Water Restriction Conditions Research Articles

Traditional Varieties of Caupi Submitted to Water Deficit: Physiological and Biochemical Aspects

The cowpea (Vigna unguiculata (L.) Walp) it is a leguminous widely cultivated in Northeast of Brazil. In the state of Ceara, its cultivation is performed mainly by family farms who make use of traditional varieties of good adaptation to the growing region. Thus, characterizing traditional varieties with characteristics of adaptation to regions with water shortage is essential for the production of food in the world, especially in semi-arid regions. In this sense, the objective was to evaluate the physiological and biochemical responses in three genotypes of cowpea, being two traditional varieties grown in Ceara (Sempre-Verde and Cabeça-de-Gato) and a genotype characterized as a standard of drought tolerance (Pingo-de-Ouro-1,2) under three water regimes: irrigated, moderate deficit and severe water deficit. The parameters evaluated were: gas exchange, chlorophyll a fluorescence, photosynthetic pigments, organic solutes (proline, total carbohydrates, reducing and non-reducing carbohydrates), starch and enzyme activity (APX, G-POD, CAT and SOD). The genotype Pingo-de-Ouro-1,2 confirmed its tolerance pattern in a water deficit condition, presenting greater water potential, higher photosynthetic rate, high levels of total carbohydrates and high accumulation of proline. Among the traditional varieties, the Cabeça-de-Gato presented superior photosynthesis to Sempre-Verde higher Electron Transport Rate (ETR), reflecting in a greater photochemical quenching (qP) and a greater accumulation of proline, indicating that this variety presents more pronounced adaptive characteristics for water restriction conditions, which is a common condition to the Brazilian semiarid.

Physiological Quality in Leucaena leucocephala Seeds Conditioned with Potassium Nitrate Submitted to Saline and Water Stresses

Leucaena leucocephala is a species that occurs in semi-arid regions capable of developing physiological and biochemical strategies under adverse environmental situations, such as saline soils and water deficiency. Even so, there are still losses in germination and initial development of plants, mainly due to abiotic stress effects, making it necessary to implement alternatives which are able to diminish the impact on the seeds with the use of potassium nitrate. The objective of this work was to evaluate the physiological quality in L. leucocephala seeds conditioned in potassium nitrate solution and subjected to saline and water stresses. After scarification, the unconditioned leucine seeds were separated and identified, and the conditioners were immersed in the 1.0 Mmol/L solution of potassium nitrate for 24 hours. The treatments were NaCl: 0; 30; 60; 90; 120 and 150 Mmol/L and the water potential: 0, 0; -0.2; -0.4; -0.6, and -0.8 MPa. The seeds were distributed over two Germitest® sheets, moistened with distilled water 2.5 times the dry weight and incubated in a B.O.D. at 25°C for 10 days. Then, the germination speed index, seedling length and seedling mass were measured for the normal seedlings. Eleven treatments with four replicates of 50 seeds were used. The design was completely randomized, and the statistical analyzes were performed in SAS. The use of potassium nitrate (KNO3) contributed to maintaining the physiological quality of L. leucochephala seeds under conditions of saline stress and water restriction.

Evaluation of common bean genotypes for drought tolerance

ABSTRACT The aim of this study was to evaluate twelve genotypes of common bean for intermittent drought stress and for root growth angle. The water deficit experiments were conducted in 2015 and 2016in a randomized block experimental design with split plots and three replications. Two treatments were applied: an irrigated treatment and a water deficit treatment, in which irrigation was suspended in pre-flowering and remained suspended up to the time at which the matrix potential of the soil was measured to be near –199 kPa. Atthe maximum point of water deficit, physiological and morphological traits were evaluated, and at physiological maturity, the yield compounds and grain yield. To evaluate root growth angle in 2016, a growth pouch system was used in a randomized block design, with five replications. Water deficit reduced genotype performance for all the traits except leaf temperature and first pod height. In relation to grain yield, the genotypes SEA 5 and Carioca Precoce performed better under water restriction conditions in both evaluations. The genotype Gen TS 4-7 performed better in the 2015 evaluation, and Gen TS 3-1 andGen TS 3-3 in 2016. SEA 5, Gen TS 3-1, and Carioca Precoce had the highest harvest indexes in 2015; and Gen TS 3-1, Gen TS 3-2,Gen TS 3-3, Gen P5-4-3-1, IAPAR 81, Carioca Precoce, and SEA 5 in 2016. SEA 5 and Carioca Precoce had the best root growth angle and were considered sources of tolerance to water deficit.

