Source: UNIVERSITY OF FLORIDA submitted to NRP
RESPONSES OF SUBTROPICAL AND TROPICAL FRUIT TREES TO FLOODING STRESS
Sponsoring Institution
National Institute of Food and Agriculture
Project Status
COMPLETE
Funding Source
HATCH
Reporting Frequency
Annual
Accession No.
0232717
Grant No.
(N/A)
Cumulative Award Amt.
(N/A)
Proposal No.
(N/A)
Multistate No.
(N/A)
Project Start Date
Mar 1, 2013
Project End Date
Sep 30, 2017
Grant Year
(N/A)
Program Code
[(N/A)]- (N/A)
Recipient Organization
UNIVERSITY OF FLORIDA
G022 MCCARTY HALL
GAINESVILLE,FL 32611
Performing Department
Tropical Research and Education Center, Homestead
Non Technical Summary
In many regions of the world, including southern Florida, productivity of subtropical and tropical fruit trees are negatively impacted by low soil oxygen content as a result of flooding or poor soil drainage. Additionally, increasing occurrences of catastrophic weather events such as tropical storms or hurricanes as a result of global climate change are expected to increase the potential for severe periodic flooding throughout the world. Since the 1950s, the water table in southern Florida has been lowered by a system of canals built to provide flood protection to the adjacent urban and agricultural areas, resulting in a negative impacting to the natural ecosystem. To revitalize the flora and fauna of the Everglades ecosystem, the most costly wetland restoration project in history is underway to restore the Everglades hydrology as close as possible to the natural conditions. This will undoubtedly have an impact on crops growing adjacent to this natural ecosystem, particular subtropical and tropical fruit crops, which are perennial, compared to vegetable crops that are annual and generally not planted during the rainy season. The project will improve our understanding of the effects of flooding on the physiology of subtropical and tropical fruit crops and will aid in the selection of species or cultivars adapted to flooded or poorly drained soil. Additionally, this project will help identify methods to mitigate the effects of flooding on flood-prone subtropical and tropical fruit trees. This information will be beneficial for southern Florida and other areas of the world were subtropical and tropical fruit trees are subjected to flooding or poor soil drainage.
Animal Health Component
(N/A)
Research Effort Categories
Basic
(N/A)
Applied
(N/A)
Developmental
(N/A)
Classification

Knowledge Area (KA)Subject of Investigation (SOI)Field of Science (FOS)Percent
1021030102010%
1021099102020%
1021099106020%
2031030102010%
2031099102020%
2031099106020%
Knowledge Area
102 - Soil, Plant, Water, Nutrient Relationships; 203 - Plant Biological Efficiency and Abiotic Stresses Affecting Plants;

Subject Of Investigation
1099 - Tropical/subtropical fruit, general/other; 1030 - Papaya;

Field Of Science
1060 - Biology (whole systems); 1020 - Physiology;
Goals / Objectives
1. To determine the effects of short-term and cyclical flooding on physiology and growth of selected subtropical and tropical fruit crops grown commercially in south Florida. 2. To investigate horticultural methods to improve flood tolerance of subtropical and tropical fruit crops grown commercially in south Florida.
Project Methods
The effects of flooding on physiology and growth of subtropical and tropical fruit crops will be assessed to provide a framework for identifying or managing these crops to tolerate periodic flooding. Grafted and seedling trees will be grown in either potting media (to reflect nursery conditions) or Krome very gravelly loam soil (to reflect field conditions in south Florida) in containers in a glasshouse under constant day/night temperatures. It has been previously observed that potted plants in native south Florida soil respond similarly to flooding as young plants in the field. Trees will be divided into the following flooding treatments: 1) continuously flooded; 2) cyclically flooded (flooded and unflooded in repeated cycles); and 3) nonflooded (control). The length of the flooding period will vary according to the crop species being tested. For some species, the cyclical flooding treatment may be excluded, depending on their sensitivity to a single flooding cycle. Experiments will also be conducted to determine the effects of different simulated water-table heights on physiology, growth and survival of various subtropical and tropical fruit crops. Treatments will consist of a varying percentages (depths) of roots flooded by submerging plant pots in plastic buckets filled with water to varying levels below the soil surface. In each experiment, the physio-chemical properties of the soil and physiological condition of the plants will be determined before, and at periodic intervals during and after the flooding and drought stress period. Soil measurements will include pH, soil redox potential of the soil solution and soil temperature. Whole-plant physiological measurements will include: leaf gas exchange, chlorophyll fluorescence, leaf chlorophyll content, and xylem sap flow. Biochemical measurements will include measurement of alcohol dehydrogenase (ADH) activity in the roots and measurements of reactive oxygen species (ROS) such as hydrogen peroxide and superoxide. Biomass of plant organs will also be determined at the end of each experiment. Additional experiments will be conducted to determine the potential for improving flooding tolerance of subtropical and tropical fruit crops grown commercially in south Florida through horticultural manipulation. For some crops, the relative flood tolerance of different rootstock/scion combinations will be compared. For some scion/rootstock combinations of specific crop species, the effects of altering the shoot/root ratio by pruning of the canopy and determining the effectiveness time of pruning relative to the time of root submergence.

