Periods Of Waterlogging Research Articles

Glycolysis and the Tricarboxylic Acid Cycle Are Linked by Alanine Aminotransferase during Hypoxia Induced by Waterlogging of Lotus japonicus

The role of nitrogen metabolism in the survival of prolonged periods of waterlogging was investigated in highly flood-tolerant, nodulated Lotus japonicus plants. Alanine production revealed to be a critical hypoxic pathway. Alanine is the only amino acid whose biosynthesis is not inhibited by nitrogen deficiency resulting from RNA interference silencing of nodular leghemoglobin. The metabolic changes that were induced following waterlogging can be best explained by the activation of alanine metabolism in combination with the modular operation of a split tricarboxylic acid pathway. The sum result of this metabolic scenario is the accumulation of alanine and succinate and the production of extra ATP under hypoxia. The importance of alanine metabolism is discussed with respect to its ability to regulate the level of pyruvate, and this and all other changes are discussed in the context of current models concerning the regulation of plant metabolism.

Evidence of ecotypic differentiation between populations of the tree species Parapiptadenia rigida due to flooding

The tree species Parapiptadenia rigida, native to southern South America, is frequently used in reforestation of riverbanks in Brazil. This tree is also a source of gums, tannins and essential oils, and it has some medicinal uses. We investigated flooding tolerance and genetic diversity in two populations of P. rigida; one of them was naturally exposed to flooding. Plants derived from seeds collected from each population were submitted to variable periods of experimental waterlogging and submergence. Waterlogging promoted a decrease in biomass and structural adjustments, such as superficial roots with aerenchyma and hypertrophied lenticels, that contribute to increase atmospheric oxygen intake. Plants that were submerged had an even greater reduction in biomass and a high mortality rate (40%). The two populations varied significantly in their RAPD marker profiles, in their ability to produce aerenchyma when waterlogged and to survive when submerged, suggesting ecotypic differentiation between them. Hence, the seasonal flooding that has been challenging the tropical riparian forest appears to be genetically modifying the P. rigida populations exposed to it by selecting individuals with increased ability to live under this condition.

Morpho-anatomical and physiological responses of two Dendranthema species to waterlogging

The responses to waterlogging of the two Dendranthema species D. nankingense (Nakai) Tzvel. and D. zawadskii (Herb.) Tzvel. contrast considerably. Although the stress induced wilting and leaf chlorosis in both species, symptoms were more apparent and appeared earlier in the intolerant D. nankingense. In the more tolerant D. zawadskii, adventitious roots formed above the flooding level, and aerenchyma developed in the root, stem and leaf. The D. zawadskii palisade parenchyma was thicker, and larger intercellular spaces developed in the spongy mesophyll. The activities of alcohol dehydrogenase, pyruvate decarboxylase and lactate dehydrogenase were enhanced in roots of both species following the imposition of stress. In D. zawadskii the rise in ADH activity was more pronounced, while D. nankingense showed a significantly higher LDH activity. The activities of superoxide dismutase, ascorbate peroxidase and catalase were all higher in the leaves of D. zawadskii than in D. nankingense, and the leaves of D. nankingense showed a higher content of malondialdehyde throughout the period of waterlogging. Photosynthesis was decreased in both species, and there was a significant fall in the intercellular CO 2 concentration in D. zawadskii. These data suggested that the greater relative waterlogging tolerance of D. zawadskii appears to depend on a combination of metabolic and morpho-anatomical responses.