Characterization of the superoxide dismutase gene family in seeds of two Ricinus communis L. genotypes submitted to germination under water restriction conditions

Abiotic stresses are the most important environmental factors that negatively affects crop production worldwide, whereas germination is the most critical phase in the plants life cycle. Water availability is essential for proper seed imbibition and vigorous germination and often scarce for Ricinus communis (castor bean) cultivated in semiarid regions of Brazil. Water restriction generally leads to the generation of reactive oxygen species (ROS) and one of the major families of enzymes that counteract ROS are superoxide dismutases (SODs). The objective of this study was to identify and characterize the SOD gene family of R. communis by phylogenetic, biochemical and gene expression analysis and link it to the effect of osmoconditioning on seed vigor. We characterized the effect of osmotic conditioning treatments of seeds of two contrasting R. communis cultivars, EBDA MPA34 and PARAGUAÇU, on germination performance. We also searched the R. communis genome for SOD genes and analyzed them phylogenetically and evaluated their activity and expression in embryos of seeds imbibed under different PEG concentrations (water restriction stress). We could show that some of these treatments improved germinability and vigor of seeds and seedlings in a cultivar-dependent manner. Additionally, R. communis seeds turned out to be very sensitive to the inhibition of germination by osmotic stress even at relative low concentrations. Eight SOD genes were found in the R. communis genome and classified based on phylogenetic analysis, protein domains and prediction of subcellular localization. SOD gene expression was mostly induced during seed imbibition, although their expression was generally inhibited in osmotic potentials below −0.6 MPa and showed partly different gene expression profiles between contrasting cultivars. Cv. PARAGUAÇU showed increased seed vigor after osmoconditioning as compared to cv. EBDA MPA34 which could be related to higher responses of some cv. PARAGUAÇU SOD genes to stress. Our results indicate that SOD genes might be of special interest for R. communis genetic engineering aimed at the increase of production in semiarid regions.

Water restriction in viviparous lizards causes transgenerational effects on behavioral anxiety and immediate effects on exploration behavior

Behavioral plasticity induced by maternal effects is crucial in adjusting offspring phenotype to match the environment. In particular, changes in water availability during development may initiate a range of behavioral responses, such as natal dispersal, but the contribution of maternal effects from water stress in explaining behavioral variation has been overlooked so far. In this study, we examined behavioral plasticity of juvenile common lizards (Zootoca vivipara) in response to changes in pre-natal and post-natal hydric conditions. We exposed pregnant mothers either to a moderate water restriction or to ad libitum access to water. We used neutral arena tests to measure repeatedly activity and space use behaviors of their offspring, either in dry or wet soil conditions, at two distinct life stages (juveniles and yearlings) in order to quantify behavioral flexibility, age differences, and personalities (consistent inter-individual differences). Juveniles and yearlings had greater exploration scores in dry than wet conditions regardless of the pre-natal conditions. Pre-natal water restriction and dry post-natal conditions enhanced thigmotaxis (i.e., a behavior related to anxiety) in juveniles. Maternal environment did not influence behavioral flexibility nor the behavior of yearlings. Behaviors were barely repeatable in juveniles and inconsistent through early life. Assuming that dry conditions may initiate flight responses, these results suggest complex relationships between the developmental timing of water stress, exploration and anxiety behaviors, and dispersal syndromes. Water restriction should initiate a range of behaviors related to a flight response. However, there is little evidence that changes in water availability across development influence offspring behavior in wild animals. Experiments with lizards demonstrate that maternal water restriction increased the anxiety of their juveniles, whereas their exploration was higher in dry environments. Thus, water availability may be a critical determinant of space use behavior and dispersal syndromes.

