Water relations of cucumber, tomato, and sweet pepper

The ever increasing importance of water as a critical resource for agricultural production has encouraged more research on water relations in recent years. Most attention has been paid to field crops and less information is available for horticultural crops, especially vegetables. The results of studies on water relations of cucumber, tomato, and pepper are reported and discussed in this thesis.Drying cycle experiments were carried out with tomato, cucumber, and sweet pepper at two temperatures and three light intensities in order to: (1) examine suitability of some plant parameters as criteria for expression of plant water status; (2) investigate which parameter is most suitable as a basis for timing of irrigation; and (3) observe the change of various parameters during a drying cycle as affected by environment. Measurements were carried out on transpiration rate, stomatal diffusive resistance ( rs ), leaf temperature, plant and soil water potentials, and relative water content. The transpiration rate at 25°C was in general higher than that at 21°C due to the higher vapour pressure deficit (vpd) at the former temperature. For all the three species, a more pronounced stomatal closure was demonstrated at 25°C as compared to that at 21°C when drought was imposed on the plants. This result could be due to the fact that at 25°C the vpd and/or the internal CO 2 concentration was higher. Various levels of irradiance did not invoke different responses of stomata or transpiration rates throughout the drying cycles. The difference among the three light intensities used are thought to have been too small to show distinct responses. Moreover, relatively low intensities were used in this series of experiments. The measured rs , values did not always correlate significantly with soil water potentials because rs , measurements were carried out on single leaves at only one point in the photoperiod and the measurements were also affected by other environmental factors, such as humidity, prevailing during the measurements. Calculated rs , values showed better correlations with soil water potential, presumably because transpiration rates of the whole plants over the entire photoperiod were used for their calculation. Relative water content and leaf water potential correlated significantly with soil water potential. Among the plant parameters studied, the plant water potential as measured with the pressure chamber, was judged as the most suitable parameter expressing plant water status.Some physical aspects of the internal plant water relations were considered for the three species. The measured parameters were relative water content, sap electrical conductivity, and leaf water potential and its components (osmotic, pressure, and matric potentials). The contribution of matric potential to the total plant water potential was considerable. Neglecting the matric component would result in unrealistically low levels of pressure potential for the three species. Tomato was considered to have the best osmotic and matric adjustments, followed by cucumber and pepper. Sap osmotic potential and electrical conductivity were found to be significantly correlated with leaf water potential. Electrical conductivity was considered as an easy and accurate method to determine the osmotic potential indirectly. From the regression of relative water content on leaf water potential, cucumber, tomato, and pepper showed, in this order, decreasing drought resistance. Examination of some other parameters, however, such as osmotic and matric adjustments and reduction of photosynthesis in stress conditions, confirmed a better drought resistance property to tomato, followed by cucumber and pepper. Relative position of cucumber and tomato in drought resistance was discussed. For all the criteria examined, pepper was considered to be the least drought resistant. It was concluded that a better understanding of the drought resistance mechanisms in plants is required.Carbon dioxide exchange and transpiration rates were measured in a gas exchange assembly in two series of experiments. In the first series, measurements were carried out on cucumber and pepper at light saturation and in darkness. In the second series, photosynthesis-light curves for cucumber, tomato, and pepper were obtained. For both series, well-watered as well as stressed plants were used. Both photosynthesis and transpiration were reduced as stress set in. It was shown that both stomatal and nonstomatal mechanisms were involved in the reduction of photosynthesis. For all the three species, an increase in mesophyll resistance was observed as a result of water stress. In experiments with different levels of irradiance, it was observed that the stressinduced reduction of photosynthesis was more pronounced at light saturation compared to low light. After showing some initial opening reaction to light, the stomata of stressed plants showed a closing pattern, especially for cucumber and pepper, regardless of irradiance levels. It was proposed that the closing effect of drought overrode the opening effect of light. Severely stressed plants of cucumber and pepper were rewatered to study their recovery. Photosynthesis did not reach the pre-stress level one day after rewatering, this was due to an aftereffect of drought on stomata in cucumber and pepper and a damage to the photosynthetic system in pepper.Diurnal changes in water relations parameters were measured in a glasshouse for tomato and pepper. In a constant environmental condition, gas exchange rates were monitored throughout the photoperiod for cucumber, pepper, and two cultivars of tomato. Both well-watered and stressed plants were used for the above measurements. In the glasshouse, transpiration, leaf water potential, stomatal diffusive resistance, as well as the diurnal changes in environmental factors such as radiation, temperature, vpd, and evaporation were measured. It was observed that the diurnal variation in leaf water potential followed that of transpiration. Changes in the whole plant transpiration were not necessarily accounted for by the rs values measured on single leaves. Multiple regression relationships were obtained for plant water potentials on radiation and temperature and suggestions were made to their use in timing of irrigation. In a constant environmental condition, all species showed maximum rates of transpiration and photosynthesis during the first hour of the photoperiod. The rates steadily declined thereafter, and the decline was more pronounced in stressed plants. A decrease in leaf water potential could not account for these diurnal phenomena, and other internal control mechanisms were thought to be involved. It has been suggested that photorespiration increased under the high irradiance employed. Internal CO 2 levels then increased, causing stomatal closure, leading to a decline in transpiration. Photosynthesis also decreased through both stomatal closure and a decrease in the CO 2 gradient. Increases in mesophyll. resistance in the case of cucumber and pepper also occurred.<p/

