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1.
Almond plants (Amygdalus communis L.) of the Garrigues variety were grown in the field drip irrigated and rainfed. Leaf water potential (Ψ) and leaf conductance
(g1) were determined throughout one growing season. Pre-dawn measurement for Ψ in the irrigated treatment was consistent through
the growing season, whereas in the rainfed treatment it decreased gradually. Ψ values at midday (Ψ minimum) was closely dependent
on atmospheric evaporative demand, and their recovery was quicker in the wet treatment than in the dry. The g1 values were higher in the wet than dry treatments, decreasing in both cases by leaf ageing. Maximum values for g1 were reached when evaporative demand was highest in the day. The relationship between Ψ and g1 revealed a decrease in the hysteresis throughout the growing season, being most marked in the dry treatment. The results
highlight the close dependence of Ψ and g1 on evaporative demand, leaf ageing and irrigtion treatment during the growing season. 相似文献
2.
Caragana korshinskii seedlings maintain positive photosynthesis during short-term,severe drought stress 总被引:1,自引:0,他引:1
Seedling performance may determine plant distribution, especially in water-limited environments. Plants of Caragana korshinskii commonly grow in arid and semiarid areas in northwestern China, and endure water shortage in various ways, but little is
known about their performance when water shortage occurs at early growth stages. The water relations, photosynthetic activity,
chlorophyll (Chl) content and proline accumulation were determined in 1-year-old seedlings growing in a 1:1 mixture of Loess
soil and Perlite and subjected to (1) a water deficit for 20 days and (2) kept adequately watered throughout. The water deficit induced low (−6.1 MPa) predawn leaf water potentials (LWP), but did
not induce any leaf abscission. Stomatal conductance (g
s), leaf transpiration rate (E), and net photosynthetic rate (P
N) decreased immediately following the imposition of the water deficit, while the maximal photochemical efficiency of photosystem
II (PSII) (Fv/Fm) and the effective quantum yield of PSII (ΦPSII) decreased 15 days later. An early and rapid decrease in g
s, reduced E, increased Chl (a+b) loss, increased the apparent rate of photochemical transport of electrons through PSII (ETR)/P
N, as well as a gradual increase in non-photochemical quenching of fluorescence (NPQ) and proline may have contributed to preventing
ΦPSII from photodamage. C. korshinskii seedlings used a stress-tolerance strategy, with leaf maintenance providing a clear selective advantage, considering the
occasional rainfall events during the growing season. 相似文献
3.
Lemon plants (Citrus limonum L. cv. Verna) were grown in the field under two different flood irrigation treatments. The dry treatment received four irrigations
per year (March, July, September and November) and the wet treatment one monthly. The amounts of water applied per year for
dry and wet treatments were 340.0 mm and 1020.0 mm, respectively. The effects of the two treatments on certain aspects of
the plant water relations during the period between flowering and the end of rapid fruit growth (critical period) were studied.
Soil matric potential (ψm) and leaf water potential (ψi) values in the dry treatment revealed development of water stress
during the experimental period. The water supply in the wet treatment seems sufficient to achieve the crop water requirements.
The g1 values in July were higher in the wet than dry treatments. Pronounced oscillations in g1 from sunrise to afternoon were found especially in the dry treatment. 相似文献
4.
Mature apricot (Prunus armeniaca L. cv. Búlida) trees, growing under field conditions, were submitted to two drip irrigation treatments: a control (T1), irrigated
to 100 % of seasonal crop evapotranspiration (ETc), and a continuous deficit (T2), irrigated to 50 % of the control throughout
the year. The behaviour of leaf water potential and its components, leaf conductance and net photosynthesis were studied at
three different times during the growing season, when they revealed a diurnal and seasonal pattern in response to water stress,
evaporative demand of the atmosphere and leaf age. The deficit-irrigated trees showed, among other effects, a pronounced decrease
in leaf water potential (ψw), decreased in leaf conductance (gs) and no osmotic adjustment. For this reason, gl and ψw can be considered good indicators of mature apricot tree water status and can therefore be used for irrigation scheduling. 相似文献
5.