Determination of water-yield basil function under deficit irrigation conditions and use of nano fertilizer

Basil (Ocimum basilicum L.) is one of the important aromatic plants belonging to the family Lamiaceae, which is used as an herb, spice as well as fresh vegetable.The present study was performed to determine the irrigation depth index under different management conditions with evaluating the effect of deficit irrigation, soil texture and nano fertilization on basil. The experiment was performed as a factorial based on randomized complete block design (RCBD) with 18 treatments and three replications at weather station, Ferdowsi University of Mashhad. Deficit irrigation treatments consisted of three levels of irrigation (I1=100% ETc), (I2=75% ETc), (I3=50%ETc) and three levels of nano fertilizers, containing nano fertilizer with full concentration (F1), 70% (F2), and nonusing of nano fertilizer (F3) were implemented in two light soil texture (S1) and medium soil texture (S2). The results showed that the average actual evapotranspiration estimation by REC-P55 device has been equal to 3.38 mm at the beginning of the growing period of basil, which amount has increased to 8.60 mm during basil development in the middle of growth period. The results of crop coefficient analysis showed that the maximum kc of basil (1.42) was detected in July. The results also indicated that the highest water use efficiency (WUE) was obtained in terms of fresh and dry herb yield as 2.06 and 0.37 kg/m3 in S2I3F3 treatment, respectively, while the maximum water use efficiency in terms of seed yield (0.37 kg/m3) was obtained in S1I2F2 treatment. Using the research results, according to different levels of water use of functions of yield Y(w), cost C(w), and benefit B(w) for basil based on mathematical and economic analysis of these functions, irrigation index and optimal irrigation depths were evaluated. It was found that with deficit irrigation under water restriction conditions, with the aim of maximum use of water volume unit, the optimal water consumption depth will be reduced by 20% compared to maximum irrigation mode. Also, with this amount of deficit irrigation, the maximum Rial return per cubic meter of water consumption would be as 1849 Rials.

Differential expression of water channel- and noncoding RNA biogenesis-related genes in three lines of chickens under a short-term water restriction

Genetic selection for high growth rate has resulted in tremendous changes not only in feed efficiency, but also in water consumption between modern broilers and their ancestor jungle fowl (JF). However molecular mechanisms involved in water homeostasis are still not well defined. This study aimed, therefore, to determine the effect of short-term water restriction on the expression of water channel- and noncoding RNA biogenesis-related genes in the kidney and whole blood of JF, broiler population from the 1990s (RB1995), and modern broiler population developed in 2015 (ARB2015). Body weight-matched birds from each population were subjected to water restriction (WR) for 3 h or had ad libitum access to water in a 3 × 2 factorial design. The expression of target genes was determined by real-time quantitative PCR. WR significantly reduced body weight in RB1995, but not in JF or ARB2015. In the kidney, WR up-regulated the expression of AQP2 in all chicken populations, AQP3 in the RB1995, and ATP1B1 in JF and ARB2015. However, it down-regulated the expression of AQP4 in ARB2015 but had no effect on AVP expression. The expression of RNase III family enzymes also was altered by WR in a population-dependent manner, with DICER1 being down-regulated in JF and RB1995, Drosha was decreased in RB1995, and ARG2 was up-regulated in ARB2015. The expression of DGCR8 and TRBP1 was not affected by WR in any population; however, DGCR8 mRNA levels were significantly lower in RB1995 and ARB2015 compared to JF under both conditions. TRBP1 gene expression was significantly lower in RB1995 and ARB2015 compared to JF under WR conditions. In the blood, the expression of these genes also was altered by WR, but with different patterns than the kidney. The mRNA abundances of AQP, AVP, DICER1, DGCR8, AGO2, and TRBP1 were significantly decreased by WR in RB1995. However, the expression of AQP2, AVP, DGCR8, and TRBP1 was increased in WR-ARB2015 compared to the control. In the JF, there was no difference in the expression of these genes except for a significant up-regulation of TRBP1 in WR compared to the control group. To the best of our knowledge, this is the first report showing that water channels and the RNase III enzymes are differentially regulated by WR in a population-dependent manner, which may be due to differential postnatal growth and maturation. Their expression in the circulation could open new vistas for identification of new molecular signatures involved in adaptation to water-deprivation stress.

