Abstract:
The objective of this work was to evaluate the feasibility of using physiological parameters for water deficit tolerance, as an auxiliary method for selection of upland rice genotypes. Two experiments - with or without water deficit - were carried out in Porangatu, in the state of Goiás, Brazil; the water deficit experiment received about half of irrigation that was applied to the well-watered experiment. Four genotypes with different tolerance levels to water stress were evaluated. The UPLRI 7, B6144F-MR-6-0-0, and IR80312-6-B-3-2-B genotypes, under water stress conditions, during the day, showed lower stomatal diffusive resistance, higher leaf water potential, and lower leaf temperature than the control. These genotypes showed the highest grain yields under water stress conditions, which were 534, 601, and 636 kg ha-1, respectively, and did not differ significantly among them. They also showed lower drought susceptibility index than the other genotypes. 'BRS Soberana' (susceptible control) was totally unproductive under drought conditions. Leaf temperature is a easy-read parameter correlated to plant-water status, viable for selecting rice genotypes for water deficit tolerance.
Index terms:
Oryza sativa; leaf diffusive resistance; leaf temperature; leaf-water potential.
Resumo:
O objetivo deste trabalho foi avaliar a possibilidade de uso de parâmetros fisiológicos de tolerância à deficiência hídrica como método auxiliar na seleção de genótipos de arroz de terras altas. Dois experimentos - um com e outro sem deficit hídrico - foram realizados em Porangatu, GO; o com deficit hídrico recebeu cerca da metade da irrigação que foi aplicada ao tratamento bem irrigado. Avaliaram-se quatro genótipos com diferentes níveis de tolerância ao estresse hídrico. Os genótipos UPLRI 7, B6144F-MR-6-0-0 e IR80312-6-B-3-2-B, em condições de estresse hídrico ao longo do dia, apresentaram menor resistência difusiva estomática, maior potencial de água nas folhas e menor temperatura das folhas do que a testemunha. Esses genótipos apresentaram as maiores produtividades em condições de deficiência hídrica, que foram respectivamente 534, 601 e 636 kg ha-1, e não diferiram significativamente entre si. Eles também apresentaram menores índices de susceptibilidade à seca do que os outros genótipos. 'BRS Soberana' (testemunha suscetível) foi totalmente improdutiva em condições de deficiência hídrica. A temperatura das folhas é um parâmetro de fácil leitura correlacionado à condição hídrica da planta, viável para selecionar genótipos de arroz quanto à tolerância ao deficit hídrico.
Termos para indexação:
Oryza sativa; resistência difusiva foliar; temperatura foliar; potencial de água na folha.
Introduction
Rice is the basic food for over half of the world population. It is
widely cultivated in conditions subjected to water stress (Manickavelu et al.,
2006MANICKAVELU, A.; NADARAJAN, N.; GANESH, S.K.;
GNANAMALAR, R.P.; BABU, R.C. Drought tolerance in rice:
morphological and molecular genetic consideration.
Plant Growth Regulation, v.50, p.121-138, 2006. DOI:
10.1007/s10725-006-9109-3.
https://doi.org/10.1007/s10725-006-9109-...
), both in Asia and in Brazilian upland
systems. Upland rice encompasses 12% of global rice production
area, and it is of a proportionately greater importance in
Africa and Latin America, where it accounts for around 40 and
45% of the rice-growing areas, respectively (Bernier et al.,
2008BERNIER, J.; ATLIN, G.N.; SERRAJ, R.; KUMAR, A.;
SPANER, D. Breeding upland rice for drought resistance.
Journal of the Science of Food and Agriculture, v.88,
p.927-939, 2008. DOI:
10.1002/jsfa.3153.
https://doi.org/10.1002/jsfa.3153....
).
Productivity in these areas is severely affected by water stress, due
to unpredictable, insufficient, and uneven rainfall during the
growing period. To reduce the risk for the crop, the use of new
cultivars, with a greater capacity to adapt to the irregular
distribution of rainfall, is recommended, besides the most
appropriate practices which enable plants for better use of soil
water (Manickavelu et al.,
2006MANICKAVELU, A.; NADARAJAN, N.; GANESH, S.K.;
GNANAMALAR, R.P.; BABU, R.C. Drought tolerance in rice:
morphological and molecular genetic consideration.