Progress 03/01/13 to 09/30/17

Outputs
Target Audience:The target audience was researchers, university research and extension faculty, and the agricultural community. Changes/Problems: Nothing Reported What opportunities for training and professional development has the project provided?This project trained several graduate students and a post doctoral associate. How have the results been disseminated to communities of interest?The results of this project were disseminated though research and extension publications and presentions. What do you plan to do during the next reporting period to accomplish the goals? Nothing Reported

Impacts
What was accomplished under these goals? Effect of root zone hypoxia and solid oxygen fertilizers on soil redox potential, leaf gas exchange (net CO2 assimilation, stomatal conductance and transpiration), and root alcohol dehydrogenase (ADH) activity were assessed. Different concentrations of fast-release or slow-release oxygen fertilizers for mitigating flooding stress in papaya were examined in order to improve papaya production in flood-prone areas. Papaya is very sensitive to flooding (both seedlings and larger plants). Larger plants were able to recover from short-term (2-3 days) of flooding of all or ~75% of roots after plants were unflooded. Papaya seedlings in Krome very gravelly loam soil (native to south Florida) did not recover from 100% root submergence without solid oxygen fertilizer added to the soil. However, adding oxygen fertilizer to Krome very gravelly loam soil slightly hastened recovery of papaya from flooding stress. Thus, adding solid oxygen fertilizer to Krome very gravelly loam soil has the potential to help young papaya plants recover from short-term flooding. Experiments were conducted with avocado to determine methods to alleviate flooding stress by removal of all or a portion of the canopy prior or immediately after a flooding event. Results showed that pruning (removal of 1/2 to 2/3 of the canopy) immediately after a flooding event improves survival and recovery of avocado tress. This was due to restoring the root:shoot balance and thereby reducing stress caused by water lost to traspiration which was higher than root uptake due to root damage in flooded avocado trees flooding. However, pruning immediately after flooding exacerbates flooding stress. This was due to a reduction of photosynthesis, thereby reducing carbohydrates as a substrate for root respiration during flooding. Experiments with papaya in the field and greenhouse confirmed that papaya is able to quickly adapt to drought stress and light stress. Also, papaya shows a short-term but no long-term physiological response to water deficit priming. Studies using sunn hemp as an intercrop for papaya showed that sunn hemp can reduce wind stress of papaya, but does not negatively affect light absorption or physiological variables in papaya. Also, mowing the sunn hemp intercrop and using it as a mulch for papaya can increase papaya crop growth.