Improving water use efficiency for ornamental crops grown in greenhouses: a substrate-plant-atmosphere model validation for transpiration prediction

In greenhouses, reducing water consumption by increasing water efficiency is of high interest. Water need is linked to the plant transpiration, which itself depends on the stomatal resistance (Rs). Up until now however, prediction of Rs through models was mainly conducted for well-watered plants in open field conditions and very few models exist for greenhouse plants grown in pots. The aim of this work was to develop a dynamic model of Rs based on the full factorial design (FFD) under water restriction conditions. Then, the model was validated inside a greenhouse. The FFD is based on an optimization process to establish a polynomial relationship between Rs and the radiation, humidity and temperature. To implement the model, a set of experiments was conducted inside a 10 m2 growth chamber equipped with Impatiens New Guinea planted in 0.74-L pots under well-watered conditions. Rs was measured with a porometer and nine climatic scenarios were tested. First the FFD model was implemented for well-watered conditions. Then it was adapted to calculate Rs under water restriction, through the introduction of a new multiplicative function depending on the growing media matric potential. Once these parameters had been determined, the obtained transpiration model was validated against experimental data recorded inside a greenhouse Impatiens crop. The transpiration model derived from the FFD method showed its ability to correctly simulate Rs under water restriction conditions. Hence, it could be useful to accurately predict the evolution of transpiration.

Stomatal resistance modelling under water restriction conditions by means of design of experiments: comparison with the Jarvis method

Stomatal resistance modelling under water restriction conditions by means of design of experiments: comparison with the Jarvis method

Development of a CFD crop submodel for simulating microclimate and transpiration of ornamental plants grown in a greenhouse under water restriction

Predictive models of soil-plant-atmosphere water transfers may be helpful to better manage water inputs to plants in greenhouses. In particular, Computational Fluid Dynamics appears to be a powerful tool to describe the greenhouse microclimate and plant behavior. Up until now, most models for potted plants grown in greenhouses were established for well-watered conditions. In this context, the aim of this work is to develop a specific submodel to simulate the distributed transpiration and microclimate during plants grown in pots inside greenhouses under water restriction conditions. A 2D transient CFD (Computational Fluid Dynamics) model was implemented and user-defined functions were adapted to take account of the crop interactions with the climate inside the greenhouse. The crop was considered as a porous medium and specific source terms for transpiration and sensible heat transfers were added. A specific submodel was also implemented to calculate the substrate water content based on the water balance between irrigation and transpiration. Particular care was paid to the modeling of stomatal resistance. In order to obtain the input data and to validate the CFD simulations, an experiment was conducted over 16weeks inside a greenhouse equipped with New Guinea impatiens ornamental plants grown in containers on shelves. Both well-watered and restriction conditions were analyzed. The results of the CFD simulations showed the ability of the model to correctly predict transpiration, air and leaf temperatures as well as air humidity inside the greenhouse for both water regimes. Different irrigation scenarios were then tested, progressively reducing the water supply by providing a lesser amount of water than the growing media water capacity. The simulations made it possible to assess the model response to different irrigation regimes on plant transpiration, usual growing media water potential and climate distribution inside the greenhouse. The tests also showed that the water supply could be reduced by 20% without significantly impacting the transpiration rate and, therefore, potential plant growth. The CFD model could thus be useful to test different irrigation scenarios and better manage water inputs.

Ecophysiological Responses of Two Olive Tree Cultivars (Olea europaea L. CV Koroneiki and Chemlali) Under Three Water Treatments

In this paper, our objective is to assess and compare the effects of three levels of irrigation application on the ecophysiological behavior and plant dry matter accumulation of two young olive tree cultivars Koroneiki, a promising greek cultivar, and Chemlali, the best local cultivar. According to this assessment, we can determine the most efficient water treatment that could be suitable for Mediterranean environments subjected to water shortage conditions. Measurements were made in the green house of the Tunisian Olive tree Institute under normal day-light conditions from March, 16th to April, 21st 2015. Three water treatments were applied which are T100% (control treatment: Daily irrigation at 100% of Available Water Content (AWC)), T50% (Daily irrigation at 50% of AWC) and T0% (Without watering). The results showed that the two olive tree cultivars possess important mechanisms to overtake limited water resources. However, some striking variations existed between the two cultivars studied. Indeed, as water stress increased (T0%), Chemlali maintained longer a high midday leaf water potential compared (- 4.54 MPa) to Koroneiki (- 5.8 MPa). T50% treatment seems to be sufficient for both cultivars. Measurements of total Osmotic Adjustment (OA) showed that olive trees use this mechanism to create very negative leaf water potentials in order to be able to extract water from a dry root environment. The root/shoot ratio of Chemlali plants at T50% treatment was the highest (1.08) comparatively with the other two treatments (0.70 and 0.79 for T100% and T0% AWC water treatments, respectively). This result shows that Chemlali plants valorize low quantities of water (T50%) rather than high quantities (T100%) and Koroneiki plants behave better when it is irrigated at 100% AWC. To conclude, Chemlali plants irrigated at 50% AWC, compared to Koroneiki plants, are the most suitable to tolerate water restriction conditions.