Plant Growth Regulation, v.50, p.121-138, 2006. DOI:
10.1007/s10725-006-9109-3.
https://doi.org/10.1007/s10725-006-9109-...
).
Gains from rice improvement for water-stress tolerance have been
modest. Plant breeders rely on direct selection for grain yield
as the main criterion for selection. That process might be made
more efficient by the use of indirect traits associated with
water deficit (Jongdee et al.,
2006JONGDEE, B.; PANTUWAN, G.; FUKAI, S.; FISCHER,
K. Improving drought tolerance in rainfed lowland rice:
an example from Thailand. Agricultural Water
Management, v.80, p.225-240, 2006. DOI:
10.1016/j.agwat.2005.07.015.
https://doi.org/10.1016/j.agwat.2005.07....
). The incorporation of secondary components
in phenotyping for water-deficit tolerance, in the selection
criteria adopted in conventional breeding programs conducted in
adequately prepared environments, from the standpoint of water
for such trait to be expressed, may contribute to the selection
of plants for areas with occurrence of irregular rainfall
distribution (Manickavelu et
al., 2006MANICKAVELU, A.; NADARAJAN, N.; GANESH, S.K.;
GNANAMALAR, R.P.; BABU, R.C. Drought tolerance in rice:
morphological and molecular genetic consideration.
Plant Growth Regulation, v.50, p.121-138, 2006. DOI:
10.1007/s10725-006-9109-3.
https://doi.org/10.1007/s10725-006-9109-...
).
The adaptation to water stress, among other factors, results from the
maintenance of good water status in plant tissues, which can be
evaluated by leaf-water potential, stomatal diffusive resistance
and leaf temperature. Guimarães
et al. (2006)GUIMARÃES, C.M.; STONE, L.F.; BRUNINI, O.
Adaptação do feijoeiro comum (Phaseolus
vulgaris L.) à seca. Revista Brasileira
Engenharia Agrícola e Ambiental, v.10, p.70-75, 2006.
DOI: 10.1590/S1415-43662006000100011.
https://doi.org/10.1590/S1415-4366200600...
reported that a water-deficit
tolerant common bean cultivar, subjected to water-stress
conditions, showed higher leaf-water potential and lower
stomatal diffusive resistances than a susceptible cultivar.
Leaf temperature is a function of leaf energy balance; and the higher
is the leaf temperature, the lower is the energy loss. This loss
occurs in several ways, one of which is the transpiration, which
is more intense as better is plant-water status. The infrared
thermometry can thus infer the water status of the plant (Jones, 2007JONES, H.G. Monitoring plant and soil water
status: established and novel methods revisited and
their relevance to studies of drought tolerance.
Journal of Experimental Botany, v.58, p.119-130, 2007.
DOI: 10.1093/jxb/erl118.
https://doi.org/10.1093/jxb/erl118....
), which
stands out because of its rapid and nondestructive measurement,
in comparison to those of rolling leaves, wilt, change color,
thickness, diameter stem, stomatal diffusive resistance, and
leaf-water potential,
The objective of this work was to evaluate the feasibility of using physiological parameters of water deficit tolerance, as an auxiliary method for the selection of upland rice genotypes.
Materials and Methods
Two experiments were carried out in a Latossolo Vermelho (Typic
Hapludox) (Santos et al.,
2006SANTOS, H.G. dos; JACOMINE, P.K.T.; ANJOS,
L.H.C. dos; OLIVEIRA, V.A. de; OLIVEIRA, J.B. de;
COELHO, M.R.; LUMBRERAS, J.F.; CUNHA, T.J.F. (Ed.).
Sistema brasileiro de classificação de solos. 2.ed. Rio
de Janeiro: Embrapa Solos, 2006. 306p.), at Embrapa Arroz e Feijão
drought-phenotyping site, located at Emater experimental
station, in Porangatu, GO, Brazil. The experimental design was
performed in a randomized complete block, with four replicates,
and one experiment were with and the other were without water
deficit. Four genotypes were evaluated: 'BRS Soberana', an
upland cultivar of the Japonica group, and the lines
B6144F-MR-6-0-0, IR80312-6-B-3-2-B, and UPLRI 7 (UPLRI 7) of the
Indica group. 'BRS Soberana' was susceptible to water deficit
(Heinemann et al.,
2011HEINEMANN, A.B.; STONE, L.F.; FAGERIA, N.K.
