Progress 01/01/02 to 09/30/07
Outputs
OUTPUTS: Water, carbon, mineral nutrients and other plant growth regulators control root-shoot communication, plant growth and quality. Site-specific soil-weevil-tree simple and multivariate linear models based on time series and soil characteristics describe practices for predicting and controlling the Diaprepes root weevil populations and decline of citrus trees. Predicting populations allow for variable rate and less frequent sprays to effectively manage the weevil. Increasing acidic soil pH by 1 unit would be an option for promoting integrated management of Diaprepes root weevil in citrus. Warm, wet conditions contributed to the root weevil outbreaks, and environmental temperature and rainfall were the variables most closely related to weevil distribution in time. Based on water relations and net gas exchange, Cleopatra mandarin was more tolerant to short-term drought and flooding stress than Carrizo citrange. Plants preconditioned by salinity stress maintained a better leaf water status during drought stress due to osmotic adjustment and the accumulation of Cl- and Na+. However, high levels of salt ions impeded recovery of leaf water status and photosynthesis after re-irrigation with non-saline water. The addition of the silicone-based L-77 surfactant to a Cu-Kocide suspension markedly increased the spread of the droplets on citrus cuticles and increased the penetration of Cu through fruit and abaxial leaf cuticles, both with stomatal pores, but not through astomatous adaxial leaf cuticles which had much lower permeability. Urea and petroleum spray oil adjuvants had no effect on surface area of droplets or the penetration of Cu through leaf and fruit cuticles. Spray tank mixes of Cu fungicides with organosilicone surfactants should be avoided because these surfactants can enhance the penetration of Cu into citrus leaves and fruit thereby leading to phytotoxicity. Yields of relatively high producing groves were not enhanced by winter or spring foliar applications of N, P or K products. Strategies for mid to late summer flush synchronization by summer hedging were devised and tests started. Early fall hedging was shown to enhance overall flowering compared to winter hedging. Criteria for successful development of under-produced horticultural crops were outlined. Several aspects of medium and high resolution satellite and aerial image analysis were advanced in citrus area determination, tree counting and disease detection. PARTICIPANTS: Water, carbon, mineral nutrients and other plant growth regulators control root-shoot communication, plant growth and quality. Site-specific soil-weevil-tree simple and multivariate linear models based on time series and soil characteristics describe practices for predicting and controlling the Diaprepes root weevil populations and decline of citrus trees. Predicting populations allow for variable rate and less frequent sprays to effectively manage the weevil. Increasing acidic soil pH by 1 unit would be an option for promoting integrated management of Diaprepes root weevil in citrus. Warm, wet conditions contributed to the root weevil outbreaks, and environmental temperature and rainfall were the variables most closely related to weevil distribution in time. Based on water relations and net gas exchange, Cleopatra mandarin was more tolerant to short-term drought and flooding stress than Carrizo citrange. Plants preconditioned by salinity stress maintained a better leaf water status during drought stress due to osmotic adjustment and the accumulation of Cl- and Na+. However, high levels of salt ions impeded recovery of leaf water status and photosynthesis after re-irrigation with non-saline water. The addition of the silicone-based L-77 surfactant to a Cu-Kocide suspension markedly increased the spread of the droplets on citrus cuticles and increased the penetration of Cu through fruit and abaxial leaf cuticles, both with stomatal pores, but not through astomatous adaxial leaf cuticles which had much lower permeability. Urea and petroleum spray oil adjuvants had no effect on surface area of droplets or the penetration of Cu through leaf and fruit cuticles. Spray tank mixes of Cu fungicides with organosilicone surfactants should be avoided because these surfactants can enhance the penetration of Cu into citrus leaves and fruit thereby leading to phytotoxicity. -- Syvertsen, J. P. 2007. Mechanisms of Root - Shoot Communication. HortSci. 42: 1101-1102. --Li, Hong, S.H. Futch, R.J. Stuart, J. P. Syvertsen and C.W. McCoy. 