Field Capacity Treatment Research Articles

Isolasi dan Identifikasi Endomikoriza pada Perakaran Tanaman Jagung (Zea mays L.) Dataran Sedang serta Perbanyakannya pada Tingkat Kadar Air Tanah Berbeda

Isolation and Identification of Endomycorrhizal on Corn Root (Zea mays L.) at Medium Plain and its Propagation at Different Soil Water Level. Endomycorrhizal has several benefits that can increase the absorption of water and nutrients, protect plants from root pathogens and toxic elements, play a role in the improvement of soil structure, and increase the solubility of nutrients. The purpose of this research is to find out the types endomycorrhizal contained in the corn roots at medium plains in Gianyar Regency, and the influence of different soil water level to endomycorrhizal ability to reproduce spores. This research was conducted from September 2017 to February 2018. The method of the research includes exploration, isolation, identification, propagation of spores endomycorrhizal, and soil samples analysis. Isolation and identification result found 2 genus of spores endomycorrhizal that was Glomus and Acaulospora, with various spore amount and the level of infection endomycorrhizal was very high with percentage of 83.33-86.67%. Spores propagation test results showed that the highest percentage enhacement of spores endomycorrhizal amount was found in the third soil sampling location in soil water level of 40% field capacity treatment with percentage of 551.85%. The level of endomycorrhizal infections at the roots of all treatment of soil sampling location and soil water level were very high with percentage of 100%.

Pertumbuhan Bibit Anggur Prabu Bestari Asal Okulasi pada Berbagai Campuran dan Kandungan Air Media Tanam

The Growth and Development of the Prabu Bestari Grape Seedling on Various Compositions and Water Content of Growing Media. The growth and development of the grape seedling influenced by the presence of solar and ground water energy. Prabu Bestari is a originally variety introduced by Balitjestro from Australia after being assembled with the selection process. The need for this variety of agroclimates is in accordance with the North Bali region as a production center. The bud break in grape plant can be affected by condition of plant media during the seedling procession. Shoot failure in grapes can be caused by the condition of the planting medium in the nursery process. This study aims to determine the growth of grape seedlings that are treated with the use of planting media (soil, soil, chaff, soil + cocopeat, and soil compost) 1: 1 (v / v) mixture ratio. The planting media treatment will be combined with different water content (100%, 75%, and 50% of the field capacity conditions). The study was conducted in a green house at the Experimental Station of Faculty of Agriculture Udayana University from May to August 2018. The research used factorial method (4 x 3) which was designed randomly in groups with three replications. The results showed no interaction on all parameters observed. Increasing length of tendrils (148.16 cm) and number of leaves (26.58 strands) looks better with increasing groundwater content up to 100% of field capacity, whereas the resistant mixture + compost gave the highest increase in tendril length (131.91 cm) and the number of leaves (26.56 pieces). The highest chlorophyll content of the leaves reached 28.68 SPAD unit in a mixture of soil + compost treatment and the lowest was in land use + cocopeat with 18.99 SPAD unit. While the highest leaf chlorophyll content due to water content treatment was shown in 100% of field capacity treatment of 27.84 SPAD unit.

Growth of Typha domingensis as related to leaf physiological and anatomical modifications under drought conditions

Global climate change may lead to reduced water supply to terrestrial environments owing to diminished rainfall. Wetlands are no exception, and macrophytes growing in these ecosystems may experience severe droughts. However, some macrophytes, such as Typha domingensis, can be found on partially dry sites. This study aimed to examine the mechanisms by which T. domingensis survives in dry sites. We examined whether water deficiency reduced the growth capacity of individual T. domingensis plants and the T. domingensis population. We hypothesized that T. domingensis can overcome some level of water deficiency by adjusting physiological parameters related to leaf anatomy, such as transpiration, photosynthesis, and water use efficiency. We evaluated the effects of drought on growth, leaf anatomy, gas exchange, and water potential of T. domingensis under controlled greenhouse conditions at different water availability levels. Waterlogged and field capacity treatments had similar effects on growth, water potential, and net photosynthesis. Population growth was inhibited at 50% and 25% of field capacity water availability. Drought resulted in reductions in photosynthesis, leaf area, water potential, stomatal density, and thickness of the palisade parenchyma. Therefore, although T. domingensis can cope with mild drought stress, the decrease in functional leaf area eventually limits plant growth under severe drought conditions.