Stomatal and non-stomatal limitations to photosynthesis in field-grown grapevine cultivars 总被引:1,自引:1,他引:0
Diurnal changes of photosynthesis in the leaves of grapevine (Vitis vinifera × V. labrusca) cultivars Campbell Early and Kyoho grown in the field were compared with respect to gas exchanges and actual quantum yield
of photosystem 2 (ΦPS2) in late May. Net photosynthetic rate (PN) of the two cultivars rapidly increased in the morning, saturated at photosynthetic photon flux density (PPFD) from 1200
to 1500 μmol m−2 s−1 between 10:00 and 12:00 and slowly decreased after midday. Maximum PN was 13.7 and 12.5 μmol m−2 s−1 in Campbell Early and Kyoho, respectively. The stomatal conductance (gs) and transpiration rate changed in parallel with PN, indicating that PN was greatly affected by gs. However, the decrease in PN after midday under saturating PPFD was also associated with the observed depression of ΦPS2 at high PPFD. The substantial increase in the leaf to air vapour pressure deficit after midday might also contribute to decline
of gs and PN. 相似文献
6.
B. R. Lee L. S. Li W. J. Jung Y. L. Jin J. C. Avice A. Ourry T. H. Kim 《Biologia Plantarum》2009,53(3):505-510
The objective of this study was to determine the development of the antioxidant enzymes induced by drought stress in white
clover (Trifolium repens L.) leaves. Water stress was imposed during 28 d by decreasing the daily irrigation. Leaf water potential (Φw) gradually decreased from −0.46 to −2.33 MPa. For the first 7 d, dry mass (DM), H2O2 and lipid peroxidation were not significantly affected by water deficit. From 14 d of treatment, water stress decreased dry
mass and increased content of reactive oxygen species (O2
·− and H2O2) and oxidative stress (malondialdehyde content). The ascorbate peroxidase (APOD) was activated most rapidly, already during
the first week of water stress, but then its activity slowly decreased. Activation of superoxide dismutase (SOD) and catalase
(CAT) by water deficit continued during the 14 d (Φw ≥ −1.65 MPa) and then their activities remain on the similar level. The activity of guaiacol-peroxidase (GPOD) increased
mostly under progressive water stress and was correlated with increase in lipid peroxidation and growth restriction. 相似文献
7.
Photochemical efficiency of PSII of Ctenanthe setosa was investigated to understand the photosynthetic adaptation mechanism under drought stress causing leaf rolling. Stomatal
conductance (g
s), the levels of photosynthetic pigments and chlorophyll (Chl) fluorescence parameters were determined in leaves that had
four different visual leaf rolling scores from 1 to 4, opened after re-watering and mechanically opened at score 4. g
s value gradually decreased in adaxial and abaxial surfaces in relation to scores of leaf rolling. Pigment contents decreased
until score 3 but approached score 1 level at score 4. No significant variations in effective quantum yield of PSII (ΦPSII), and photochemical quenching (qp) were found until score 3, while they significantly decreased at score 4. Non-photochemical quenching (NPQ) increased at
score 2 but then decreased. After re-watering, the Chl fluorescence and other physiological parameters reached to approximately
score 1 value, again. As for mechanically opened leaves, g
s decreased during drought period. The decrease in adaxial surface was higher than that of the rolled leaves. NPQ was higher
than that of the rolled leaves. ΦPSII and qp significantly declined and the decreases were more than those of the rolled leaves. In conclusion, the results indicate that
leaf rolling protects PSII functionality from damage induced by drought stress. 相似文献
8.