Transpiration rate response to water deficit during
vegetative and reproductive phases of upland rice
cultivars. Scientia Agricola, v.68, p.24-30, 2011. DOI:
10.1590/S0103-90162011000100004.
https://doi.org/10.1590/S0103-9016201100...
), and the lines were stres-tolerant to that
(Guimarães et al.,
2009GUIMARÃES, C.M.; BRESEGHELLO, F.; CASTRO, A.P.
de; STONE, L.F.; MORAIS JÚNIOR, O.P. de. Comportamento
produtivo de linhagens de arroz do grupo indica sob
irrigação adequada e sob deficiência hídrica. Santo
Antônio de Goiás: Embrapa Arroz e Feijão, 2009. 4p.
(Embrapa Arroz e Feijão. Comunicado técnico,
180).).
The experiments were sown on 4/30/2009, in plots with six 5 m long rows, and 40 cm apart. Fertilization was applied at sowing at 20, 120 and 60 kg ha-1 of N, P2O5 and K2O, respectively, and 30 kg N ha-1 as ammonium sulfate for top dressing, 45 days after emergence. Weed control was done via oxadiazon at 1,000 g a.i. ha-1 at plant pre-emergency.
The experiment without water stress was well irrigated throughout the
plant development; and the experiment subjected to water stress
was irrigated only up to 30 days after emergency, when water
deficiency was imposed from the final growing season stage up to
harvest. For this, irrigations were applied on the first
experiment, and during the phase without water deficit of the
second experiment, by applying about 25 mm of water irrigation,
when soil-water potential at 0.15 m depth reached -0.025 MPa
(Pinheiro et al.,
2006PINHEIRO, B. da S.; CASTRO, E. da M. de;
GUIMARÃES, C.M. Sustainability and profitability of
aerobic rice production in Brazil. Field Crops
Research, v.97, p.34-42, 2006. DOI:
10.1016/j.fcr.2005.08.013.
https://doi.org/10.1016/j.fcr.2005.08.01...
). In the water stress period, approximately
half of the amount of irrigation water was furnished to the
experiment under water stress conditions. During the crop cycle,
there were no rain, and soil-water was totally controlled.
Leaf-water potential, photosynthetically active solar radiation,
stomatal diffusive resistance, and leaf temperature were
monitored on 66th and 79th days after
emergency. Leaf-water potential, photosynthetically active solar
radiation, and temperature were monitored continuously from dawn
to sunset, while the monitoring of stomatal diffusive resistance
began after the disappearance of dew, to not compromise the
readings. Stomatal diffusive resistance (s m-1) was
measured in two samples, on the superior surface of fully
expanded, apical leaves, at good solar exposure, with SC-1 leaf
porometer (Decagon Devices, Pullman, WA, USA). Leaf-water
potential (MPa) was determined with pressure chambers, model
3005 (Soilmoisture Equipment, Santa Barbara, CA, USA), also on
fully expanded, apical leaves. The value of leaf-water potential
was the average of two individual readings. The equipment was
installed in the center of the experiment, to minimize the time
between sample collection and readings of water potential in
leaves; all recommended precautions to this operation were
taken. Leaf temperatures (ºC) were measured with a model 66
infrared thermometer (Fluke Corporation, Everett, WA, USA), and
the considered value was the average of two individual readings
on fully expanded upper leaves. The photosynthetically active
radiation (μE s-1 m-2) was measured,
with both LI-191SB Line Quantum solar sensor and LI-1776 solar
monitor (LI-COR, Lincoln, NE, USA). In addition, grain yield was
determined on four central lines of each plot, leaving a 0.50 m
border at both ends, and based on it, the drought susceptibility
index was determined according to Fischer & Maurer (1978)FISCHER, R.A.; MAURER, R. Drought resistance in
spring wheat cultivars. I. Grain yield responses.
Australian Journal of Agricultural Research, v.29,
p.897-912, 1978. DOI:
10.1071/AR9780897.
https://doi.org/10.1071/AR9780897....
.
The joint variance analysis of the two experiments for grain yield and the comparison of means were performed by Tukey's test, at 5% probability.
