Increase Plant Performance Research Articles

Exergy losses in a multiple-effect stack seawater desalination plant

The use of the Second Law of Thermodynamics to describe and quantify the exergy losses involved in the different processes taking place in desalination plants is of considerable importance both for the design and operation of these plants. Although the First Law of Thermodynamics is adequate in giving the overall plant performance indices, it does not show the actual irreversibilities in the different parts of the plant. An estimation of the exergy destruction involved in each part of the plant gives a quantitative measure of these irreversibilities which, if reduced during design or operation, can result in a reduction of energy consumption and increase plant performance. Based on actual measured data from a multiple-effect stack seawater desalination plant now in operation in the solar plant near Abu Dhabi, the exergy destruction was calculated for each source of irreversibility. The major exergy destruction was found to be caused by irreversibilities in the different pumps with the vacuum pump representing the main source of destruction. Major exergy losses are associated with the effluent streams of distillate, brine blow-down and seawater. Exergy destruction due to heat transfer and pressure drop in the different effects, in the preheaters and in the final condenser and in the flashing of the brine and distillate between the successive effects represents an important contribution to the total amount of exergy destruction in the evaporator.

Experimental evidence on the importance of disturbance intensity for invasion of Lantana camara L. in dry rainforest–open forest ecotones in north-eastern NSW, Australia

The invasion of Lantana camara (a thicket-forming, woody weed) into dry rainforest–open forest ecotones was evaluated over a range of disturbance intensities associated with fire and livestock grazing. Three manipulation experiments were established in which wildfire (unburnt, low, and high intensity), overstorey damage (different levels of biomass removal), and nutrient addition (NPK) were used as disturbance categories in pair-wise factorial combinations across the chosen disturbance intensity range. The availability of key resources to the invading species resulting from disturbances was also measured over the established environmental gradients of light and soil fertility. Seedling establishment occurred in control treatments but growth was weak (averaging 0.85 g plant −1 year −1) and they failed to flower during the 27 months experimental period. High levels of nutrient addition (60–80 g m −2) without other forms of disturbance significantly increased growth (to 0.95 g plant −1 year −1) and germination (41.6–44.5%), while survival increased modestly (14.1–15.9 plants plot −1). Biomass increased significantly to 1.78 g plant −1 year −1 when the shrub layer was removed or burnt by a low intensity wildfire while germination and survival increased by 13.5 and 22.0% respectively over the control. Invasion increased further when the overstorey was physically removed or burnt with a high intensity wildfire as biomass increased significantly to 2.42 g plant −1 year −1, while germination and survival significantly increased by a further 35.6% and 40.7% respectively over the low intensity wildfire and shrub removal. Invasion was positively increased with disturbance intensity and increased resource availability. Light at ground level increased from 21.3 to 30.5% of ambient light when the shrub layer was damaged while it increased to 84.3% when the overstorey was damaged. A pattern of increasing plant performance with increasing intensity and number of combined disturbances was evident, although nutrient addition alone had little or no effect on plant performance, including flowering. The impact of low intensity fire on L. camara invasion was primarily produced by a response to increased light rather than increased nutrient availability while high intensity wildfire produced a secondary but minor response to increased soil fertility. Management of disturbances is critical for the long-term viability of dry rainforests and their ecotones. Shading by intact canopies is an effective barrier against successful invasion by L. camara and is the most appropriate strategy for managing invasion. This strategy will also contribute to the maintenance of conservation values and provide opportunities for dry rainforest development and expansion.

Induced responses to herbivory and increased plant performance

Plant resistance to herbivores was induced in a field experiment to evaluate the consequences of induced responses for subsequent herbivory and plant fitness. Induction early in the season resulted in halving of herbivory by chewing herbivores and a reduction in the abundance of phloem-feeding aphids when compared with controls. A correlate of lifetime plant fitness, seed mass, was enhanced by over 60 percent for individuals that were induced.

Behavioural response in plants: adjustment in algal recruitment induced by herbivores

Behavioural responses to chemical cues are common among animals, whereas there is still intense debate as to whether plants are able to detect environmental information and adjust their behaviour accordingly. Here, I report that several freshwater algal species respond to the presence or absence of grazers in the water column by regulating their recruitment rate from sediment to water. In lakes, as well as in controlled laboratory experiments with low abundances of grazers, recruitment of certain flagellated algal species was high, whereas recruitment was negligible when grazer abundances were high. Hence, certain plants equipped with locomotion organelles can use cues released from herbivores to adjust the timing of recruitment from the 'seed-bank', thereby reducing the exposure to grazing. Such an adaptation may have important consequences for dominance and temporal succession in algal communities. In an evolutionary context, this study shows that consumer-avoidance behaviour is not an adaptation exclusive to animals.