Aquaporins seem essential for the regulation of plant water status and expenses. Richter-110 is a Vitis hybrid (Vitis
berlandieri × rupestris) reputed to be strongly drought-tolerant. Three irrigation treatments were established in Richter-110 plants growing outdoors
defined by the resulting maximum stomatal conductance (g
s), and ensuring water stress situations not severe enough as to stop photosynthesis and growth: well-watered plants (g
s about 250 mmol H2O m−2 s−1), moderate water stress (g
s about 150 mmol H2O m−2 s−1) and severe water stress (g
s about 50 mmol H2O m−2 s−1). Plants under water stress were kept at constant water availability for 7 days to check for possible acclimation. Finally,
plants were re-watered, and allowed to recover, for 3 days. Stomatal conductance, leaf water potential, xylem abscisic acid
(ABA) content and root and stem hydraulic conductivity were determined. The relative amounts of expression of mRNA encoding
seven putative aquaporins were determined in roots and leaves by RT-PCR. The decrease in stomatal conductance with moderate
and severe water stress was associated with increasing ABA contents, but not with the leaf water potential and hydraulic conductivities,
which remained unchanged during the entire experiment. Aquaporin gene expression varied depending on which aquaporin, water
stress level and the plant organ. We suggest that aquaporin expression was responsive to water stress as part of the homeostasis,
which resulted in constant leaf water potential and hydraulic conductivity. 相似文献
9.
Victoria J. Stokes Michael D. Morecroft James I. L. Morison 《Trees - Structure and Function》2010,24(2):297-306
The seasonal trends in water use efficiency of sun and shade leaves of mature oak (Quercus robur) and sycamore (Acer pseudoplatanus) trees were assessed in the upper canopy of an English woodland. Intrinsic water use efficiency (net CO2 assimilation rate/leaf conductance, A/g) was measured by gas exchange and inferred from C isotope discrimination (δ13C) methods. Shade leaves had consistently lower δ13C than sun leaves (by 1–2‰), the difference being larger in sycamore. Buds had distinct sun and shade isotopic signatures
before bud break and received an influx of 13C-rich C before becoming net autotrophs. After leaf full expansion, δ13C declined by 1–2‰ gradually through the season, emphasising the importance of imported carbon in the interpretation of leaf
δ13C values in perennial species. There was no significant difference between the two species in the value of intrinsic water
use efficiency for either sun or shade leaves. For sun leaves, season-long A/g calculated from δ13C (72–78 μmol CO2 [mol H2O]−1) was 10–16% higher than that obtained from gas exchange and in situ estimates of leaf boundary layer conductance. For shade
leaves, the gas exchange–derived values were low, only 10–18% of the δ13C-derived values. This is ascribed to difficulties in obtaining a comprehensive sample of gas exchange measurements in the
rapidly changing light environment. 相似文献
10.
Z. -M. Ge X. Zhou S. Kellomäki K. -Y. Wang H. Peltola P. J. Martikainen 《Photosynthetica》2011,49(2):172-184
The effects of elevated growth temperature (ambient + 3.5°C) and CO2 (700 μmol mol−1) on leaf photosynthesis, pigments and chlorophyll fluorescence of a boreal perennial grass (Phalaris arundinacea L.) under different water regimes (well watered to water shortage) were investigated. Layer-specific measurements were conducted
on the top (younger leaf) and low (older leaf) canopy positions of the plants after anthesis. During the early development
stages, elevated temperature enhanced the maximum rate of photosynthesis (P
max) of the top layer leaves and the aboveground biomass, which resulted in earlier senescence and lower photosynthesis and biomass
at the later periods. At the stage of plant maturity, the content of chlorophyll (Chl), leaf nitrogen (NL), and light response of effective photochemical efficiency (ΦPSII) and electron transport rate (ETR) was significantly lower under elevated temperature than ambient temperature in leaves
at both layers. CO2 enrichment enhanced the photosynthesis but led to a decline of NL and Chl content, as well as lower fluorescence parameters of ΦPSII and ETR in leaves at both layers. In addition, the down-regulation by CO2 elevation was significant at the low canopy position. Regardless of climate treatment, the water shortage had a strongly
negative effect on the photosynthesis, biomass growth, and fluorescence parameters, particularly in the leaves from the low
canopy position. Elevated temperature exacerbated the impact of water shortage, while CO2 enrichment slightly alleviated the drought-induced adverse effects on P
max. We suggest that the light response of ΦPSII and ETR, being more sensitive to leaf-age classes, reflect the photosynthetic responses to climatic treatments and drought
stress better than the fluorescence parameters under dark adaptation. 相似文献
11.
