Source: UNIVERSITY OF CALIFORNIA, DAVIS submitted to
FRUIT AND NUT TREES IN A DYNAMIC ENVIRONMENT – QUANTIFYING SPECIES RESISTANCE TO ABIOTIC STRESSES (FREEZING, SALINITY AND DROUGHT) AND THEIR COMBINATIONS
Sponsoring Institution
National Institute of Food and Agriculture
Project Status
NEW
Funding Source
HATCH
Reporting Frequency
Annual
Accession No.
1002507
Grant No.
(N/A)
Project No.
CA-D-PLS-2224-H
Proposal No.
(N/A)
Multistate No.
(N/A)
Program Code
(N/A)
Project Start Date
Feb 18, 2014
Project End Date
Sep 30, 2018
Grant Year
(N/A)
Project Director
Zwieniecki, MA, .
Recipient Organization
UNIVERSITY OF CALIFORNIA, DAVIS
410 MRAK HALL
DAVIS,CA 95616-8671
Performing Department
Plant Sciences
Non Technical Summary
The changing climate is considered a major threat to the future of agriculture around the world. California is not immune to this threat. Increasing the use of ground water to replace diminishing surface water, the inevitable soil salinization that occurs with irrigated agriculture and increased variability in climatic conditions characterized by warmer fall temperatures that exacerbate the potential for early frost damage are at the base of incoming problems. Here, I propose a multi-year project to study the tolerance of orchard trees (fruit and nuts) to salt exposure, drought stress and freezing (including combinations of these environmental perturbations) in the context of tree biology. The project aims to provide knowledge that can be translated to inform orchard management practices across California within the context of a changing climate.The short term goals are to describe the frost, salt and drought stress tolerances of major fruit and nut crop trees,linking this information to species morphological and biological traits. Determination of the tree biology/physiology behind resistance to changes in micro-environmental conditions will provide a short-term outcome that may be an invaluable tool in orchard protection now and that also will aid the long-term goals of future breeding programs
Animal Health Component
0%
Research Effort Categories
Basic
30%
Applied
40%
Developmental
30%
Classification

Knowledge Area (KA)Subject of Investigation (SOI)Field of Science (FOS)Percent
1021199100025%
2031219102025%
2061219104025%
2061219106025%
Knowledge Area
102 - Soil, Plant, Water, Nutrient Relationships; 203 - Plant Biological Efficiency and Abiotic Stresses Affecting Plants; 206 - Basic Plant Biology;

Subject Of Investigation
1199 - Deciduous and small fruits, general/other; 1219 - Edible tree nuts, general/other;

