Progress 06/01/20 to 05/31/23
Outputs
Target Audience:The primary target audience for this reporting period was: Horticultural Scientists and Practitioners Changes/Problems:
Nothing Reported
What opportunities for training and professional development has the project provided?Over the course of the project, training was provided for three postdoctoral scholars (one now tenure-track faculty, one now permanent federal staff scientist, one now a staff scientist at a non-profit), two summer undergraduate research students (still completing their education), 25 undergraduate students engaged in a plant biology course, and 40 practitioners in a workshop on plant water stress in commercial horticulture at an international conference. These opportunities led to conference presentations led by those trainees at American Society for Horticultural Science, International Society for Horticultural Science, the Society for Integrative and Comparative Biology and the Schmid College of Science and Technology summer undergraduate research conference. How have the results been disseminated to communities of interest?To date, the project has produced two peer-reviewed publications (Valverdi et al., 2022 Acta Hort.; Valverdi et al. 2023 Applications Plant Sci.) and two publications in revision (Valverdi et al.; Berry et al.). Conference presentations were made at the American Society for Horticultural Science, International Society for Horticultural Science, the Society for Integrative and Comparative Biology and the Schmid College of Science and Technology summer undergraduate research conference. A workshop was also organized at the International Society for Horticultural Science. In addition, a project focused on public engagement in science produced avocado anatomy posters distributed to the community-at-large. What do you plan to do during the next reporting period to accomplish the goals?
Nothing Reported
Impacts
What was accomplished under these goals?
Photosynthesis occurring in green stems of woody plants has the potential to increase plant growth and has long been recognized to offer advantages to plants bearing this trait. Avocados are rare among fruit trees in that they have green stems that may play important roles in plant water and carbon balances. Therefore, understanding the implications of green stem photosynthesis in avocado plants can inform our ability to select and breed new cultivars that maximize the benefit of this trait. This is especially important in a hotter and drier future that will challenge our ability to produce enough nutritious food. Our research has explored the potential for green stem photosynthesis to play a role in helping avocado trees tolerate drought. The key outcomes are as follows: A comparison of stem functional and structural traits in 10 different avocado cultivars growing in a common garden setting, including key commercial cultivars. The results include measures of stem hydraulic conductivity, stem photosynthesis, stem chlorophyll, wood density and leaf-to-stem area ratios, as well as measures of non-structural carbohydrates in the wood and bark. Such data can inform selective breeding of productive new drought-resistant cultivars. The development of best practices for the measurement of stem photosynthesis and respiration through a methods comparison. Making such methods available to the broader research community will facilitate better research into stem photosynthesis that will improve our understanding of the physiology of agricultural plants. Research on the relationship between stem photosynthesis and the movement of water through stems among key cultivars of avocado subject to irrigation and drought treatments. The results provide both foundational insights into the role of stem photosynthesis in plant function and have the potential to inform priorities for both selective breeding and management of existing cultivars. Key results from each objective of the project include the following: We compared different materials to exclude light from photosynthetically-active green stems to prevent stem CO2 exchange (i.e., photosynthesis), without affecting stem conductance to water vapor, surface temperature, and relative humidity, The experiment featured three materials: aluminum foil, paper?based wrap, and mineral?based paint. We studied stem CO2 exchange with and without the light exclusion treatments. All materials reduced PAR and stem CO2 exchange. However, some materials resulted in experimental