Long-term water deficit modulates antioxidant capacity of peppermint (Mentha piperita L.)

Abstract Study of metabolite profile changes in peppermint is crucial due to its food and medicinal properties. In the current study, the effect of water deficit (normal irrigation as control, 0.75 field capacity (FC), 0.5 and 0.25 FC) investigated on the growth parameters, physiological response, phenolic compounds and content of l -ascorbic acid in peppermint plant. The morphological properties of peppermint reduced due to water deficit. The maximum essential oil percentage observed in 0.25 FC treatment (1.1%). Water deficit leads to a significant increment in the concentration of hydrogen peroxide (H2O2) and malondialdehyde (MDA). In the other word, the highest concentration of H2O2 and MDA measured in plants which exposed to the 0.25 FC treatment. Moreover, polyphenol oxidase (PPO) and superoxide dismutase (SOD) show the highest activity in the 0.5 FC and 0.25 FC, respectively. However, drought stress had a negative impact on the total phenol content (TPC) and flavonoid content which cause a reduction from 72.5 to 68.1 in control and 0.25 FC treatments. The elevated content of flavone observed in the 0.5 FC treatment. The radical scavenging activity of peppermint extracts against stable DPPH (2,2-diphenyl-2-picrylhydrazyl hydrate) decreased under long-term water stress. While the content of l -ascorbic acid in water deficit treated plants was more than control plants. These results suggest that moderate water deficit (0.5–0.75 FC) in peppermint will be appropriate to enhance its biological properties.

Responses of Grain Maize to Plant Density at Different Irrigation Regimes

In order to examine the effects of different plant densities, plant patterns and irrigation regimes on yield, yield components and harvest index of grain maize, a field experiment was conducted at Miyandoab Agricultural Research Station, Iran. A strip split plot experiment was conducted based on randomized complete block design with three replications. The results showed that the effect of plant density was significant on kernel yield, harvest index, 1,000 kernel weight. The highest kernel yield was obtained from 90,000 plants ha-1 density. Maximum grain yield (18.530 t ha-1) was obtained from furrow irrigation. However, there was no significant difference between moisture levels of 100% and 120% of field capacity. The lowest kernel yield was obtained at 80% field capacity. This study also showed that mean kernel weight and the number of kernels per row were the most determinant factors in grain yield formation. The highest and the lowest harvest indices were obtained at 120% and 80% treatments of field capacity treatment, respectively.

Influence of different irrigation and nitrogen levels on crude oil and fatty acid composition of maize (<em>Zea mays</em> L.)

The effect of irrigation and nitrogen fertilizer levels on the crude oil and fatty acid composition of maize cultivars was studied. Three levels of irrigation (50, 75 and 100% of field capacity) and nitrogen (100, 200 and 300 kg·ha-1) were used for treatment groups. After harvest, the crude oils were extracted and fatty acid profiles were determined by Gas Chromatography system. The study was repeated for two years and the interaction effects of fertilizer and irrigation were determined. Our results show that the crude oil content was affected positively by the fertilizer and the irrigation applications. As expected, the most abundant fatty acid was linoleic and the harvest year did not alter it. The highest linoleic acid content value was obtained with a 50% field capacity and 300 kg·ha-1 fertilizer treatment combination. In addition, fatty acid contents varied with the changing of interaction effects except for myristic and palmitic acid. Oleic acid was the second abundant fatty acid in the oil samples and the lowest oleic acid value was obtained with a 50% field capacity and 300 kg·ha-1 fertilizer treatment combination. Oleic acid content tended to increase with 75% field capacity but 100% field capacity treatment decreased in it.

