Soil Moisture Treatments Research Articles

Effect of plant moisture stress on absorption and translocation of triclopyr in oak seedlings

Ways to maximize herbicide efficacy are of great concern to most forest managers. Many factors influence the efficacy of herbicides, including the physiological status of the plant and its effect on the translocation of herbicides. This study investigated how plant moisture status affected herbicide absorption and translocation. The ester formulation of [14C]triclopyr was applied to the foliage of 8-month-old, container-grown water oak (Quercusnigra L.) and southern red oak (Quercusfalcata Michx.) seedlings. At the time of treatment, seedlings were in soil with average moisture contents of 5 and 35% by weight. Corresponding seedling xylem water potentials averaged −1.8 and −0.3 MPa, respectively. Triclopyr absorption was not significantly affected by the soil moisture treatment. However, translocation to stems and roots was 62 and 48% lower, respectively, in water-stressed seedlings. Water oak absorbed 23% less than southern red oak when averaged over the soil moisture treatments. Scheduling herbicide applications when moisture is plentiful could improve triclopyr efficacy.

Root Growth of Wheat Genotypes in Hydroponic Culture and in the Greenhouse under Different Soil Moisture Regimes

Root characteristics of wheat (Triticum aestivum L.) genotypes are believed to be important in tolerance to drought and flooding, yet neither the extent of differences in root size among modern soft red wheat cultivars nor the degree of association between root size and drought or flooding tolerance is known. This study was conducted to see whether genotypes differ in root size, and to see if root size is associated with tolerance to flooded soil and to drought during early vegetative growth. We found differences in root fresh weight (RFW), shoot fresh weight (SFW), number of roots longer than 40 cm (NR), longest root length (LRL) and total root length (TRL) of 40 winter wheat genotypes grown in hydroponic culture for 4 wk. Each of these parameters was positively correlated with all others. Twelve genotypes with different root sizes selected from these 40 were grown in a greenhouse soil experiment for 3 wk, after which soil moisture treatments of control, flooding, and drought were imposed for a period of 21 d. Flooding did not affect SFW and number of tillers (NT), but decreased RFW. Drought drastically decreased all three parameters. The genotype × moisture treatment interactions for SFW, RFW, and NT were significant. Root and shoot growth of these genotypes in hydroponic culture were correlated to their root and shoot growth under both control and flooded conditions, but not under drought. Thus, it appears that the expression of genotypic root growth potential may be influenced by the availability of soil moisture, and that selection of wheat seedlings for vigorous growth in hydroponic culture will select for vigorous early growth in soil with adequate or excess moisture, but not under severe drought.

Varietal Differences of Wet Endurance in Autumn Soybean Plants.

The objective of this study was to examine the effects of excessive soil moisture on seed weight and yield components of autumn soybean cultivers and to find the varietal differences in their wet endurance. Twenty soybean cultivers, belonging to ecotypes of IIIc, IVc and Vc were grown in an upland field converted from paddy. The experiments were conducted in 1983 and in 1984. Excessive soil moisture treatment was conducted at the third or fourth foliage leaf stage and continued until the maturing stage. As the experiments yielded nearly the same results for both years, the data obtained in 1984 is presented in this paper. The seed weight of 12 cultivers was reduced but that of eight cultivers was not reduced by the treatment at the 5% significant level. The reduction ratio of seed weight, which was calculated as the mean value of excessive moisture plots divided by the mean value of control plots multiplied by 100, correlated positively with that of stem weight, branch number and total node number at the 0.1% significant level. As a result of regression analysis, the reduction ratio of the total node number had the greatest influence on the reduction ratio of seed weight. The results suggest that the smaller reduction in the seed weight of the wet endurance cultivers was caused by a smaller reduction in the vegetative growth e.g., the total node number, the stem weight and the branch number.