artifacts. For example, aluminum foil reduced stem surface temperature and increased relative humidity. Among the methods tested, we found that mineral?based paint effectively reduced PAR without affecting stem surface temperature and relative humidity around the stem. We evaluated the variability in stem photosynthetic re-assimilation rate and associated stem functional and structural traits in branches of 10 different avocado cultivars growing in a common garden. Our results demonstrate that green stems of avocado plants recycle respired CO2 at rates that vary from 0.2 to 4.8 μmol m-2 s-1, which corresponds to re- assimilation of 12 to 96% of CO2 that would otherwise leave the branch. Cultivars had no significant differences in stem photosynthesis, water potential wood density or chlorophyll content. However, there was a significant difference in hydraulic conductivity per unit leaf area and per unit stem area, which indicates greater variability in the capacity of stems to supply water to the leaves. Stem photosynthesis was not correlated with either hydraulic conductivity, but there was a significant relationship between wood and bark non-structural carbohydrate concentrations, supporting the movement of sugars between these two plant tissues. We investigated how stem photosynthesis in avocados affects drought tolerance and drought recovery by providing additional sugars that could affect plant water relations. We applied a light exclusion and water limitation to 3-year-old potted trees of the cultivars 'Hass' and 'Fuerte.' Green stems of avocado re-assimilate some CO2, but mean values between the 'Fuerte' (0.64 µmol m-2 s-1) and 'Hass' (0.58 µmol m-2 s-1) cultivars did not significantly differ. In addition, we found that light exclusion treatments reduced stem photosynthesis by 65% (0.57 µmol m-2 s-1) in 'Fuerte' and 30% (0.32 µmol m-2 s-1) in 'Hass.' The drought treatment reduced stem re-assimilation by 60% compared to well-watered controls. During recovery from drought, there were no treatment, nor cultivar effects on stem photosynthesis. There was higher hydraulic conductivity in 'Hass' (84.7 mg mm-1KPa-1 s-1) than 'Fuerte' (50.6 mg mm-1KPa-1 s-1) during all three phases of treatment. Our results also showed no effect of light treatment on hydraulic conductivity during initial, dry and recovery phases meaning that there is no clear effect of stem photosynthesis on the drought tolerance of avocado trees. The contribution of carbon gain through stem photosynthesis may not play a significant role in hydraulic functioning.
Publications
- Type:
Journal Articles
Status:
Published
Year Published:
2023
Citation:
Valverdi, N., C. Acosta, G. Dauber, G.R. Goldsmith, & E. �vila-Lovera. 2023. A comparison of methods for excluding light from stems to evaluate stem photosynthesis. Applications in Plants Sciences e11542.
- Type:
Journal Articles
Status:
Under Review
Year Published:
2023
Citation:
Valverdi, N.A., P. Guzman-Delgado, G.R. Goldsmith, & E. �vila-Lovera. In Review Does green stem photosynthesis affect plant drought tolerance and recovery in avocado?
- Type:
Conference Papers and Presentations
Status:
Published
Year Published:
2022
Citation:
Valverdi, N.A., P. Guzman-Delgado, C. Acosta, G.R. Dauber, K.B. Cooper, G.R. Goldsmith & E.A. Avila-Lovera. 2022. Is green stem photosynthesis in avocado related to plant hydraulics? Annual Meeting of the International Society for Horticultural Science.
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Progress 06/01/21 to 05/31/22
Outputs
Target Audience:The target audiences and associated efforts during the current reporting period included the following: Dr. Valverdi developed a poster and presented results to >150 scientists who attended the 8th Annual Southwest Regional Meeting of Organismal Biologists (Chapman University, Orange, CA). The meeting provided the opportunity for Dr. Nadia A. Valverdi to present preliminary data from one of the research projects focused on a survey among avocado cultivars to study variability of stem traits, especially stem photosynthesis and hydraulic conductivity, as well as the importance of this diversity for developing new cultivars in the light of global change. Dr. Valverdi also presented a summary of the research and results during an oral presentation at the Schmid College Science Forum (Chapman University, Orange, CA), which gives the opportunity for researchers to present their latest research to the campus community. The presentation had an audience of >20 people including faculty, staff and students. Dr. Valverdi continues to participate in regular meetings of the California Avocado Commission, strengthening the ties between the academic community and industry partners. Dr. Valverdi was also invited to present her research to students in Biology 301 Laboratory - Plant Biology at Schmid College, who were learning about plant hydraulics and leaf traits. The class was composed of 25 students; the students who take the class are primarily biology and environmental studies majors. A workshop proposal entitled "Why is regulated water stress not widely used in commercial horticulture?" was conducted at the Adaptation of Horticultural Plants to Abiotic Stresses Symposium occurring during International Horticultural Congress in August 2022. Drs. Nadia A. Valverdi, Eleinis Ávila-Lovera and Giverson Mupambi were moderators and Bernardita Sallato, Washington State University Extension specialist, served as representative for the Pacific Northwest fruit industry in a panel discussion targeted to an audience between 25-50 scientists. Changes/Problems:
Nothing Reported
What opportunities for training and professional development has the project provided?The project has provided training for a postdoctoral research associate (Dr. Nadia Valverdi) who has a background in fruit tree physiology and is receiving additional training in mechanistic plant physiology, project management skills, statistical analysis and writing. The postdoctoral research associate has attended three scientific conferences and one workshop on mentorship offered at Chapman University using curriculum fromthe Center for the Improvement of Mentored Experiences in Research. The work of the postdoctoral research associate is guided by an individual development plan created in collaboration with the PD (Goldsmith). The postdoctoral research associate has recently received an offer for a permanent position in applied agricultural science. The project has also provided training opportunities in the field of ecophysiology for two undergraduate students. The students have learned how to collect and process data on important plant physiological traits, such as taking measurements of stem carbon gain and stem water transport efficiency. In addition, students were able to practice their oral and written communication skills in service of public outreach/engagement. Students take part in weekly lab meetings. How have the results been disseminated to communities of interest?Results from the project have been presented at three scientific conferences, one published paper, twomanuscriptsin review, and two manuscripts in preparation. In addition, Dr. Valverdi presented a summary of the research and results during an oral presentation at the Schmid College Science Forum (Chapman University, Orange, CA), which gives the opportunity for researchers to present their latest research to the campus community. The presentation had an audience of >20 people including faculty, staff and students. Dr. Valverdi continues to participate in regular meetings of the California Avocado Commission, strengthening the ties between the academic community and industry partners.Dr. Valverdi was also invited to present her research to students in Biology 301 Laboratory - Plant Biology at Schmid College, who were learning about plant hydraulics and leaf traits. The class was composed of 25 students; the students who take the class are primarily biology and environmental studies majors. Finally, aworkshop proposal entitled "Why is regulated water stress not widely used in commercial horticulture?" wasconducted at the Adaptation of Horticultural Plants to Abiotic Stresses Symposium occurring during International Horticultural Congress in August of 2022. Drs. Nadia A. Valverdi, Eleinis Ávila-Lovera and Giverson Mupambi were moderators and Bernardita Sallato, Washington State University Extension specialist, served as representative for the Pacific Northwest fruit industry in a panel discussion targeted to an audience between 25-50 scientists. What do you plan to do during the next reporting period to accomplish the goals?We will complete the submission of two additional manuscripts in preparation, as well as make public the associated data. We also plan to write a commentary on the effects of managed drought on agricultural productivity. Finally, we will continue to disseminate results to broader audiences as appropriate.
Impacts
What was accomplished under these goals?