Soil water stress attenuate the growth and development but enhance the saponin synthesis of Panax notogesing during flowering stage

Water stress can affect the growth and secondary metabolites of plants. Thus, this study identified the effects of soil water conditions on the growth and development of Panax notoginseng, especially saponin synthesis. Panax notoginseng was grown in different soil water conditions (0.40, 0.55, 0.70, 0.85, 1.00 field capacity) for 30days, and related indicators were determined every 10days. Panax notoginseng could not survive under the content of 0.40 and 1.00 field capacity. Thus, their cultures were set at 0.55, 0.70, and 0.85 field capacity for experimental purposes. The results showed that agronomic traits, leaf water contents, chlorophyll contents, and photosynthetic efficiency in 0.70 field capacity were significantly higher than in 0.55 and 0.85 field capacity. In addition to flowers, contents of soluble total sugars and proteins increased significantly in all the parts under 0.55 and 0.85 field capacity. Compared with 0.70 field capacity treatment, total saponin content of aboveground organs increased significantly under 0.55 and 0.85 field capacity. And 18 key genes increased significantly but 2 key genes changed insignificantly in saponin synthesis pathway. These results suggested that 0.70 field capacity was the most suitable soil water condition for flowering stage Panax notoginseng and produced the best agronomic traits, while water stress (0.55 and 0.85 field capacity) produce more saponin contents by improving the expression of key genes in saponin synthesis pathway.

The effect of soil moisture depletion on Stevia (Stevia rebaudiana Bertoni) grown in greenhouse conditions: Growth, steviol glycosides content, soluble sugars and total antioxidant capacity

The purpose of the present study was to determine threshold values of soil moisture content for Stevia (Stevia rebaudiana Bertoni) and to evaluate the effects of drought stress on the main metabolites of this species. For these purposes, a greenhouse experiment was carried out with four soil moisture levels and plant growth, steviol glycoside (SVglys) contents, soluble sugars and antioxidant capacity were investigated at variable soil moisture content. Irrigation was scheduled at 3, 6, 9 and 12-day irrigation intervals, based on soil moisture content at 90, 75, 60 and 45% of field capacity (FC) respectively. The results showed that soil water depletion up to 60% FC (9-day irrigation interval) had no negative effect on plant growth and leaf dry weight, whereas a significant growth reduction occurred at 45% FC (12-day irrigation interval). Similarly, the total SVglys content increased when soil moisture was depleted to 60% FC (9-day irrigation interval), but these metabolites contents decreased by 45% FC treatment. Although Stevia growth and SVglys content significantly decreased under severe drought stress (45% FC), the total antioxidant capacity and soluble sugars increased in the identical condition. The obtained results suggest that Stevia plants can grow well with a soil water content near to 60% FC, showing a good SVglys content. The Stevia tolerance to mild water stress is noteworthy, especially in water limited regions. In addition, it was found that soil water depleted to 45% FC was detrimental to Stevia in greenhouse conditions. The improvement of antioxidant capacity and soluble sugar content by soil water stress conditions could be considered as physiological and biochemical responses to a progressive drought stress in Stevia and may be an acclimation response to drought stress.

RESPONSES OF ROOTING TRAITS IN PEANUT GENOTYPES UNDER PRE-FLOWERING DROUGHT STRESS

The root is an important plant part contributing to peanut productivity under water-limited conditions. Root volume, root surface area and root diameter may be characters responding to pre-flowering drought (PFD) in peanut. The objectives of this study were to investigate the responses to PFD for root surface area, root volume and root diameter and to determine the inter-relationships among the response of rooting traits and the response of yield. The experiment was conducted under field conditions in the dry season 2007 and 2009. A split-plot experiment in a randomized complete block design was used. The main plots were field capacity (FC) and PFD and six peanut genotypes as the sub-plots. Root volume, root diameter and root surface were measured by auger method at 25 days after emergence (DAE), first seed (R5) and physiological maturity (R7). Total dry weight and pod yield were measured at harvest. Root surface area of ICGV 98305 with increase in pod yield was greater in deeper soil layers under PFD compared to FC treatment at both stress and recovery periods. Under PFD conditions, the correlations between drought tolerance index (DTI) for root surface area at deeper soil layer and DTI for pod yield in both seasons were positive and significant at stress and recovery periods, but the correlations were not significant for root diameter and root volume. The response of peanut for root surface area at deeper soil layer contributed to pod yield. This finding could be useful for peanut production in these drought conditions.

