LIBRO-CONGRESO-CITRUS

S08
S08P15
Flooding and soil temperature affect photosynthesis of citrus rootstock leaves.
Otero A. 1 , Goñi Altuna C.T. 2 and Syvertsen J.P. 3
1 Instituto Nacional de Investigacion Agropecuaria (INIA), Ecophysiology Laboratory, Uruguay; 2 Instituto Nacional de Investigacion
Agropecuaria (INIA), Soil and Plant Nutrition Laboratory, Uruguay; and 3 University of Florida. IFAS Citrus Research and Education
Center (UF-IFAS), Citriculture, USA. aotero@sg.inia.org.uy
We evaluated the effects of the soil temperature (15ºC, 25ºC and 35ºC) and soil anoxia from flooding for
20 days on citrus rootstock seedlings of trifoliate (‘CT33’), ‘Carrizo’ citrange and ‘Troyer’ citrange along with
‘Tucuman’, ‘Pomeroy’ and ‘Rubidoux’ trifoliates in a greenhouse. Flooding had no effect on shoot water
potential (Ψs) and leaf relative water content (RWC) at 25ºC but at 15ºC and 35ºC, there were differences
from non-flooded trees. ‘Carrizo’ and ‘Troyer’ had higher Ψs than ‘CT33’, and ‘Tucuman’ had the highest Ψs
among the trifoliates. Soil temperature was more important than flooding in determining plant water status.
In ‘Troyer’ at 25ºC, flooding decreased net assimilation of CO2 (ACO2) faster than in ‘Carrizo’ and ‘CT33’.
At 35ºC, ACO2 was reduced up to 14% of non-flooded plants in only 4 days. ‘Tucuman’ had higher ACO2
than ‘Rubidoux’ and ‘Pomeroy’. Higher values of internal CO2 concentration in leaves were associated with
a reduction in maximum quantum efficiency (Fv/Fm) indicating that non-stomatal factors were more limiting
to ACO2 than stomatal conductance at 25ºC and 35ºC, but not at 15ºC. In flooded plants, the decrease
of Fv-Fm was highest at 35ºC. ‘Carrizo’ and ‘CT33’ maintained higher ACO2 at different soil temperatures
but ‘Troyer’ had the lowest. Based on leaf net gas exchange, chlorophyll fluorescence and water relations,
‘Troyer’ citrange was less tolerant to flooding than ‘Carrizo’ and’ CT33’ whereas ‘Tucuman’, ‘Pomeroy’ and
‘Rubidoux’ had similar tolerance to anoxia regardless of temperature.
S08P16
Flooding affects fruitlet abscission in satsuma mandarin
Goñi Altuna C.T. 1 , Otero A. 2 and Syvertsen J.P. 3
1 Instituto Nacional de Investigacion Agropecuaria (INIA), Soil and Plant Nutrition Laboratory, Uruguay; 2 Instituto Nacional de
Investigacion Agropecuaria (INIA), Ecophysiology Laboratory, Uruguay; and 3 University of Florida. IFAS Citrus Research and Education
Center (UF-IFAS), Citriculture, USA. aotero@sg.inia.org.uy
A field trial tested the effect of soil anoxia and flooding on fruit drop in a mature orchard of satsuma mandarin
(Citrus unshiu) on ‘Pomeroy’ (Poncirus trifoliata) rootstock. Flooded trees were maintained with 10 cm water
above the soil surface using a 60 cm high aluminum barrier which was buried to depth a 45 cm around the
trees. Flooding lasted for 30 days, from flower anthesis to early fruit set. Waterlogging reduced the soil oxygen
levels from 5 to 2 µg O 2 cm -2 min -1 . Relative fruit drop rate was higher in flooded trees than in non-flooded
trees. Flooding reduced the spring flush shoot numbers but not the shoot length of the fewer shoots. Flooding
reduced shoot water potential was but leaf chlorophyll was not affected. Flooding reduced net CO 2 assimilation
rate (ACO2) and stomatal conductance but there were only small changes in internal CO 2 concentration in leaves
and no changes in maximum quantum efficiency (Fv/Fm) or basal chlorophyll florescence (Fo). Thus, stomatal
factors were more important than non-stomatal factors in limiting ACO2 in leaves of flooded trees. Proline was
high in roots of flooded plants but not in leaves. Leaf starch was high in flooded trees however total reducing
carbohydrates were unchanged. Low soil oxygen reduced root function and stomatal conductance and caused
an accumulation leaf starch and early fruit drop. Soil anoxia from anthesis to early fruit set induced fruitlet
abscission in satsuma mandarin and caused changes in tree water relations
S08P17
Frost damage in lemon orchards in the region of Murcia
Conesa A. 1 , Martinez-Nicolas J. 2 , Manera J. 3 and Porras I. 2
1 Miguel Hernandez University (UMH), Department of Vegetable Production and Microbiology, Spain; 2 Murcian Institute of Agriculture
and Food Research and Development (IMIDA), Department of Citriculture, Spain; and 3 Miguel Hernandez University (UMH),
Department of Physics and Architecture of Computers, Spain. agustin.conesa@umh.es
Every few years frosts importantly affect the cultivation area surrounding the Region of Murcia (Spain). The
most important frost period in recent years occurred at the winter of 1994-95 and the latest ones at 2004-
126 - VALENCIA CONFERENCE CENTER, 18th-23rd NOVEMBER 2012