EFFECTS OF SOIL WATER DISTRIBUTION ON THE LATERAL ROOT DEVELOPMENT OF THREE SPECIES OF CALIFORNIA OAKS

The responses of seedling root systems of three species of oaks in California to two experimental soil moisture regimes were studied by comparing lateral root development, root and shoot weights, and root: shoot ratios. In the first soil moisture treatment the taproot was allowed to extend into moist soil throughout the duration of the experiment (control), while in the second treatment (shallow) the taproot grew into a dry substrate below 30 cm of moist soil. The treatments were intended to approximate soil moisture conditions experienced by oak seedlings in the field when deep soil water sources vary in their accessibility (control: accessible, shallow: inaccessible). Lateral root growth of Quercus agrifolia did not increase significantly when the primary root tip died in the shallow treatment, resulting in an overall decrease in the percent of the root system composed of lateral roots. Q. douglasii and Q. lobata increased lateral root weights by 80% and 70%, respectively, on the upper 30 cm of the primary root when the primary root tip died. Q. lobata was the only species that decreased in shoot and root weight (25% and 21%, respectively) with the loss of the root tip, indicating that, unlike the other species, it was dependent on the primary root for maximum growth. The morphological responses of these species correspond with their distributions and also may be a factor that influences their interactions with other species.

Effects of Soil Water Distribution on the Lateral Root Development of Three Species of California Oaks

The responses of seedling root systems of three species of oaks in California to two experimental soil moisture regimes were studied by comparing lateral root development, root and shoot weights, and root: shoot ratios. In the first soil moisture treatment the taproot was allowed to extend into moist soil throughout the duration of the experiment (control), while in the second treatment (shallow) the taproot grew into a dry substrate below 30 cm of moist soil. The treatments were intended to approximate soil moisture conditions experienced by oak seedlings in the field when deep soil water sources vary in their accessibility (control: accessible, shallow: inaccessible). Lateral root growth of Quercus agrifolia did not increase significantly when the primary root tip died in the shallow treatment, resulting in an overall decrease in the percent of the root system composed of lateral roots. Q. douglasii and Q. lobata increased lateral root weights by 80% and 70%, respectively, on the upper 30 cm of the primary root when the primary root tip died. Q. lobata was the only species that decreased in shoot and root weight (25% and 21%, respectively) with the loss of the root tip, indicating that, unlike the other species, it was dependent on the primary root for maximum growth. The morphological responses of these species correspond with their distributions and also may be a factor that influences their interactions with other species.

Carbohydrate, Nitrogen and Dry Matter Accumulation and Partitioning of Maize Hybrids Under Drought Stress

Maize (Zea mays L.) productivity under drought stress depends to some extent upon a hybrid's capacity to produce and translocate assimilate to its developing kernels during the stress period and/or after the stress is relieved. The objective of this study was to evaluate differences in carbon and nitrogen accumulation and partitioning under drought stress among maize hybrids that differ in yield potential and/or physiological metabolism during reproductive development. The hybrids B73 × LH38, FS854, B73×Mol7 and US13 were subjected to drought stress from the 7th leaf stage until pollination was completed, at which time the soil of the stressed plots was replenished with water. For d. wt and chemical constituent determinations, plants of each hybrid were harvested from the irrigated and drought stressed plots at silking, mid-grain fill, and physiological maturity. Averaged over hybrids, vegetative biomass at silking was reduced 25% as a result of the drought stress treatment, with B73 × LH38 and FS854 accumulating more total biomass during the later portion of grain fill than the other two hybrids under both soil moisture treatments. At silking, the total non-structural carbohydrate content of the hybrids' vegetative tissue was not changed as a result of drought stress, whereas their reduced nitrogen (N) contents were decreased by an average of 33%. B73 × LH38 and FS854 had greater grain carbohydrate and reduced N contents under irrigation and smaller decreases in those variables as a result of soil moisture deficit than did the other two hybrids. These results indicate that the greater drought tolerance of B73 × LH38 and FS854 to stress imposed during vegetative and early reproductive development resulted from their more active N uptake and assimilation and sugar production during the later portion of grain fill and from their more efficient partitioning of assimilate to the developing kernels.