2007. Associations of soil iron with citrus tree decline and variability of sand, soil water, pH, magnesium and Diaprepes abbreviatus root weevil: Two-site study. Environmental & Experimental Botany 59:321-333. --Li, Hong, Clay W. McCoy and J. P. Syvertsen. 2007. Controlling factors of environmental flooding, soil pH and Diaprepes abbreviatus (L.) root weevil feeding in citrus: Larval survival and larval growth Applied Soil Ecology 35:553-565. --Li, Hong, S.H. Futch, R.J. Stuart, C.W. McCoy and J. P. Syvertsen. 2007. Time series forecast and soil characteristics-based simple and multivariate linear models for management of Diaprepes abbreviatus root weevil in citrus. Soil Biology & Biochemistry 39:2436-2447. -- Li, Hong, Stephen H. Futch and J.P. Syvertsen. 2007. Cross-Correlation Patterns of Air and Soil Temperatures, Rainfall and Diaprepes abbreviatus Root Weevil in Citrus. Pest Management Science 63: 1116-1123. TARGET AUDIENCES: Water, carbon, mineral nutrients and other plant growth regulators control root-shoot communication, plant growth and quality. Site-specific soil-weevil-tree simple and multivariate linear models based on time series and soil characteristics describe practices for predicting and controlling the Diaprepes root weevil populations and decline of citrus trees. Predicting populations allow for variable rate and less frequent sprays to effectively manage the weevil. Increasing acidic soil pH by 1 unit would be an option for promoting integrated management of Diaprepes root weevil in citrus. Warm, wet conditions contributed to the root weevil outbreaks, and environmental temperature and rainfall were the variables most closely related to weevil distribution in time. Based on water relations and net gas exchange, Cleopatra mandarin was more tolerant to short-term drought and flooding stress than Carrizo citrange. Plants preconditioned by salinity stress maintained a better leaf water status during drought stress due to osmotic adjustment and the accumulation of Cl- and Na+. However, high levels of salt ions impeded recovery of leaf water status and photosynthesis after re-irrigation with non-saline water. The addition of the silicone-based L-77 surfactant to a Cu-Kocide suspension markedly increased the spread of the droplets on citrus cuticles and increased the penetration of Cu through fruit and abaxial leaf cuticles, both with stomatal pores, but not through astomatous adaxial leaf cuticles which had much lower permeability. Urea and petroleum spray oil adjuvants had no effect on surface area of droplets or the penetration of Cu through leaf and fruit cuticles. Spray tank mixes of Cu fungicides with organosilicone surfactants should be avoided because these surfactants can enhance the penetration of Cu into citrus leaves and fruit thereby leading to phytotoxicity. -- Syvertsen, J. P. 2007. Mechanisms of Root - Shoot Communication. HortSci. 42: 1101-1102. --Li, Hong, S.H. Futch, R.J. Stuart, J. P. Syvertsen and C.W. McCoy. 2007. Associations of soil iron with citrus tree decline and variability of sand, soil water, pH, magnesium and Diaprepes abbreviatus root weevil: Two-site study. Environmental & Experimental Botany 59:321-333. --Li, Hong, Clay W. McCoy and J. P. Syvertsen. 2007. Controlling factors of environmental flooding, soil pH and Diaprepes abbreviatus (L.) root weevil feeding in citrus: Larval survival and larval growth Applied Soil Ecology 35:553-565. --Li, Hong, S.H. Futch, R.J. Stuart, C.W. McCoy and J. P. Syvertsen. 2007. Time series forecast and soil characteristics-based simple and multivariate linear models for management of Diaprepes abbreviatus root weevil in citrus. Soil Biology & Biochemistry 39:2436-2447. -- Li, Hong, Stephen H. Futch and J.P. Syvertsen. 2007. Cross-Correlation Patterns of Air and Soil Temperatures, Rainfall and Diaprepes abbreviatus Root Weevil in Citrus. Pest Management Science 63: 1116-1123. PROJECT MODIFICATIONS: Water, carbon, mineral nutrients and other plant growth regulators control root-shoot communication, plant growth and quality. Site-specific soil-weevil-tree simple and multivariate linear models based on time series and soil characteristics describe practices for predicting and controlling the Diaprepes root weevil populations and decline of citrus trees. Predicting populations allow for variable rate and less frequent sprays to effectively manage the weevil. Increasing acidic soil pH by 1 unit would be an option for promoting integrated management of Diaprepes root weevil in citrus. Warm, wet conditions contributed to the root weevil outbreaks, and