Structure and productivity along a tree height gradient in a Kandelia obovata mangrove forest in the Manko Wetland, Okinawa Island, Japan

Tree height (H) of Kandelia obovata trees decreased sharply from 5 m at the forest interior behind the terrestrial forest to 1.5 m at the forest edge near the river bank according to an increase in the yearly waterlogged period along a belt transect. The decreasing tree stature was attributed to a decrease in the asymptote of H in the D 0.1 (stem diameter at H/10)-H relationship toward the edge. The K. obovata trees were well classified into interior and edge types using a discriminant function based on the habitat-specific D 0.1–H relationships. Allometric equations, as a function of D 0.1 2 H, differed significantly between the interior and edge types in the estimation of the phytomasses of stems and leaves, and the leaf area per tree. On the other hand, common allometric equations were successfully established in the estimation of respective phytomasses of aboveground parts and branches. Biomass and leaf area index decreased toward the forest edge. The biomass allocation to stems decreased toward the edge, whereas those to branches and leaves increased. A dramatic change in stem diameter increment resulted in differences in the D 0.1–H relationship along the tree height gradient. Relative growth rate of biomass and light-saturated net photosynthesis, which paralleled net assimilation rate from the interior to the edge, showed their maximum peaks in the middle of the belt transect. This indicates that there exists an optimal environmental condition for growth of K. obovata trees. Leaf nitrogen content tended to increase to the edge with increasing waterlogged period.

Waterlogging Tolerance of Kentucky Bluegrass Cultivars

Waterlogging (WL) affects the growth and physiological responses of turfgrass. The objectives of this study were to compare the relative WL tolerance of Kentucky bluegrass (Poa pratensis L.) cultivars and to investigate the physiological responses of shoots and roots to WL. Ten cultivars differing in growth habit were subjected to 30 d of WL. The turf quality (TQ) and soil redox potential (Eh), as well as the chlorophyll concentration (Chl), decreased with increasing periods of WL. Among all cultivars, root dry weight (RDW) decreased 16.7% to 39.9% under 10 d and 30.0% to 60% under 30 d of WL, respectively. Waterlogging increased the root electrolyte leakage (REL) from 0.6% to 53.2% under 10 d and from 29.1% to 98.0% under 30 d of WL for all cultivars, respectively. The best correlations were observed between Eh and TQ (r = 0.74), REL and TQ (r = 0.75), RDW and root water-soluble carbohydrate content (RWSC) (r = 0.74), and root oxidase activity and RWSC (r = 0.63), respectively. ‘Moonlight’, ‘Serene’, and ‘Champagne’ showed better tolerance to short-term WL conditions, whereas ‘Kenblue’ and ‘Eagleton’ were the least tolerant cultivars. ‘Limousine’, ‘Unique’, ‘Awesome’, ‘Julia’, and ‘Midnight II’ ranked in the middle group. Variations in WL tolerance among Kentucky bluegrasses could potentially be used for enhancing turfgrass management.

Floodplain and upland populations of Amazonian Himatanthus sucuuba: Effects of flooding on germination, seedling growth and mortality

Himatanthus sucuuba is a tree species that occurs in Central Amazonian white water floodplains and in non-flooded uplands. The objective of this paper was to verify whether flooding causes differences in germination percentages, seedling mortality as well as alterations of leaf number and biomass increments, related to the habitat of origin of the seeds (várzea floodplain versus terra firme upland, in the following V and TF, respectively). To test this effect, seeds from populations of both habitats were collected, and germination percentages were calculated under different experimental conditions. One hundred seeds collected in three sites of the floodplain and one hundred seeds from three sites of the upland were placed in trays for germination in a greenhouse in the Amazon Research Institute (INPA) in Manaus, Brazil. Seedlings with a height of 7 cm were then subjected to a period of 120 days of flooding in tanks with three treatments: control, waterlogging (root system and the base of the stem), and complete submersion. Ground water from the INPA was used in the tanks and was changed at weekly intervals. Germination percentages were high in most treatments. Seedling mortality was significantly higher in seedlings originating from upland, reaching 100% in submerged seedlings. On the other hand, várzea-originated seedlings showed no mortality under waterlogging or submergence. Height growth of waterlogged seedlings from floodplains exceeded that of the control. Submerged seedlings did not grow, independently of the origin, and those originating from uplands died after about 100 days. Number of leaves and leaf area were significantly lower under partial submersion than in the control, independently of the origin of the seeds. Under total submersion abscission of all leaves was verified 30 days after inundation for seedlings of both origins. In the V population, all seedlings survived the waterlogged period, whereas in the TF population, 30% of the seedlings died when subjected to waterlogging. With complete submergence, in the V population 30% of the seedlings had died after 120 days, in the TF population after 90 days mortality was 100%. The results show that germination, seedling growth and seedling survival in H. sucuuba differ among populations of floodplain and upland sites: V plants performed better than TF plants under waterlogging and under submersion. The results strongly indicate that ecotypic differentiation exists between these two populations of H. sucuuba individuals in the two habitat types, which may be enforced by a strong selective pressure due to the regular occurring flood pulse.