GAS EXCHANGE AND FERN WATER POTENTIALS OF WATER-STRESSED ASPARAGUS

Asparagus is considered a relatively drought tolerant plant, but few studies are available on the gas exchange response to soil moisture stress. Seedlings were grown in the greenhouse for six months before initiation of the water stress treatments. Soils were allowed to dry to matric potentials of -0.05, -0.3 and -0.5 MPa before rewatering to pot capacity. Gas exchange and fern water potentials were measured diurnally on asparagus plants when soil matric potentials reached their minima. Decreasing soil matric potentials decreased net carbon dioxide assimilation, stomatal conductance and fern water potential. Assimilation rates (6 am) were between 3 and 5 umols m-2 s-1 for all soil moisture treatments. Carbon assimilation rates of 10, 8, and 7 umols m-2 s-1 were recorded at 10 am for the -0.05, -0.3 and -0.5 MPa soil matric potentials, respectively. Assimilation rates decreased sharply over the remainder of the day. The diurnal pattern for conductance were similar to the assimilation rates. Fern water potentials were greater in the -0.05 MPa than in the -0.5 MPa treatment for all measurement periods with an intermediate response for soil matric potentials of -0.3 MPa. Fern water potentials were highest at 6 am (-0.2 to -0.6 MPa) before declining to their minima (-1.5 to -1.8 MPa) at 10 am. Water potentials remained at these low levels throughout the day before recovering slightly at 6 pm.

GAS EXCHANGE AND FERN WATER POTENTIALS OF WATER-STRESSED ASPARAGUS

Asparagus is considered a relatively drought tolerant plant, but few studies are available on the gas exchange response to soil moisture stress. Seedlings were grown in the greenhouse for six months before initiation of the water stress treatments. Soils were allowed to dry to matric potentials of -0.05, -0.3 and -0.5 MPa before rewatering to pot capacity. Gas exchange and fern water potentials were measured diurnally on asparagus plants when soil matric potentials reached their minima. Decreasing soil matric potentials decreased net carbon dioxide assimilation, stomatal conductance and fern water potential. Assimilation rates (6 am) were between 3 and 5 umols m-2 s-1 for all soil moisture treatments. Carbon assimilation rates of 10, 8, and 7 umols m-2 s-1 were recorded at 10 am for the -0.05, -0.3 and -0.5 MPa soil matric potentials, respectively. Assimilation rates decreased sharply over the remainder of the day. The diurnal pattern for conductance were similar to the assimilation rates. Fern water potentials were greater in the -0.05 MPa than in the -0.5 MPa treatment for all measurement periods with an intermediate response for soil matric potentials of -0.3 MPa. Fern water potentials were highest at 6 am (-0.2 to -0.6 MPa) before declining to their minima (-1.5 to -1.8 MPa) at 10 am. Water potentials remained at these low levels throughout the day before recovering slightly at 6 pm.

Osmotic and Turgor Adjustment in Rosa Foliage Drought-stressed under Varying Irradiance

The influence of irradiance and drought on osmotic and turgor adjustment was examined in leaves of rose (Rosa hybrida L. `Samantha'). Plants cultured under full ambient light in the greenhouse were placed in shade chambers and, after 2 weeks of acclimation, exposed to drought for 21 days. Treatments consisted of a water stress factor (well-watered and drought-stressed) and an irradiance factor (100%, 70%, and 30% of ambient irradiance). Pressure-volume analyses of leaves indicated that osmotic potentials at full turgor were decreased 0.42, 0.36, and 0.23 MPa by drought in the 100%, 70%, and 30% irradiance treatments, respectively. Plants stressed under 100% and 70% irradiance exhibited similar osmotic adjustments. Plants under 30% irradiance had higher osmotic potentials at full turgor under well-watered conditions than plants in the other two irradiance treatments and showed only 55% as much adjustment to drought. In each irradiance treatment, drought induced an increase in elastic modulus and a decrease in relative water content at zero turgor. Turgor pressures were higher across a range of relative water contents in plants in the two higher irradiance treatments under both soil moisture treatments. Turgor also was higher at any particular water potential at 100% and 70% irradiance than 30% irradiance, within each soil moisture treatment. Heavy, but not mild, shading inhibited osmotic and turgor adjustments in leaves during drought.