Publications

  • Type: Journal Articles Status: Accepted Year Published: 2017 Citation: 1. Vincent, C., B. Schaffer, D.L. Rowland, K.W. Migliaccio, J.H. Crane, and Y. Li. 2017. Sunn hemp intercrop and mulch increases papaya growth and reduces wind speed and virus damage. Scientia Horticulturae (in press).
  • Type: Journal Articles Status: Accepted Year Published: 2017 Citation: 2. Sarkhosh, A., A.I. Vargas, B. Schaffer, A.J. Palmateer, P. Lopez, A. Soleymani and M. Farzaneh. 2017. Postharvest management of anthracnose affecting stored avocado (Persea americana Mill.) fruit with plant-extracted essential oils. Food Packaging and Shelf Life (in press).
  • Type: Journal Articles Status: Accepted Year Published: 2017 Citation: Vincent, C., D.L. Rowland and B. Schaffer. 2017. Primed acclimation of papaya increases short-term water use but does not confer long-term drought tolerance. HortScience (in press).
  • Type: Journal Articles Status: Accepted Year Published: 2017 Citation: 4. Pe�anha, A.L., J. Rangel da Silva, W. Pereira Rodrigues, T. Massi Ferraz, A. Torres Netto, R.S. Nunes Lima, T. Silva Lopes, T. Rangel da Silva, B. Schaffer, and E. Campostrini. 2017. Leaf gas exchange and growth of two papaya (Carica papaya L.) genotypes are affected by elevated electrical conductivity of the nutrient solution. Scientia Horticulturae (in press).
  • Type: Journal Articles Status: Published Year Published: 2014 Citation: Sanclemente, M.A., B. Schaffer, P.M. Gil, A.I. Vargas and F.S. Davies. 2014. Pruning after flooding hastens recovery of flood-stressed avocado (Persea americana Mill.) trees. Scientia Horticulturae 169:27-35.
  • Type: Journal Articles Status: Published Year Published: 2013 Citation: 17. Sanclamente, M.A., B. Schaffer, P.M. Gil, J.H. Crane and F.S. Davies 2013. Leaf removal before flooding influences recovery of avocado (Persea americana Mill.) trees from flooding stress. Scientia Horticulturae 150:154-163.
  • Type: Books Status: Published Year Published: 2013 Citation: . B. Schaffer, B.N. Wolstenholme and A.W. Whiley (eds.). 2013. Avocado: Botany Production and Uses, 2nd Edition. CAB International Press, Wallingford, U.K. 560 pp.
  • Type: Journal Articles Status: Accepted Year Published: 2017 Citation: 5. Ploetz, R.C., M.A. Hughes, P.E. Kendra, S.W. Fraedrich, D. Carillo, L.L. Stelinski, J. Hulcr, A.E. Mayfield III, T.L. Dreaden, J.H. Crane, E.A. Evans, B. Schaffer, J. Rollins. 2017. Recovery plan for laurel wilt of avocado, caused by Raffaelea lauricola. Plant Health Progress (in press).
  • Type: Journal Articles Status: Accepted Year Published: 2017 Citation: 6. Vincent, C.V., D.L. Rowland, C. Na and B. Schaffer. 2016. A high-throughput method to quantify root hair area in digital images taken in situ. Plant and Soil (published online, awaiting publication in journal), doi:10.1007/s11104-016-3016-9.
  • Type: Journal Articles Status: Published Year Published: 2016 Citation: 7. Thani, A.W., B. Schaffer, G. Liu, A.I. Vargas and J.H. Crane. 2016. Chemical oxygen fertilization reduces stress and increases recovery and survivial of flooded papaya (Carica papaya L.) plants. Scientia Horticulturae 202:173-181.
  • Type: Journal Articles Status: Published Year Published: 2015 Citation: 9. Vincent, C.I., D.L. Rowland and B. Schaffer. 2015. The potential for primed acclimation in papaya (Carica papaya L.): determination of critical water deficit thresholds and physiological response variables. Scientia Horticulturae 194:344-352.
  • Type: Journal Articles Status: Published Year Published: 2015 Citation: 10. Ploetz, R.C., B. Schaffer, A.I. Vargas, J.L. Konkol, J. Salvatierra and R. Wideman. 2015. Impact of laurel wilt, caused by Raffaela lauricola, on leaf gas exchange and xylem sap flow of avocado, Persea americana. Phytophathology 105:433-440
  • Type: Journal Articles Status: Published Year Published: 2014 Citation: Gil, P.M., J. Saavedra, B. Schaffer, R. Navarro, C. Fuentealba and F. Minoletti. 2014. Quantifying effects of irrigation and soil water content on electrical potentials in grapevines (Vitis vinifera) using multivariate statistical methods. Scientia Hortiulturae 173:71-78.
  • Type: Book Chapters Status: Published Year Published: 2013 Citation: 2. Schaffer, B., P.M. Gil, M. Mickelbart and A.W. Whiley. 2013. Ecophysiology. In: Avocado: Botany Production and Uses, 2nd Edition. B. Schaffer, B.N. Wolstenholme and A.W. Whiley (eds.). CAB International Press, Wallingford, U.K. pp. 168-199.