Corn Yield Response to Reduced Water Use at Different Growth Stages

To develop an efficient water use strategy for crop irrigation, we need to know how much water can be reduced without decreasing yield. A study was designed to determine corn growth stages at which water could be reduced without affecting grain yield, and at what soil moisture level water deficit stress begins in the plants in a silt loam soil. An experiment was conducted in a randomized complete block with a 3 × 4 factorial design in four replications, where treatments consisted of three soil moisture levels [100%, 75%, and 50% of field capacity (FC) of a silt loam soil by weight] and four growth stages [fourteen leaf stage (V14), silking (R1), milk (R3), and dent (R5) stages] in a greenhouse. Growth stages at the reproductive and grain fill stages of corn were selected because this study was intended for the Mississippi Delta, where there is frequent drought during these growth stages making irrigation necessary for corn production, whereas there is usually adequate rainfall during the vegetative growth stages. Results from this study showed that reducing soil moisture from 100% FC (fully irrigated) to 75% FC of a silt loam soil starting at the R1 growth stage in corn did not reduce yield significantly compared to yield from the 100% FC, while saving a significant amount of water. Physiological investigations at the three soil moisture treatments showed that a mild moisture deficit stress might have started at the 75% FC treatment. With further investigation, if savings in water at 75% FC result in a significant reduction in energy cost, it may be profitable to reduce soil moisture to 75% FC in a silt loam soil.

Effect of intermittent irrigation with saline water on rice yield in Rasht, Iran

Guilan, a well-known province in rice production in Iran, has been facing water shortage and water degradation. In order to study the effects of salinity stress as well as water stress on rice a pot experiment was conducted at Rice Research Institute of Iran. Five water salinity levels: fresh water (EC = 1 dS m-1), 2, 4, 6 and 8 dS m-1 and five irrigation regimes: continues flooding, Alternative Wetting and Drying (AWD), intermittent irrigation at 100, 90 and 80 percent of field capacity (FC) were considered as irrigation treatments. The results showed severe effects of water and salinity stresses on rice yield and yield components. Fresh water produced the highest yield, 18.57 gr pot-1, whereas, the yield in salinity levels of 2, 4, 6 and 8 dS m-1 were 13.78, 5.78, 3.61 and 0.74 gr pot-1, respectively, with the yield losses of 25, 70, 80 and 97%, respectively. Intermittent irrigation at FC produced the highest yield. The yield increased 8 and 13% in AWD and intermittent irrigation at FC treatments respectively, while it decreased 8 and 27% in intermittent irrigation at 80 and 90% of FC treatments as compared with continues flooding treatment. The highest yield with application of intermittent irrigation at FC was valid only in water salinity less than 4 dS m-1. When water salinity was higher than 4 dS m-1 all irrigation methods gave the same yield. This study showed that the best method to use saline water was intermittent irrigation at FC with EC = 2 dS m-1. In case of more salinity, mixing fresh and saline water and intermittent irrigation can mitigate the severe effects of salinity on rice.

Soil residue analysis and degradation of saflufenacil as affected by moisture content and soil characteristics

Saflufenacil dissipation in soils under different moisture conditions is not available in the scientific literature. The objective of this study was to evaluate saflufenacil degradation and persistence in soils from rice regions under field capacity (non-flooded) and saturated (flooded) conditions. The accelerated solvent extraction (ASE) residue analytical method developed to conduct the study resulted in recovery greater than 80% for the combinations of soils and moisture conditions. Saflufenacil degradation was faster at field capacity for all soils, except for Morey soil. Herbicide half-life was 28.6, 15.0 and 23.1 days under field capacity treatments and 58.8, 36.9 and 79.7 under saturated conditions for Nada, Crowley and Gilbert soils respectively. A half-life no longer than 80 days was observed for the combination of soils and moisture treatments. An ASE method was developed and used to extract saflufenacil from soil samples. Half-life averaged among soils was 59 and 33 days for saturated and field capacity respectively. Saflufenacil persistence in the environment was 2-3 times longer under flooded conditions for most of the soils studied.