environmental temperature and rainfall were the variables most closely related to weevil distribution in time. Based on water relations and net gas exchange, Cleopatra mandarin was more tolerant to short-term drought and flooding stress than Carrizo citrange. Plants preconditioned by salinity stress maintained a better leaf water status during drought stress due to osmotic adjustment and the accumulation of Cl- and Na+. However, high levels of salt ions impeded recovery of leaf water status and photosynthesis after re-irrigation with non-saline water. The addition of the silicone-based L-77 surfactant to a Cu-Kocide suspension markedly increased the spread of the droplets on citrus cuticles and increased the penetration of Cu through fruit and abaxial leaf cuticles, both with stomatal pores, but not through astomatous adaxial leaf cuticles which had much lower permeability. Urea and petroleum spray oil adjuvants had no effect on surface area of droplets or the penetration of Cu through leaf and fruit cuticles. Spray tank mixes of Cu fungicides with organosilicone surfactants should be avoided because these surfactants can enhance the penetration of Cu into citrus leaves and fruit thereby leading to phytotoxicity. -- Syvertsen, J. P. 2007. Mechanisms of Root - Shoot Communication. HortSci. 42: 1101-1102. --Li, Hong, S.H. Futch, R.J. Stuart, J. P. Syvertsen and C.W. McCoy. 2007. Associations of soil iron with citrus tree decline and variability of sand, soil water, pH, magnesium and Diaprepes abbreviatus root weevil: Two-site study. Environmental & Experimental Botany 59:321-333. --Li, Hong, Clay W. McCoy and J. P. Syvertsen. 2007. Controlling factors of environmental flooding, soil pH and Diaprepes abbreviatus (L.) root weevil feeding in citrus: Larval survival and larval growth Applied Soil Ecology 35:553-565. --Li, Hong, S.H. Futch, R.J. Stuart, C.W. McCoy and J. P. Syvertsen. 2007. Time series forecast and soil characteristics-based simple and multivariate linear models for management of Diaprepes abbreviatus root weevil in citrus. Soil Biology & Biochemistry 39:2436-2447. -- Li, Hong, Stephen H. Futch and J.P. Syvertsen. 2007. Cross-Correlation Patterns of Air and Soil Temperatures, Rainfall and Diaprepes abbreviatus Root Weevil in Citrus. Pest Management Science 63: 1116-1123.
Impacts
Several of the studies during this project have led to usefull applications in citrus production. Better management of flowering of citrus under Florida conditions is one of these. Most recently timing of hedging appears important to maximizing flowering. Satellite image studies have shwon that citrus areas can be identified, trees can be counted and general area-wide disease or tree health can be monitored at medium resolution. Our understanding of tree response to salinity and other stresses was advanced. Application of major elements as a foliar spray was shown to be useful only if root health is compromised. Root and shoot balance in response to biotic and abiotic stresses was shown to play an important role in plant response.
Publications
- Syvertsen, J. P. 2007. Mechanisms of Root - Shoot Communication. HortSci. 42: 1101-1102.
- Li, Hong, S.H. Futch, R.J. Stuart, J. P. Syvertsen and C.W. McCoy. 2007. Associations of soil iron with citrus tree decline and variability of sand, soil water, pH, magnesium and Diaprepes abbreviatus root weevil: Two-site study. Environmental & Experimental Botany 59:321-333.
- Li, Hong, Clay W. McCoy and J. P. Syvertsen. 2007. Controlling factors of environmental flooding, soil pH and Diaprepes abbreviatus (L.) root weevil feeding in citrus: Larval survival and larval growth Applied Soil Ecology 35:553-565.
- Li, Hong, S.H. Futch, R.J. Stuart, C.W. McCoy and J. P. Syvertsen. 2007. Time series forecast and soil characteristics-based simple and multivariate linear models for management of Diaprepes abbreviatus root weevil in citrus. Soil Biology & Biochemistry 39:2436-2447.
- Li, Hong, Stephen H. Futch and J.P. Syvertsen. 2007. Cross-Correlation Patterns of Air and Soil Temperatures, Rainfall and Diaprepes abbreviatus Root Weevil in Citrus. Pest Management Science 63: 1116-1123.
- Garcia-Sanchez, F., J.P. Syvertsen, P. Botia and J.G. Perez-Perez. 2007. Physiological Responses of Two Citrus Rootstock Seedlings to Flooding and Drought Stress. Physiologia Plantarum 130: 532-542. Perez-Perez, J.G., J.P. Syvertsen, P. Botia and F. Garcia-Sanchez. 2007. Leaf water relations and net gas exchange responses of salinized Carrizo citrange seedlings during drought stress and recovery. Ann. Bot. 100: 335-345.