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

Outputs
Target Audience:The targeted audience was agricultural and biological researchers, university research and extension faculty and the agricultural community. Changes/Problems: Nothing Reported What opportunities for training and professional development has the project provided?Two graduate students earned M.S. degrees working on these projects. How have the results been disseminated to communities of interest?Through extension presentations and research and extension publications. What do you plan to do during the next reporting period to accomplish the goals? Nothing Reported

Impacts
What was accomplished under these goals? We identified the physiological effects of flooding on several tropical and subtropical fruit crops including avocado and papaya and methods to mitigate flooding stress. Flooding stress of avocado can be reduced by pruning immediately after flooding, therefore re-balancing the root:shoot ratio. Flooding stress of papaya may be reduced by application of solid oxygen fertilizers, such as calcium peroxide, to the soil prior to flooding.

Publications

  • Type: Journal Articles Status: Accepted Year Published: 2017 Citation: Vincent, C., B. Schaffer, D.L. Rowland, K.W. Migliaccio, J.H. Crane, and Y. Li. 2017. Sunn hemp intercrop and mulch increases papaya growth and reduces wind speed and virus damage. Scientia Horticulturae (in press).
  • Type: Journal Articles Status: Accepted Year Published: 2017 Citation: Vincent, C., D.L. Rowland and B. Schaffer. 2017. Primed acclimation of papaya increases short-term water use but does not confer long-term drought tolerance. HortScience (in press).
  • Type: Journal Articles Status: Accepted Year Published: 2017 Citation: 3. Ploetz, R.C., M.A. Hughes, P.E. Kendra, S.W. Fraedrich, D. Carillo, L.L. Stelinski, J. Hulcr, A.E. Mayfield III, T.L. Dreaden, J.H. Crane, E.A. Evans, B. Schaffer, J. Rollins. 2017. Recovery plan for laurel wilt of avocado, caused by Raffaelea lauricola. Plant Health Progress (in press).
  • Type: Journal Articles Status: Accepted Year Published: 2017 Citation: Vincent, C.V., D.L. Rowland, C. Na and B. Schaffer. 2016. A high-throughput method to quantify root hair area in digital images taken in situ. Plant and Soil (published online, awaiting publication in journal), doi:10.1007/s11104-016-3016-9.
  • Type: Journal Articles Status: Accepted Year Published: 2017 Citation: Sarkhosh, A., A.I. Vargas, B. Schaffer, A.J. Palmateer, P. Lopez, A. Soleymani and M. Farzaneh. 2017. Postharvest management of anthracnose affecting stored avocado (Persea americana Mill.) fruit with plant-extracted essential oils. Food Packaging and Shelf Life (in press).
  • Type: Journal Articles Status: Accepted Year Published: 2017 Citation: 1. Pe�anha, A.L., J. Rangel da Silva, W. Pereira Rodrigues, T. Massi Ferraz, A. Torres Netto, R.S. Nunes Lima, T. Silva Lopes, T. Rangel da Silva, B. Schaffer, and E. Campostrini. 2017. Leaf gas exchange and growth of two papaya (Carica papaya L.) genotypes are affected by elevated electrical conductivity of the nutrient solution. Scientia Horticulturae (in press).
  • Type: Journal Articles Status: Published Year Published: 2016 Citation: 4. Thani, A.W., B. Schaffer, G. Liu, A.I. Vargas and J.H. Crane. 2016. Chemical oxygen fertilization reduces stress and increases recovery and survivial of flooded papaya (Carica papaya L.) plants. Scientia Horticulturae 202:173-181.
  • Type: Journal Articles Status: Published Year Published: 2015 Citation: 7. Vincent, C.I., D.L. Rowland and B. Schaffer. 2015. The potential for primed acclimation in papaya (Carica papaya L.): determination of critical water deficit thresholds and physiological response variables. Scientia Horticulturae 194:344-352.
  • Type: Journal Articles Status: Published Year Published: 2015 Citation: 8. Ploetz, R.C., B. Schaffer, A.I. Vargas, J.L. Konkol, J. Salvatierra and R. Wideman. 2015. Impact of laurel wilt, caused by Raffaela lauricola, on leaf gas exchange and xylem sap flow of avocado, Persea americana. Phytophathology 105:433-440