Field Of Science
1020 - Physiology; 1060 - Biology (whole systems); 1000 - Biochemistry and biophysics; 1040 - Molecular biology;
Goals / Objectives
The goal of the proposed research is to build a fundamental knowledge base for understanding the biological responses of fruit and nut crop trees to drought, salinity and freezing stresses and their interactive effects on plant survival, vitality and yield.While my general goal is to establish a long-term tree research program at UC Davis, I expect this to happen in smaller steps in collaboration with researchers and specialists across the UC system and Commodity Research Boards. This proposal serves as the first step and is focused on learning the principles of tree resistance to major abiotic stresses--namely, freezing, salinity and drought. The specific objectives of this proposal are:Establish biological/physiological responses of fruit and nut trees (both rootstocks and scions) to variable temperature (freezing), salinity and drought as well as combinations of these abiotic stresses. Proposed areas of research include:Study of plant hydraulics in the context of a changing climateRole of carbohydrates in mitigation of drought, salinity and freezing stresses Role of parenchyma tissue in salt toleranceStudy transcription level responses of selected species to abiotic stresses to determine shared signaling/metabolic pathways triggered by a diverse range of abiotic stresses that could be targeted in future breeding programs. We would like to:Compare whole transcriptome response of selected species to stress Determine metabolic pathways that are perturbed by environmental stress and variations in the transcription of associated genes Determine species tolerance limits to environmental perturbations as well as temporal dynamics of exposure to stresses that maycause scion/rootstock death or permanent damage and reduced yield, including:Greenhouse/lab studiesin controlled environments - freezing, salt, and drought. Field experiments in commercial orchards under current management practices Provide biological bases for mitigation of adverse environmental conditions via management practices including:Water irrigation regimes for drought stress mitigation under saline conditionsBiology of salt stress mitigationControl of freezing damageProvide biological bases for physiological/morphological traits that may be used by breeding programs aiming to improve tree tolerance to freezing, salinity and drought
Project Methods
Establish experimental greenhouse and field studies to test plant response to environmental cues - salt, temperature and drought. Greenhouse experiments will provide data regarding specifics of dynamic changes in plant hydraulic properties in response to environmental perturbation (using classical and newly developed techniques for determination pant hydraulic properties). Stems, leaves and roots will be collected for the analysis of carbohydrates content in response to stress. Plant tissue will be analyzed for salt location and content (both tissue level and sub-cellular level using available imaging techniques). Field study (environmental data, tissue sample collection and physiological measurements) on mature selected sites will provide additional information about natural variation of parameters describing trees stress response and resistance as well as magnitude of changes in natural growing conditions.Same plant material as in (1) will be used for transcriptome analysis and molecular studies. Plant samples will be collected at multiple times to capture dynamics and long term changes of the transcription level changes in prescribed conditions. Subset of plants in greenhouse studies will be exposed to extreme environmental conditions to established limits to plant survival. Plants will be exposed to sudden changes in temperature, severe water stress and salt overdose as well as combination of these conditions. Experiments will be conducted in such a way that a progressive increase of particular stressors will be applied to eventually kill the plants. Established limits will be used in assessments of field conditions (from environmental observations) in respect to their potential to cause damage. Once limits of plant tolerance to stressors and biological understanding of damage/death will be established research will enter into the next step. Conditions will be manipulated to approach the limit of survival and mitigation approach will be tested. As of today mitigation techniques are limited mostly to irrigation regimes (and those will be tested first) but we will try other approaches that might evolved from the better understanding of tree stress biology.Results will be continuously assessed for their usefulness in breeding programs. Morphological/biological traits will be discussed from the perspective of their usefulness for commercialization.

Progress 10/01/16 to 09/30/17

Outputs
Target Audience:Targeted audience: Pistachio Research Board, Almond Board of California and Walnut Board of California. Growers, Farm advisors and Crop extension specialist with interests in nut crops Efforts included seminar presentation at Almond Conference in Sacramento, and Pistachio Day held in Fresno, as well as Walnut board meeting in Bodega Bay, Pistachio Board Meeting in Kern Station. In addition I had have several meeting with growers and Farm advisors. Changes/Problems: Nothing Reported What opportunities for training and professional development has the project provided?Training and mentoring activities: Provide postdoc opportunity for Adele Amico Roxas - she is currently supported by Pistachio Research Board Provide postdoc opportunity for Aude Tixier - she is currently supported by Almond Board of California Provide postdoc opportunity for Anna Davidson - she is currently supported by Walnut Board of CaliforniaT How have the results been disseminated to communities of interest?See Carbohydrate observatory website: http://www.plantsciences.ucdavis.edu/plantsciences_faculty/zwieniecki/CR/cr.html What do you plan to do during the next reporting period to accomplish the goals? Establish experimental tools for studying shoot physiology under variable environmental conditions in the lab and in the field including detailed analysis of starch and soluble sugar concentration dynamics, carbohydrate metabolism enzyme activity, and expression pattern of genes encoding enzymes from carbohydrate metabolism pathways. · Using existing and novel tools to determine the seasonal pattern of carbohydrate management by the nut trees with a special focus on winter to determine the dynamics between trees' activity in spring and shoot carbohydrate reserves. · Determine cumulative impact of environmental stresses on carbohydrate management including the combined effects of thermal and water stress (and possibly include salinity stress in the future). · Evaluate current management practices (paints, winter chill substitutes, winter irrigation) on carbohydrate status of the tree. Proposed research · Analysis of temperature monitoring in phloem and bark of commercial cultivated matured trees; This field research will establish the real-life dynamics of cooling and heating events occurring in the orchards and provide thermal information to guide future laboratory research. Understanding pre-chill biology to address the issue of tree memory of chill events (memory here is understood as time that protective compounds reside in parenchyma cells after the chill event) that would allow well-irrigated trees to withstand freezing events. Analysis of the diurnal and seasonal carbohydrate dynamics in almond stems and branches, including detailed information about enzymatic activity of selected enzymes from starch synthesis and degradation pathways in conjunction with evaluation of protein levels in shoots and branches. · Determination of carbohydrate transport and relocation in trees during winter, the period of preparation for dormancy breaking and during bud break and flowering including the effects on successful fruit set. · Further research concerning cell lipids, freezing related amino acid (proline), and additional pseudo-drought stress substances (e.g. abscisic acid) are also highly related to our research topic and would be included in future research. · Development of a model for tree carbohydrate analysis that includes tree thermal status and the associated enzymatic pathway activity to guide future research.