Strategy for selection of soybean genotypes tolerant to drought during germination.

Water deficit is the main reason for instability in the context of soybean culture. The development of strategies for the selection of more tolerant genotypes is necessary. These strategies include the use of polyethylene glycol 6000 solutions (PEG-6000) for conducting the germination test under conditions of water restriction. Thus, the objective of this study was to determine the osmotic potential and the main characteristics that promote the discrimination of soybean genotypes with regard to water stress tolerance during germination and the vigor test. Thirteen soybean cultivars were used. The seeds were allowed to germinate on sheets of germitest paper moistened in solution with PEG-6000, simulating different levels of water availability, which is expressed as osmotic potential (0.0, -0.2, -0.4, and -0.6 MPa). We assessed germination, length, and dry mass for seedlings and seeds, as well as reserve dynamics. Germination and variables related to the dynamics of reservation have great influence on the expression of variability in environments under stress. Among the different osmotic potentials, the -0.2 MPa was the most efficient for the expression of genetic variability among the cultivars. Conducting the germination test with PEG-6000 solution to -0.2 MPa was efficient for selecting soybean cultivars tolerant to water stress. This was accomplished by evaluating the percentage of germination, along with variables related to the dynamics of reservation.

Role of fructose and fructokinase in acute dehydration-induced vasopressin gene expression and secretion in mice

This study increases our understanding of the mechanisms leading to vasopressin release under conditions of water restriction (acute dehydration). Specifically, these studies suggest that the aldose reductase-fructokinase pathways may be involved in vasopressin synthesis in the hypothalamus and secretion by the pituitary in response to acute dehydration. Nevertheless, mice undergoing water restriction remain capable of maintaining sufficient vasopressin (copeptin) levels to allow normal urinary concentration. Further studies of the aldose reductase-fructokinase system in vasopressin regulation appear indicated.

Osmoconditioning prevents the onset of microtubular cytoskeleton and activation of cell cycle and is detrimental for germination of Jatropha curcas L. seeds.

Jatropha curcas is an oilseed crop renowned for its tolerance to a diverse range of environmental stresses. In Brazil, this species is grown in semiarid regions where crop establishment requires a better understanding of the mechanisms underlying appropriate seed, seedling and plant behaviour under water restriction conditions. In this context, the objective of this study was to investigate the physiological and cytological profiles of J.curcas seeds in response to imbibition in water (control) and in polyethylene glycol solution (osmoticum). Seed germinability and reactivation of cell cycle events were assessed by means of different germination parameters and immunohistochemical detection of tubulin and microtubules, i.e. tubulin accumulation and microtubular cytoskeleton configurations in water imbibed seeds (control) and in seeds imbibed in the osmoticum. Immunohistochemical analysis revealed increasing accumulation of tubulin and appearance of microtubular cytoskeleton in seed embryo radicles imbibed in water from 48h onwards. Mitotic microtubules were only visible in seeds imbibed in water, after radicle protrusion, as an indication of cell cycle reactivation and cell proliferation, with subsequent root development. Imbibition in osmoticum prevented accumulation of microtubules, i.e. activation of cell cycle, therefore germination could not be resumed. Osmoconditioned seeds were able to survive re-drying and could resume germination after re-imbibition in water, however, with lower germination performance, possibly due to acquisition of secondary dormancy. This study provides important insights into understanding of the physiological aspects of J.curcas seed germination in response to water restriction conditions.