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

Outputs
Target Audience:Researchers, extension workers and growers of subtropical and tropical fruit crops. Changes/Problems: Nothing Reported What opportunities for training and professional development has the project provided?A graduate student earned his M.S. degree in Horticultural Sciences working on this project. How have the results been disseminated to communities of interest?The results were published in an M.S. thesis, and submitted to a refereed journal and a proceedings for publications. A seminar about the project was given to the University of Florida faculty, staff and subtropical and tropical fruit growers. What do you plan to do during the next reporting period to accomplish the goals? Nothing Reported

Impacts
What was accomplished under these goals? Experiments were conducted at the Tropical Research and Education Center in Homestead, FL during spring 2015, summer 2015 and fall 2015. Effect of root zone hypoxia and solid oxygen fertilizers on soil redox potential, leaf gas exchange (net CO2 assimilation, stomatal conductance and transpiration), and root alcohol dehydrogenase (ADH) activity were assessed. Different concentrations of fast-release or slow-release oxygen fertilizers for mitigating flooding stress in papaya were examined in order to improve papaya production in flood-prone areas. Papaya is very sensitive to flooding (both seedlings and larger plants). Larger plants were able to recover from short-term (2-3 days) of flooding of all or ~75% of roots after plants were unflooded. Papaya seedlings in Krome very gravelly loam soil (native to south Florida) did not recover from 100% root submergence without solid oxygen fertilizer added to the soil. However, adding oxygen fertilizer to Krome very gravelly loam soil slightly hastened recovery of papaya from flooding stress. Thus, adding solid oxygen fertilizer to Krome very gravelly loam soil has the potential to help young papaya plants recover from short-term flooding.

Publications

  • Type: Theses/Dissertations Status: Accepted Year Published: 2016 Citation: Thani, Q. 2016. EFFECTS OF FLOODING AND OXYGEN FERTILIZATION ON PHYSIOLOGY, GROWTH, SURVIVAL, AND RECOVERY OF PAPAYA (Carica papaya L.). MS Thesis, University of Florida
  • Type: Journal Articles Status: Submitted Year Published: 2016 Citation: Thani, Q., B. Schaffera, G. Liu, A.I. Vargas, J.H. Crane. 2016. Chemical oxygen fertilization reduces stress and increases recovery and survival of flooded papaya (Carica papaya L.) plants. Scientia Hort. (submitted).


Progress 10/01/13 to 09/30/14

Outputs
Target Audience: Agricultural and Biological Research Scientistists, Extension Workers, Subtropical and Tropical Fruit Growers Changes/Problems: Nothing Reported What opportunities for training and professional development has the project provided? A graduate (MS) student's thesis research is focused on this project. A Biological Scientist and Visiting International Scholar were trained under this project. How have the results been disseminated to communities of interest? Presentations at scientific meetings, refereed journal articles and publised abstracts. What do you plan to do during the next reporting period to accomplish the goals? Continue conducting research on the effects of flooding on physiology and development of subtropical and tropical fruit crops and methods to mitigate flood stress of these crops.

