Photosynthesis and water relations of almond tree cultivars grafted on two rootstocks

Five cultivars of Prunus amygdalus Batsch (Ferragnes, Ferrastar, Marcona, Garrigues, and Non Pareil) grafted on two different rootstocks (Garrigues and GF677), and two cultivars (Ferraduel and Casa Nova) grafted on GF677, were grown for three years under rainfed conditions in an orchard in northeast Portugal. Net photosynthetic rate (PN), leaf conductance for water vapour (gs), leaf water potential (Ψ), instantaneous water use efficiency (WUE), and internal CO2 concentration (Ci) were measured at three periods of the growing season: spring, summer (June or July) and late summer (September) over two years. Ferraduel, Ferrastar, and Marcona presented the best performance in the periods when environmental conditions were not very hard (May or September). Casa Nova and Non Pareil were well adapted to high air evaporative demand, preventing the increase of leaf temperature (T1). Ferrastar, although having a good performance in May and September, did well adapt to hard climatic conditions in June 1994. In the following year, although it presented the highest T1, the values were not limiting (30.6 ± 2.1 °C), and PN was only decreased from May to July. Marcona was highly dependent on T1, but prevented its increasing. Garrigues showed lower PN in most measurement periods. GF677 frequently induced the highest PN, WUE, and Ψ. PN was mainly dependent on T1, radiation, Ci, month, and year. WUE depended on the same factors. Ψ depended mainly on gs, air temperature, month, and year.     

Photosynthesis of soybean cultivars released in different decades after grafting onto record-yield cultivars as rootstocks

While photosynthesis of soybean has been enhanced by breeding, it remains to be clarified whether the improvement of root function could bring a further increase of photosynthetic capacity for the development of soybean cultivars. The objective of this grafting experiment was to determine the influence of record-yield soybean cultivars, Liaodou14 (L14) and Zhonghuang35 (Z35), as rootstocks on photosynthetic traits of cultivars released in different decades. Grafting of various soybean cultivars onto L14 or Z35 rootstocks showed a higher root physiological activity, which resulted in significant increases in some photosynthetic traits at the late grain-filling stage compared with the non-grafted and self-grafted plants. The genetic gain for some photosynthetic traits of cultivars released from 1966 to 2006 increased by using L14 and Z35 as rootstocks. It suggested that the photosynthetic traits of the recently released cultivars could increase more if their root functions are improved.     

The pathogenicity and increase of Heterodera rostochiensis on tomato cultivars, self-rooted or grafted on to rootstocks.

Self-rooted tomatoes ‘Ailsa Craig’ and ‘Kingley Cross’, and scions of ‘Ailsa Craig’ grafted on to different rootstocks, were grown in soil infested with different numbers of Heterodera rostochiensis (Mainly pathotype A). Three rootstocks (RS₄, RSKN, ISKVF) tolerated damage from nematode populations of up to 125 eggs/g soil, but nematodes increased up to x45 on them. Two nematode-resistant F₁ hybrid rootstocks, B66₃₃ (ex Lycopersicon pimpinellifolium B6₁₇₃) and B6₀₁₅ (ex L. hirsutum var. glabratum B6₀₁₃), tolerated up to 125 eggs/g soil; nematode populations declined as much as 80% under B66₃₃, and increased little under B6₀₁₅. On the self-rooted ‘Ailsa Craig’ and ‘Kingley Cross' the numbers of nematodes increased markedly (maximum increase x40), and greatly affected growth and yield so that initial populations greater than 62 eggs/g soil caused crop failure.     

Gas exchange and leaf water relations in two peanut cultivars of different drought tolerance

In summer seasons of 1991 and 1992 the gas exchange and leaf water relations were analysed in two peanut cultivars: drought tolerant cv. GG 2 (DT) and drought sensitive cv. JL 24 (DS). Soil moisture stress was imposed by withholding irrigation at pod development phase. The decrease in photosynthesis (P_N) under stress was associated with a decrease in stomatal conductance (g_s) and relative water content (RWC). The P_N and RWC were significantly higher under stress in DT than DS. On relief of stress the g_s and RWC recovered more quickly in DT than DS. The maintenance of higher RWC (>80 %), g_s and P_N under stress appears to be imparting drought tolerance in peanut.     

Water relations of Fino lemon plants on two rootstocks under flooded conditions

Potted two-year-old Fino lemon plants (Citrus limon (L.) Burm. fil.) grafted on two different rootstocks: sour orange (C. aurantium) (SO), and C. macrophylla (CM) were submitted to two different treatments: non-flooded (control) and flooded for 8 days, under field conditions. Lemon/CM plants had lower plant plus soil resistance to water flow (R_(p+s)) values for both treatments. The decrease in leaf water potential (Ψ_l) and leaf turgor potential (Ψ_p) values, observed in the last part of the flooding period, in both flooded scion/rootstock combinations, can be related to the increase in the resistance to water flow. The maintenance in Ψ_l and Ψ_p values in flooded plants at values similar to those of the control plants, at the beginning of the flooding period and during the recovery period, can be ascribed to the stomatal control observed (decrease in leaf conductance (g₁) values). The later g₁ recovery in lemon/CM than in lemon/SO flooded plants, could explain the lower vegetative growth of lemon/CM plants by flooding effect. The observed g₁ response to soil flooding suggested that porometry is a reliable indicator of the altered behaviour caused by flooding in lemon plant.     

