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Field windbreaks have been planted primarily for soil erosion control; subsequently, research has shown that windbreaks have an effect on microclimate and on growth and yield of crops. Other research has shown that plant water relations respond to changes in microclimate. The present work was undertaken to determine the effect of microclimate changes induced by a slat‐fence windbreak on the plant water relations of field‐grown wheat (Triticum aestivumL.). Slat‐fence barriers were used as windbreaks for studying effects of shelter‐modified microclimte on plant water relations of ‘Waldron’ spring wheat, grown on Parshall fine sandy loam (Pachic Haploboroll), under irrigated and dryland soil water regimes. Data were collected on leaf water potential (Ψl), xylem water potential (Ψx), stomatal diffusion resistance (rs), canopy temperature (Tc), soil water potential (Ψs), soil water extraction, and grain yield. Plant water status of the wheat crop was strongly affected by shelter and soil water content. The treatment combination of shelter plus irrigation produced a higher Ψland lower Tcand, overall, was the most beneficial treatment in creating a favorable plant water status. The dryland treatments were under considerable water stress from early heading to maturity. The presence of the shelter did not alleviate the water stress on the dryland‐grown plants. Water‐use efficiency was significantly higher for the irrigated‐sheltered as compared with the irrigated‐exposed treatments. Water‐use efficiency of the dryland treatments was lower than the irrigated treatments, but the dryland treatments did not differ from each other. The results of our study indicated that windbreaks will be most beneficial to a wheat crop only if soil water is adequate for good crop growth throughout the growing season. Because soil water varies considerably from year to year in the northern Great Plains, crop responses to windbreaks can also be expected to vary considerably.

In the Northern Great Plains, windbreaks have historically been used to protect crops and soils from winds, but data on the effects of windbreaks on growth and yield of small grains is limited. ‘Waldron’ wheat (Triticum aestivumL.) was grown on Parshall fine sandy loam (Pachic Haploboroll) with and without shelter (slat‐fence enclosures), both with and without irrigation, to determine the effects of soil water and shelter on wheat growth and yield. In 1973 and 1974, plant height, tiller production, leaf area index (LAI), specific leaf weight (SLW), and dry matter were measured at tillering, heading, and grain‐filling growth stages. Also, grain yield, kernel weight, number of heads, straw yield, and plant height were measured at crop maturity. The combination of shelter and irrigation resulted in greater dry matter production, higher LAI, lower SLW, more tillers per plant and taller plants than irrigation alone. Shelter for dryland (nonirrigated) wheat did not increase vegetative growth, other than plant height early in the growing season. With irrigation, sheltered wheat yields increased 6.4 q/ha or 21.8% over the exposed wheat. Dryland sheltered wheat yield was 3.8 q/ha or 19.4% less than that for the exposed crop. Number of heads and straw production for each treatment responded the same to soil water and shelter as did grain yield. Results of this study show that growth and yield of spring wheat in the Northern Great Plains is increased significantly when grown under sheltered vs. exposed conditions provided soil water supply is adequate.

In an inner-shell ionization of RbF generated in a heat pipe by laser-produced soft x rays, continua in the XUV have been observed at 130.4 and 155 nm. These continua show the same properties as the analogous transitions in the rare-gas fluoride molecules. The 130.4-nm fluorescence is attributed to the B–X transition, and a discussion of the origin of the 155-nm fluorescence is provided.

Lasing spectra and output efficiency have been measured for four Ne/Xe/NF_3 laser mixtures from 300 to 450 K. These high resolution spectra have been correlated with a theoretical rotational bandhead structure to identify rotational states contributing to two narrowband emissions in the 351-nm band. Rotational–vibrational population shifts appear to be the most important mechanisms responsible for the increase in laser efficiency with temperature. Increased ground-state dissociation and decreased narrowband absorption may not be as important as previously thought.

An analysis is presented of the lasing spectrum of the rovibronic XeF(B–X) transition as observed in an electron-beam pumped laser. The intricate spin–split rotational and vibrational structure in the 351- and 353-nm lasing emission is investigated, and insight is gained on the processes responsible for the vibrational, rotational, and spin inhomogeneities manifested in the spectra. Explanations of the data are developed in terms of near-resonant vibration–rotation energy transfer, rotational relaxation rate differences in the B and X states, rapid dissociation of the rotational resonances near the dissociation limit of the ground state, relatively slow collisional spin relaxation, and optical coupling of spin states. The implications for narrowband extraction in the 351- and 353-nm bands are noted. The rotational relaxation rates of the X and B states of XeF are estimated in the Appendix.

Response of ‘Norman’ soybeans [Glycine max(L.) Merr.] to a shelter‐induced microclimate was studied under dryland and irrigated soil water regimes. Leaf water potential (Ψ1), xylem water potential (ΨX), stomatal diffusion resistance (rB), canopy temperature, dry matter accumulation, leaf area, leaf density, plant height, and yield components were measured to determine the effects of shelter influences on a soybean crop. Plant water status, characterized by measuring Ψ1, ΨX, rB, and canopy temperature during selected days, was strongly affected by soil water regime and sheltered conditions. The treatment combination of shelter plus irrigation resulted in the most favorable plant water status. Under dryland, where soil water was limiting, plant water status of the sheltered and exposed treatments was similar. Dry matter production, green leaf area, and plant height were generally increased under sheltered treatments if soil water was not limiting. Dryland sheltered treatments showed early vegetative stimulation when compared to exposed treatments, but the resulting depletion of soil water in the sheltered treatment restricted later growth. Both irrigated and dryland sheltered plants had a lower leaf density compared to exposed plants. Soybean yields were increased from 20.4 hl/ha for the irrigated exposed treatment to 24.0 hl/ha for the irrigated sheltered treatment. Under dryland, the yields were 11.8 and 12.8 hl/ha for exposed and sheltered treatments, respectively.

The Penman formula in three modifications accounts reasonably well for the observed values. Roughly, evapotranspiration was equivalent to 0.8 of net radiation over the crop.

The roots of tobacco plants were subjected to a wide range of simulated aeration conditions. In general plant functions were not appreciably reduced until the CO2concentration became greater than the O2concentration but were sharply reduced after the CO2to O2ratio became larger than one.

The roots of tobacco plants were subjected to a wide range of simulated aeration conditions. In general nutrient uptake remained relatively constant until oxygen concentrations dropped below 10%. However, a concentration of 5% carbon dioxide apparently stimulated phosphorus uptake.

In this article, the effect of two variables namely nickel content and austempering heat treatment temperature on mechanical and microstructural properties of ADI were investigated. Four Nickel content levels of 0.0, 0.6, 0.8 and 1% and three austempering temperatures of 320, 340 and 360degC were selected. Prior to austempering, all the samples were austenitized for 30 min at 840degC. The microstructure of austempered alloys mainly consisted of a mixture of needle like acicular ferrite and carbon stabilized austenitic matrix. The increase in Ni content improved the strength and hardness and it reached its peak at 0.8%. The microstructures also became finer with increase in Ni content as confirmed by Impact energy and elongation. Nodularity was found to be above 90% for all alloys at all austempering temperatures. However, the nodule counts increased with increase in Ni content up to 0.8% and then dropped. XRD analysis was done to estimate the retained austenite content present in the ausferrite matrix and it was concluded that for any given Nickel content level, the retained austenite content increases with austempering temperature. Nickel of 0.8% was found to be optimum for all austempering temperatures.