Bandit-Based Policy Invariant Explicit Shaping for Incorporating External Advice in Reinforcement Learning

A key challenge for a reinforcement learning (RL) agent is to incorporate external/expert1 advice in its learning. The desired goals of an algorithm that can shape the learning of an RL agent with external advice include (a) maintaining policy invariance; (b) accelerating the learning of the agent; and (c) learning from arbitrary advice [3]. To address this challenge this paper formulates the problem of incorporating external advice in RL as a multi-armed bandit called shaping-bandits. The reward of each arm of shaping bandits corresponds to the return obtained by following the expert or by following a default RL algorithm learning on the true environment reward.We show that directly applying existing bandit and shaping algorithms that do not reason about the non-stationary nature of the underlying returns can lead to poor results. Thus we propose UCB-PIES (UPIES), Racing-PIES (RPIES), and Lazy PIES (LPIES) three different shaping algorithms built on different assumptions that reason about the long-term consequences of following the expert policy or the default RL algorithm. Our experiments in four different settings show that these proposed algorithms achieve the above-mentioned goals whereas the other algorithms fail to do so.Comment: ALA workshop, AAMAS 202

Quality attributes of pistachio nuts as affected by rootstocks and deficit irrigation

BACKGROUND: In this work, the influence of two regulated deficit irrigation (RDI) treatments and three different rootstocks on the quality of pistachios was evaluated by analyzing different parameters: morphological analysis, physicochemical analysis and sensory analysis. RESULTS: The results obtained in terms of the choice of rootstock revealed that Pistacia atlantica had increased production yields, nut weight, mineral content, higher intensities of characteristic sensory attributes and a higher degree of consumer satisfaction, than the other rootstocks studied. Moreover, the results established that the application of RDI on pistachio cultivation had no significant influence on production yield, weight, size, colour, water activity or mineral composition. Furthermore, T1 treatment (stem water potential?<?-1.3 MPa) resulted in higher intensities of characteristic sensory attributes and a greater level of satisfaction among international consumers. CONCLUSION: These results confirm that the application of deficit irrigation (T1) contributes to an increase in overall product quality. Furthermore, Pistacia atlantica rootstock provided better yield and quality than the other rootstocks studied. © 2014 Society of Chemical Industr

Irrigation and fruit canopy position modify oil quality of olive trees (cv. Frantoio)