Impacts
What was accomplished under these goals? http://www.plantsciences.ucdavis.edu/ plantsciences_faculty/zwieniecki/CR/cr.html) suggests a high variability in NSCs content between orchards. This variability is related to significant differences between observed content in older and younger orchards. Older orchards accumulate more NSCs prior to winter dormancy. This difference disappears in the summer suggesting that higher amount of the NSCs can be utilized for bud break and spring growth. It is yet to be determined if this higher amount can be linked to increased yield. (Objective 5)

Publications

  • Type: Journal Articles Status: Published Year Published: 2017 Citation: Tixier, A., Amico Roxas, A., Godfrey, J., Saa, S., Lightle, D., Maillard, P., Lampinen, B., Zwieniecki, M.A. 2017. Role of Bark Color on Stem Temperature and Carbohydrate Management during Dormancy Break in Persian Walnut (Juglans regia L.). Journal of American Society for Horticultural Science 142:454-463
  • Type: Journal Articles Status: Published Year Published: 2017 Citation: Tixier, A., Sperling, O., Orozco, J., Lampinen, B., Amico Roxas, A., Saa, S., Earles, J.M., Zwieniecki M.A. 2017. Spring bud growth depends on sugar delivery by xylem and water recirculation by phloem M�nch flow in Juglans regia. Planta 246:495-508 DOI: 10.1007/s00425-017-2707-7
  • Type: Journal Articles Status: Published Year Published: 2017 Citation: Sperling, O., Silva, L., Tixier, A., Th�roux-Rancourt, G., Zwieniecki, M.A. 2017. Temperature gradients assist carbohydrate allocation within trees. Scientific Reports 7, Article number: 3265 doi:10.1038/s41598-017-03608-w
  • Type: Journal Articles Status: Published Year Published: 2017 Citation: Th�roux-Rancourt, G., Earles, J., Gilbert, M., Zwieniecki, M.A., Boyce, C.K., McElrone, A., Brodersen, C. 2017. The bias of a two-dimensional view: comparing two-dimensional and three-dimensional mesophyll surface area estimates using noninvasive imaging. New Phytologist 215:1609-1622