Impacts
What was accomplished under these goals? Two experiments (Expts.1 and 2)were conducted at different times with avocado (Persea americana Mill. cv. Choquette) trees in containers to test the effects of leaf pruning immediately after removing trees from short-term floodingon tree recovery. Trees in each experimentwere divided intotwo flooding treatments: (1) flooded, or (2) non-flooded. Trees in each flooding treatment were divided into two pruning treatments: (1) pruned; approximately two-thirds of the canopy removed by pruning immediately after trees were removed from flooding (unflooded), or (2) non-pruned. In each experiment, net CO2 assimilation (A), stomatal conductance of water vapor (gs), transpiration (E), water use efficiency (WUE, calculated as A/E) and xylem sap flow (in Expt. 2) were determined daily during the flooding period and periodically after trees were unflooded until harvest time in each flooding/pruning treatment. Tissue dry weightswere determined for trees in all treatments at the end of the experiment (several weeks after trees were unflooded). Net CO2 assimilation, gs, E and WUE of flooded trees decreased after 2 and 5 days and trees were unflooded after 3 and 6 days in Expts. 1 and 2, respectively. After trees were unflooded, A, gs, E andWUEwere lower in flooded trees than in non-flooded trees for a fewweeks, but these reductions were greater for pruned than non-pruned trees. Eventually, A, gs, E andWUEof flooded trees in both the pruned and non-pruned treatments returned to values similar to those of non-flooded trees. After trees were unflooded, for trees in the pruned treatment, xylem sap flow was generally not significantly affected by flooding. However, for non-pruned trees, xylem sap flow was usually lower in the flooded than nonflooded trees. In each experiment, leaf dry weight and total plant dry weight were significantly lower for flooded than non-flooded trees only in the non-pruned treatments. In Expt. 2, root and stem dry weights were also lower in flooded than non-flooded trees only in the non-pruned treatment. The results indicate that pruning the canopy of avocado immediatelyafter trees areremoved from short-term flooding hastens plant recovery. It is postulated that the hastened recovery was due to pruning bringing the shoot to root ratio of flooded trees (with damaged roots) and the subsequent supply and demand for water and nutrients into better equilibrium in flooded trees, allowing pruned trees to recover more quickly from flooding compared to non-pruned trees. Flooding for as little as 1 day has been shown to cause a dramatic decline in leaf gas exchange of potted papaya (Carica papaya L.) plants. However, the ability of papaya to recover from different durations of short-term flooding has not been reported. Therefore, a study was conducted to determine the effects of flooding duration on physiology, survival and recovery of 10-month-old 'Red Lady' papaya plants. During a 7-day period, plants in 11.3-L containers in Pro-Mix® potting medium were subjected to one of 6 different flooding durations: 0, 1, 2, 3, 4, or 5 days of root submersion in a completely randomized design with 6 single-plant replications per treatment. The study was conducted in a greenhouse where the mean air temperature was 26.1oC (range19.4 to 33.4oC). Plants were unflooded immediately after treatment. Soil redox potential in flooded pots was measured daily; these measurements indicated that the soil became anaerobic after 24 hours of flooding. Leaf gas exchange [net CO2 assimilation (A), transpiration (E), and stomatal conductance (gs)], the ratio of variable to maximum chlorophyll fluorescence (Fv/Fm), and leaf chlorophyll index (determined with a SPAD meter) were determined daily for 10 days for all plants. These measurements began 1 day before plants were flooded, continued until 1 day after plants in the 5-day flooding treatment were unflooded, and concluded 4 days later. At the end of the study period, plant survival was recorded. All plants flooded for 0 or 1 day survived. After 1 day of flooding, A, E, gs, Fv/Fm and leaf chlorophyll index of flooded plants began to decline compared to the non-flooded controls, but values for these variables recovered to those of the non-flooded controls 9 days after unflooding. For plants flooded for 2 or more days, A, E, gs, Fv/Fm and leaf chlorophyll index continued to decline during flooding. Nearly all plants flooded for 2 or more days permanently wilted by day 11. In a subsequent experiment where plants were flooded by inundating 100%, 75%, 50% or 0% (control) of the root system for 3 days, only plants with the root system totally submerged did not recover after unflooding. The data indicate that, under the conditions of this study, papaya plants are very intolerant of total root submersion, but can tolerate up to 75% of the root system continuously submerged for at least 3 days.

Publications

  • Type: Journal Articles Status: Published Year Published: 2014 Citation: Sanclemente, M.A., B. Schaffer, P.M. Gil, A.I. Vargas and F.S. Davies. 2014. Pruning after flooding hastens recovery of flood-stressed avocado (Persea americana Mill.) trees. Scientia Horticulturae 169:27-35.
  • Type: Conference Papers and Presentations Status: Published Year Published: 2014 Citation: Rodr�guez, G., B. Schaffer and C. Basso. 2014. Effect of floding duration and portion of roots submerged on physiology, growth and survival of papaya (Carica papaya L.). HortScience (Abstract) HortScience 49:S293.