- Orbovic, Vladimir and J. P. Syvertsen. 2007. Adjuvants affect penetration of copper through isolated cuticles of Citrus leaves and fruit. HortScience 42: 1405-1408. Albrigo, L. Gene, James P. Syvertsen and Timothy M. Spann. 2007. Citrus leaf flush control for management of canker and greening - the tree's side of the equation. Citrus Industry 88(3):.
- Albrigo, L. G. 2007. Effect of winter and spring time applications of foliar urea, NPK or K-phosphite sprays on productivity of citrus Central Florida. Proc. Fla. State Hort. Soc. 120: (in press).
- Saraswat, D., J.C. Neto, L. G. Albrigo and R. Ehsani. 2008. Comparison of A Hierarchical Machine-Learning Technique and the GeoCitrus Algorithm for Obtaining Citrus Tree Count and Area from Digital Aerial Imagery. ASABE (submitted).
- Srivastava, A.K., Shyam Singh and L. G. Albrigo. 2008. Diagnosis and Remediation of Nutrient Constraints in Citrus. Hort Review (in press).
- Albrigo, L. G. 2007. Citrus Improvement as a Model for Horticultural Development in Pakistan. In 'Prospects of Horticultural Industry in Pakistan' International symposium, March 2007, Faisalabad, Pakistan.
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Progress 10/01/05 to 09/30/06
Outputs
Based on leaf growth, water use efficiency and salt ion accumulation, elevated CO2 increased salinity tolerance in seedlings of the relatively salt sensitive Carrizo citrange more than in salt tolerant Cleopatra mandarin. The modifications of citrus seedling responses to salinity by the higher growth and lower transpiration at elevated CO2 were not only species dependent, but also involved whole plant growth and allocations of Na+ and Cl- between roots and shoots. Diaprepes abbreviatus root weevil larval survival was 25% higher in sandy soil than in loamy soil. Citrus roots that had been previously flooded for 20 days were more water stressed and more susceptible to Diaprepes larval feeding injury than previously well drained roots. The growth reduction and leaf Na+ concentration from salinity was greater in shaded than for sunlit Valencia trees on both Carrizo and Cleo rootstocks. Foliar urea penetration decreased with increase leaf cuticle weight until leaves were 6
mo-old depending on leaf waxes. The following progress was made on a remote sensing project to detection estimate yield of citrus: citrus reflectance was separated from forest, rubber, eucalyptus, coffee and mango crop signatures in medium resolution satellite images, trees were counted with about 95 % accuracy from high resolution images, acreage was measured in Florida and Brazil with 5 to 10 % accuracy, yield prediction models were developed for Florida and Sao Paulo, Brazil, citrus greening was characterized with hyperspectral reflectance.
Impacts
Work under this project allows Florida growers to better adjust their production practices to the various biotic and abiotic factors that impact citrus trees and their fruit development. A better understanding of the physiological behavior of citrus under Florida conditions also furthers our basic understanding so that progress can be made in overcoming adverse environmental conditions. Some of this work is designed to provide Florida growers with better information in order to compete in international markets.
Publications
- Garcia-Sanchez,F.and J.P.Syvertsen. 2006. Salinity tolerance of Cleopatra mandarin and Carrizo citrange citrus rootstock seedlings is affected by CO2 enrichment during growth. J.Amer.Soc.Hort.Sci.131:24-31.
- Li, Hong, J.P. Syvertsen, Clay W. McCoy, Robin J. Stuart, and Arnold W. Schumann. 2006. Water Stress and Root Injury from Simulated Flooding and Diaprepes abbreviatus Root Weevil Larval Feeding in Citrus. Soil Science 171: 138-151.
- Garcia-Sanchez, F., J. P. Syvertsen, V. Martinez and J. C. Melgar. 2006. Salinity tolerance of Valencia orange trees grafted on contrasting rootstocks is not improved by moderate shade. J. Exp. Bot. 57: 3697-3706.
- Bondada, B.R., P.D. Petracek, J.P. Syvertsen and L.G. Albrigo. 2006. Cuticular penetration characteristics of urea in citrus leaves. Journal of Horticultural Science and Biotechnology 81:219-224.