Direct seeding of ash ( Fraxinus excelsior L.) and sycamore ( Acer pseudoplatanus L.): The effects of sowing date, pre-emergent herbicides, cultivation, and protection on seedling emergence and survival

Direct seeding is an alternative method to conventional planting for woodland establishment that has several potential advantages. This study reports the effects of sowing date, pre-emergent herbicides, and cultivation and protection on the emergence and survival of direct-sown ash ( Fraxinus excelsior L.) and sycamore ( Acer pseudoplatanus L.) on three sites in southern England situated on former pasture and arable land, and on a windblown site in beech ( Fagus sylvatica L.) woodland. Few seedlings emerged at the woodland site probably due to excessive seed predation by small mammals. At the other sites, the effects of sowing date on emergence reflected seasonal variation in soil moisture content and temperature. Periods of soil waterlogging in seed beds during winter resulted in greatly reduced seedling emergence of early sown seeds, and seedling emergence of both species ceased once the daily maximum soil temperature exceeded 25 °C, which was in late April in this study. Analysis of the thermal time requirements for complete emergence of both species under the recorded soil-temperature regime suggested that the latest sowing date that would allow emergence before soil temperatures were too high was the beginning of March. Ash seedlings were particularly vulnerable to freezing injury after spring frosts that occurred during the seedling emergence period in one experiment. This study also confirmed earlier work identifying the potential of the herbicides napropamide, pendimethalin, and isoxaben for use on direct seeded ash and sycamore, and the results show the importance of adequate vegetation management for maintaining seedling survival and growth. For winter sowing, protecting seed beds with fleece was found to enhance seedling establishment, but reduced subsequent seedling survival after the protection was removed. Compared with cultivated soil, direct-drilling tree seed between the stubble of preceding cereal crop had no effect on seedling emergence, and increased seedling survival.

Clay Dispersion of Hardsetting Inceptisols in Southeastern Nigeria as Influenced by Soil Components

Hardsetting soil properties are undesirable in agricultural soils because they hamper moisture movement and soil aeration. The soils of the floodplain of Niger River in eastern Nigeria hardsets upon drying, following dispersion, puddling, and slaking during the waterlogged period. Ten soil samples collected from a depth of 0–20 cm were analyzed for their properties. The soils are classified as Fluvaquentic Eutropepts or Dystric Gleysol (FAO). The objective was to investigate the influence of some soil properties on water‐dispersible clay (WDC) of the soils, which is the precursor of the hardsetting process. The total clay content (TC) correlated significantly with WDC (r=0.94**), whereas the water‐dispersible silt (WDSi) was higher than its corresponding total silt content. The WDC showed a positive correlation with dithionite extractable Fe (Fed), Al (Ald), and oxalate extractable Fe (Feo) (r=0.75*, 0.89**, and 0.76* respectively). Exchangeable Mg2+ correlated significantly with WDSi (r=0.70). Principal component analysis of the soil variables indicates that 15 soil components, which influence WDC as hardsetting properties, were reduced to 5 orthogonal components. The parameters that influence hardsetting properties are exchangeable Na+, K+, Ca2+, Mg2+, Fed, Alo, and Feo. Other soil properties are kaolinite, smectite, illite, and WDC, including soil organic carbon (OC), electrical conductivity (EC), and ESP. Therefore, those soil properties, which explain hardsetting characteristics most, are exchangeable Na+, Fed, OC, Mg2+, and Alo. There are negative consequences on the erodibility, runoff, infiltration and tillage of the soils at both submerged and dry conditions due to clay dispersion, low OC, and hardsetting behavior of the soil.