BACKGROUND: Fruit development and oil quality in Olea europaea L. are strongly influenced by both light andwater availability. In the present study, the simultaneous effects of light environment and irrigation on fruit characteristics and oil quality were studied in a high-density orchard over two consecutive years. Olive fruits were harvested from three canopy positions (intercepting approximately 64%, 42% and 30% of above canopy radiation) of fully-productive trees subjected to full, deficit or complementary irrigation. RESULTS: Fruits receiving 61–67% of above canopy radiation showed the highest fruit weight, mesocarp oil content and maturation index, whereas those intercepting only 27–33% showed the lowest values. Palmitoleic and linoleic acids increased in oils obtained from fruits exposed to high light levels, whereas oleic acid and the oleic-linoleic acid ratio decreased. Neither canopy position, nor irrigation affected K232, K270, K and the concentration of lignan in virgin olive oils (VOOs). Total phenols, 3,4-DHPEA-EDA [2-(3,4-hydroxyphenyl)ethyl (3S,4E)-4-formyl-3-(2-oxoethyl)hex-4-enoate] and p-HPEA-EDA (decarboxymethyl ligstroside-aglycone) increased in VOOs produced from fruits harvested from the top of the canopy, whereas full irrigation decreased total phenols and 3,4-DHPEA-EDA concentrations with respect to the complementary irrigation treatment. CONCLUSION: Light and water availability are crucial not only for tree productivity, but also they clearly affect olive oil quality. © 2017 Society of Chemical Industr

Comparative analysis of the responses to water stress in eggplant (Solanum melongena) cultivars

[EN] Little information is available on the physiological and biochemical responses to water stress in eggplant (Solanum melongena). We valuated four genetically diverse eggplant varieties (MEL3-MEL6) under control and water stress conditions. Measurements were taken for plant growth, tissue water content, levels of chlorophylls a and b, carotenoids, roline, malondialdehyde, total phenolics, total flavonoids, superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase APX), and glutathione reductase (GR) activities. For most traits, the water stress treatment had a greater contribution than the variety effect to the total sums of squares in an ANOVA analysis, except for total flavonoids, SOD, APX, and GR. The water stress treatment had a strong effect on plant growth and tissue water content. In general, water tress reduced the three photosynthetic pigments, increased proline, malondialdehyde, total phenolics, and total flavonoids, although some varietal differences were ob- served. Different patterns were also detected in the activities of the four enzymes evaluated, but few differences were observed for individual varieties between the control and water stress treatments. Many significant phe- notypic orrelations were observed among the traits studied, but only eight environmental correlations were detected. A PCA analysis distinctly separated individuals according to the treatment, and revealed a clearer separation of varieties under water stress than under control conditions, pointing to varietal differences in the responses to stress. Our results suggest that proline could be used as a marker for drought stress tolerance in this species. The information obtained provides new insight on the physiological and biochemical responses of eggplant to drought stressAuthors are grateful to the European Union's Horizon 2020 Research and Innovation Programme under grant agreement No 677379 (G2P-SOL project: Linking genetic resources, genomes and phenotypes of Solanaceous crops), to Ministerio de Economfa, Industria y Competitividad and Fondo Europeo de Desarrollo Regional (grant AGL2015-64755-R from MINECO/FEDER), to Ministerio de Ciencia, Innovation y Universidades, Agencia Estatal de Investigation and Fondo Europeo de Desarrollo Regional (grant RTI-2018-094592-B-100 from MCIU/AEI/FEDER, UE), to the Generalitat Valenciana and Fondo Social Europeo (Ayuda a Grupos Emergentes; GV/2019/033), to the Vicerrectorado de Investigacien, Innovation y Transferencia de la Universitat Politecnica de Valencia (Ayuda a Primeros Proyectos de Investigation; PAID-06-18), and to the initiative "Adapting Agriculture to Climate Change: Collecting, Protecting and Preparing Crop Wild Relatives", which is supported by the Government of Norway. This latter project is managed by the Global Crop Diversity Trust with the Millennium Seed Bank of the Royal Botanic Gardens, Kew and implemented in partnership with national and international gene banks and plant breeding institutes around the world. For further information see the project website: http://www.cwrdiversity.org/. Mariola Plazas is grateful to Generalitat Valenciana and Fondo Social Europeo for a post-doctoral contract (APOSTD/2018/014). The contribution of Huu Trong Nguyen to this paper has been developed as a result of a mobility stay funded by Erasmus + KA1 Erasmus Mundus Joint Master Degrees Programme of the European Commission under the PLANT HEALTH project.Plazas, M.; Nguyen, HT.; González-Orenga, S.; Fita, A.; Vicente, O.; Prohens Tomás, J.; Boscaiu, M. (2019). Comparative analysis of the responses to water stress in eggplant (Solanum melongena) cultivars. Plant Physiology and Biochemistry. 143:72-82. https://doi.org/10.1016/j.plaphy.2019.08.031S728214