Overcoming drought-induced decreases in soybean leaf photosynthesis by measuring with CO2-enriched air

Soybean [Glycine max (L.) Merr. cv. Williams 82 and A3127] plants were grown in the field under long-term soil moisture deficit and irrigation to determine the effects of severe drought stress on the photosynthetic capacity of soybean leaves. Afternoon leaf water potentials, stomatal conductances, intercellular CO2 concentrations and CO2-assimilation rates for the two soil moisture treatments were compared during the pod elongation and seed enlargement stages of crop development. Leaf CO2-assimilation rates were measured with either ambient (340 μl CO2 l(-1)) or CO2-enriched (1800 μl CO2 l(-1)) air. Although seed yield and leaf area per plant were decreased an average of 48 and 31%, respectively, as a result of drought stress, leaf water potentials were reduced only an average of 0.27 MPa during the sampling period. Afternoon leaf CO2-assimilation rates measured with ambient air were decreased an average of 56 and 49% by soil moisture deficit for Williams 82 and A3127, respectively. The reductions in leaf photosynthesis of both cultivars were associated with similar decreases in leaf stomatal conductance and with small increases in leaf intercellular CO2 concentration. When the CO2-enriched air was used, similar afternoon leaf CO2-assimilation rates were found between the soil moisture treatments at each stage of crop development. These results suggest that photosynthetic capacity of soybean leaves is not reduced by severe soil moisture deficit when a stress develops gradually under field conditions.

Husk size and underdevelopment of husks under excess soil moisture condition in malting barley.

The objective of this study was to clarify the factors causing underdevelopment of husks in malting barley. Materials were grown under six different excess soil moisture treatments combined with shading treatment or low (high) temperature treatment during the husk-size-determination period, i.e., from flag leaf emergence stage to heading stage, when the length and width of lemma and palea rapidly increased. The degree of excess soil moisture treatment was expressed by I (flooding condition) -VI (good soil moisture condition). The growth of lemma and palea were inhibited with the degree of soil moisture treatments (VI→I), and were extremely inhibited by the excess soil moisture treatment combined with shading treatment or low temperature treatment. The growth of kernel in IV∼VI plots, in which the damage were little, were not inhibited. But those in I-IV plots were inhibited with the degree of soil moisture treatments. The husk underdevelopment, which resulted in the exposure of caryopsis through lemma and palea, was severe in IV and V plots under all treatments, and was occured when excess soil moisture was combined with shading and/or low temperature, because of the unbalance between husk and kernel sizes.

Index of screening for wet endurance in malting barley.

ビールオオムギの耐湿性を高める目的で,耐湿性の異なる品種間で交配を行い,雑種F4～F6世代での耐湿性の選抜結果から遺伝率を推定し,耐湿性の選抜をより的確に行うためにはどの形質を用いればよいかの検討を行った.過湿処理は節間伸長期に行い,過湿区の葉枯程度および稈長と子実重の対照区比(過湿区/対照区,以下同じ)を指標形質とした.葉枯程度を指標とした場合,供試した4組み合わせの遺伝率は0.12～O.48であった.選抜次代の上位と下位の系統群の葉枯程度の平均値を比較すると,いずれの組み合わせとも上位の系統群の方が少なく,そのうち3組み合わせで有意差が認められた.稈長および子実重の対照区比を指標とした場合,供試した3組み合わせの遺伝率は前者が0.47,-0.02,1.06および後者が0.32,-0.12,0.23であった.選抜次代の上位と下位の系統群の稗長および子実重の対照区比の平均値を比較すると,前者は2組み合わせで上位の系統群の方が大きく,ともに有意差が認められ,後者は2組み合わせで上位の系統群の方が大きく,そのうち1組み合わせで有意差が認められた. 以上の結果から,ビールオオムギにおける過湿区の葉枯程度は稈長および子実重の対照区比を指標とした場合よりも安定した選抜効果や遺伝率の推定値が得られるので,雑種初期世代における耐湿性を選抜するための有効な指標形質である.

Effects of Ozone and Water Stress, Separately and in Combination, on Soybean Yield