Consequences of aggregation for the trace element distribution in the subsoil of a Planosol naturally rich in trace metal

Element distribution at the aggregate scale was studied in a soil naturally rich in trace elements. The studied soil was a Planosol developed in gneiss parent material (Massif Central, France) that exhibits a well-structured clayey pedological (B) horizon. This horizon was sampled for aggregates that showed a strong differentiation between an inner part and an outer part. Element distribution in these aggregates was studied (1) after manual separation of their inner and outer parts; (2) on aggregate thin sections after polyester resin impregnation. The concentrations of trace and major elements and the main mineralogical phases (X-ray diffraction) were determined on the two fractions. Chemical speciation of TEs was also performed on these fractions. Thin sections were observed by optical and scanning electron microscopy and major elements were mapped by electron microprobe. Manual fractionation and electron microprobe mapping showed a clear differentiation in element distribution between the inner and outer parts of the aggregates. The inner part was richer in Fe, Cu, Ni, Co, Al, K and Mn than the outer one. This last one was however richer in Si. Extractions showed that this distribution is explained by the presence of silicate minerals rich in TEs and by the larger amount of oxides in the inner part of the aggregate compared to the outer part which was richer in coarse sand, mainly quartz. Microscopic studies also showed that the inner part was rather complex. Pores surroundings were also depleted in Fe and enriched in Si as aggregate outer parts. This uneven distribution was most likely the result of two different mechanisms: (1) input of material coming from the upper horizons due to swelling and shrinking according to seasonal changes; and (2) preferential weathering of the outer part of aggregates due to preferential flow during the water logging period in winter. This differentiation was especially marked for Co, Zn and Cu and was linked to oxide dynamics.

Dry-wet evolution in Guangdong province during last 500 years

Based on the historical records in Guangdong Province during the last 500a, the moist index sequence was reconstructed and analyzed by the correlation analysis, wavelet analysis and the power spectrum analysis. The results indicate that: 1) The El Nino events have evident correlations with the droughts happened in the west and north of Guangdong Province, which intensified the dryness and wetness distribution patterns in these areas in a certain degree. 2) Good correspondence relations exist among the moist index sequence, Greenland ice core oxygen isotope record and the winter-half-year temperature sequence in the eastern China, which showed an apparent monsoonal disposal pattern of moisture and temperature. 3) By applying the wavelet analysis to deal with the data, several apparent periodicities are revealed, among which some can be attributed to the solar activities. At the same time, the ENSO event, monsoon (especially the East Asian monsoon) activity and the human activity may also have some influences on the periodicities of the climatic changes in Guangdong Province. 4) Guangdong will persist in dry period before 2040 (±5 years) though some little waterlogged period will also exist in this interval, and after that great floods maybe take place in Guangdong. We think that the variety range of the dryness and wetness has increasing tendency in Guangdong Province in future several even hundred years.