Progress 10/01/15 to 09/30/16

Outputs
Target Audience:Targeted audience: Pistachio Research Board, Almond Board of California and Walnut Board of California. Growers, Farm advisors and Crop extension specialist with interests in nut crops Efforts included seminar presentation at Almond Conference in Sacramento, and Pistachio Day held in Fresno, as well as Walnut board meeting in Bodega Bay, Pistachio Board Meeting in Kern Station. In addition I had have several meeting with growers and Farm advisors. Changes/Problems: Nothing Reported What opportunities for training and professional development has the project provided?Training and mentoring activities: Provide postdoc opportunity for Or Sperling - resulted in Or receiving tenure track position in Volcani Institute in Israel Provide postdoc opportunity for Aude Tixier - she is currently supported by Almond Board of California Provide postdoc opportunity for Anna Davidson - she is currently supported by Walnut Board of California How have the results been disseminated to communities of interest?See Carbohydrate observatory website: http://www.plantsciences.ucdavis.edu/plantsciences_faculty/zwieniecki/CR/cr.html What do you plan to do during the next reporting period to accomplish the goals?Objectives · Establish experimental tools for studying shoot physiology under variable environmental conditions in the lab and in the field including detailed analysis of starch and soluble sugar concentration dynamics, carbohydrate metabolism enzyme activity, and expression pattern of genes encoding enzymes from carbohydrate metabolism pathways. · Using existing and novel tools to determine the seasonal pattern of carbohydrate management by the nut trees with a special focus on winter to determine the dynamics between trees' activity in spring and shoot carbohydrate reserves. · Determine cumulative impact of environmental stresses on carbohydrate management including the combined effects of thermal and water stress (and possibly include salinity stress in the future). · Evaluate current management practices (paints, winter chill substitutes, winter irrigation) on carbohydrate status of the tree. Proposed research · Analysis of temperature monitoring in phloem and bark of commercial cultivated matured trees; This field research will establish the real-life dynamics of cooling and heating events occurring in the orchards and provide thermal information to guide future laboratory research. Understanding pre-chill biology to address the issue of tree memory of chill events (memory here is understood as time that protective compounds reside in parenchyma cells after the chill event) that would allow well-irrigated trees to withstand freezing events. Analysis of the diurnal and seasonal carbohydrate dynamics in almond stems and branches, including detailed information about enzymatic activity of selected enzymes from starch synthesis and degradation pathways in conjunction with evaluation of protein levels in shoots and branches. · Determination of carbohydrate transport and relocation in trees during winter, the period of preparation for dormancy breaking and during bud break and flowering including the effects on successful fruit set. · Further research concerning cell lipids, freezing related amino acid (proline), and additional pseudo-drought stress substances (e.g. abscisic acid) are also highly related to our research topic and would be included in future research. · Development of a model for tree carbohydrate analysis that includes tree thermal status and the associated enzymatic pathway activity to guide future research. · Determine ATP content during dormancy and bud break. Expected practical applications · Development of methods and analytical techniques for analysis of almond trees carbohydrate management with easy to follow protocols · Formulation of physiological baseline for using dynamics of almond carbohydrate status in future filed trials to develop specific orchard management guidelines · Determination of almond trees carbohydrate management dynamics as proxy for orchard health status.

