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Notes: Summary Measurement of leaf water potential (ψ l ) with a pressure chamber is usually regarded as a reliable and practical field technique. However, recent evidence indicates that results depend on the measurement techniques employed. Field experiments were conducted to identify the magnitude and sources of error affecting pressure chamber measurements of ψ l in cotton (Gossypium hirsutum L.) and to develop an accurate and operationally flexible procedure. Water potential of bare cotton leaves was about 0.2 MPa less than aluminum foil wrapped leaves when the elapsed time between excision to chamber pressurization was less than 30 s. The water potential of intact leaves increased 0.3 MPa after 15 s of enclosure in aluminum foil. 5 to 30 min of enclosure were sufficient to reach equilibrium between ψ l and water potential within the plant stem. Aluminum foil wrapped leaves maintained their ψ l for 2 h stored in a humid, dark box at 21–28 °C while wet wrapped (cheesecloth) or bare leaf ψ l increased after one hour because of hydration. An accurate and operationally flexible ψ l measurement procedure, suitable for large scale sampling, was defined.

Notes: Summary Characterization of root growth and distribution is fundamental in explaining crop responses to irrigation and in determining appropriate management of irrigation systems, particularly with drip systems since it is widely believed that drip irrigation may limit the extent of root development. An experiment was conducted to study root distribution of sweet corn grown under high frequency surface (S) and subsurface (SS) drip irrigation, fertilized daily through drip systems at three phosphorus levels of P0 (no injected P), P1 (P injected at 67 kg/ha) and P2 (P injected at 134 kg/ha). Root sampling at the end of the growing season indicated that: (1) Root extension continued at depths in excess of 2 m in both the surface and subsurface drip at all P levels. (2) The greatest differences between SS and S treatments were observed in the top 45 cm depth. Higher root length density was observed in the surface 30 cm in S plots while the sweet corn in the SS plots had greater root length density than S plots below 30 cm, and (3) the greater root length density in the SS irrigated sweet corn was not reflected in a similar increase in total above-ground dry matter.

Notes: Summary Soil and dust samples from beneath citrus trees contained relatively high concentrations of paraoxon and parathion for at least 45 days after parathion was applied at normal rates. These data indicate that parathion dripping on dry soil from sprayed crops, or sprayed directly on the soil surface, can persist for long periods and be oxidized to the highly toxic paraoxon. The residue concentrations are much higher on the loose dust particles than in the bulk soil. The data indicate that the soil or grove floor should be considered as a possible contributing source of toxicant along with foliage, or dust on foliage, to workers reentering treated fields. In any event, the data confirmed the high rates of oxidation of parathion to paraoxon on particulate matter, whether on foliage (SPEAR et al., 1974) or at the soil surface. The particulate matter appears to contribute to the accumulation of paraoxon, either by enhancing oxidation of parathion to paraoxon or by decreasing dissipation of paraoxon.

Notes: Summary A field experiment was conducted on the west side of the San Joaquin Valley in California to determine water use, crop growth, yield and water use efficiency of Acala (SJ-2) cotton (Gossypium hirsutum L.) grown in 0.5 m spaced rows on a Panoche clay loam soil (Typic Torriorthents). Evapotranspiration was determined by water balance techniques utilizing neutron soil moisture measurements. All neutron measurements were made within a 3 m soil profile in 0.20 m increments. The measured evapotranspiration was compared to climatic estimates of potential evapotranspiration, and to calculations using a one-dimensional soil water balance model that separately computed soil water evaporation and plant transpiration. Crop growth was determined by weekly destructive plant sampling. Leaf area was determined along with dry matter components of leaves, stems, fruiting parts (flowers and squares) and bolls. Final yield was determined by machine harvesting (brush stripper) 720 m2 from each plot. Lint yields and fiber quality were determined by sample ginning and fiber analysis at the U.S. Cotton Research Station at Shafter, California. Three irrigation regimes were established that resulted in an evapotranspiration range from a high deficit condition to full irrigation at the calculated atmospheric demand. The measured evapotranspiration of narrow row cotton under a full irrigation regime was 778 mm, 594 mm under a limited irrigation regime and 441 mm under a regime with no post-plant irrigation. The evapotranspiration from these irrigation treatments was accurately simulated by a water balance model. that used inputs of potential evapotranspiration, leaf area index, soil water holding capacity and root development. The average lint yield from narrow row cotton with a full irrigation regime was 1583 kg/ha, the average lint yield from a limited irrigation regime was 1423 kg/ha and the average lint yield from a treatment with no postplant irrigation (fully recharged soil profile at planting) was 601 kg/ha. The full irrigation regime resulted in a dry matter production of approximately 16 t/ha while the limited irrigated regime produce 11 t/ha and the no-postplant irrigation regime produced 7 t/ha of dry matter. The fiber quality results indicated significant (0.05 level) differences only in 50% span length and micronaire, with the 2.5% span length, uniformity index, elongation and strength indicating no difference. Cotton lint yield was found to be directly related to total evapotranspiration although the relationship was slightly non-linear while dry matter yield was found to be linearly related to evapotranspiration. Both lint and dry matter yield were found to have a linear relationship to estimated transpiration from the water balance model calculations.

Notes: Summary Swollen orbital extraocular muscles may mimic an orbital apex tumor on computed tomography. In five of our patients, in spite of highly suggestive findings on CT scanning, indicating the presence of an orbital apex lesion, the correct diagnosis proved to be endocrine exophthalmos. The value of complementary CT projections and of orbital ultrasonography to assist in the differential diagnosis is discussed, and the additional contribution of orbital phlebography for the confirmation of lesions in the orbital apex is emphasized.

Notes: Summary In cases with radiation necrosis of the brain, conventional neuroradiological examinations usually demonstrate only an avascular mass lesion impossible to differentiate from intracerebral tumor or hemorrhage. Computed tomography, performed in addition to angiography in three cases, consistantly demonstrated the radiation necrosis as a low density area exhibiting enhancement following infusion of contrast medium. The importance of recognizing radiation necrosis as a differential diagnosis to brain neoplasm is emphasized.

Notes: Summary A young, previously healthy patient developed embolic occlusions of the posterior cerebral, superior cerebellar, and posterior inferior cerebellar arteries. This patient also demonstrated positional occlusion of the left vertebral artery which may have been the etiology for his embolic stroke.

Notes: Summary Computed tomography (CT) is an extremely valuable noninvasive method for evaluating orbital softtissue structures. The possibility of scanning in the coronal plane has added a new dimension to the study. Direct enlargement viewing of scans on the display console has disclosed minute anatomic and pathologic details.