Plant growth, water relations and proline content of three vetch species under water‐limited conditions

AbstractVetch species (Vicia narbonensis, V. sativa and V. villosa) are widely used for fodder production in Tunisia. This study aims to investigate vetch strategies involved in drought resistance through morphological and physiological criteria. Plants were sown in pots and subjected to four soil‐water levels: 100% (control), 80, 60 and 40% of field capacity (FC). After 133 d of water treatment, and under well‐watered conditions, V. narbonensis showed the largest plant height and shoot and root dry matter and the highest leaf relative water content and water potential (Ψw), whereas V. sativa had the greatest leaf area (LA). At the 40% FC treatment, V. narbonensis showed smaller decreases in plant height and LA, and the greatest reduction in Ψw (140%). Thus, it shows better adaptation and a more equilibrated water balance, despite having accumulated less proline than the two other species. Vicia sativa and V. villosa showed a similar behaviour under water stress with a superiority of the latter. Vicia sativa was the species most affected in terms of its growth and water‐status parameters. Vetch species mainly used avoidance mechanisms to withstand drought, with V. narbonensis showing the highest tolerance.

MAXIMIZING PRODUCTIVITY AND WATER USE EFFICIENCY OF ALFALFA UNDER PRECISE SUBSURFACE DRIP IRRIGATION IN ARID REGIONS

ABSTRACTA field experiment studying the effect of water stress on alfalfa (Medicago sativa) productivity and water use efficiency was conducted at the Agricultural Experimental Station of King Abdelaziz University. The design of the experiment was randomized complete block design (RCBD) with four replicates. It consisted of three treatments, namely: field capacity treatment (FC) as a control, 85% FC and 70% FC as stress treatments. The irrigation water for all treatments was precisely supplied using recent technology known as the water electronics module (WEM).Results indicated that decreasing water supply decreased fresh and dry yield of alfalfa but increased irrigation water use efficiency (IWUE). As a result, 13 and 27% of irrigation water were saved from 85% FC and 70% FC treatments respectively in each cut compared with the FC treatment. The reduction of water supply resulted in a yield reduction of 12 and 21.7% for 85% FC and 70% FC, respectively. The results also proved that WEM is a practical tool to precisely supply irrigation water and can be used effectively to control deficit irrigation. Copyright © 2013 John Wiley & Sons, Ltd.

Jatropha curcas seedlings show a water conservation strategy under drought conditions based on decreasing leaf growth and stomatal conductance

Abstract Jatropha curcas L. has recently drawn the attention of the international research community due to its potential as a biodiesel crop. In addition, it is very well adapted to arid and semiarid climate conditions. In this research, the effects of drought on growth, leaf water relation and organic solutes, leaf and root mineral concentration, chlorophyll fluorescence parameters, leaf gas exchange and carbohydrate concentration were studied in seedlings of J. curcas to elucidate the physiological and morphological mechanisms related to their drought tolerance. Four-week-old seedlings were grown in growth chambers with five different water regimes corresponding to 100, 75, 50, 25, and 0% field capacity (FC) for four weeks. Seedlings, maintained a good water status regardless of the drought stress treatment because all water regimes affected the leaf relative water content, whereas the leaf water potential was only reduced in the water-stressed plants from the 0% and 25% FC treatments. Drought treatments reduced leaf, stem and root growth. However, the decrease in growth was higher in the aerial part of the plant than in the root, so that the root-to-shoot ratio in drought-stressed plants increased compared to that in the well-watered plants. Net assimilation of CO2 ( A CO 2 ) and stomatal conductance (gs) decreased in all treatments, although A CO 2 gradually declined as the water supply was decreased, while the reduction in stomatal conductance was similar in all drought stress treatments. Hence, we conclude that the strong control of transpirational water loss by reducing both stomatal conductance and biomass from aerial parts could be involved in the ability of this plant to resist drought conditions.