Photosynthesis occurring in green stems of woody plants has the potential to increase plant growth and has long been recognized to offer advantages to plants bearing this trait. However, most of the research on stem photosynthesis has been carried out within the native ecosystems of the plants, while few studies have examined it in the context of agricultural production. Avocados are rare among fruit trees in that they have green stems that may play important roles in plant water and carbon balances. Therefore, understanding the implications of green stem photosynthesis in avocado plants can inform our ability to select and breed new cultivars that maximize the benefit of this trait. This is especially important in a hotter and drier future that will challenge our ability to produce enough nutritious food. Our research has explored the potential for green stem photosynthesis to play a role in helping trees tolerate drought. Our results show that stem photosynthesis is relatively small and therefore may assist in overall growth (5-10% of total carbon taken up), but is unlikely to assist in helping trees when there is a shortage of water. In fact, avocado stems are particularly vulnerable to sunburn when grown in high light environments and this trait may be disadvantageous for their long-term health in commercial settings. Our results help understand avocado tree structure and function and will inform breeding efforts in the context of a rapidly changing climate. We have completed the following activities in the second year with respect to Objective 1: -Data analysis and manuscript submission describing the ecophysiological variation among 10 avocado cultivars growing in a common garden (Valverdi et al.In ReviewActa Horticulturae).The accompanying dataset has been lodged at the Dryad Data Repository awaiting final publication of the manuscript.We found limited variation in the traits surveyed, suggesting that the current cultivars may all be similarlyvulnerable to global climate change. -Data analysis and manuscript submission describing variation in leaf and stem gas exchange in response to variation in light quality, as well as exploration of the mechanisms governing the observed variation (Berry et al.In ReviewPlant Physiology). We found that photosynthesis varied predictably with an increasing amount of diffuse light, providing critical insights into how changes in direct/diffuse light (i.e., cloudiness) may affect avocado tree function in the future. -Data analysis and drafting of a manuscript describing novel methods for excluding light from green stems. Such methods are critical for experiments testing the impacts of green stems of plant gas exchange through stem photosynthesis (Valverdi et al.In Preparation). By comparing key methods, we identified a novel approach to acheiving stem light exclusion with minimal experimental artifacts that can be adopted by the community as a whole. We have completed the following activities in the second year with respect to Objective 1: -Data analysis and drafting of a manuscript describing the combined effects of stem light exclusion and drought on avocado function (Valverdi et al.In Preparation). We found a distinct relationship between the rate of water flow through stems and the amount of sugars in the stems, suggesting that the relocation of recently formed sugars can help rescue trees from drought stress.
Publications
- Type:
Conference Papers and Presentations
Status:
Under Review
Year Published:
2022
Citation:
Valverdi, N.A., Guzman-Delgado, P., Acosta C., Dauber, G.R., Goldsmith, G.R., Avila-Lovera, E. Is avocado green stem photosynthesis related to plant hydraulics? Acta Horticulturae (In Review).
- Type:
Journal Articles
Status:
Under Review
Year Published:
2022
Citation:
Berry, Z.C., �vila-Lovera, E., Ellertson K., Goldsmith, G.R. Increased conductance associated with higher photosynthesis in leaves and green stems of avocado exposed to diffuse light. Plant Physiology (In Review).
- Type:
Conference Papers and Presentations
Status:
Published
Year Published:
2022
Citation:
Valverdi, N.A., G.R. Goldsmith & E.A. Avila-Lovera. 2022. The role of green stem photosynthesis in drought tolerance and recovery. Annual Meeting of the American Society for Horticultural Science.
- Type:
Conference Papers and Presentations
Status:
Published
Year Published:
2021
Citation:
Valverdi, N.A., C. Acosta*, G.R. Dauber*, E.A. Avila-Lovera, & G.R. Goldsmith. 2021. Photosynthesis in green stems and its contribution to plant hydraulic function. 8th Annual Southwestern Meeting of the Society of Integrative and Comparative Biology.