Results and Discussion
Based on the joint variance analysis, the genotypes were differently
affected by water treatments because genotype x water treatment
interaction was significant (Table 1). Lafitte et al. (2006)LAFITTE, H.R.; LI, Z.K.; VIJAYAKUMAR, C.H.M.;
GAO, Y.M.; SHI, Y.; XU, J.L.; FU, B.Y.; YU, S.B.; ALI,
A.J.; DOMINGO, J.; MAGHIRANG, R.; TORRES, R.; MACKILL,
D. Improvement of rice drought tolerance through
backcross breeding: evaluation of donors and selection
in drought nurseries. Field Crops Research, v.97,
p.77-86, 2006. DOI:
10.1016/j.fcr.2005.08.017.
https://doi.org/10.1016/j.fcr.2005.08.01...
and Guimarães et al. (2013)GUIMARÃES, C.M.; STONE, L.F.; RANGEL, P.H.N.;
SILVA, A.C. de L. Tolerance of upland rice genotypes to
water deficit. Revista Brasileira de Engenharia
Agrícola e Ambiental, v.17, p.805-810, 2013. DOI:
10.1590/S1415-43662013000800001.
https://doi.org/10.1590/S1415-4366201300...
also observed
that rice genotypes showed different responses to water deficit
in relation to grain yield.
Genotypes were significantly affected by both water treatments. The average productivity of plants under water-deficit treatment was 443 kg ha-1, and at the treatment without water deficit, it was 3,121 kg ha-1 (Table 2), so, the average of water stress depression on grain yield was 85.8%. The genotypes UPLRI 7, B6144F-MR-6-0-0, and IR80312-6-B-3-2-B had the highest yields, which were 534, 601, and 636 kg ha-1 respectively, under water stress conditions, and did not differ significantly among them. They also showed the lowest drought susceptibility index. 'BRS Soberana' (susceptible control) was totally unproductive at the applied level of water deficit.
Under well-irrigated conditions, there was not a remarkable reduction
of leaf-water potential during the day, as observed under water
stress (Figure 1). Minimum
potential of the genotypes were also similar, -2.30, -2.24,
-2.08, and -2.16 MPa, for 'BRS Soberana', B6144F-MR-6-0-0,
IR80312-6-B-3-2-B, and UPLRI 7, respectively. Under water stress
conditions, the values observed at 7:30 h were -1.85, -1.39,
-1.68, and -1.49 MPa, for the same genotypes, respectively.
Minimum leaf-water potential under this treatment were -2.81,
-2.59, -2.35, and -2.50 MPa for 'BRS Soberana', B6144F-MR-6-0-0,
IR80312-6-B-3-2-B, and UPLRI 7, respectively. These results
agree with those found by He
& Serraj (2012)HE, H.; SERRAJ, R. Involvement of peduncle
elongation, anther dehiscence and spikelet sterility in
upland rice response to reproductive-stage drought
stress. Environmental and Experimental Botany, v.75,
p.120-127, 2012. DOI:
10.1016/j.envexpbot.2011.09.004.
https://doi.org/10.1016/j.envexpbot.2011...
, who observed that under
water stress there was a reduction of leaf-water potential by an
average of 0.43 MPa, compared to the well-watered treatment.
Diurnal variation of leaf-water potential in the upland rice genotypes 'BRS Soberana', B6144F-MR-6-0-0, IR80312-6-B-3-2-B, UPLRI 7, on 07/15/2009 and 07/28/2009, at 66 and 79 days after emergency, respectively: A, with water stress; B, without water stress.
The most productive genotypes under water stress conditions showed
higher leaf-water potential during the day, while 'BRS Soberana'
showed lower leaf-water potential, in comparison to the others
genotypes. 'BRS Soberana' did not show the level of water
deficit recuperation, with the reduction of solar radiation
(Figure 2), as
observed for the other genotypes; its water potential at 18:00 h
was -2.49 MPa, while the average water potential in the other
genotypes was -2.02 MPa. Similar results were observed by Kato et al. (2011)KATO, Y.; HENRY, A.; FUJITA, D.; KATSURA, K.;
KOBAYASHI, N.; SERRAJ, R. Physiological
characterization of introgression lines derived from an
indica rice cultivar, IR64,
adapted to drought and water-saving irrigation. Field
Crops Research, v.123, p.130-138, 2011. DOI:
10.1016/j.fcr.2011.05.009.
https://doi.org/10.1016/j.fcr.2011.05.00...