EFFECTS OF WATERLOGGING ON THE GAS EXCHANGE, CHLOROPHYLL FLUORESCENCE AND WATER POTENTIAL OF QUERCUS VARIABILISAND PTEROCARYA STENOPTERA

Cork oak (Quercus variabilis) and China wingnut (Pterocarya stenoptera) are important species in the subtropical riparian and drawdown areas of reservoirs and ponds in China. We investigated the effect of waterlogging on morphological and physiological characteristics of these species. We measured the maximum net photosynthesis rate (P_(max)), stomatal conductance (G_(s)), Chlafluorescence maximum quantum efficiency (F_(v)/F_(m)), chlorophyll content and water potential on different days during a period of waterlogging. Key Results Throughout a 70-day waterlogged period, the survival rates of seedlings of the two species were 100%. The earliest effects of waterlogging were significantly decreased P_(max), G_(s) andF_(v)/F_(m). On the 5th day of waterlogging, F_(v)/F_(m) of cork oak and China wingnut decreased to 0.694 and 0.757, respectively. On the 7th day, significant reduction of P_(max) (cork oak, 39% of control; China wingnut, 42%) and G_(s) (cork oak, 38.8% of control; China wingnut, 71.9%) were observed. With prolonged waterlogging, P_(max), G_(s) and F_(v)/F_(m) recovered gradually to control values in China wingnut, but not in cork oak where values decreased continuously. On the 70th day, P_(max) of cork oak was reduced by 94.1% of control and F_(v)/F_(m) was only 0.537.Waterlogged China wingnut seedlings developed hypertrophied lenticels and adventitious roots at their stem base and exhibited no visible symptoms of injury (neither mortality, leaf chlorosis, leaf necrosis, leaf abscission nor reduced chlorophyll content). However, cork oak showed leaf necrosis with waterlogging. The chlorophyll content of cork oak steadily declined from the 33rd day and the Chla/Chlb ratio also deceased. Predawn leaf water potential was higher in waterlogged cork oak seedlings compared to the control on the 10th and 70th days, but lower in waterlogged China wingnut seedlings. This indicated that water potential changes under waterlogging are species specific. All results show that cork oak exhibits damage to its photosynthetic apparatus under waterlogging. In contrast, although the photosynthetic apparatus of China wingnut is initially affected, it can recover, indicating that China wingnut seedlings can tolerate prolonged soil waterlogging better than cork oak seedlings. We conclude that it is more suitable to plant China wingnut in the drawdown areas of reservoirs and ponds than cork oak.

Effects of soil flooding on leaf gas exchange and growth of two neotropical pioneer tree species

Schinus terebinthifolius Raddi (Anacardiaceae) and Rapanea ferruginea (Ruiz & Pavon) Mez (Myrsinaceae) are two neotropical pioneer trees with wide geographical distribution in South America, highly degree of adaptation to different soil conditions and intense regeneration in areas with anthropic activities. With the aim to recommend the use Schinus and Rapanea in gallery forest restoration programs, we conducted an experiment with the objective to analyze the capacity of these two pioneer trees to tolerate soil flooding, mainly by accessing the effects of flooding on leaf gas exchange, growth and dry matter partitioning. Seedling survival throughout the 56-day flooding period were 100 and 90% for Schinus and Rapanea, respectively. The mean values of stomatal conductance (g s ) and net photosynthesis (A) observed in the control seedlings were, respectively, 0.4 mol m−2s−1 and 14 mmolm−2s−1, for Schinus, and 0.5 mol m−2s−1 and 14 mmolm−2s−1, for Rapanea. On day 20 flooding reduced gs and A by 36 and 29% in Schinus, and 81 and 61% in Rapanea. At the end of the experiment, significant decreases were also observed for root and whole plant biomass, in both species. Based on the results, we concluded that seedlings of Schinus and Rapanea can survive and grow throughout a medium period of soil waterlogging, in spite of the alterations observed in their physiological behavior, such as the decreases in stomatal conductance and in whole plant biomass.