Progress 03/01/13 to 09/30/13

Outputs
Target Audience: Agricultural and biological scientists, extension faculty and sibtropical and tropical fruit growers Changes/Problems: Nothing Reported What opportunities for training and professional development has the project provided? An M.S. student received a degree in Horticultural Sciences under this project. A graduate student internand two undergraduate interns were trained under this project. A new full-time biological scientist was trained under this project. How have the results been disseminated to communities of interest? The results were dissiminated by publishing them in refereed scientific journals and as part of a text book chapter. What do you plan to do during the next reporting period to accomplish the goals? Conduct further studies on the effects of flooding on physiology, growth and production of subtropical and tropical fruit crops and methods for avoiding or reducing flooding stress. Current work is underway with avocado trees and papaya plants.

Impacts
What was accomplished under these goals? Three experiments (Expts. 1, 2 and 3) were conducted to test the effects of removing a portion of the leaf canopy of avocado trees (Persea americana Mill.) prior to flooding on plant stress, survival and recovery from short-term flooding. Trees in each experiment were divided into two flooding treatments: (1) flooded, or (2) non-flooded. Trees in each flooding treatment were divided into two pruning treatments in Expt. 1: (1) approximately two-thirds of the canopy removed by pruning, or (2) non-pruned (control). In Expt. 2, trees in each flooding treatment were divided into three “canopy” treatments: (1) removal of twothirds of the total number of leaves from the bottom of the canopy upward (2/3 LR), (2) foliar application of a chemical photosynthetic inhibitor and no leaf removal (CP), or (3) no leaf removal or photosynthetic inhibitor applied (control). Trees in each flooding treatment in Expt. 3 were divided into two treatments: (1) two-thirds of the total number of leaves removed from the bottom of the canopy upward, or (2) no leaves removed (control). In each experiment, net CO2 assimilation (A) and stomatal conductance of water vapor (gs) were determined daily during the flooding period and periodically after the flooding period until trees were harvested. Plant survival and tissue dry weights were determined several weeks after plants were removed from flooding (unflooded) in Expts. 1 and 2. Root carbohydrate concentrations were determined immediately after the flooding period in Expt. 3. Pruning, leaf removal or foliar application of a chemical photosynthetic inhibitor immediately prior to flooding resulted in significantly lower A of flooded compared to non-flooded trees. Concentration of the C7 sugar, d-mannoheptulose, was higher in non-flooded than in flooded plants. In flooded plants, concentration of the C7 sugar alcohol, perseitol, was higher in plants with no leaves removed than those in the 2/3 LR treatment. Reducing photosynthesis of avocado trees prior to flooding, either by pruning, leaf removal, or the application of a chemical photosynthetic inhibitor, makes trees more susceptible to flooding stress. Reducing A prior to flooding limits carbohydrate transport to the roots, thereby limiting the amount of substrate for respiration of flooded roots, making the plants more susceptible to flooding stress.

Publications

  • Type: Journal Articles Status: Published Year Published: 2013 Citation: Sanclemente, M.A., B. Schaffer, P.M. Gil, F.S. Davies and J.H. Crane . 2013. Leaf removal before flooding influences recovery of avocado (Persea americana Mill.) trees from flooding stress. Scientia Horticulturae 150:154-163.
  • Type: Journal Articles Status: Accepted Year Published: 2014 Citation: Sanclemente, M.A., B. Schaffer, P.M. Gil, A.I. Vargas and F.S. Davies. 2014. Pruning after flooding hastens recovery of flood-stressed avocado (Persea americana Mill.) trees. Scientia Horticulturae (in press).
  • Type: Book Chapters Status: Published Year Published: 2013 Citation: Schaffer, B., P.M. Gil, M.V. Mickelbart, A.W. Whiley. 2013. Ecophysiology. In: Avocado: Botany, Production and Uses. 2nd Edition. B. Schaffer and B.N. Wolstenholme and A.W. Whiley (eds.). CAB International Press, Wallingford, U.K. pp. 168-199..
  • Type: Journal Articles Status: Published Year Published: 2013 Citation: Gil, P.M., C. Bonomelli, B. Schaffer, R. Ferreyra and C. Gentina . 2012. Effect of soil water-to-air ratio on biomass and mineral nutrition of avocado trees. Journal of Soil Science and Plant Nutrition 12(3):609-630.