Common bean yield under water suppression and application of osmoprotectants

ABSTRACT The objective of this study was to evaluate the performance of the common bean crop grown with application of osmoprotectants based on algae of the genus Durvillaea potatorum in the winter crop season, with occurrence or not of water suppression. The experiment used a randomized block design, in split plots, arranged in a 4x7 factorial scheme, in which the plots were composed of four treatments - periods of water suppression (7, 14, 21 days and the control treatment: 100% of field capacity throughout the crop cycle) and the subplots consisted of seven types of osmoprotectants. The treatments with osmoprotectants was applied during the full flowering of the common bean. Three days after application of osmoprotectants, the treatments with suppression of irrigation were established. The use of osmoprotectants based on algae of the genus Durvillaea does not affect the variables plant height, stem diameter, stem and pod dry matter, first pod height, number of pods per plant and number of grains per pod in common bean plants cultivated with occurrence of water suppression. Common bean plants under water restriction conditions have lower leaf and shoot dry matter and lower 100-grain weight. Common bean grain yield was influenced by the type of osmoprotectants and the water suppression period.

Stomatal resistance of New Guinea Impatiens pot plants. Part 2: Model extension for water restriction and application to irrigation scheduling

In greenhouses, reducing water consumption by increasing water efficiency is of high interest. To reach this goal, predictive models of soil-plant-atmosphere water transfer could be helpful. However, such models have been mainly developed for open field conditions, and very few models exist for greenhouse plants grown in pots. Moreover, most of these models were implemented under well-watered conditions, but very few are available under water restriction. The aim of this study is to develop an integrated soil-plant-atmosphere water balance model applied to potted plants grown in greenhouses, to predict plant transpiration under different restrictive irrigation regimes. Implementing such a model requires an accurate estimation of stomatal resistance R s under water restriction conditions. R s is then used in the Penman-Monteith model to evaluate transpiration. To establish the model parameters, an experiment was conducted for sixteen weeks inside a greenhouse with ornamental plants (New Guinea Impatiens) grown in containers on shelves. Well-watered and water restriction conditions were applied. The peat matric potential, radiation, temperature and humidity were continuously recorded, while R s was measured and transpiration was assessed every half-hour from 8:00 am to 8:00 pm 10, 11, 12, 14, and 16 weeks after planting. The resulting model was first validated against experimental measurements during the twelfth week of the experiment. It displayed good correlations for both the instantaneous data and integrated total transpiration. Different scenarios of irrigation reduction (frequency x volume) were tested and the results indicated real potential for water use reduction. Indeed, by reducing water application by 50% and by applying one irrigation per day, transpiration was not affected.

<b>Behavior of <em>Jatropha curcas</em> L. seeds under osmotic stress: germination and cell cycle activity

Jatropha curcas is an oil-rich Euphorbiaceae seed species renowned for its apparent tolerance to environmental stresses. It is considered a promising source of renewable feedstock for biodiesel production in the Brazilian semiarid region where crop establishment requires a better understanding of the mechanisms leading to proper seed and plant behavior under water restrictive conditions. This study describes physiological and cytological profiles of J. curcas seeds imbibed in water restriction conditions by means of osmotic stress or osmoconditioning. Seeds were characterized by size, weight, moisture content and dry mass, germinability, and cell cycle activation by means of tubulin and microtubule cytoskeleton accumulation. Osmoconditioning at -0.8 MPa did not induce priming effects as it did not improve the physiological quality of the seed lots. Western blotting and immunocytochemical analysis revealed an increasing accumulation of tubulin and microtubule cytoskeleton in seeds imbibed in water for 48h onwards, culminating in the onset of mitotic configurations after germination. Only cortical microtubules were observed during seed osmoconditioning, whereas mitotic microtubules only occurred after re-imbibition of osmoconditioned seeds in water and subsequent germination.

Características morfogênicas, estruturais e produtivas de capim-buffel sob diferentes turnos de rega

