence of starch grains and activities of sucrose-catalysing enzymes reflect the level of the photoassimilate imported into fruits.
In order to analyze the growth of corn plants and the level of salinization in and around an irrigated field in the Yellow River basin, surveys of plant growth, soil and water quality were conducted in August and September 2007. Plant growth parameters such as height, leaf nitrogen content and maximum quantum yield of photosystem II (Fv/Fm), and chemical characteristics of the Yellow River water, irrigation canal water, ground water, drainage canal water, saline seep water and field soils were measured. There was a significant difference in corn growth in the irrigated field, that is, plant height, leaf nitrogen content and Fv/Fm decreased as the drainage canal for removing the saline seep water was approached. The electrical conductivity (EC) and various dissolved ion concentrations of the ground water in the field exhibited remarkable high values compared to those of the Yellow River water and the irrigation canal water. When a comparison between three survey points in the field (the nearest, middle and the farthest to the drainage canal) was made, it became clear that there existed clear gradients of those concentrations, that is, they showed the highest values at the nearest point and caused the poorest growth of corn plant at the point. The EC and ion concentrations of the saline seep at the foot of the river terrace made of loess showed extremely high values. The drainage canal for removing the seep water, which separated the survey field and the terrace, was not lined and hence the salty water in this canal seemed to seep into the surrounding fields. These results obtained from this study suggest that the cultivation system such as irrigation techniques and drainage facilities should be improved for sustaining productive irrigated agriculture in this area.
In the soil-less culture, root zone environment can be easily modified to create stress conditions such as low and high temperatures, drought and high salinity by applying physical and chemical properties of water. Low temperature stress to plant body can induce adaptive functions in plant such as osmoregulation and antioxidation, which are expected to result in production of value-added vegetables enriched in sugars and antioxidants, etc. In this study, production of value-added vegetables was examined by applying low temperature stress only to roots in a soil-less culture. Spinach plants (Spinacia oleracea L. cv. Orai) were grown in a soil-less culture, where the root zone temperature was controlled at a normal temperature of 20°C. Two weeks before the harvest, the low temperature stress treatment with a root zone temperature of 5°C was applied for only one week. This low temperature stress to roots induced plant adaptive functions of osmoregulation and antioxidation, and healthful substances for human health such as sugars, ascorbic acid and Fe were significantly enriched in edible shoots. Furthermore, concentrations of nitrates and oxalic acid in shoots, which are harmful substances, were extremely decreased with depression in water and nutrient absorption by roots. These suggest that the only one week treatment with low temperature stress only to roots is applicable for production of value-added leafy vegetables.
Thermal imaging was applied to micropropagated plantlets to predict wilting after ex vitro transfer. Potato plantlets were cultured from nodal cuttings under photoautotrophic and heterotrophic/ mixotrophic culture conditions for various time periods. A pair of culture vessels, each with a single potato plantlet, was placed in a laminar flow hood. Images of the two plantlets were simultaneously acquired using thermal and digital cameras after removing the cover of the vessels to analyze the relationships between leaf temperature and the onset of wilting. Plantlets with lower leaf temperatures wilted earlier in all measurements. Plantlets grown under heterotrophic/ mixotrophic culture conditions had lower leaf temperatures than those grown under photoautotrophic conditions. Furthermore, these plantlets were more susceptible to wilting, suggesting greater water loss from poorly developed stomata and/or cuticle. The temperature reduction index (TRI) was developed to normalize the difference between air and leaf temperatures for comparing results from different measurements. A negative correlation was observed between the time to the onset of wilting and TRI just after opening the culture vessels. These findings suggest that thermal imaging can be applied as a non-invasive assessment of water loss in micropropagated plantlets and thus, contribute to the prediction of wilting after ex vitro transfer.
The water uptake inducing cracking of sweet cherry fruit (Prunus avium L.) was investigated in relation to the reduced pressure in flesh intercellular space caused by respiration of the fruit. The respiratory quotient decreased from 0.74 on 28 DAB to 0.43 on 60 DAB, and highly correlated with DAB in a quadratic equation. Flesh intercellular space capacity was increased from the immature stage with fruit growth, then it attained maximum of 129.4 μL/fruit on 55 DAB. However it decreased greatly to 95.6 μL/fruit on 57 DAB, and it did not change until 60 DAB. The pressure of flesh intercellular space was around 3–10 Pa lower than ambient air pressure, and negative correlation was found between the respiratory quotient of the fruit and the flesh intercellular space pressure. These results suggested that water on the fruit surface was apparently sucked into flesh intercellular spaces by that decreased pressure, which resulted from the decrease of the respiratory quotient.