Combined effects of waterlogging and salinity on electrochemistry, water-soluble cations and water dispersible clay in soils with various salinity levels

The combination effects of waterlogging and salinity on redox potential (Eh), pH, electric conductivity (EC), water-soluble cations (NH4 +, K+, Na+, Ca2+, Mg2+, Fe2+, and Mn2+) and water-dispersible clay (WDC) were studied in six soils collected near salt lakes in western Australia. The soils with various salinity levels were incubated under a waterlogged condition at 30 °C for 12 weeks. The Eh, pH, EC, and cations of soil solutions were monitored over the waterlogged period. The Eh values generally dropped to the lowest point within 12 days of waterlogging, then increased slightly, and reached equilibrium after 4 weeks of waterlogging. Increasing salinity levels increased soil Eh. While waterlogging increased soil pH in the first 3–4 weeks, increasing salinity level decreased soil pH during the entire waterlogging period. Waterlogging increased the EC values in the first 2 weeks, partly due to dissolution of insoluble salts. The concentrations of water-soluble NH4 + were significantly increased with salinity level and waterlogging, and reached maximum values at week 2, and then declined to the initial level. Waterlogging and salinity increased the concentrations of water-soluble K+, Ca2+, Mg2+, Fe2+, and Mn2+ ions, but the magnitudes of changes were greatly affected by soil properties. Increases in water-soluble K+, Ca2+ and Mg2+ were attributed to increased solubility of insoluble salts, and increased competition for the adsorption sites of the soil exchange complex due to elevated concentrations of Na+, Fe2+ and Mn2+. Increases in water-soluble Fe2+ and Mn2+ induced by waterlogging were attributed to the dissolution of Fe and Mn oxides under reduced conditions. Waterlogging increased, but salinity decreased, the amounts of water-dispersible clay in the soils of low EC value. The higher salinity level can counteract the adverse effect of waterlogging on clay flocculation.

Long-term fluctuation of the soil fauna (Collembola and Oribatida) at groundwater-near sites in an alder wood

Collembola and oribatid mites were investigated at four sites along a cross section in an alder wood at a lake margin (northern Germany) over a period of 7 years. Monthly samples of the litter and the mineral layer were taken. Additionally, fluctuations of groundwater level, soil moisture, precipitation and soil temperature at 2 cm depth were measured. The alder wood was characterised by a depression between the lake margin and the foot of a hill slope, where waterlogged periods occurred. Groundwater level was the main environmental factor influencing the composition of collembolan and oribatid mite assemblages. Climatic factors, e.g. July temperature and July precipitation were also found to be significant factors, but with a much lower influence. Collembola predominantly showed higher variation in time than in space indicating that more collembolan species migrate within the investigated cross section or react with higher abundance fluctuations on the groundwater level changes, while Oribatida had a higher part of space variation, indicating that migration potential is lower and the environmental gradient is of higher influence on the distribution. Reaction time of soil fauna species on the groundwater fluctuation varies between 1 and 12 months. Retreat of Collembola from the waterlogged situation was between 4 and 6 months in the litter layer and 3 months in the mineral layer. Recolonisation of the waterlogged site lasted approximately 12 months. A positive reaction by precipitation was observed in four collembolan species that was 1 month in the edaphic species and between 9–10 months in the larger litter dwelling species. Only few oribatid mites reacted on the waterlogged situation.

Study of the root antioxidative system of tomatoes and eggplants under waterlogged conditions

The aim of our work was to study the response of antioxidative enzymes, and antioxidants of tomato and eggplant roots to waterlogged conditions. The roots of four entries, eggplants EG117 and EG203, and tomatoes TNVEG 6 and L4422 ( Lycopersicon pimpinellifolium Mill), were subjected to seven flooding treatments. A split-plot design with three replications was used. The activity of APX in roots significantly increased during the period of continuous waterlogging. Slight increases in total ASA, reduced ASA, GSH, and total glutathione contents in the roots were also observed throughout the entire waterlogging period. However, the activities of CAT, SOD and GR, and the contents of ASA, GSSG and α-tocopherol in the roots were unaffected by waterlogging. Entries responded differently to oxidative injury according to their various antioxidative systems. The results indicate that total ASA could be involved in flooding damage to tomato roots. Overall, following the waterlogging treatments, APX activity in the eggplants was generally higher than in the tomatoes. Our work suggests that the brownish roots of tomatoes induced by flooding may be the consequence of H 2O 2 scavenging possibly controlled by APX activity. The H 2O 2 scavenging system as represented by APX was clearly limiting or less efficient in the tomatoes, leading to an accumulation of H 2O 2. The ability to maintain a balance between the formation and detoxification of activated oxygen species appeared likely to increase the survival potential and the tolerance of the roots against varying oxidative stress. On the basis of our observations, we conclude that increased APX activity provides plant roots with increased waterlogged stress tolerance.