RESUMO As condições de restrição hídrica no semiárido brasileiro são um dos fatores limitantes ao estabelecimento e produtividade de gramíneas forrageiras. Objetivou-se, com este estudo, avaliar o efeito de diferentes turnos de rega sobre as características morfogênicas, estruturais e produtivas de capim-buffel. O delineamento experimental foi o de blocos casualizados, com cinco tratamentos e seis repetições. Os tratamentos consistiram de cinco turnos de rega, correspondentes aos intervalos de 2, 4, 6, 8 e 10 dias. As variáveis analisadas foram: taxa de aparecimento foliar, filocrono, taxa de alongamento foliar e de colmo, taxa de senescência foliar, comprimento final da folha, número de folhas vivas por perfilho, número de perfilhos, altura do colmo, relação lâmina/colmo, índice de área foliar, massa seca de lâmina e colmo verde, massa seca de forragem verde, morta e total, massa seca de raiz, matéria seca e relação massa seca verde/massa seca morta. Não foi constatado efeito dos turnos de rega sobre o comprimento final da folha e massa seca de forragem morta. A relação lâmina/colmo apresentou comportamento quadrático, mantendo-se a 0,51, até o turno de rega de quatro dias. As demais características morfológicas, estruturais e produtivas decresceram linearmente com o aumento dos turnos de rega. O espaçamento dos turnos de rega promoveu reduções nos parâmetros morfológicos, estruturais e produtivos do capim-buffel, quando cultivado em casa-de-vegetação. O turno de rega de 2 dias destaca-se como o menos restritivo ao desenvolvimento do capim-buffel.

Multitraits evaluation of Pakistani ecotypes of berseem clover (Trifolium alexandrinum L.) under full-irrigation and water restriction conditions

Summary Berseem clover ( Trifolium alexandrinum L.) is an important forage crop in Pakistan and many ecotypes are grown across the country. Its yield is however frequently affected by insufficient irrigation due to unavailability of water. In the present study, twenty Pakistani ecotypes of berseem clover have been evaluated in lysimeters under full irrigation and water restriction conditions. In the full irrigation treatment soil humidity was maintained at field capacity, while in the water restriction treatment water was only supplied after severe wilting and to maintain humidity in the deep profile of the soil. Assessed traits included forage yield, calculated as the sum of the biomass harvested at 70 and 110 DA days after emergence, and morpho-physiological traits. Significant effects of water restriction were noted on yield, leaf gas exchange parameters, canopy temperature and osmotic adjustment. Most morpho-physiological traits had higher broad sense heritability than forage yield, both under full irrigation and water restriction conditions. Water restriction increased genetic and phenotypic variability and heritability of most traits under study. Under these conditions forage yield was positively associated to leaf temperature and recovery rate index and, under full irrigation, to net photosynthetic rate, canopy depression temperature and leaf area. The possible use of these traits as indirect selection criteria in berseem clover breeding programs is discussed. Some ecotypes with favorable traits such as high forage yield potential, good adaptation to water restriction and aptitude to multiple harvesting have also been identified.

Effects of water restriction on the growth performance, carcass characteristics and organ weights of naked neck and ovambo chickens of southern Africa.

In semi-arid areas of Southern Africa, dehydration can compromise the performance and welfare of local chickens, particularly during the growing period when confinement is curtailed and birds are left to scavenge for feed and water. The effect of water restriction on the growth performance was compared in Naked Neck (NNK) and Ovambo (OVB) chickens that are predominant in Southern Africa. A total of 54 eight-wk-old pullets each of NNK and OVB chickens with an initial average weight of 641±10 g/bird were randomly assigned to three water intake treatments, each having six birds for 8 wk. The water restriction treatments were ad libitum, 70% of ad libitum and 40% of ad libitum intake. Nine experimental pens with a floor space of 3.3 m2 per strain were used. The pens were housed in an open-sided house with cement floor deep littered with a 20 cm layer of untreated wood shavings. Feed was provided ad libitum. Average daily water intake (ADWI), BW at 16 weeks of age (FBW), ADG, ADFI, feed conversion ratio (FCR) and water to feed ratios (WFR) were determined. Ovambo chickens had superior (p<0.05) FBW, ADG and ADWI than NNK chickens. Body weight of birds at 16 weeks of age, ADG, ADFI, ADWI, and WFR declined progressively (p<0.05) with increasing severity of water restriction while FCR values increased (p<0.05) as the severity of water restriction increased. Naked Neck chickens had better FCR at the 40% of ad libitum water intake level than Ovambo chickens. The dressing percentage per bird was higher in water restricted birds than those on ad libitum water consumption, irrespective of strain. Heart weight was significantly lower in birds on 40% of ad libitum water intake than those on ad libitum and 70% of ad libitum water intake, respectively. In conclusion, NNK chickens performed better than OVB chickens under conditions of water restriction and would be ideal to raise for meat and egg production in locations where water shortages are a major challenge.