Assessment of production and dispersal of inoculum ofAlternaria Macrospora in various parts of the cotton canopy
Morning and evening counts of spores ofAlternaria macrospora in a cotton (Gossypium barbadense) field were assessed for the number of spores (a) produced on the last night, (b) dispersed during the day, and (c) retained in the spore reserve on leaves. Throughout the season, 1 m2 of the field produced (P) and dispersed (D) approximately 163 x 106 and 137 x 106 spores, respectively. The 16% discrepancy between P and D values reflects experimental errors. Most spores were produced on shed leaves on the ground, fewer on leaves in the lower part of the canopy, and least on leaves in the upper canopy. The contribution to total D decreased from leaves in the lower part of the canopy, to shed leaves, and to leaves in the upper canopy. In tests with potted plants with spore-bearing lesions attached to various heights of the canopy under various conditions of weather, dispersal of spores at these heights was conditioned mainly by wind velocity, which decreased from the upper to the lower part of the canopy. In leaves close to the ground, approximately 29% of the released spores were removed by sedimentation to the ground. On any one day, the daily rate of D differed from the daily rate of P. On days in which D was higher than P, the difference was due to a reserve of spores remaining on lesions after dispersal during the previous days. In weather adverse for production of new spores, the reserve was depleted within 4 and 6 days in the top and bottom leaves, respectively, but remained relatively high in the shed leaves on the ground; a similar number of days was needed to restore the depleted reserve in sporulation-favorable weather.
The Effect of Ultraviolet and Solar Radiation and Temperature on Survival of Fungal Propagules
Survival of spores, spore aggregates, sclerotia, and pycnidia of fungi was evaluated after exposure to high temperature in the dark, or exposure to ultraviolet (UV) radiation or sunlight. Under most conditions survival decreased from the most resitant Sclerotium rolfsii to Alternaria macrospora, Mycosphaerella pinodes, Aspergillus niger and Botrytis cinerea, in that order. There was no difference in survival among organisms stored in darkness at 45°C as single spores or aggregated into a mass of spores; or between spores of M. pinodes exposed before and after being released from pycnidia. Exposure to UV reduced survival much more than exposure in darkness. Longevity under UV ranged from more than 7 days for S. rolfsii to approximately 50 min for A. macrospora and 3 min for B. cinerea. Much longer survival occurred for spores of all fungi aggregated together; of spores of M. pinodes irradiated when inside rather than outside pycnidia; and in bigger, darker and older rather than in smaller, paler and younger sclerotia of S. rolfsii. Survival of sclerotia cut into slices and exposed to UV increased with thickness, irrespective of exposure to UV with the outer pigmented or innernonpigmented side. As tested with spore aggregates of A. niger, the rate of survival was linearly proportional to the number of conidia aggregated in each body. Irradiation by sunlight affected survival as described for irradiation by UV. The best protection from the detrimental effects of sun and UV radiation was provided by the infected host tissue.
Energy and exergy analysis of a new cogeneration system based on an organic Rankine cycle and absorption heat pump in the coal-fired power plant
Abstract A new cogeneration system based on ORC (organic Rankine cycle) and AHP (absorption heat pump) is presented to achieve the dual effects of improving power output and heating capacity in a coal-fired power plant. The heat source for heating is firstly led into the ORC to generate power, and then is led into the AHP as the driving heat source to recycle waste heat from exhausted steam of the ST (steam turbine) when the energy grade is reduced to a level that matches with the heating energy grade. On the basis of the thermodynamic first and second law, focusing on 135 MW coal-fired power plant, the energy and exergy analyses of traditional cogeneration system and new cogeneration system with ORC and AHP have been completed. Compared to the traditional cogeneration system, the power output and heating capacity are respectively increased by 1.47 MW and 32,106.64 kW when the flow rate of heating extraction steam is 40 kg/s. The integral thermal and exergy efficiencies are improved by 9.38% and 1.71%. Moreover, the coal consumption decrement for power generation and heat-supplying both augments with increasing heating extraction flow rate and decreasing load. The new presented scheme can not only reduce the irreversible loss of the cogeneration system but also save coal consumption.