Impacts
What was accomplished under these goals? Background and research incentives: Recent years exhibited remarkable changes in temperature and precipitation patterns. While much was already said about summer's drought and heatwaves, crop conditions during winter are generally overlooked by researchers. Yet this is not true for the farmers, they follow soil conditions, realize the absence of the valley's famous fog, and count hours of cold weather (chilling hours). They see how this prominent environmental variability during recent winters influences their yield loads and potentially cut their profits. Our research goal is to explain pistachio's physiological responses to winter conditions and derive better farming management practices to mitigate climate hazards. We focus on the tree's major currency - carbohydrates. This is the main source of energy in plants and it fuels every metabolic process. This is also the structure bone for vegetative growth and reproduction, i.e. fruits. Tree crops in optimal farming conditions (on irrigated and fertilized fields) produce excess of carbohydrates that is stored as starch throughout summer in preparation for dormancy. It is the winter's carbohydrates balance that will determine winter survival and tree's ability to cope with winter imposed stresses (frost, availability of water, flooding etc.). Additionally, it's the depleted sugar reservoirs that is used during initiation of flowering in early spring and sustain the first stages of fruit development, leaf and early wood growth. In this part of the research we investigate the annual carbohydrates dynamics and their availability for winter/spring activities, i.e. frost protection and supporting bloom. We base our studies on a working hypothesis that temperature is the prominent environmental cue which drives phenology at the critical periods of senescence and bud break (Sperlling et al. 2015; Zwieniecki et al. 2015). Objectives: 1. To derive the optimal conditions for trees to withstand early frosts 2. Establish experimental tools for studying shoot physiology under variable environmental conditions in the lab and in the field including detailed analysis of starch and soluble sugar concentration dynamics, carbohydrate metabolism enzyme activity, and expression pattern of genes encoding enzymes from carbohydrate metabolism pathways. 3. Using existing and novel tools continue to determine the seasonal pattern of carbohydrate management by the pistachio tree with a special focus on winter to determine the dynamics between trees' activity in spring and shoot carbohydrate reserves. 4. Provide insight to physiology of chilling requirements with specific goal of improvement to chilling models. Objective 1. To derive the optimal conditions for pistachio trees to withstand early frosts. We have evaluated the role of the drought as a treatment to protect trees from early frost. Results were recently published: Sperling, O., Secchi, F., Godfrey, J., Zwieniecki, M.A. 2016. Acclimation of Pistacia integerrima trees to frost in semi-arid environments depends on autumn's drought. Planta. DOI 10.1007/s00425-016-2629-9. Main conclusion is that low level of drought in fall stimulate defense mechanisms that can protect young trees from early frost events. Objective 2. Establish experimental tools for studying shoot physiology under variable environmental conditions in the lab and in the field including detailed analysis of starch and soluble sugar concentration dynamics, carbohydrate metabolism enzyme activity, and expression pattern of genes encoding enzymes from carbohydrate metabolism pathways. We have established standard procedure for analysis of soluble sugars and starch content in woody tissue of pistachio that gave consistent and repetitive results (see attachment 1). Key aspect of the procedure is the use of a standard grind tissue of the pistachio wood with known sugar and starch content along with every analysis performed. Currently we are developing methods for enzyme activity analysis. Objectives 3(a). Using existing and novel tools continue to determine the seasonal pattern of carbohydrate management by the pistachio tree with a special focus on winter to determine the dynamics between trees' activity in spring and shoot carbohydrate reserves. We are expanding this objective to a new more comprehensive statement: Determine cumulative impacts of environmental stresses on carbohydrate management including the combined effects of thermal and water stress. Specifically, we decided to determine seasonal pattern of carbohydrate content in pistachio trees under variable climatic conditions, for different tree age groups, and different management treatments in the context of yield and phenology. This ambitious undertaking of carbohydrate analysis run as a typical research experiment would require large expensive experimental setups established in multiple locations and run for many years. We have decided to overcome typical limitations of such an approach by encouraging participation of managers and growers in citizen research approach called `Carbohydrate Observatory', this way we can avoid expensive university run experiments, extend data collection to the entire geographical range of walnut orchards (different climates, winter chilling etc.), representing all ages and diverse management treatments. Twig samples are being collected by growers, managers, or participating farm advisors and shipped to us for analysis, in addition for some fields we collect samples to increase frequency and geographical distribution. This part of the project is being actively developed with first samples from September and October collection being currently analyzed. We will continue this effort to develop a comprehensive coverage of the pistachio farming in CA. An outline of the project and its map interface can be found at: http://www.plantsciences.ucdavis.edu/plantsciences_faculty/zwieniecki/CR/cr.html . Objective 4. Provide insight to physiology of chilling requirements with specific goal of improvement to chilling models. We are developing technology to determine role of chilling in breaking dormancy in pistachio. Currently this technology is used on almond trees, with plans to use it next year on pistachio. Experimental setup allows for reduction in chill hour accumulation to subset of buds (buds only) on a single tree and compare the bud break between the two population of buds on the same tree. This technique may allow for determination of chill influence on older trees. Work is in progress. Practical application Carbohydrate balance of the tree is highly dependent on the thermal conditions of the environment. Late fall and early spring are crucial periods when priming of the tree for dormancy and bud-break occurs. If thermal conditions during these two periods are not met the yield potential of the trees might be reduced and application of management techniques with potential to influence either tree thermal conditions or carbohydrate management might be advised - this would include paints, reflective material, oils, etc.