- Albrigo, L.G.. 2006. Impact of late harvest on citrus crop losses and juice quality. Proc. Fla. State Hort. Soc. 119: (in press).
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Progress 10/01/04 to 09/30/05
Outputs
Abiotic and biotic stress can combine with salinity stress to have negative synergistic effects on growth and physiolgical responses citrus trees. Nondestructive leaf greenness meters can yield good estimates of citrus leaf chlorophyll and thus, can be good stress indicators. Such meters yield less reliable estimates of leaf N depending on leaf age and growth conditions. N deficiency as well as excess N can lead to excess starch accumulation in citrus chloroplasts. Mechanical harvesting of oranges using a trunk shaker can interact with drought stress to decrease tree water relations but physiological responses and return yield of healthy, well watered trees are not affected by mechanical harvesting at recommended intensities. Mechanical harvesting can remove about 20% of the leaves in the canopy but this level of annual defoliation for three years had no effect on tree canopy size, fruit yield or juice quality. Manually removing 50% of leaves for three successive
years did, however, reduce average leaf size. Although vigorous growth conditions can lead to increasing grapefruit elongation and sheepnosing, low crop load was a dominant factor leading to excessive fruit growth and more sheepnosed shape. The multiple hurricanes in Florida during 2004, not only removed leaves and fruit and damaged many trees, but also stimulated vegetative flushes in the late fall that impacted spring bloom in 2005 by creating more available buds, but insufficient shoot maturity if the new shoots had less than 6 to 8 weeks to mature before cold weather commenced. Chlorosis from biuret toxicity in urea foliar sprays was more like chloroplast degradation in natural leaf senescence with non-recovery rather than nutritional chlorosis that can be corrected by application of the nutrient. Reflectance data from satellite images of citrus changed by season of growth and whether the trees were irrigated or non-irrigated. These changes will be studied further in 2006 for both
Florida and Sao Paulo, Brazil.
Impacts
Work under this project allows Florida growers to better adjust their production practices to the various biotic and abiotic factors that impact citrus trees and their fruit development. A better understanding of the physiological behavior of citrus under Florida conditions also furthers our basic understanding so that progress can be made in overcoming adverse environmental conditions.
Publications
- --Syvertsen, J.P. and Y. Levy. 2005. Salinity Interactions with Other Abiotic and Biotic Stresses in Citrus. HortTech. 15: 100-103.
- --Jifon, J.L., J.P. Syvertsen, and E. Whaley. 2005. Growth environment and leaf anatomy affect nondestructive estimates of leaf chlorophyll and nitrogen in Citrus sp. leaves. J. Amer. Soc. Hort. Sci. 130:152-158.
- -- Li, Kuo-Tan and J.P. Syvertsen. 2005. Mechanical Harvesting has little effect on water status and leaf gas exchange in citrus trees. J. Amer. Soc. Hort. Sci. 130: 661-666.
- --Yuan, R., F. Alferez, I. Kostenyuk, S. Singh, G. Zhong, J. Syvertsen and J. Burns. 2005. Partial defoliation can decrease average leaf size but has little effect on orange tree growth, fruit yield and juice HortSci. 40: (in press)
- --Syvertsen, J. P, L. G. Albrigo, M. A. Ritenour, J. M. Dunlop, A. W. Schumann, R. C. Vachon. 2005. Growth Conditions, Crop Load and Fruit Size Affect Sheepnosing in Grapefruit. FSHS (Reviewed) 118: (in press)
- --Albrigo, L.G., J. Attaway, K. Bowman, R.S. Buker, W.S. Castle, K.W. Hancock, C.W. McCoy, R.P. Muraro, M.E. Rogers, M.A. Ritenour, T. Spreen, P.D. Spyke, J.P. Syvertsen, L.W.Timmer and R.C. Vachon. 2005. The impact of three hurricanes in 2004 on the Florida Citrus Industry: Lessons learned, what we know and what we do not know. Proc. FSHS. 118: (in press)
- --Albrigo, L.G. 2005. The potential for the 2005-06 crop after the 2004 hurricanes. Citrus Industry Mag. 86(2):13-14.