,
who found that a water stress tolerant genotype increased
leaf-water potential by 30%, in comparison to a susceptible one,
under water deficit conditions (when soil moisture at 0,40 m
reached −70 kPa). Maintenance of high leaf-water potential is
associated with large xylem size and, hence, with higher
internal water conductance (Sibounheuang et al., 2006SIBOUNHEUANG, V.; BASNAYAKE, J.; FUKAI, S.
Genotypic consistency in the expression of leaf water
potential in rice (Oryza sativa L.).
Field Crops Research, v.97, p.142-154, 2006. DOI:
10.1016/j.fcr.2005.09.006.
https://doi.org/10.1016/j.fcr.2005.09.00...
).
Average photosynthetically active solar radiation on 07/15/2009 (full square), and on 07/28/2009 (leaked square), at 66 and 79 days after emergency, respectively.
According to Bernier et al.
(2008)BERNIER, J.; ATLIN, G.N.; SERRAJ, R.; KUMAR, A.;
SPANER, D. Breeding upland rice for drought resistance.
Journal of the Science of Food and Agriculture, v.88,
p.927-939, 2008. DOI:
10.1002/jsfa.3153.
https://doi.org/10.1002/jsfa.3153....
and He
& Serraj (2012)HE, H.; SERRAJ, R. Involvement of peduncle
elongation, anther dehiscence and spikelet sterility in
upland rice response to reproductive-stage drought
stress. Environmental and Experimental Botany, v.75,
p.120-127, 2012. DOI:
10.1016/j.envexpbot.2011.09.004.
https://doi.org/10.1016/j.envexpbot.2011...
, leaf-water potential is
strongly correlated with spikelet sterility under water stress.
These last authors also found that grain yield was highly
associated with spikelet fertility and leaf-water potential.
Because of this, most of the genotypes, identified as tolerant
to water stress, maintained a significantly higher leaf-water
potential than the more susceptible genotypes (Kato et al., 2007KATO, Y.; KAMOSHITA, A.; YAMAGISHI, J.
Evaluating the resistance of six rice cultivars to
drought: restriction of deep rooting and the use of
raised beds. Plant and Soil, v.300, p.149-161, 2007.
DOI: 10.1007/s11104-007-9397-z.
https://doi.org/10.1007/s11104-007-9397-...
).
They had higher fertility of panicles, and the highest
percentage of well-formed grains, which accounts for their
higher productivity.
The effect of water stress on the plant depends on the stage it
occurs. If it coincides with the anther development, genotypes
with higher leaf-water potential will have a greater quantity of
pollen grains and, consequently, a higher yield (Nguyen & Sutton,
2009NGUYEN, G.N.; SUTTON, B.G. Water deficit reduced
fertility of young microspores resulting in a decline
of viable mature pollen and grain set in rice. Journal
of Agronomy and Crop Science, v.195, p.11-18, 2009.
DOI: 10.1111/j.1439-037X.2008.00342.x.
https://doi.org/10.1111/j.1439-037X.2008...
). These authors observed 34% average
reduction of grain set, under water stress conditions, at -0,90
MPa leaf-water potential, in comparison to the control.
When leaf-water potential decreases, at the panicle emergence stage,
it affects panicle exsertion and anthesis dehiscence, also
occurring spikelet desiccation, which results in sterility
increase. If low leaf-water potential occurs after anthesis,
pollination, and fertilization, it may induce embryo abortion
and reduce grain weight (He &
Serraj, 2012HE, H.; SERRAJ, R. Involvement of peduncle
elongation, anther dehiscence and spikelet sterility in
upland rice response to reproductive-stage drought
stress. Environmental and Experimental Botany, v.75,
p.120-127, 2012. DOI:
10.1016/j.envexpbot.2011.09.004.
https://doi.org/10.1016/j.envexpbot.2011...
). The best productivity of the
genotypes B6144F-MR-6-0-0, IR80312-6-B-3-2-B, and UPLRI 7 can be
explained by the maintenance of leaf-water potential, before and
after the emergence of panicles, which improved the overall
water condition of plants as a result of the best establishment
of grains with higher weight. These water conditions induced
better fertility of pollen grains, emission of panicles,
pollination, fertilization, and grain formation, by reducing
embryo abortion.
The temperature of leaves (Tl) responded to the oscillations of solar radiation, inferred by the photosynthetic active radiation (Figure 2), in both water treatments, and, irrespectively of the water treatments and genotypes, it varied throughout the day, according to quadratic equations (Figure 3).