Nitrate ammonification and its relationship to the accumulation of ammonium in a Vertisol subsoil

High concentrations of ammonium (up to 270 kg N/ha) have been observed in a Vertisol soil below 1 m depth near Warra in south-east Queensland. This study examined the possibility that increased water movement into the subsoil after the removal of native vegetation, and a subsequent increase in periods of waterlogging, could have triggered nitrate ammonification and be responsible for the production of ammonium. Two incubation experiments were conducted to test this hypothesis. The first involved the incubation of repacked cores that had been amended with 30 mg N/kg of 5 atom% 15N nitrate under low oxygen conditions for a period of 360 days. Over this time period the 15N enrichment of the exchangeable ammonium fraction was monitored in order to detect any reduction of nitrate to ammonium. The second experiment involved the incubation of soil amended with 30 mg N/kg of 5 atom% 15N nitrate under waterlogged and low oxygen conditions for 75 days. During this period the redox potential of the soil was monitored using a field test to determine if reducing conditions would develop in this soil over a period of waterlogging, combined with the monitoring of any nitrate reduction to ammonium. The results of these experiments indicated that a small amount of nitrate ammonification (<0.1 mg N/kg) could be observed in the Warra subsoil, but that unless the rate of reduction were to significantly increase with time, this could not account for the accumulation of ammonium observed in the field. The environmental conditions that would make either dissimilatory or abiotic nitrate ammonification favourable were not observed to develop. Consequently, it has been concluded that the observed nitrate ammonification occurred via an assimilatory pathway. Due to the low rate of microbial activity in this subsoil it is considered unlikely that this process was responsible for the subsoil ammonium accumulation at Warra.

Comparative analysis of variables associated with germination and seedling establishment for Prosopis nigra (Griseb.) Hieron and Acacia caven (Mol.) Mol.

The purpose of this work was to compare different variables associated with the germination and growth of Prosopis nigra and Acacia caven seedlings. Fieldwork was carried out in 1999 on materials collected in Entre Rı́os province, Argentina. Germination percentages and rates were measured in order to determine the effect of immersion in water for different periods of time and of the ingestion of P. nigra fruits by the greater rhea. Seedling growth was compared for both species as a function of stem elongation, increase in volume, leaf production rate and survival percentage during the first 60 days following germination. Results indicate that, unlike A. caven, P. nigra seeds are negatively affected by immersion in water as seeds submitted to different immersion periods showed a significant decrease in final germination percentages with respect to untreated seeds. P. nigra seeds ingested by the greater rhea also showed lower final germination percentages as compared to those not ingested. Nevertheless, those that succeeded in germinating achieved significantly higher germination velocities. A. caven seedlings attained significantly higher heights than those of P. nigra from the 20th day onwards. Volume growth for A. caven was also higher, as well as leaf production and survival until the 60th day. Results suggests that in order to maintain P. nigra dominance, practices favoring prolonged waterlogging periods should be avoided, thus promoting a high seedling yield.