Effect of Seasons and Irrigation Regimes on Plant Growth and Water-Use of Container-Grown Photinia × fraseri

Abstract Water-use and plant growth of Fraser photinia (Photinia × fraseri Dress) were studied under varying irrigation regimes during 2 different growing seasons, winter and summer. Rooted cuttings were transplanted into 7.57 1 (2 gal) plastic containers containing Metro-mix 500 and greenhouse-grown under 2 irrigation frequencies (3.5 or 7-day intervals) and 3 replacement amounts (100%, 75% or 50% replacement of actual water-use). Increased irrigation frequency significantly reduced plant growth parameters of winter-grown plants, including shoot growth, leaf number, leaf area and shot dry weight. Decreased irrigation amount significantly increased root dry weight. Significant differences were not detected in growth measurements of summer-grown plants suggesting differences between experiments are seasonal in nature. Frequent irrigation resulted in poor plant pelformance under winter growing conditions of lower evapotranspiration (ET); however under summer growing conditions, frequent irrigation did not significantly affect plant growth. Decreased irrigation frequency significantly increased total water-use for winter-grown plants due to increased plant performance. No significant differences in water-use due to frequency in summer-grown plants was found.

Coal Waste Reclamation using Automated Weathering to Predict Lime Requirement

AbstractAbandoned coal waste exhibits adverse physical and chemical properties which preclude vegetation establishment. Coal waste from a site in Montana was acidic (pH 2.8), black, 85% coarse fragments and had a low water holding capacity. Incorporation of cement kiln dust (CaO) and limestone (CaCO3) to 35 cm at rates recommended by a weathering procedure neutralized coal waste acidity in the surface 10 cm. Incorporating CaO to 100 cm neutralized coal waste to the 30‐cm depth. Seeded vegetation was healthy and vigorous where lime was applied, though percent canopy cover and aboveground production were low after 2 yr. Application of kiln dust five times the recommended rate significantly reduced plant performance. Application of coversoil significantly increased plant performance compared to sites without coversoil by providing a more suitable germination medium. Increasing coversoil application from 15 to 30 cm did not significantly increase plant performance. Depth of root penetration was a function of depth of lime incorporation and coversoil thickness. Root distribution was neither confined to nor concentrated in the coversoil. Root proliferation into limed coal waste was similar to that present in overlying coversoil.

WATER SHARING AMONG RAMETS IN A DESERT POPULATION OF DISTICHLIS SPICATA (POACEAE)

Clonal growth enables plants to transport resources among separately rooted but connected ramets, a potential advantage in patchy or unpredictable habitats. Nevertheless, clonal plants are relatively scarce in deserts. To test whether clonal integration of water relations can increase plant performance under natural conditions in a desert species, water movement was traced and connection among ramets was manipulated in the rhizomatous grass Distichlis spicata in Death Valley, California. To examine potential costs of clonal growth form, connections were mapped and analyzed for dry mass and nitrogen content. Movement of dye showed potential transport of water among five ramets up to 1.4 m apart. Severance of connecting rhizomes increased mortality and decreased water potential of individual ramets within 36 hr, indicating that water sharing among ramets could be of significant benefit. However, plants had a high investment of mass and nitrogen in underground organs, which might be a cost of clonal growth associated with desert environments.

Water Sharing Among Ramets in a Desert Population of Distichlis spicata (Poaceae)

Clonal growth enables plants to transport resources among separately rooted but connected ramets, a potential advantage in patchy or unpredictable habitats. Nevertheless, clonal plants are relatively scarce in deserts. To test whether clonal integration of water relations can increase plant performance under natural conditions in a desert species, water movement was traced and connection among ramets was manipulated in the rhizomatous grass Distichlis spicata in Death Valley, California. To examine potential costs of clonal growth form, connections were mapped and analyzed for dry mass and nitrogen content. Movement of dye showed potential transport of water among five ramets up to 1.4 m apart. Severance of connecting rhizomes increased mortality and decreased water potential of individual ramets within 36 hr, indicating that water sharing among ramets could be of significant benefit. However, plants had a high investment of mass and nitrogen in underground organs, which might be a cost of clonal growth associated with desert environments.