A. L. García L. Marcelis F. Garcia-Sanchez N. Nicolas V. Martínez 《Biologia Plantarum》2007,51(4):707-712
The responses of water relations, stomatal conductance (gs) and growth parameters of tomato (Lycopersicon esculentum Mill. cv. Royesta) plants to nitrogen fertilisation and drought were studied. The plants were subjected to a long-term, moderate
and progressive water stress by adding 80 % of the water evapotranspirated by the plant the preceding day. Well-watered plants
received 100 % of the water evapotranspirated. Two weeks before starting the drought period, the plants were fertilised with
Hoagland’s solution with 14, 60 and 110 mM NO3
− (N14, N60 and N110, respectively). Plants of the N110 treatment had the highest leaf area. However, gs was higher for N60 plants and lower for N110 plants. At the end of the drought period, N60 plants showed the lowest values
of water potential (Ψw) and osmotic potential (Ψs), and the highest values of pressure potential (Ψp). N60 plants showed the highest Ψs at maximum Ψp and the highest bulk modulus of elasticity. 相似文献
12.
Water relations and gas exchange in olive trees under regulated deficit irrigation and partial rootzone drying 总被引:2,自引:1,他引:1
J. E. Fernández A. Díaz-Espejo J. M. Infante P. Durán M. J. Palomo V. Chamorro I. F. Girón L. Villagarcía 《Plant and Soil》2006,284(1-2):273-291
It is widely believed that partial root drying (PRD) reduces water losses by transpiration without affecting yield. However,
experimental work carried out to date does not always support this hypothesis. In many cases a PRD treatment has been compared
to a full irrigated treatment, so doubt remains on whether the observed benefits correspond to the switching of irrigation
or just to PRD being a deficit irrigation treatment. In addition, not always a PRD treatment has been found advantageous as
compared to a companion regulated deficit irrigation (RDI) treatment. In this work we have compared the response of mature
‘Manzanilla‘ olive trees to a PRD and an RDI treatment in which about 50% of the crop evapotranspiration (ETc) was supplied daily by localised irrigation. We alternated irrigation in the PRD treatment every 2 weeks in 2003 and every
3 weeks in 2004. Measurements of stem water potential (Ψstem), stomatal conductance (g
s) and net CO2 assimilation rate (A) were made in trees of both treatments, as well as in trees irrigated to 100% of ETc (Control trees) and in Rain-fed trees. Sap flow was also measured in different conductive organs of trees under both PRD
and RDI treatments, to evaluate the influence of alternating irrigation on root water uptake and tree water consumption. We
found small and random differences in Ψstem, g
s and A, which gave no evidence of PRD causing a positive effect on the olive tree performance, as compared to RDI. Stomatal conductance
decreased in PRD trees as compared to Control trees, but a similar decrease in g
s was also recorded in the RDI trees. Sap flow measurements, which reflected water use throughout the irrigation period, also
showed no evidence of g
s being more reduced in PRD than in RDI trees. Daily water consumption was also similar in the trees of the deficit irrigation
treatments, for most days, throughout the irrigation period. Alternating irrigation in PRD trees did not cause a change in
either water taken up by main roots at each side of the trees, or in the sap flow of both trunk locations and main branches
of each side. Results from this work, and from previous work conducted in this orchard, suggest that transpiration is restricted
in trees under deficit irrigation, in which roots are left in drying soil when water is applied by localised irrigation, and
that there is no need to alternate irrigation for achieving this effect.
