Robert P. Patterson

Effects of elevated atmospheric CO2 on water relations of soya bean

Abstract Soya bean (Glycine max (L.) Merr. ‘Bragg’) plants were grown in large containers in open-top field chambers under five atmospheric CO2 concentrations (349–946 μl1−1) and two water regimes. Rate of soil water depletion for the high CO2 treatments started to decrease under well-watered conditions during anthesis and by early pod formation under water-stressed conditions. During reproductive growth, normal and stressed plants at 349 μl1−1 (ambient level) received irrigation water 29 and 12 times, respectively, compared with 21 and 9 times, respectively, at 946μl1−1 CO2. At both anthesis and pod fill, plants grown under CO2 enrichment exhibited greater leaf area. Nevertheless, water use per plant either remained constant (stressed plants at anthesis) or else declined (well-watered plants at pod fill; both moisture levels during pod fill) in response to CO2 enrichment. At pod fill, leaves of CO2-enriched plants generally displayed a higher stomatal resistance, except near the end of the sampling period when a sudden increase in resistance was observed under low CO2 owing to low soil water availability. Midday xylem potential for well-watered plants was greater than values for stressed plants and was unaffected by CO2 treatment. Under low moisture conditions, elevated CO2 had no effect on xylem potential at anthesis; however, during pod fill potential increased significantly with increasing CO2 concentration, as elevated CO2 decreased water use rates, lowering soil water stress. Alleviation of water stress during critical reproductive phases was strongly suggested.

Response of soluble sugars and starch in field-grown cotton to ozone, water stress, and their combination

Abstract Ozone (O3) stress is known to reduce the growth and yield of a number of crops, and water stress can modify the extent of these effects. Both O3 and water stress alter the carbohydrate status of plants. Little is known, however, concerning O3 effects on carbohydrate pools of field-grown plants and whether water stress will modify the carbohydrate response to O3. Cotton (Gossypium hirsutum L. “McNair-235”) plants were exposed to five O3 concentrations in open-top field chambers for 12 hr/day throughout the growing season at two levels of soil water (well-watered or periodically water-stressed). The O3 concentrations ranged from 0.021 to 0.073 μl/l (seasonal mean 12 hr/day concentration). Plants were sampled from each plot on four occasions encompassing the early- to late-reproductive stages of growth. Soluble sugars (glucose, fructose and sucrose) and starch were measured in leaves, stems and roots at each sampling date. Analysis of variance was performed for main effects and interactions of O3 and water treatments at each sampling date (O3 effects were partitioned in linear and quadratic components). Effects of O3 and water stress on soluble carbohydrates and starch were most common in stems and roots. Ozone suppressed carbohydrate concentrations in all cases where significant O3 effects were detected in the absence of O3 × water interactions. On the other hand, soluble carbohydrate concentrations were greater in water-stressed plant tissues when effects were significant and in the absence of interactions. Water-stress effects on starch were variable. Interactions of O3 and water stress were not consistent but often included interaction with the quadratic O3 component.

GENOTYPIC DIFFERENCES IN ROOT ANATOMY AFFECTING WATER MOVEMENT THROUGH ROOTS OF SOYBEAN

The ability of root systems to absorb water was determined as the root hydraulic conductance for five exotic genotypes (PI 416937, H2L16, N95‐SH‐259, PI 407859‐2, and PI 471938) and the commercial cultivar Young of soybean (Glycine max [L.] Merrill). The genotypes were grown for 28 d in flowing hydroponic culture to minimize possible variations in physical or chemical constraints on root development and functioning. Root hydraulic conductance was determined in response to applied hydrostatic pressure to the solution inside a pressure vessel to induce solution flow through the root system to the nonpressurized cut‐stem surface. Almost twofold differences in hydraulic conductance of from 0.43 to \documentclass{aastex} \usepackage{amsbsy} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{bm} \usepackage{mathrsfs} \usepackage{pifont} \usepackage{stmaryrd} \usepackage{textcomp} \usepackage{portland,xspace} \usepackage{amsmath,amsxtra} \usepackage[OT2,OT1]{fontenc} \newcommand\cyr{ \renewcommand\rmdefault{wncyr} \renewcommand\sfdefault{wncyss} \renewcommand\encodingdefault{OT2} \normalfont \selectfont} \DeclareTextFontCommand{\textcyr}{\cyr} \pagestyle{empty} \DeclareMathSizes{10}{9}{7}{6} \begin{document} \landscape

Field drought tolerance of a soybean plant introduction.

0.79\times 10^{-7}

Assimilate Distribution in Soybeans as Affected by Photoperiod During Seed Development 1

\end{document} m3 s−1 MPa−1 among the six genotypes were statistically significant. External root surface area and surface area of the stele were determined as estimates of the dimensions of exodermal and endodermal Casparian bands as barriers to radial movement of water. Volume of the cortex was considered to be proportional to the possible resistance of the symplastic pathway through the cortical cells themselves. Abundance of large metaxylem elements with radii 20 μm or greater was determined for comparison of relative axial conductance through root sections. Root hydraulic conductivity based on external surface area, which ranged from 2.20 to \documentclass{aastex} \usepackage{amsbsy} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{bm} \usepackage{mathrsfs} \usepackage{pifont} \usepackage{stmaryrd} \usepackage{textcomp} \usepackage{portland,xspace} \usepackage{amsmath,amsxtra} \usepackage[OT2,OT1]{fontenc} \newcommand\cyr{ \renewcommand\rmdefault{wncyr} \renewcommand\sfdefault{wncyss} \renewcommand\encodingdefault{OT2} \normalfont \selectfont} \DeclareTextFontCommand{\textcyr}{\cyr} \pagestyle{empty} \DeclareMathSizes{10}{9}{7}{6} \begin{document} \landscape

Root distribution and soil moisture depletion pattern of a drought-resistant soybean plant introduction

3.82\times 10^{-7}