Publications

  • Type: Journal Articles Status: Published Year Published: 2016 Citation: Zwieniecki, M.A., Haaning, K.S., Boyce, C.K., Jensen, K.H. 2016. Stomatal Design principles in synthetic and real leaves. Royal Society Interface. 13, DOI: 10.1098/rsif.2016.0535
  • Type: Journal Articles Status: Published Year Published: 2016 Citation: Sperling, O., Secchi, F., Godfrey, J., Zwieniecki, M.A. 2017. Acclimation of Pistacia integerrima trees to frost in semi-arid environments depends on autumn's drought. Planta. DOI: 10.1007/s00425-016-2629-9
  • Type: Journal Articles Status: Published Year Published: 2016 Citation: Secchi, F., Pagliarani, C., Zwieniecki, M.A. 2016. The functional role of xylem parenchyma cells and aquaporins during recovery from severe water stress. Plant Cell and Environment. DOI:10.1111/pce.12831


Progress 10/01/14 to 09/30/15

Outputs
Target Audience:Targeted audience: Pistachio Research Board, Almond Board of California and Walnut Board of California. Growers, Farm advisors and Crop extension specialist with interests in nut crops Efforts included seminar presentation at Almond Conference in Sacramento, and Pistachio Day held in Visalia, as well as Walnut board meeting in Bodega Bay, Pistachio Board Meeting in Kern Station. In addtion I had have several meeting with growers and Farm advisors. Changes/Problems: Nothing Reported What opportunities for training and professional development has the project provided?Training and mentoring activities: Provide postdoc opportunity for Or Sperling - resulted in Or receiving tenure track position in Volcani Institute in Israel Provide postdoc opportunity for Aude Tixier - she is currently supported by Almond Board of California How have the results been disseminated to communities of interest?Presentation at major commodity group meetings: Pistachio Day in Visalia, Almond Meeting in Sacramento and Walnut Board Meeting in Bodega Bay What do you plan to do during the next reporting period to accomplish the goals? Nothing Reported

Impacts
What was accomplished under these goals? Introduction Currently, evaluating the physiological status of trees for guiding orchard management decisions are limited to analyses of tree water status, leaf nutrient levels, and visual observations. Until recently these methods were adequate and produced dramatic improvement in pistachio yields. However, as the climate becomes more erratic and the abiotic stresses more severe, these proven approaches may become less effective. Research effort described here focuses on the development of new approaches to measure trees physiological status that complement the currently used methods. Specifically we aim at understanding aspects of tree carbohydrate management in the context of dormancy, chilling requirements and yield performance. We also aim to develop simple protocols for determination of carbohydrate tree levels. Results and Practical Applications Our initial investigations of UCB1 rootstock freezing tolerance revealed an unusual physiological response to sudden frost events. As stem was exposed to near freezing temperatures, there was a simultaneous increase in stem respiration. This respiration decreased the stem's total carbohydrate reserves. While observed carbohydrate decrease was small at a diurnal scale, the repeated frost events could significantly reduce the stem's total carbohydrate reserves over entire winter. The negative effect of frost on carbohydrate reserves was magnified if it was followed by unusually warm days. The immediate effect of decreased stem carbohydrate storage would be premature and poor leaf-out and flowering following winters with multiple frost events, potentially followed by drop in excessive amount of blanks. Follow up study was focused on following seasonal carbohydrate management in mature trees ~20 years old (Figure 1). In this study we found a strong link between tree phenology and mobilization of stored carbohydrates (starch), as well as we were able to mechanistically link mobilization and relocation of carbohydrates along the thermal gradients in trees that form during day/night cycles (warm-crown/cold-roots during a day and cold-crown/warm-roots during the night). Specifically, we showed that sugar concentration in xylem sap of healthy pistachio scions depends on branch temperature. The results suggest that degradation of starch occurs below 54 F (increase in soluble carbohydrate content in xylem), while observed decrease in soluble carbohydrate concertation in xylem at temperatures above 54F suggests accumulation of starch in xylem parenchyma cells - thus 54F being carbohydrate management neutral temperature. This finding might provide mechanistic explanation of chilling requirements in pistachio trees. Practical application Carbohydrate balance of the tree is highly dependent on the thermal conditions of the environment. Late fall and early spring are crucial periods when priming of the tree for dormancy and bud-break occurs. If thermal conditions during these two periods are not met the yield potential of the trees might be reduced and application of management techniques with potential to influence either tree thermal conditions or carbohydrate management might be advised - this would include paints, reflective material, oils, etc.

