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Xue-Min Hou, Zi-Hua Wang, Xi-Min Deng, and Guo-Hui Li

The P-V curve has been used to estimate symplastic water volume, ψ S , pressure potential, turgor loss point, and elastic modulus of plant cells, tissue, and organs ( Holbrook and Sinclair, 1992 ; Richter, 1978 ; Scholander et al., 1965 ; Tyree

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Fan Cao, Yunchu Wei, Xinwang Wang, Yongrong Li, and Fangren Peng

was loaded, the air pressure was added using the Scholand-Hammel method at room temperature ( Scholander et al., 1965 ). The sap was collected for weighing using a pipetting gun. The PV was recorded during the whole process. A complete PV curve was

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Andre Luiz Biscaia Ribeiro da Silva, Joara Secchi Candian, Elizanilda Ramalho do Rego, Timothy Coolong, and Bhabesh Dutta

cabbage grown in Georgia are estimated to range from $1 million to $3 million ( Little, 2019 ). BR of cabbage caused by Xanthomonas campestris pv. campestris ( Xcc ) is one of the major disease issues for cabbage production in Georgia. Symptoms of BR

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Robert Augé

The determination of tissue water potential components is important for understanding plant growth and response to the environment. Pressure-volume (PV) analysis is often considered to give the most accurate estimate of symplastic osmotic potential. Additional information about tissue water relations can also be computed from PV curves estimates of bulk cell wall elasticity, symplastic water volume, and turgor potential at various states of tissue water content. The generation of PV curves is a time-consuming procedure, however, and involves considerable computation. This presentation describes a computer spreadsheet template for traditional evaluation of a PV curve through linear regression of the zero turgor segment. The template allows real-time plotting of the inverse ψ/ water loss relating, provides estimates of most commonly calculated PV characteristics and permits instant graphic visualizations of changes in water potential components and elasticity with changes in water potential, total tissue water and symplastic water content. The advantages of spreadsheet analysis of PV curves are simplicity, consistency, thoroughness and speed. A fleeting acquaintance with spreadsheet software and a thorough understanding of pressure-volume theory on the part of the user is assumed.

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Leonardo Lombardini, Mauro Falusi, Roberto Calamassi, and James A. Flore

Aleppo Pine (Pinus halepensis Mill.) is known to be the most drought-resistant Mediterranean Pine. This species is widely distributed throughout the Mediterranean region and displays a high intraspecific variability, with respect to its physiological and morphological response to environmental conditions. In this experiment we evaluated the response of Pinus halepensis seedlings to drought. Sixty germinated seeds (accession A6, Shaharia, Israel) were grown in soil for 8 weeks and then transferred to black plexiglass tanks containing half-strength air-sparged Hoagland solution. After 6 weeks of acclimation to hydroponics, the osmotic potential of the solution was lowered by adding polyethylene-glycol (PEG) 8000. Water potential was lowered in 0.2 MPa increments every 4 days, until a final value of –0.8 was reached. The seedlings were then maintained at –0.8 MPa for a further 8 days. Ultrasonic acoustic emissions, pressure–volume (P–V) curves, shoot and root growth, leaf area, xylem diameter, root apex mitotic index and cell length were measured on control and stressed seedlings. Seedlings were then transferred to normal Hoagland solution for 24 hours to simulate rewatering, and P–V curves and ultrasonic emissions measurements were repeated. Results showed that the final root growth is maintained in the stressed seedlings at the same rate as controls, whereas shoot growth was significantly reduced. The leaf area was reduced by stress to 36%, but the xylem diameter only to 10%, leading to a lower leaf area:xylem section ratio in the stressed plants. Ultrasonic emissions in the stressed plants were 365% of the control, and 182%, after rewatering. Specific details of the growth and physiology data are presented.

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J.E. Flaherty, G.C. Somodi, J.B. Jones, B.K. Harbaugh, and L.E. Jackson

A mixture of host-range mutant (h-mutant) bacteriophages specific for tomato race 1 (T1) and race 3 (T3) of the bacterial spot pathogen, Xanthomonas campestris pv. vesicatoria (Doidge) Dye was evaluated for biological control of bacterial spot on `Sunbeam' tomato (Lycopersicon esculentum Mill.) transplants and field-grown plants for two seasons (Fall 1997 and Fall 1998). Foliar applications of bacteriophages were compared with similar applications of water (control) and of copper/mancozeb bactericides, the commonly used chemical control strategy for tomato seedling and field production. In 1997, the incidence of bacterial spot on greenhouse-grown seedlings was reduced from 40.5% (control) to 5.5% or 0.9% for bactericide- or bacteriophage-treated plants, respectively. In 1998, the incidence of bacterial spot was 17.4% on control plants vs. 5.5% and 2.7% for bactericide- and bacteriophage-treated plants, respectively, although these differences were not statistically significant at P ≤ 0.05. Applications of bacteriophages to field-grown tomatoes decreased disease severity as measured by the area under the disease progress curve (AUDPC) by 17.5% (1997) and 16.8% (1998) compared with untreated control plants. Preharvest plant vigor ratings, taken twice during each field season, were higher in the bacteriophage-treated plants than in either bactericide-treated plants or nontreated controls except for the early vigor rating in 1998. Use of bacteriophages increased total weight of extra-large fruit 14.9% (1997) and 24.2% (1998) relative to that of nontreated control plants, and 37.8% (1997) and 23.9% (1998) relative to that of plants treated with the chemical bactericides. Chemical names used: manganese, zinc, carboxyethylene bis dithiocarbamate (mancozeb).

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W. Patrick Wechter, Mark W. Farnham, J. Powell Smith, and Anthony P. Keinath

-spot control measures, while Johnston (2000) gives only crop rotation away from Brassica spp. as a control measure for unspecified leaf spot. Bacterial leaf spot, peppery leaf spot, or pepper spot, incited by Pseudomonas syringae pv. maculicola ( Psm

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Charles J. Wasonga, Marcial A. Pastor-Corrales, Timothy G. Porch, and Phillip D. Griffiths

set of 12 cultivars grown in different geographical regions. ‘Amy’ (Seminis), ‘PV 712’ (Pop Vriend, Andijk, The Netherlands), ‘Teresa’ (Seminis), and ‘PV 698’ (Pop Vriend) are currently grown in eastern Africa; ‘Barrier’ (Alpha Seeds) and ‘Juliet

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Jeb S. Fields, William C. Fonteno, and Brian E. Jackson

50% and 25% MC. Three mixes × two IMs × four replications totaled 24 samples/treatments in this experiment. Hydration efficiency. Data from the 10 hydration events were used to develop wettability curves for each of the samples tested in this

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Matthew D. Taylor, Rachel Kreis, and Lidia Rejtö

are presented as a titration curve at each lime rate, comparing compost rates with combined data from the four measurement times ( Fig. 3 ). Initial pH of substrates ranged from 4.20 to 7.23 and increased with both lime rates and compost rates