Crop Updates 2000 - Pulses

This session covers fifty nine papers from different authors: 1.1999 PULSE INDUSTRY HIGHLIGHTS 2. CONTRIBUTORS 3. BACKGROUND 4. SUMMARY OF PREVIOUS RESULTS 5. 1999 REGIONAL ROUNDUP 6. Northern Agricultural Region, W. O’Neill, AGWEST 7. Central Agricultural Region J. Russell and R.J. French AGWEST 8. Great Southern and Lakes N. Brandon, C. Gaskin and N. Runciman, AGWEST 9. Esperance Mallee M. Seymour, AGWEST PULSE PRODUCTION AGRONOMY AND GENETIC IMPROVEMENT 10. Faba Bean 11. Desi chickpea Traits associated with drought resistance in chickpea, J. Berger, N.C. Turner, CLIMA and CSIRO Plant Industry, R.J. French, AGWEST, R. Carpenter, C. Ludwig and R. Kenney, CSIRO Plant Industry 12. Genotype x environment analysis of chickpea adaptation, J. Berger and N. Turner, CLIMA and CSIRO Plant Industry, and K.H.M. Siddique, AGWEST 13. Carbon fixation by chickpea pods under terminal drought, Q. Ma, CLIMA, M.H. Behboudian, Massey University, New Zealand, N.C. Turner and J.A. Palta, CLIMA, and CSIRO Plant Industry 14. Influence of terminal drought on growth and seed quality, M.H. Behboudian, Massey University, New Zealand, Q. Ma, CLIMA, N.C. Turner and J.A. Palta, CSIRO Plant Industry 15. Resistance to chilling at flowering and to budworm, H. Clarke, CLIMA Chickpea nodulation survey, J. Stott and J. Howieson, Centre for Rhizobium Studies, Murdoch University 16. Kabuli chickpea 17. Premium quality kabuli chickpea development in the ORIA, K.H.M. Siddique CLIMA and AGWEST, K.L. Regan, AGWEST, R. Shackles, AGWEST 18. International screening for Ascochyta blight resistance, K.H.M. Siddique CLIMA and AGWEST, C. Francis, CLIMA, K.L. Regan, AGWEST, N. Acikgoz and N. Atikyilmaz, AARI, Turkey and R.S. Malholtra, ICARDA, Syria 19. Agronomic evaluation of Ascochyta resistant kabuli germplasm in WA, K.H.M. Siddique CLIMA and AGWESTC. Francis, CLIMA, K.L. Regan and M. Baker, AGWEST 20. Field Pea 21. Lentil 22. ACIAR project J. Clements, K.H.M. Siddique CLIMA and AGWEST and C. Francis CLIMA 23. Vetch 24. Rust, M. Seymour, AGWEST 25. Narbon bean 26. Agronomy, M. Seymour, AGWEST 27. Lupinus species 28. Screening lupins for tolerance to alkaline/calcareous soils, C. Tang, CLIMA andUniversity of WAand J.D. Brand, WAITE, University of Adelaide 29. Lathyrus development, C. Hanbury and K.H.M. Siddique, CLIMA and AGWEST 30. Sheep feeding studies, C. White, CSIRO, Perth, C. Hanbury, CLIMA and K.H.M. Siddique, CLIMA and AGWEST 31. Lathyrus: a potential new ingredient in pig diets, B.P. Mullan, C.D. Hanbury and K.H.M. Siddique, AGWEST 32. Species comparison 33. Species for horticultural rotations, K.H.M. Siddique, AGWEST, R. Lancaster and I. Guthridge AGWEST 34. Marrow fat field pea shows promise in the southwest, K.H.M. Siddique, AGWEST, N. Runciman, AGWEST, and I. Pritchard, AGWEST, 35. Pulses on grey clay soils, P. Fisher, M. Braimbridge, J. Bignell, N. Brandon, R. Beermier, W. Bowden, AGWEST 36. Nutrient management of pulses 37. Summary of pulse nutrition studies in WA, M.D.A. Bolland, K.H.M. Siddique, G.P. Riethmuller, and R.F. Brennan, AGWEST 38. Pulse species response to phosphorus and zinc, S. Lawrence, Zed