Appropriate nitrogen supply could improve soil microbial and chemical characteristics with Sophora davidii seedlings cultivated in water stress conditions

A greenhouse experiment was conducted to investigate the changes of soil microbial activities and chemical properties under different water and nitrogen (N) supply conditions. A completely randomized design was subjected to three water regimes (80%, 40% and 20% water field capacity (FC)) and three N supply regimes (control, N0: 0 mg N kg−1 soil; low N supply, Nl: 92 mg N kg−1 soil; and high N supply, Nh: 184 mg N kg−1 soil) by potting with 2-month-old Sophora davidii seedlings. Water stress decreased the content of soil organic carbon (C), available N and phosphorus (P), the ratio of C/N, the ratio of C/P, as well as activities of soil invertase, urease and alkaline phosphatase, but not reduced microbial biomass C, N and P contents. Soil microbial and chemical characteristics also exhibited strong responses to N supply, and these responses were inconsistent among N supply levels. The contents of soil organic C and available P showed stronger positive responses to Nl than to Nh, while the available N content increased with increasing N supply. Additionally, Nl rather than the other two N treatments led to increased microbial biomass N and invertase activity under 20% FC treatment, even though the invertase activity increased in Nh treatment under 40% FC and 80% FC treatments. Nl treatment also increased the C/P ratio and alkaline phosphatase activity. These results suggest that water and N co-limited nutrient mineralization and microbial activity, and that these characteristics responded positively to Nl. Therefore, appropriate or low N supply is recommended to increase soil quality restrained by water stress, thereby facilitating S. davidii seedling establishment under water deficit conditions.

Changes in essential oil content and composition of Agastache foeniculum under water stress at second harvest

To study the effect of different levels of water stress on essential oil content and composition of Agastache foeniculum Kuntze at second harvest, a field experiment in randomized complete block design with three replications was conducted. Water stress treatments were: 100% of field capacity (FC), 85% of FC, 70% of FC, 55% of FC, 100–85% of FC (100% at vegetative and 85% at reproductive phases), 100–70% of FC (100% at vegetative and 70% at reproductive phases), 85–100% of FC (85% at vegetative and 100% at reproductive phases). The highest of essential oil content was observed at 70% of FC (1.69) and 100–85% of FC (1.67). Also the treatment 85% of FC (1.33) caused the lowest of essential oil content. There was not significant different between other treatments. The main essential oil constituent was methyl chavicol which showed a increasing with progress water stress till 70% of FC and then decreased at 55% of FC treatment. Limonene, another main component was decreased with increasing water stress levels from 100 of FC to 70% of FC. The highest amount of methyl chavicol (98.3%) and limonene (2.4%) were found at 70% of FC and 85–100% of FC, respectively.

Análise do crescimento de mudas de jatobá (Hymenaea courbaril L.) em diferentes níveis de água no solo

O objetivo deste trabalho foi analisar o crescimento de mudas de jatobá (Hymenaea courbaril L.) sob déficit hídrico. As plantas foram cultivadas em vasos contendo 8 kg de solo oriundo do local de coleta das sementes. Foram utilizados blocos casualizados como delineamento experimental, com quatro tratamentos hídricos (100%, 75%, 50% e 25% da capacidade de pote) e seis repetições. Semanalmente foram avaliados a altura das plantas, o número de folhas e o diâmetro do caule. No final do período experimental, foram determinados a área foliar, a razão de área foliar e a área foliar específica, a produção de matéria seca das folhas, do caule, das raízes e total, e a alocação de biomassa para as folhas, o caule e as raízes. Verificou-se que o déficit hídrico afetou o crescimento das plantas quanto à altura, ao diâmetro do caule e à produção de matéria seca para os diversos órgãos, quando cultivadas em níveis a partir de 50% da CP. O número de folhas reduziu-se em todos os níveis de estresse, quando comparados com o tratamento 100% da CP. O padrão de alocação de biomassa, a relação raiz/parte aérea, razão de área foliar e área foliar específica, mas, não foram afetados pelo estresse. O número de folhas foi a variável mais sensível ao estresse. Mudas de jatobá não paralisaram o seu crescimento quando cultivadas com baixa disponibilidade de água no solo, na fase inicial do desenvolvimento. No entanto, seu crescimento foi severamente afetado em níveis de água abaixo de 50% da capacidade de retenção de água no solo.