Publications

  • Type: Journal Articles Status: Accepted Year Published: 2015 Citation: 1) Zwieniecki, M.A., Tixier, A., Sperling, O. 2015. Temperature assisted redistribution of carbohydrates in trees. American Journal of Botany 102:1216-1218 doi: 10.3732/ajb.1500218
  • Type: Journal Articles Status: Accepted Year Published: 2015 Citation: 1) Zwieniecki, M.A. Secchi, F. 2015. Threats to xylem hydraulic function of trees under `new climate normal' conditions. Plant Cell and Environment 38:1713-1724. DOI: 10.1111/pce.12412
  • Type: Journal Articles Status: Accepted Year Published: 2015 Citation: 1) Sperling, O., Earles, J.M., Secchi, F., Godfrey, J., Zwieniecki, M.A. 2015. Frost induces respiration and accelerates carbon depletion in trees. PLoS ONE 10(12): e0144124. doi:10.1371/journal.pone.0144124


Progress 02/18/14 to 09/30/14

Outputs
Target Audience: Pistachio, Almond, Walnut farmers, local (Central Valley CA) crop advisors, and extension specialists (meetings and personal discussions). Other Researchers studying tree crop physiology (Journal publications). Presentations at Annual Meeting of Ecological Society of America. Changes/Problems: Nothing Reported What opportunities for training and professional development has the project provided? Nothing Reported How have the results been disseminated to communities of interest? Via report and presentation at Pistachio Board Meeting What do you plan to do during the next reporting period to accomplish the goals? · Analysis of temperature monitoring in phloem and bark of commercial cultivated matured trees; preliminary data collected during winter of 2013-2014. This field research will establish the real-life dynamics of cooling and heating events occurring in the orchards and provide thermal information to guide future laboratory research. Field temperature monitoring is especially important as the climate proceeds to change. For pistachio cultivation warmer falls may postpone or inhibit dormancy and defoliation, increasing water uptake in late autumn and exposing the trees to severe frost hazards. · Understanding pre-chill biology to address the issue of tree memory of chill events (memory here is understood as time that protective compounds reside in parenchyma cells after the chill event) that would allow well-irrigated trees to withstand freezing events. This knowledge will not only result in practical recommendation for avoiding frost damage, but will enable laboratory simulation of the processes through the year making research progress much faster. If we can better characterize the physiology of cold acclimation, we can better determine the physiological activity of the chemical or irrigation treatments used for enhancing chilling, and therefore determine better application rates and timings. · Analysis of the diurnal and seasonal carbohydrate dynamics in pistachio stems and branches, including detailed information about enzymatic activity of selected enzymes from starch synthesis and degradation pathways in conjunction with evaluation of protein levels in shoots and branches. · Determination of carbohydrate transport and relocation in trees during winter, the period of preparation for dormancy breaking and during bud break and flowering including the effects on successful fruit set. · Introducing the factor of saline irrigation water to frost damage research. Irrigation solutes play a crucial role in water transport, osmotic imbalance, drought stress, and freezing point depression; all these processes are tightly associated with cold acclimation. As use of saline water is now common and its effects should be incorporated into cold damage research. · Further research concerning cell lipids, freezing related amino acid (proline), and additional pseudo-drought stress substances (e.g. abscisic acid) are also highly related to our research topic and would be included in future research. · Development of a model for tree carbohydrate analysis that includes tree thermal status and the associated enzymatic pathway activity to guide future research.