- --Albrigo, L.G. 2004. Climatic Effects on Flowering, Fruit Set and Quality of Citrus, A Review. Proc. Int. Soc. Citriculture X Congress, (in press)
- --Albrigo, L.G., J.I Valiente, and C. Van Parys de Wit. 2004. Influence of Winter and Spring Weather on Year-To-Year Citrus Fruit Set and Yield Variation in Sao Paulo, Brazilian. Proc. Int. Soc. Citriculture X Congress, (in press)
- --Russ, P.K. and L.G. Albrigo, 2004. The Role of the Citrus Research and Education Center in Collecting, Preserving and Indexing Citrus Literature. Proc. Int. Soc. Citriculture X Congress, (in press)
- --Albrigo, L.G., H. W. Beck, and J. I. Valiente. 2004. Testing a flowering expert system for the Decision Information System for Citrus. Proc. 7th Internl. Symp. Computer Modeling fruit Res. & Orch. Manag. Acta Hort. (in press)
- --Salvatore, J. J., M. A. Ritenour, B. T. Scully, and L.G. Albrigo. 2005. The effect of the 2004 hurricanes on citrus flowering potential for the 2005 season. Proc. Fla. State Hort. Soc. 118 (in press)
- --Achor, D.S. and L.G. Albrigo. 2005. Biuret Toxicity Symptoms in Citrus Leaves Mimics Cell Senescence Rather Than Nutritional Deficiency Chlorosis. J. Amer. Soc. Hort. Sci. 130:667-673.
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Progress 10/01/03 to 09/30/04
Outputs
There are interactions between salinity and physical environmental factors as well between salinity, pests, and diseases. Not all effects of salinity are negative, however, as moderate salinity stress can reduce physiological activity and growth allowing citrus seedlings to survive cold stress and can even enhance flowering after the salinity stress is relieved. Soil amendments of a hydrophilic gel to pots of sandy soil enhanced citrus seedling growth, increased N uptake efficiency, and reduced N losses. Diaprepes root weevil populations were correlated to flooding stress and soil pH in the field. Citrus seedlings that were previously stressed by flooding were more susceptible to Diaprepes root weevil feeding than non flooded seedlings. The loss of chloroplast ultrastructural integrity brought about by excessive starch accumulation facilitated reductions in chlorophyll (Chl) and CO2 assimilation in N deficient citrus leaves. Relationships between Chl meter readings,
analytically determined Chl and measured leaf N concentrations were generally more linear and stronger at low Chl concentrations than at higher Chl concentrations, reflecting increased variability in Chl meter readings with increasing leaf Chl. Elevating early season temperature in tree canopies by placing clear plastic tents over trees from before bloom (February) until July, increased the percentage of sheepnosed grapefruit above that of the uncovered control trees in four different grapefruit cultivars growing both on the Central Ridge and in the Indian River area. Ruby Red grapefruit trees previously fertilized with 250 lb N/Ac per year had more sheepnosed fruit (14%) than trees that received 100 lb N/Ac per year (3%). Evaluation of reported adverse changes in grapefruit quality in the Indian River area were not supported by official sampling data. Lower acidity the past 3 years did appear to be related to warmer spring and fall weather patterns over the previous 3 to 4 years.
There were no major negative effects of mechanical harvesting on physiological or growth responses in Hamlin and early season Valencia. Healthy citrus trees in a well-managed grove appear to be able to tolerant minimal injury from trunk or canopy shakers. Many citrus groves experienced 1 to 3 hurricanes this season, the worst year in Florida history, with associated fruit and leaf loss. Excessive fall flush was stimulated that creates bud maturation issues such as ability to flower next spring. Sound management practices that first support bud maturation and then shoot and root re-growth where necessary to restrict the future negative impacts from storm damage. A Flower Monitoring Expert System and a Copper Spray Scheduling Recommendation System (both part of a comprehensive Decision Information System for Citrus (DISC) program) were tested for up to 4 years with growers. Both systems appeared to work correctly and provide growers with useful aids in planning and timing production
practices.
Impacts
Work under this project allows Florida growers to better adjust their production practices to the various biotic and abiotic factors that impact citrus trees and their fruit development. A better understanding of the physiological behavior of citrus under Florida conditions also furthers our basic understanding so that progress can be made in overcoming adverse environmental conditions.