Rengel, University of WA, S.P. Loss, CSBP futurefarm, M.D.A. Bolland, .H.M. Siddique, W. Bowden, AGWEST 39. Gypsum 40. Antitranspirants seed priming DEMONSTRATION OF PULSES IN THE FARMING SYSTEM 41. Foliar and soil applied nutrients for field peas in the south coast mallee,M. Seymour, AGWEST, and P. Vedeniapine, Phosyn Ltd 42. Demonstration of pulse species at Kendenup, C. Kirkwood, Farmer, Katanning, R. Beermier, N. Runciman and N. Brandon, AGWEST 43. Kabuli chickpea demonstration at Gnowangerup, R. Beermier and N. Brandon, AGWEST 44. Lathyrus sativus demonstration at Mindarabin, N. Brandon and R. Beermier, AGWEST 45. New field pea varieties in the central eastern region, J. Russell, AGWEST DISEASE AND PEST MANAGEMENT 46. Ascochyta blight of chickpea 47. Botrytis grey mould (BGM) of chickpea 48. Fungal disease diagnostics, Pulse disease diagnostics, D. Wright, AGWEST Plant Laboratories 49. Viruses in pulses, Luteovirus infection in field pea and faba bean crops, and viruses in seed, L. Latham, CLIMA and AGWEST, R. Jones, AGWEST 50. Screening of pulse species for pea seed-borne mosaic virus, L. Latham, CLIMAand AGWEST, and R. Jones, AGWEST 51. CMV in chickpea: effect of seed-borne sources on virus spread and seed yield, R. Jones, AGWEST and L. Latham, CLIMA and AGWEST 52. Insect pests 53. Evaluation of transgenic field pea against the pea weevil,M.J. de Sousa Majer, School of Environmental Biology, Curtin University of Technology,, D. Hardie, and N.C. Turner, CSIRO Division of Plant Industry 54. Development of a molecular marker for pea weevil resistance in field pea, Oonagh Byrne, CLIMA, Darryl Hardie, AGWEST and Penny Smith, UWA 55. Aphid feeding damage to faba bean and lentil crops, Françoise Berlandier, AGWEST 56. Taxonomy and control of bruchids in pulses, N. Keals, CLIMA, D. Hardie and R. Emery, AGWEST, 57. ACKNOWLEDGMENTS 58. PUBLICATIONS BY PULSE PRODUCTIVITY PROJECT STAFF 59. VARIETIES PRODUCED AND COMMERCIALLY RELEASE

Chickpea and temperature stress

Chickpea is an important food grain legume and an essential component of crop rotations throughout the world. However, the adaptation and productivity of chickpea is often limited by low and high temperatures. Cold stress generally occurs in the late vegetative and reproductive stages across the geographical areas of chickpea production. Cold and freezing temperatures (−1.5°C to 15°C) are considered a major problem during the seedling stage of winter-sown chickpea in Mediterranean areas and autumn-sown crops in temperate regions (Singh, 1993). South Australia and parts of north India are most affected by chilling temperatures at flowering (Berger et al., 2011). On the other hand, high day and night temperatures (>30/16°C) may cause damage during the reproductive stage on winter-sown chickpea in Mediterranean inseason rainfall areas, south Asia and spring-sown regions (Berger et al., 2011). In chickpea, temperature is a major environmental factor regulating the timing of flowering thus influencing grain yield (Summerfield et al., 1990; Berger et al., 2004). Both low and high temperatures can limit the growth and grain yield of chickpea at all phenological stages..