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Progress 06/01/20 to 05/31/21
Outputs
Target Audience:The target audiences during the current reporting period include students, faculty and staff in the Schmid College of Science and Technology at Chapman University, who attended the summer student research showcase. The showcase provided the opportunity for two undergraduate students (Cami Acosta and Gabriella Dauber) to present their summer research project, which was focused on developing an outreach/engagement product on the diversity of avocado cultivars and the importance of this diversity for developing new cultivars in the light of global change. The students developed a 'fine art' poster and accompanying handout; they distributed these materials to the ca. 75 individuals in attendance and solicited feedback in anticipation of handing out these materials this fall at the local farmer's market. Changes/Problems:Due to COVID-19, we delayed the beginning of field data collection by one year and carried out only a small pilot project in summer 2020 in order to ensure the safety of all involved. We also changed the number of cultivars for our ecophysiological survey from 24 to 10 to make sure we have enough time to fulfill the two objectives we set out in the proposal. Despite these changes, we are continuing our efforts in advancing the project. We have completed all the activities related to objective one and have initiated activities pertaining to objective two. This indicates that we will be able to complete the project by June 2022. However, we anticipate requesting a one year, no-cost extension in order to complete the project. We have been in consistent contact with the sponsored projects office to apprise them of our progress and to facilitate communications with USDA-NIFA where appropriate.? What opportunities for training and professional development has the project provided?The project has provided training for a postdoctoral research associate who has a background in fruit tree physiology and is receiving additional training in mechanistic plant physiology, project management skills, statistical analysis and writing. The work of the postdoctoral research associate is guided by an individual development plan created in collaboration with the PD (Goldsmith). The project has also provided training opportunities in the field of ecophysiology for three undergraduate students (Kendra Ellertson, Cami Acosta and Gabriella Dauber). The students have learned how to collect and process data on important physiological aspects of plants, such as taking measurements of stem carbon gain and stem water transport efficiency. In addition, students were able to practice their oral and written communication skills in service of public outreach/engagement. All students take part in weekly lab meetings. How have the results been disseminated to communities of interest?A review paper establishing what is known about the properties of bark in relation to stem photosynthesis was recently published. The results of the ecophysiological survey have not yet been disseminated to the communities of interest. A preliminary outreach and engagement project focused on the reasons for the project and its import was recently piloted at a summer undergraduate research showcase. What do you plan to do during the next reporting period to accomplish the goals?We will work on completing the data collection, analysis and dissemination of results related to the greenhouse experiment, as well as disseminating the results from the ecophysiological survey.
Impacts
What was accomplished under these goals?
The long-term goal of this project is to model how stem photosynthesis contributes to drought tolerance in plants from various habitats. In this project we aim to 1) determine variability in stem photosynthetic rate and water-use efficiency, and 2) determine the role of stem photosynthesis in hydraulic functioning. For objective one, we have completed: -A greenhouse study assessing the effects of direct versus diffuse light on leaf and stem photosynthetic rates. -The eco-physiological survey data collection for ten avocados cultivars growing in a common garden at South Coast Research and Extension Center (SCREC), Irvine, CA. -An intra-cultivar evaluation of Hass growing in the same common garden at SCREC. For objective two, we have completed: -A pilot light-exclusion experiment to find the best material to exclude light from the stems in the greenhouse experiment (aluminum foil, tree wrap paper and organic plant guard). -Setup of light-exclusion greenhouse experiment, with trees currently acclimating to three conditions: control, 100% and 50% of stem light exclusion treatments. We carried out a small project measuring the effects of direct versus diffuse (e.g. cloudy) light on leaf and stem photosynthetic rates. This pilot project allowed us to determine the magnitude of photosynthesis and respiration in stems, while also providing evidence for differences in the magnitude of photosynthesis depending on directional light quality.? We have collected data on stem photosynthetic rate (Astem), midday stem water potential, stem hydraulic conductivity, wood density, and chlorophyll a, b and a+b concentrations for the survey of objective one. We also measured the same traits in the intra-cultivar evaluation of Hass. Finally, we collected light, stem surface temperature and Astem in the pilot light-exclusion experiment during three weeks of experimentation. One-way ANOVA showed that there are no significant differences in midday stem water potential, wood density, chlorophyll a+b, and stem hydraulic conductivity among the 10 avocados cultivars of the eco-physiological survey. Similarly, no differences were found among individual trees of Hass. For the pilot light-exclusion experiment we compared light transmission using (aluminum foil, tree wrap paper and organic plant guard and found that the aluminum foil reduced light to 0.1% of full sun intensity, paint reduced light to 3.2%, and paper to 3.3%. Given the easier application and still high light exclusion of the paint, we chose the paint as the material to be used for the greenhouse experiment.
Publications
- Type:
Journal Articles
Status:
Published
Year Published:
2021
Citation:
Berry Z.C., �vila-Lovera E., De Guzman M.E., OKeefe K., Emery N.C. (2021) Beneath the bark: assessing woody stem water and carbon fluxes and its prevalence across climates and he woody plant phylogeny. Frontiers in Forests and Global Change4:675299. doi: 10.3389/ffgc.2021.675299
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