Publications
- --Levy, Y. and J. P. Syvertsen. 2004. Irrigation water quality and salinity effects in citrus trees. In: J. Janick (ed.). Horticultural Reviews vol 30: AVI Pub., Westport, CT. p. 37-82. --Syvertsen, J. P. and J. Dunlop. 2004. Hydrophilic gel amendments to a sandy soil can increase growth and nitrogen uptake efficiency of citrus seedlings. HortSci. 39:267-271. --Li, Hong, J. P. Syvertsen, R.J. Stewart, C.W. McCoy, A.W. Schumann and W.S. Castle. 2004. Soil and Diaprepes abbreviatus Root Weevil Spatial Variability in a Poorly Drained Citrus Grove. Soil Sci. 169: 650-662. --Bondada, B. R. and J. P. Syvertsen. 2004. Concurrent changes in net CO2 assimilation and chloroplast ultrastructure in nitrogen deficient citrus leaves. Environ. & Expt. Bot. (in press) --Jifon, J.L., J. P. Syvertsen and Eric L.Whaley. 2004. Growth environment and leaf anatomy affect nondestructive estimates of leaf chlorophyll and nitrogen in Citrus species. J. Amer. Soc. Hort. Sci. (in press).
--McCoy, C. W, W. S. Castle, J. H. Gr
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Progress 10/01/02 to 10/01/03
Outputs
In N deficient citrus leaves, small chloroplasts had no starch granules, disintegrated grana and stroma lamellae that coincided with the accretion of numerous large plastoglobuli in the stroma. High N leaves had large chloroplasts with well developed grana, stroma lamellae and numerous large starch granules that apparently disrupted chloroplasts such that photosynthesis was no greater than in high n leaves than in moderate N leaves. Fifty percent shade cloth and kaolin particle film reduced midday leaf temperature and leaf-to-air vapor pressure difference such that stomatal conductance and photosynthesis were increased above that of sunlit leaves. Photoinhibition of photo system II was greater in sunlit than in shaded leaves so non-stomatal factors were more important than stomatal limitations on photosynthesis during radiation and high temperature stress. Diaprepes root weevil populations were correlated to flooding stress and soil pH in the field. Citrus seedlings
that were previously stressed by flooding were more susceptible to Diaprepes root weevil feeding than non flooded seedlings. In Spring navel orange trees, the presence of a normal fruit load resulted in lower foliar carbohydrate concentrations and higher rates of photosynthesis than in leaves of de-fruited trees. A new Citrus Flowering Monitor Expert System was tested for the second year and performed well to predict flowering intensity and dates of bloom for all citrus districts in Florida. In most years in Florida, multiple bloom waves occur within the normal bloom period from February to April. Three times more flowers occur per summer compared to a spring shoot.
Impacts
Work under this project allows Florida growers to better adjust their production practices to the various biotic and abiotic factors that impact citrus trees and their fruit development. A better understanding of the physiological behavior of citrus under Florida conditions also furthers our basic understanding so that progress can be made in overcoming adverse environmental conditions.
Publications
- Valiente, J.I. and L.G. Albrigo. 2004. Flower bud induction of sweet orange trees [Citrus sinensis (L.) Osbeck]: Effect of low temperatures, crop load and bud age. J. Amer. Soc. Hort. Sci. 129 (in press)
- Bondada, B. R. and J. P. Syvertsen. 2003. Leaf chlorophyll, net gas exchange and chloroplast ultrastructure in citrus leaves of different nitrogen status. Tree Physiology 23: 553-559
- Jifon, J. L. and J. P. Syvertsen. 2003. Kaolin particle film applications can increase photosynthesis and water use efficiency of Ruby Red grapefruit leaves. J. Amer. Soc. Hort. Sci. 128: 107-112
- Li, H., J.P. Syvertsen, A. Schumann, C.W. McCoy, and R.J. Stuart. 2003. Correlation of soil characteristics and Diaprepes root weevil in a poorly drained citrus grove. Proc. Fla. State Hort. Soc. 116:336-343
- Li, H., J.P. Syvertsen, C.W. McCoy, and A. Schumann. 2003. Soil redox potential and leaf stomatal conductance of two citrus rootstocks subjected to flooding and Diaprepes root weevil feeding. Proc. Fla. State Hort. Soc. 116:357-368
- Syvertsen, J.P., Carmen Goni and Alvaro Otero. 2003. Fruit Load and Canopy Shading Affect Leaf Photosynthesis and Carbohydrate Status in Spring Navel Orange Trees. Tree Physiology 23: 899-906