Alterations in photosynthesis and some antioxidant enzymatic activities of mungbean subjected to waterlogging

Photosynthetic rate ( P), leaf water potential ( ψ L) and chlorophyll fluorescence were studied in mungbean plants subjected to waterlogging in a plastic greenhouse, and leaf samples were collected for the analysis of enzymes involved in anti-oxidant photoprotection. Waterlogging caused a fast decline in the photosynthetic rate and water use efficiency without changes of transpiration rate and stomatal conductance during the early waterlogging period, which indicates that reduction of photosynthetic rate might be due to a mechanism independent from stomatal closure. Early reduction of Fv/Fm value of chlorophyll fluorescence by waterlogging indicates that the early reduction of photosynthetic rate is correlated with photo inhibition of photosystem II (PSII). Stomatal conductance and water use efficiency was decreased progressively during prolonged waterlogging while ψ L was unchanged, indicating stomatal closure without water stress. The activities of active oxygen processing enzymes, such as superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX) and glutathione reductase (GR) decreased during prolonged waterlogging indicating no evidence of oxidative stress and/or damage in leaves of mungbean by waterlogging. Our results suggest that oxidative damage is not directly involved in damage to the photosynthetic machinery during waterlogging in mungbean plants.

Short‐term waterlogging has long‐term effects on the growth and physiology of wheat

Summary The effect of different durations of waterlogging and subsequent drainage is described for 3‐wk‐old wheat (Triticum aestivum) plants. In a pot experiment, plants were subjected to waterlogging to the soil surface for 0, 3, 7, 14, 21 or 28 d, and then drained to allow recovery for up to 25 d. During waterlogging, the seminal root system stopped growing. Adventitious roots grew to a maximum length of c. 150 mm. Leaf nitrogen concentration was severely decreased by waterlogging. When waterlogged pots were drained, seminal root mass did not recover to control values, even when waterlogging lasted only 3 or 7 d, due to death of existing apices and no initiation of new lateral roots. By contrast, adventitious roots resumed elongation after drainage. By the end of the experiment, shoot mass remained two‐ to threefold lower in plants from all waterlogged treatments compared with continuously drained controls, due to lower tiller numbers and shorter final leaf lengths in previously waterlogged plants. The results demonstrate that even short periods (as little as 3 d) of waterlogging have considerable long‐term effects on the growth of young wheat plants.

Effects on catchment water balance from the management of Pinus plantations on the coastal lowlands of south‐east Queensland, Australia

AbstractA paired catchment study was conducted over a 10‐year period on the hydrology of an exotic Pinus plantation in the coastal lowlands of south‐east Queensland, Australia. Each catchment was instrumented with a stream monitoring station, tipping bucket rain gauge, and a network of piezometers to monitor the shallow perched water table. After a 6‐year calibration period a harvest treatment was imposed on one catchment (Review): clearfelling approximately 90% of the catchment area, which contained a mature (44‐year‐old) Pinus elliottii plantation. This subsequently was re‐established with a second rotation plantation of a hybrid of P.elliottii × P.caribaea var. hondurensis. The control catchment (Crayfish) contained a P. elliottii plantation similar to that clearfelled at Review. The post‐harvest period was monitored for a further 4 years.Evapotranspiration was found to be the major output flux, with stream flow only a minor component of the study catchments' water budget. Areas with gleyed podzolic soils were found to remain waterlogged for periods up to 7 months following the seasonally high summer rainfall period, with other soils having water logging periods of only a few months. Little change was observed in waterlogging characteristics following harvesting, in contrast to stream flow which increased for 3 years but with evidence of a decline after 5 years.The perched‐watertable piezometric surface indicated that its lateral drainage differs from that of surface flows; the perched‐watertable drainage fluxes from the study catchments seem minor and off‐site movement of solutes (e.g. nutrients and contaminants) via them would be limited. It was identified that the interaction between the perched and deep aquifers was poorly understood, as well as the relative importance of the soil moisture storage of the aquitard clay layer between them. It was concluded that there is a need to undertake more detailed analysis using modelling, and to obtain additional field data on soil‐layer properties and piezometric levels of the deep aquifer. Copyright © 2002 John Wiley & Sons, Ltd.