Physiological responses of potato (Solanum tuberosum L.) to partial root-zone drying: ABA signalling, leaf gas exchange, and water use efficiency

The physiological responses of potato (Solanum tuberosum L. cv. Folva) to partial root-zone drying (PRD) were investigated in potted plants in a greenhouse (GH) and in plants grown in the field under an automatic rain-out-shelter. In the GH, irrigation was applied daily to the whole root system (FI), or to one-half of the root system while the other half was dried, for 9 d. In the field, the plants were drip irrigated either to the whole root system near field capacity (FI) or using 70% water of FI to one side of the roots, and shifted to the other side every 5-10 d (PRD). PRD plants had a similar midday leaf water potential to that of FI, whereas in the GH their root water potential (Psi(r)) was significantly lowered after 5 d. Stomatal conductance (g(s)) was more sensitive to PRD than photosynthesis (A) particularly in the field, leading to greater intrinsic water use efficiency (WUE) (i.e. A/g(s)) in PRD than in FI plants on several days. In PRD, the xylem sap abscisic acid concentration ([ABA](xylem)) increased exponentially with decreasing Psi(r); and the relative [ABA](xylem) (PRD/FI) increased exponentially as the fraction of transpirable soil water (FTSW) in the drying side decreased. In the field, the leaf area index was slightly less in PRD than in FI treatment, while tuber biomass was similar for the two treatments. Compared with FI, PRD treatment saved 30% water and increased crop water use efficiency (WUE) by 59%. Restrictions on leaf area expansion and g(s) by PRD-induced ABA signals might have contributed to reduced water use and increased WUE.

Effects of soil water on seed production and photosynthesis of pink smartweed (Polygonum pensylvanicum L.) in playa wetlands

Soil moisture is frequently manipulated by wetland managers to achieve a desired composition and production of plant species. Pink smartweed (Polygonum pensylvanicum) is a species valued by wetland managers because of its potential seed production and food base for migrating and wintering waterbirds. To improve ability to manage pink smartweed, we measured the influence of four growing-season soil moisture regimes (flooded, field capacity, prescribed moist-soil management, and continuously dry) in playa wetlands of the Southern High Plains of Texas. We used xylem water potential as an index of soil moisture available to the plants and compared vegetation and seed production among the four moisture treatments. Daily net photosynthesis was measured in each playa at 0900, 1200, and 1700 hours. The continuously-flooded wetland had the lowest absolute xylem water potential value (−0.294 MPa), followed by the playa at field capacity (−0.446 MPa), moist-soil managed playa (−0.758 MPa), and dry playa (−1.039 MPa). Vegetation biomass (F3,40 = 97.7, P < 0.001) and seed production (F3,40 = 54.3, P < 0.001) of pink smartweed differed among soil moisture treatments. Conducting moist-soil management (x = 6816 kg/ha) increased vegetation biomass by 44% over the dry treatment (x = 4706 kg/ha). As soil moisture increased to field capacity (x = 9010 kg/ha) vegetation increased by 32% above the moist-soil treatment. Maintaining standing water in a playa maximized vegetation production (x = 12497 kg/ha) of pink smartweed. Seed production was greatest when soil moisture was maintained at field capacity (x = 695 kg/ha). There was no difference in seed production between the moist-soil managed (x = 492 kg/ha) and flooded playas (x = 514 kg/ha), which was 28% lower than the field capacity treatment. Seed production in the dry treatment (x = 377 kg/ha) was 46% lower than the field capacity treatment and 25% below the flooded and moist-soil managed treatments. Net photosynthesis and xylem water potential decreased throughout the day in all treatments except continuously flooded, which corresponded to the increased vegetation production in this treatment. Slight increases in water stress relative to the continuously flooded treatment resulted in a redistribution of resources from vegetation to seed production. Managers should consider maintaining wetland soils at field capacity to increase seed production of pink smartweed.