Section Editor: R. E. Munns 相似文献
13.
Genotypic variation in photosynthesis in cacao is correlated with stomatal conductance and leaf nitrogen 总被引:1,自引:0,他引:1
Variation in photosynthetic parameters was observed between eight contrasting cacao (Theobroma cacao) genotypes. Net photosynthetic rate (PN) ranged from 3.4 to 5.7 μmol(CO2) m−2 s−1 for the genotypes IMC 47 and SCA 6, respectively. Furthermore, genotypic differences were detected in quantum efficiency
ranging from 0.020 to 0.043 μmol(CO2) μmol−1(photon) for UF 676 and AMAZ 15/15, respectively. Differences in PN were correlated with both stomatal conductance (gs) and leaf nitrogen per unit area. Some variation in water use efficiency was observed between genotypes, both intrinsic (PN/gs) and instantaneous (PN/transpiration rate). Both measures of water use efficiency were a negative function of specific leaf area. Evidence was found
for a trade-off mechanism between cacao genotypes in photosynthesis and leaf structure. High photosynthetic rate, expressed
on a mass basis was associated with smaller leaves. Furthermore, thinner leaves were compensated for by a higher nitrogen
content per unit mass. 相似文献
14.
The aim of this study was to extent the range of knowledge about water relations and stomatal responses to water stress to
ten Mediterranean plants with different growth forms and leaf habits. Plants were subjected to different levels of water stress
and a treatment of recovery. Stomatal attributes (stomatal density, StoD), stomatal conductance (g
s), stomatal responsiveness to water stress (SR), leaf water relations (pre-dawn and midday leaf water potential and relative
water content), soil to leaf apparent hydraulic conductance (K
L) and bulk modulus of elasticity (ε) were determined. The observed wide range of water relations and stomatal characteristics
was found to be partially depended on the growth form. Maximum g
s was related to StoD and the stomatal area index (SAI), while g
s evolution after water stress and recovery was highly correlated with K
L. Relationships between SR to water deficit and other morphological leaf traits, such as StoD, LMA or ε, provided no general
correlations when including all species. It is concluded that a high variability is present among Mediterranean plants reflecting
a continuum of leaf water relations and stomatal behaviour in response to water stress. 相似文献
15.
Leaf gas exchange in a clonal eucalypt plantation as related to soil moisture, leaf water potential and microclimate variables 总被引:7,自引:0,他引:7
M. S. Mielke M. A. Oliva N.F. de Barros R. M. Penchel C. A. Martinez S. da Fonseca A.C. de Almeida 《Trees - Structure and Function》2000,14(5):263-270
In order to determine how environmental and physiological factors affect leaf gas exchange in a 9-year-old clonal eucalypt
plantation (Eucalyptus grandis Hill ex. Maiden hybrids) in the State of Espirito Santo, Brazil, the diurnal patterns of predawn leaf water potential (Ψpd), and leaf gas exchange were monitored from November 1995 to August 1996. Soil water content (Θ) and microclimatic variables
were also recorded. Most of the rainfall during the experimental period occurred from October to December 1995 and from March
to April 1996, causing a significant variation in Θ and Ψpd. A high positive correlation (r
2=0.92) was observed between Ψpd and Θ measured at 0.3 m depth from the soil surface. During conditions of high soil water availability, the maximum values
of stomatal conductance for water vapor (g
s) and net photosynthetic rate (A) were over 0.4 mol m–2 s–2 and l5 μmol m–2 s–1, respectively. The results showed that Ψpd and leaf gas exchange of the examined trees were susceptible to changes in the water content of the upper soil layers, where
the major concentration of active roots occur. Multiple linear regression analysis indicated that photosynthetic active radiation
(Q), vapor pressure deficit (VPD), atmospheric CO2 molar fraction (C
a), and Ψpd were the most important factors controlling g
s whereas Q and VPD were the main microclimatic variables controlling A.
