LIBRO-CONGRESO-CITRUS

S07
S07P02
Daily temperature amplitude affects the vegetative growth and carbon metabolism of orange
trees in a rootstock-dependent manner
Bueno A.C.R., Prudente D.A., Machado E.C., and Ribeiro R.V.
Instituto Agronomico (IAC), Laboratorio de Fisiologia Vegetal Coaracy M Franco, Brazil. rafael@iac.sp.gov.br
Both instantaneous and average growth temperatures affect plant metabolism, and the physiological
importance of daily variations in temperature is frequently underestimated. In this study, we hypothesized
that vegetative growth would be stimulated in orange trees subjected to large daily temperature variations
even without changes in the average daily air temperature or the amount of energy. This hypothesis was tested
with orange trees grafted onto ‘Rangpur’ lime or ‘Swingle’ citrumelo rootstocks and grown for 20 days under
day/night thermal regimes of 25/25 ºC or 32.5/17.5 ºC. Such regimes imposed daily temperature variations
of 0 ºC and 15 ºC. Plant growth, photosynthesis, respiration and carbohydrate availability in leaves, stems and
roots were measured under both thermal conditions. The daily temperature variation affected the carbon
metabolism of young citrus trees; plants grown with 15 ºC of daily variation used more of the carbon stored in
mature leaves and roots and the energy generated by respiration for the biosynthesis of vegetative structures,
such as leaves and branches. Thus, there was a significant increase in the leaf area of plants subjected to the
high daily temperature variation. Current photosynthesis was similar in the two thermal regimes; however,
the photosynthetic rates increased under the 15 ºC variation when measurements were normalized to 25 ºC.
In addition to the stimulatory effect of the source-sink relationship on photosynthesis, we suggest a probable
involvement of hormonal regulation of plant growth through gibberellin metabolism. The rootstock affected
the response of the canopy to daily temperature amplitude, with the Rangpur lime improving plant growth
through higher carbohydrate availability in roots. This is the first report that highlights the importance of daily
temperature variations for citrus growth and physiology under non-limiting conditions.
S07P03
The effects of paclobutrazol and fruit on flowering and carbohydrate accumulation in roots,
branches and leaves of alternate bearing clementine mandarin
Martínez-Fuentes A. 1 , Mesejo C. 1 , Muñoz-Fambuena N. 1 , Reig C. 1 , González-Mas M.C. 2 , Iglesias D.J. 2 , Primo-Millo E. 2 ,
and Agustí M. 2
1 Instituto Agroforestal Mediterraneo. Universitat Politècnica de València (IAM-UPV), España; and 2 Instituto Valenciano de
Investigaciones Agrarias (IVIA), Citricultura y Producción Vegetal, España. carmeco@upv.es
This study aimed to determine the effects of paclobutrazol (PCB) in on- and off-bearing trees on flowering and
carbohydrate accumulation in roots, branches and leaves of ‘Hernandina’ clementine mandarin. Application
of PCB (1 g tree -1 ) to the roots during the flower bud induction period (November) significantly increased bud
sprouting and flowering in off-trees. However, this effect was prevented in on-trees. One month before the
treatment with PCB, hexose concentrations were significantly reduced in roots from both on- and off-trees
compared to untreated trees, but sucrose concentration was only reduced in on-trees. At the moment of
bud sprouting, sugar concentrations significantly increased in leaves from all treatments. PCB significantly
increased hexose concentrations in leaves from on-trees compared to untreated trees. On the other
hand, sucrose concentration was significantly higher in leaves from off-trees. No significant differences in
carbohydrate concentrations were found in branches. Neither carbohydrate contents in roots nor in leaves
and branches due to PCB treatment or fruit was related to flowering intensity.
S07P04
Fruit set in orange with phytohormones and its relation to engogeneous levels of GA 3
Galván J.J. 1 , Martínez A. 1 , López N. 1 , and Salazar O. 2
1 UAAAN (UA), Horticultura, México; and 2 Universidad Autónoma de Tamaulipas (UAT), UAMAC, México. juan.galvan@uaaan.mx,
doctorgalvanluna@hotmail.com
This research work aims to contribute to increasing the fruit set given the importance fruit set has in determining
the harvest. This work evaluated the effects of phytohormones (auxins, gibberellins and cytokinins) in fruit
110 - VALENCIA CONFERENCE CENTER, 18th-23rd NOVEMBER 2012