Diurnal variation of leaf temperature of the upland rice genotypes 'BRS Soberana', B6144F-MR-6-0-0, IR80312-6-B-3-2-B, UPLRI 7, on 07/15/2009 and 07/28/2009, at 66 and 79 days after emergency, respectively: A, with water stress; B, without water stress.
The well-irrigated plants showed lower increase of leaf temperature, due to a greater heat loss with the occurrence of higher transpiration. In this treatment, genotypes had similar leaf temperatures throughout the day, with a slight tendency to higher temperatures showed by 'BRS Soberana'. This fact was observed after dawn, at 7:30 h, and lasted until 18:00 h, when the readings were finished.
Under water stress conditions, leaf temperature of genotypes was
higher with the increase of solar radiation. At 7:30 h, the
genotypes had similar temperatures - about 18ºC; however, as
solar radiation increased, leaf temperature increased with a
greater intensity. Temperature increase was different among
almost all genotypes. Leaf temperature difference between
genotypes correlates with characters of water deficit tolerance
(Liu et al.,
2005LIU, H.; ZOU, G.; LIU, G.; HU, S.; LI, M.; YU,
X.; MEI, H.; LUO, L. Correlation analysis and QTL
identification for canopy temperature, leaf water
potential and spikelet fertility in rice under
contrasting moisture regimes. Chinese Science Bulletin,
v.50, p.317-326, 2005. DOI:
10.1007/BF02897572.
https://doi.org/10.1007/BF02897572....
; Hirayama et
al, 2006HIRAYAMA, M.; WADA, Y.; NEMOTO, H. Estimation of
drought tolerance based on leaf temperature in upland
rice breeding. Breeding Science, v.56, p.47-54, 2006.
DOI: 10.1270/jsbbs.56.47.
https://doi.org/10.1270/jsbbs.56.47....
). 'BRS Soberana' was heated more
intensely, and its observed maximum temperature was 37.1°C at
13:42 h. The other genotypes became also heated, but with lower
intensity. Observed temperatures were 33.8, 32.4, and 33.7ºC for
IR80312-6-B-3-2-B, B6144F-MR-6-0-0, and UPLRI 7, respectively.
At 18:00 h, when the observations were finished, 'BRS Soberana'
kept high the leaf temperature (Figure 3 A), which means that water status of
plants had not fully recovered, since water potential in the
leaves was not fully recovered in the treatment with water
deficit (Figure 1 A).
In both water treatments, the leaf temperature of all genotypes varied linearly, as leaf-water potential decreased (Figure 4). The thermal sensitivity of leaves was higher in the water stress treatment than in the well-irrigated one, except for the line B6144F-MR-6-0-0, which had similar thermal sensitivity in both treatments. Thermal sensitivity of 'BRS Soberana', IR80312-6-B-3-2-B, B6144F-MR-6-0-0 and UPLRI 7, under water stress treatment were 13.9, 18.0, 7.6, and 9.8°C, respectively, to a reduction of leaf-water potential of 1 MPa, and 6.0, 9.5, 8.3, and 6.2ºC, respectively, for the same genotypes under well-irrigated treatment.
Leaf temperature variation of the upland rice genotypes 'BRS Soberana', B6144F-MR-6-0-0, IR80312-6-B-3-2-B, UPLRI 7: A, with the leaf-water potential under water stress; and B, with the leaf-water potential without water stress.
The water deficit-tolerant genotypes, B6144F-MR-6-0-0,
IR80312-6-B-3-2-B, and UPLRI 7, maintained under water stress
showed better water conditions and higher leaf-water potential,
probably because they have more efficient water use. The water
deficit-tolerant genotypes are able to maintain better internal
water status, either by taking up more water through a better
root system, or by reducing the rate of plant-water use (Kamoshita et al.,
2008KAMOSHITA, A.; BABU, R.C.; BOOPATHI, N.M.;
FUKAI, S. Phenotypic and genotypic analysis of
drought-resistance traits for development of rice
cultivars adapted to rainfed environments. Field Crops
Research, v.109, p.1-23, 2008. DOI:
10.1016/j.fcr.2008.06.010.
https://doi.org/10.1016/j.fcr.2008.06.01...
). A vigorous root growth positively affects water
uptake and, hence, maintains rice transpiration (Kato & Okami,
2010KATO, Y.; OKAMI, M. Root growth dynamics and
stomatal behavior of rice (Oryza
sativa L.) grown under aerobic and
flooded conditions. Field Crops Research, v.117,
p.9-17, 2010. DOI:
10.1016/j.fcr.2009.12.003.
https://doi.org/10.1016/j.fcr.2009.12.00...