Received: 5 November 1998 / Accepted: 10 November 1999 相似文献
16.
Luca Vitale Paul Di Tommasi Carmen Arena Angelo Fierro Amalia Virzo De Santo Vincenzo Magliulo 《Acta Physiologiae Plantarum》2007,29(4):317-326
Zea mays is cultivated in the Mediterranean regions where summer drought may lead to photoinhibition when irrigation is not available.
In this work the response of maize to water stress was evaluated by gas exchange measurements at the canopy and leaf level.
Leaf gas exchange was assessed before, during and after water stress, while canopy turbulent fluxes of mass and energy were
performed on a continuous basis. In the early growth period, a linear increment of net ecosystem photosynthetic rate (P
NE) to incoming of photosynthetic photon flux density (PPFD) was found and net leaf photosynthetic rate (P
NL) showed the tendency to saturate under high irradiance. During water stress, the relationship between P
NE and PPFD became curvilinear and both P
NE and P
NL saturated in a range between 1,000 and 1,500 μmol (photons) m−2 s−1. Leaf water potential (ψl) dropped from −1.50 to −1.88 MPa during water stress, indicating that leaf and canopy gas exchanges were limited by stomatal
conductance. With the restoration of irrigation, P
NE, P
NL and ψl showed a recovery, and P
NE and P
NL reached the highest values of whole study period. Leaf area index (LAI) reached a value of 3.0 m2 m−2. The relationship between P
NE and PPFD remained curvilinear and P
NE values were lower than those of a typical well-irrigated maize crop. The recovery in P
NE and P
NL after stress, and ψl values during stress indicate that the photosynthetic apparatus was not damaged while soil moisture stress after-effects
resulted in a sub-optimal LAI values, which in turn depressed P
NE. 相似文献
17.
Water status and gas exchange of beech (Fagus sylvatica L.) and sessile oak [Quercus petraea (Mattuschka) Liebl.] were studied in a mixed stand in the Montejo de la Sierra forest (central Iberian Peninsula), one of
the southernmost locations of both species in Europe. Gas exchange and water potential were measured in leaves at different
canopy levels over several days in two growing seasons. The daily variation pattern was established with the measurements
of three selected dates per year, representative of the soil moisture content situations in early, mid- and late summer. A
similar daily time course of leaf water potential was found for the two species. Nevertheless, beech showed a most noticeable
decrease of water potential at midmorning and maintained lower leaf water potential than oak in the early afternoon. In 1994
the sessile oak saplings showed higher values of predawn water potential (Ψpd) than beech at the end of summer, when soil moisture content was lowest (20 cm depth). Beech showed a significantly lower
net assimilation rate (A) than sessile oak for leaves under the same PPFD. Maximum net photosynthesis values (A
max) for beech and sessile oak on sunny leaves were 10.1±0.4 μmol m–2 s–1 and 17.8±1.7 μmol m–2 s–1 respectively, and those for water vapour stomatal conductance (g
wv) were 265±31 mmol m–2 s–1 and 438±74 mmol m–2 s–1. Differences in A and g
wv between the two species were maintained throughout the day on all measurement dates. No clear relationship was found between
water status of saplings and stomata performance; there was only a negative correlation between Ψpd and g
wvmid in beech. Nevertheless, a significant response to the air vapour pressure gradient between leaf and air was translated into
stomata closure on an hourly basis, more intensively in beech.
Received: 4 March 1999 / Accepted: 21 December 1999 相似文献
18.