AbstractA primary concern in applying existing 03‐effects data on crop production is the relatively unknown influence of soil moisture, which may modify plant response to 03. One deficiency in field experiments that have tested the influence of soil moisture on crop response to 03 has been lack of control of soil moisture conditions in open‐top chamber plots. Most experiments have relied on the occurrence of normal drought periods during the growing season and use of irrigation to adjust soil moisture conditions. This has not allowed the control of the water stress cycles that is desirable. In 1986 a field experiment was performed with soybean [Glycine max. (L.) Merr. cv. Young] to test the influence of periodic water stress on the yield response to O3. Open‐top field chambers were used to expose plants to a range of O3 concentrations, and rain exclusion caps were used on individual chambers to help regulate soil moisture levels. Three soil moisture treatments were used [well‐watered (WW), waterstressed (WS), and well‐watered with permanent rain exclusion caps that were in place from 35 d after planting until physiological maturity (WW‐C)]. In the WW and WS treatments, the rain caps were put in place only during an exceptionally wet period from mid‐August to mid‐September. The WW and WW‐C treatments had approximately the same yield and response to O3, indicating that the presence of the caps for most of the growing season had little effect on growth or sensitivity to O3. The WS plots yielded approximately 10% less on the average than the WW and WW‐C plots, but water stress did not change the response to O3 (i.e., no significant O3 × water interaction). Based on a Weibull dose‐response model, O3 reduced yield of ‘Young’ soybean 13% at a concentration of 0.05 µL L−1 (12 h d−1 seasonal mean) compared to a hypothetical background of 0.02 µL L−1.

Phenological responses of old and modern soybean cultivars to air temperature and soil moisture treatment

Soil moisture deficits and low air temperatures frequently result in crop yield losses in the United States. Understanding how older and newer soybean ( Glycine max (L.) Merr.) cultivars differ in phenological development under various environmental conditions may aid in the selection of higher-yielding cultivars and in the development of simulation models for field-grown soybean. In this study, we examined the phenological responses of two widely adapted older (‘Dunfied’ and ‘Manchu’) and two more-recent (‘Clark 63’ and ‘Williams 82’) soybean cultivars to soil moisture deficit and monitored the development of these cultivars as a function of air temperature. These cultivars were grown under drought stress and irrigation on a Flanagan silt loam soil at Urbana, Illinois, in 1984 and 1985. The soil moisture-deficit treatment was begun approximately 2 weeks before initial flowering (R1 stage) and was continued until harvest maturity. Drought stress reduced the final number of mainstem nodes due to a decrease in the rate at which the nodes were produced, but had little effect on the date of termination of node formation. Except for Manchu, no association was observed between the number of nodes produced under irrigation and the magnitude of the decrease in node number due to drought stress. Although the correlation between cumulative growing degree-days and mainstem node formation was high, little difference was found between the old and modern cultivars in their responses to air temperature. A period of low temperatures during early flower formation in 1985 appeared to have partially contributed to a delay in flower appearance of each cultivar. The results from this study show that the old and modern cultivars do not differ in their phenological responses to drought stress.

Effects of kelp (Macrocystis integrifolia andEcklonia maxima) foliar applications on bean crop growth and nitrogen nutrition under varying soil moisture regimes

A greenhouse experiment was designed to test the effects of two kelp(Macrocystis integrifolia andEcklonia maxima) concentrates, when prepared as foliar sprays, upon bean (Phaseolus vulgaris) growth and N nutrition under three soil moisture regimes. Plant growth and developmental responses in this greenhouse experiment have demonstrated the effectiveness of the two kelp foliar sprays as plant growth regulating substances. Bean growth and developmental responses to the kelp foliar spray treatments were dependent upon the soil moisture regime to which they have been subjected. Although the two kelp foliar sprays had varying and sometimes contrasting effects on bean growth and N nutrition, which were dependent on the soil moisture treatment, their developmental effects upon the number of nodes, shoot/root ratio, leaf area ratio and specific leaf area were quite similar. A soybean callus bioassay demonstrated the presence of cytokinin-like substances and a callus growth antagonist in the kelp concentrate. Increasing dilution of the kelp concentrate disproportionately reduced the callus growth antagonist relative to the growth promoting or cytokinin-like activity.

Effects of Long-Term Ozone Exposure and Soil Moisture Deficit on Growth of a Ladino Clover-Tall Fescue Pasture

Most field studies relating seasonal ozone (O3) exposure to crop yield have been performed in the absence of plant moisture stress. The authors examined the response of a mixture of ladino clover and tall fescue to chronic doses of O3 at two soil-moisture levels over two growing seasons. The soil-moisture treatments, obtained by differential irrigation, were well-watered or water-stressed. A soil-moisture deficit occurred intermittently in water-stressed plots during both seasons. Shoots were harvested when plants reached a height of 20-25 cm. Total forage yield in the water stressed plots was 12-14% less than that in the well-watered plots. Clover was much more sensitive than fescue to O3. The decrease in total forage yield and decreased quality caused by decreased growth of clover suggest a need for ladino clover lines that are tolerant to O3.