) and keeps a lower rice leaf-temperature, ultimately
stabilizing yield under water stress. Hirayama et al. (2006)HIRAYAMA, M.; WADA, Y.; NEMOTO, H. Estimation of
drought tolerance based on leaf temperature in upland
rice breeding. Breeding Science, v.56, p.47-54, 2006.
DOI: 10.1270/jsbbs.56.47.
https://doi.org/10.1270/jsbbs.56.47....
also observed
that the cultivars of upland rice with deeper root systems had
lower leaf temperatures. These authors also found that leaf
temperature was highly correlated with the transpiration rate
and photosynthesis.
Additionally, Liu et al. (2005)LIU, H.; ZOU, G.; LIU, G.; HU, S.; LI, M.; YU,
X.; MEI, H.; LUO, L. Correlation analysis and QTL
identification for canopy temperature, leaf water
potential and spikelet fertility in rice under
contrasting moisture regimes. Chinese Science Bulletin,
v.50, p.317-326, 2005. DOI:
10.1007/BF02897572.
https://doi.org/10.1007/BF02897572....
and Guimarães et al.
(2010)GUIMARÃES, C.M.; STONE, L.F.; LORIEUX, M.;
OLIVEIRA, J.P. de; ALENCAR, G.C. de O.; DIAS, R.A.A.
Infrared thermometry for drought phenotyping of inter
and intra specific upland rice lines. Revista
Brasileira de Engenharia Agrícola e Ambiental, v.14,
p.148-154, 2010. DOI:
10.1590/S1415-43662010000200005.
https://doi.org/10.1590/S1415-4366201000...
observed that grain yield and spikelet
sterility were related to leaf temperature and that this varied
between genotypes. They also observed that leaf temperature was
highly correlated with indexes of visual water deficit-tolerance
and wilting leaves. The authors concluded that leaf temperature
constitutes a valuable tool for water deficit-tolerance
phenotyping.
The values of stomatal diffusive resistance, in the predawn, were similar among the genotypes, they were close to 100 s m-1, and varied throughout the day according to quadratic mathematical models; for these values, the genotypes showed different maximum points (Figure 5). The genotypes IR80312-6-B-3-2-B, B6144F-MR-6-0-0 and UPLRI 7 had the highest stomatal diffusive resistance between 13:30 and 13:40 h, while 'BRS Soberana' kept a constant increase of stomatal diffusive resistance up to 16:10 h, when 333 s m-1 was observed for this parameter. This can be explained by the worse water status of this cultivar, as shown by its lower leaf-water potential throughout the day, as well as by the its worse recovery of water status (Figure 1) with the reduction of solar radiation, which was confirmed by leaf temperature (Figure 3).
Diurnal variation of stomatal diffusive resistance of the upland rice genotypes 'BRS Soberana', B6144F-MR-6-0-0, IR80312-6-B-3-2-B, UPLRI 7, on 07/15/2009 and 07/28/2009, at 66 and 79 days after emergency, respectively, under water stress.
The data are indicative that 'BRS Soberana' is more susceptible to water stress, which is showed by its higher stomatal diffusive resistance, during most of the day, in response to its worse water conditions, certainly by having a lower capacity of the soil water use. The most water stress-tolerant genotypes had lower stomatal diffusive resistance, mainly the lines IR80312-6-B-3-2-B and UPLRI 7, which also had better water conditions evaluated by leaf-water potential and leaf temperature, when subjected to water deficit.
Conclusions
-
Leaf-water potential, leaf temperature, and stomatal diffusive resistance are sensitive to water deficit, and they can be used to discriminate rice genotypes for tolerance to this kind of stress.
-
Leaf temperature is a easy-read parameter correlated to plant-water status, viable for selecting rice genotypes for water deficit tolerance.
Acknowledgments
To the Experimental Station of Empresa de Assistência Técnica e Extensão Rural (Emater), in Porangatu, GO, Brazil, for the provision of infrastructure; and to Ramatis Justino da Silva, for his assistance in the conduction of this research.
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Publication Dates
-
Publication in this collection
July 2015
History
-
Received
31 Oct 2014 -
Accepted
27 May 2015