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Progress 10/01/01 to 10/01/02
Outputs
Mycorrhizal (M) sour orange (SO) seedlings were smaller than non-mycorrhizal seedlings when grown at ambient CO2 with high phosphorus. Elevated CO2 compensated for carbon cost of M in the M dependent SO (1). Salinity stress decreased photosynthesis and growth of Sunburst (SB) mandarin grafted on Carrizo citrange (Carr) rootstock more than SB on Cleopatra mandarin (Cleo). Cleo roots accumulated higher concentrations of Na and Cl than Carr roots but SB leaves on Carr accumulated more Na and Cl than leaves on Cleo. Salinity tolerance of Cleo rootstock was thus associated with ion sequestration in roots along with less transport to leaves (2). Under salinity stress, seedlings of somatic hybrid tetraploids of SO+Carr, SO+flying dragon and SO+Palestine sweet lime accumulated more Na and Cl than did the diploid SO seedlings (3). In the field, 50 percent shade cloth reduced midday leaf temperature and leaf-to-air vapor pressure difference such that stomatal conductance and
photosynthesis were increased above that of sunlit leaves. Photoinhibition of photo system II was greater in sunlit than in shaded leaves so non-stomatal factors were more important than stomatal limitations on photosynthesis of citrus leaves during radiation and high temperature stress (4). Bee activity in hybrid blocks was enhanced by specific hive placement, cross hedging, skirting and timing of placement to emphasize the peak of the hybrid bloom (5). Stylar-end russet of navel oranges initially appeared to be from peel cracking caused by peel stresses related to secondary fruit expansion in the stylar-end of the fruit. The problem was prevalent in the more humid Indian River climate in Florida (6). An expert system for `Citrus Flowering Decision Support' is in its second year of testing. The expert system tracks the level of induction, initiation of flower bud differentiation and estimated date of bloom. It includes recommendations of how and when 1. to stop unwanted initiation of
flowering, 2. to enhance flowering level and 3. to reduce flowering potential (7).
Impacts
Mycorrhizae, salinity and high temperature stress all affect tree nutrient status and growth. By evaluating physiological responses to these environmental stresses in different citrus genotypes, we will gain insights into the heritability of mechanisms of stress tolerance. A greater understanding of the biological and physical environmental constraints on flowering will impact fruit yield through our ability to control flowering intensity and enhance our ability to predict year to year variations in yield.
Publications
- Albrigo, L.G., J.I. Valiente and H.W. Beck. 2002. Flowering expert system development for a phenology based citrus decision support system. Proc. 6th Internl. Symp. Comp. Modelling Fruit Res. and Orchard Manage. Acta Hort. 584:247-254.
- Jifon, John L, James H. Graham, Diana L. Drouillard and James P. Syvertsen. 2002. Growth depression of mycorrhizal Citrus seedlings grown at high phosphorus supply is mitigated by elevated CO2. New Phytol. 153: 133-142.
- Garcia-Sanchez F., J. L. Jifon, M. Carvajal, J.P Syvertsen. 2002. Gas exchange, chlorophyll and nutrient contents in relation to Na and Cl accumulation in Sunburst mandarin grafted on different rootstocks. Plant Science 162: 705-712.
- Garcia-Sanchez, F., V. Martinez, J. Jifon, J. P. Syvertsen and J. D.Grosser. 2002. Salinity reduces growth, gas exchange, chlorophyll and nutrient concentrations in diploid Sour orange and related allotetraploid somatic hybrids. J. Hort. Sci. and Biotechnology 77 (4): 379-386.
- Jifon, J. L. and J. P. Syvertsen. 2002. Moderate shade can increase net gas exchange and reduce photoinhibition in citrus leaves. Tree Physiol. (in press).
- Albrigo, L.G. and R.V. Russ. 2002. Considerations for improving honeybee pollination of citrus hybrids in Florida. Proc. Fla. State Hort. Soc. 115: (in press).
- Albrigo, L.G., D.S. Achor and K. Townsend. 2002. Ultrastructural development and other characteristics of stylar-end russeting of navel oranges in Florida. Proc. Fla. State Hort. Soc. 115 (in press).
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