Heritability of wet endurance in malting barley.

ビールオオムギの耐湿性を高める目的で,耐湿性の異なる品種間の交配を行い,そのF1とF2の耐湿性および雑種初期世代での耐湿性の遺伝率を推定し,選抜効果を検討した.耐湿性の検定は節間伸長期に過湿処理を行い,葉枯程度を指標形質とした.葉枯程度は対照区を設定しなくても大まかな判定ができ,過湿処理が比較的簡単であった.過湿処理による葉枯程度は,過湿処理による1株子実重と稈長の被害程度と相関が認められたことから,葉枯程度は多数の系統を扱わなければならない雑種初期世代における耐湿性の指標形質として使用可能であると考えられた.葉枯程度を指標としたF1の耐湿性にはヘテロシスがみられた.また,F2集団の葉枯種皮の分布は連続的変異を示し,耐湿性はポリジーンによって発現されることが推察された.F2→F3およびF4→F5の選抜試験から推定した葉枯程度の遺伝率は0.07～0.28であった.選抜次代の上位と下位の系統群の葉枯程度の平均値についてt検定を行った結果,3組合せのうち2組合せは1%水準で有意差が認められた.以上の結果から,高耐湿性品種との交配および雑種初期世代における選抜によって,ビールオオムギ品種の耐湿性を高めることが可能であると考えられた.

Factors influencing ammonia volatilization from urea in soils of the shortgrass steppe

The effects of soil moisture, temperature, and humidity treatments on urea hydrolysis and NH3 volatilization were assessed in the laboratory. Field studies were conducted to determine seasonal NH3 losses from simulated urine patches applied to contrasting soils of a representative hillslope of the shortgrass steppe region in the North American Great Plains.

Effects of soil moisture on the character of rice seedlings.

The characteristics of rice (Oryza sativa L.) before and just after transplanting are being studied from the morphological and physio-ecological view-points. In this paper, the differences in characteristics of rice grown under different soil moisture conditions were examined, as a first step in diagnosing the quality of the seedlings: 1. In all varieties, plant length, the number of living leaves, leaf area, stem thickness, top and root dry weights all increased with increasing soil moisture. The differences in these characteristics among the treatments expanded with the passage of time, and the in the paddy nursery plot showed spindly growth. On the other hand, the dry matter production of grown in the upland nursery plot was suppressed compared with the paddy nursery plot, but the upland nursery showed the features of so-called pudgy seedlings with upright leaves and relatively stout stems (Fig. 2). 2. Rooting ability, vertical standing ability, the amount of bleeding water and the degree of leaf die-off were hardly affected by soil moisture treatments. However, upland nursery were superior in all characteristics to paddy nursery with the growth advances. Also, upland nursery had greater starch accumulation and rooting ability, vertical standing ability or the area of leaves die-off. Furthermore, it is assumed that the upland nursery maintain higher root vitality during the late growing season since the amount of bleeding water is closely related to the root vitality (Fig. 3 and 4-A, -B, -C). 3. The amylase activity and starch accumulation measurements suggested that amylase activity tended to increae with increasing soil moisture and that a certain relationship exists between starch accumulation ability and amylase activity in rice (Fig. 4-D). The questions related to these points are left for future studies.

Selection of high wet endurance cross parents for malting barley breeding program.

The objective of this study was to find high wet endurance cross parents for a malting barley breeding program. Barley cultivars containing newly developed malting barley cultivars were grown under an excess soil moisture treatment (irrigated condition) at the internode elongation stage. Principal Component Analysis (PCA) was applied for two barley populations; 78 two-rowed barley cultivars and 51 late-maturing cultivars. Characters for PCA were the reduction ratios of culm length and four yield components (number of kernels per ear, number of ears per plant, seed fertility and 1000 kernel weight) by the treatment. The reduction ratios was calculated as (the mean value of excess soil moisture plots/that of control plots)×100. Component l by the PCA was considered to be a reliable index for wet endurance of barley cultivars. Among 78 two-rowed and 51 late-maturing barley cultivars tested, several cultivars were less-damaged under the excess soil moisture condition and were selected as the wet endurance cross parents in a malting barley breeding program.