Impacts
What was accomplished under these goals? Unbudded 1 year old UCB1 pistachio rootstocks were demonstrated to be relatively resistant to freezing; surviving temperatures down to -5O C (23 F) even before entering dormancy. This resistance occurred only when no ice formed in the stem; a situation referred to as `super cooling protection'. Within the plant cells this super cooling is simultaneously accompanied by starch conversion to simpler sugars, the mono- and disaccharides, glucose and sucrose, and an accumulation of proline, a compound that acts as antifreeze. Tree water status had a small effect on super cooling properties,slightly shifting the temperature of ice formation in trees with stem water potential below -1MPa from -6O to -8 OC (21 to 17 F). Ice formation in trees not forced into dormancy, those still actively growing, had the capacity to cause damage, although damage was not imminent and level of damage strongly depended on plant water status (Fig. 1). Vigorous trees with stem water potentials above -0.5 MPa had almost 50% probability of significant damage to the xylem parenchyma and phloem with more than 30% of the cells rupturing as their contents froze. Damage dropped by half, to 25%, in trees with water potentials ranging from -0.5 to -1.0 MPa. Trees with water potentials below -1.0 MPa showed minimal damage. Practical application: Reducing irrigation to produce stem water potentials below -0.5 MPa before the time of historically recorded frosts, determined by incorporating recent temperature trends with real time temperature monitoring, will significantly decrease the probability of young tree freeze damage in the areas prone to fall frosts below -5OC (23 F).

Publications

  • Type: Journal Articles Status: Published Year Published: 2014 Citation: Zwieniecki, M.A., Boyce C.K. 2014. Evolution of a unique anatomical precision in angiosperm leaf venation lifts constraints on vascular plant ecology. Proceedings of the Royal Society B. 281: 1779 20132829 doi:10.1098/rspb.2013.2829
  • Type: Journal Articles Status: Published Year Published: 2014 Citation: Secchi, F., Zwieniecki M.A. 2014. Down-regulation of PIP1 aquaporin in poplar trees is detrimental to recovery from embolism. Plant Physiology 164:1789-1799 doi:10.1104/pp.114.237511
  • Type: Journal Articles Status: Published Year Published: 2014 Citation: Zwieniecki, M.A., Boyce C.K. 2014. The role of cellulose fibers in Gnetum gnemon leaf hydraulics. International Journal of Plant Science 175:1054-1061 DOI:10.1086/678089
  • Type: Journal Articles Status: Awaiting Publication Year Published: 2015 Citation: Zwieniecki, M.A. Secchi, F. 2015. Threats to xylem hydraulic function of trees under `new climate normal' conditions. Plant Cell and Environment (in press). DOI: 10.1111/pce.12412
  • Type: Journal Articles Status: Published Year Published: 2014 Citation: Neumann, R.B., Cardon, Z.G., Teshera-Levye, J., Rockwell, F.E., Zwieniecki, M.A., Holbrook N.M. 2014. Modeled hydraulic redistribution by sunflower (Helianthus annuus L.) matches observed data only after including nighttime transpiration. Plant, Cell & Environment 37:899-910
  • Type: Journal Articles Status: Published Year Published: 2014 Citation: Stroock, A,D., Pagay, V.V., Zwieniecki, M.A., Holbrook, N.M. 2014. The Physicochemical Hydrodynamics of Vascular Plants. Annual Review in Fluid Mechanics. 46:615-642
  • Type: Journal Articles Status: Published Year Published: 2014 Citation: Kelly, G., Sade, N., Attia, Z., Secchi, F., Zwieniecki M.A., Holbrook N.M., Levi, A., Alchanatis, V., Moshelion, M., Granot, D. (2014) Relationship between hexokinase and the aquaporin PIP1 in the regulation of photosynthesis and plant growth. PLoS ONE 9(2): e87888. doi:10.1371/journal.pone.0087888