Six months old in vitro-grown Anoectochilus formosanus plantlets were transferred to ex-vitro acclimation under low irradiance, LI [60 μmol(photon) m−2 s−1], intermediate irradiance, II [180 μmol(photon) m−2 s−1], and high irradiance, HI [300 μmol(photon) m−2 s−1] for 30 d. Imposition of II led to a significant increase of chlorophyll (Chl) b content, rates of net photosynthesis (P
N) and transpiration (E), stomatal conductance (g
s), electron transfer rate (ETR), quantum yield of electron transport from water through photosystem 2 (ΦPS2), and activity of ribulose-1,5-bisphosphate carboxylase/ oxygenase (RuBPCO, EC 4.1.1.39). This indicates that Anoectochilus was better acclimated at II compared to LI treatment. On the other hand, HI acclimation led to a significant reduction of
Chl a and b, P
N, E, g
s, photochemical quenching, dark-adapted quantum efficiency of open PS2 centres (Fv/Fm), probability of an absorbed photon reaching an open PS2 reaction centre (Fv′/Fm′), ETR, ΦPS2, and energy efficiency of CO2 fixation (ΦCO2/ΦPS2). This indicates that HI treatment considerably exceeded the photo-protective capacity and Anoectochilus suffered HI induced damage to the photosynthetic apparatus. Imposition of HI significantly increased the contents of antheraxanthin
and zeaxanthin (ZEA), non-photochemical quenching, and conversion of violaxanthin to ZEA. Thus Anoectochilus modifies its system to dissipate excess excitation energy and to protect the photosynthetic machinery. 相似文献
19.
Lubomír Adamec 《Central European Journal of Biology》2010,5(1):121-124
In this study, O2-based dark respiration rate (RD) in leaf and trap cuttings was compared in 9 terrestrial carnivorous plant species of 5 genera to decide whether traps represent
a greater energetic (maintanence) cost than leaves or photosynthetic parts of traps. RD values of cut strips of traps or leaves of terrestrial carnivorous plants submerged in water ranged between 2.2 and 8.4 nmol
g−1 s−1 (per unit dry weight) in pitcher traps of the genera Sarracenia, Nepenthes, and Cephalotus, while between 7.2 and 25 nmol g−1
DW s−1 in fly-paper or snapping traps or leaves of Dionaea and Drosera. No clear relationship between RD values of traps (or pitcher walls) and leaves (or pitcher wings or petioles) was found. However, RD values of separated Drosera prolifera tentacles exceeded those of leaf lamina 7.3 times. 相似文献
20.
The effects of nitrogen (N) supply restriction on the CO2 assimilation and photosystem 2 (PS2) function of flag leaves were compared between two contrastive Japanese rice cultivars,
a low-yield cultivar released one century ago, cv. Shirobeniya (SRB), and a recently improved high-yield cultivar, cv. Akenohoshi
(AKN). Both cultivars were solution-cultured at four N supply levels from N4 (control) to N1 (the lowest). With a reduction
in N-supply, contents of N (LNC), ribulose-1,5-bisphosphate carboxylase/oxygenase (RuBPCO), and chlorophyll (Chl) in flag
leaves decreased in both cultivars. In parallel with this, the net photosynthetic rate (P
N), mesophyll conductance (g
m), and stomatal conductance (g
s) decreased. P
N was more dominantly restricted by g
m than g
s. The values of P
N, g
m, and RuBPCO content were larger in AKN than SRB at the four N supply levels. The content of Chl greatly decreased with N
deficiency, but the reduction in the maximum quantum yield of PS2 was relatively small. Quantum yield of PS2 (ΦPS2) decreased with N deficiency, and its significant cultivar difference was observed between the two cultivars at N1: a high
value was found in AKN. The content ratio of Chl/RuBPCO was also significantly low in AKN. The low Chl/RuBPCO is one of the
reasons why AKN maintained a comparatively high P
N and ΦPS2 at N deficiency. The adequate ratio of N distribution between Chl and RuBPCO is the important prerequisite for the efficient
and sustainable photosynthesis in a flag leaf of rice plant under low N-input. 相似文献