The water relations of two evergreen tree species in a karst savanna

The ecohydrology of karst has not received much attention, despite the disproportionally large contribution of karst aquifers to freshwater supplies. Karst savannas, like many savannas elsewhere, are encroached by woody plants, with possibly negative consequences on aquifer recharge. However, the role of savanna tree species in hydrological processes remains unclear, not least because the location and water absorption zones of tree roots in the spatially complex subsurface strata are unknown. This study examined the water sources and water relations of two savanna trees, Quercus fusiformis (Small) and Juniperus ashei (Buchholz) in the karst region of the eastern Edwards Plateau, Texas (USA). Stable isotope analysis of stem water revealed that both species took up evaporatively enriched water during the warm season, suggesting a relatively shallow water source in the epikarst, the transition zone between soil and bedrock. Q. fusiformis had consistently higher predawn water potentials than J. ashei during drought, and thus was probably deeper-rooted and less capable of maintaining gas exchange at low water potentials. Although the water potential of both species recovered after drought-breaking spring and summer rain events, associated shifts in stem water isotope ratios did not indicate significant uptake of rainwater from the shallow soil. A hypothesis is developed to explain this phenomenon invoking a piston-flow mechanism that pushes water stored in macropores into the active root zones of the trees. Epikarst structure varied greatly with parent material and topography, and had strong effects on seasonal fluctuations in plant water status. The study suggests that tree species of the Edwards Plateau do not commonly reduce aquifer recharge by tapping directly into perched water tables, but more likely by reducing water storage in the epikarst. A more general conclusion is that models of savanna water relations based on Walter's two-layer model may not apply unequivocally to karst savannas.     

Differential response of two almond rootstocks to chloride salt mixtures in the growing medium

It was examined how essential cations, Ca²⁺ and K⁺, can mitigate the toxic effects of NaCl on two different almond species (Prunus amygdalus Batsch) rootstocks, Garnem (GN15) and Bitter Almond. The tree growth parameters (water potential (Ψ_w), gas exchange, nutrient uptake) and leaf chlorophyll (Chl) content were measured in control and NaCl-treated plants with or without KCl or CaCl₂ supplements. The addition of CaCl₂ and KCl to Bitter Almond trees reduced their dry weight, shoot growth and leaf number although net photosynthetic assimilation rate (A) was not affected. These results indicated that changing of photo-assimilates flux to proline and/or soluble sugars synthesis may help to increase leaf Ψ_w. The Garnem trees also did not respond to the CaCl₂ and KCl addition indicating that the plants are already getting enough of these two cations (C^a2+ and K⁺). In both rootstocks, NaCl in the medium reduced growth attributes, Ψ_w, A, stomatal conductance (g_s), and leaf Chl content. When CaCl₂ and KCl fertilizers were added together with NaCl to Bitter Almond trees, leaf K⁺ and Ca²⁺ contents increased while Na⁺ and Cl^– decreased leading to higher Ca/Na and K/Na ratios, but shoot growth was not improved and even declined compared to NaCl-treated trees. It appears that the addition of salts further aggravated osmotic stress as indicated by the accumulation of proline and soluble sugars in leaf tissues. The addition of KCl or CaCl₂ to NaCl-treated GN15 trees did not increase A, leaf Ψ_w, and shoot growth but improved ionic balances as indicated by higher Ca/Na and K/Na ratios. The reduction in A was mainly due to non-stomatal limitations in GN15, possibly due to the degradation of Chl a, unlike Bitter Almond, for which the reduction of A was due to stomata closure. The improvement in ionic balances and water status of Bitter Almond trees in response to addition of KCl or CaCl₂ was apparently offset by a high sensitivity to Cl^–; therefore, no-chloride salts should be the preferred forms of fertilizers for this rootstock. Both rootstocks were sensitive to soil salinity and cation supplements were of limited value in mitigating the effect of excessive salt concentrations.     

Photosynthesis and photorespiration in two cultivars of cotton under salt stress

Different NaCl concentrations in a nutrient medium ofGossypium hirsutum L. induced a different decrease in the rates of photosynthesis and photorespiration in two cultivars.     

Response of photosynthetic performance,water relations and osmotic adjustment to salinity acclimation in two wheat cultivars

Experiment was conducted to identify the impacts of the salinity acclimation process on the photosynthetic efficiency, osmotic adjustment, membrane integrity, and yield components in two wheat cultivars differing in their salinity tolerance. The design of the experiment was factorial randomized block, where genotype is factor 1 and acclimation treatments represent factor 2. Genotypes were grown from emergence to 30 days after sowing (DAS) by irrigating with tap water [electrical conductivity (EC) of 0.776 dS m^?1]. Thereafter, both the genotypes were divided into two groups and exposed to either irrigation with sublethal level of salinity EC of 2.09 or 3.76 dS m^?1 for 21 days. At booting stage (65 DAS), both groups were subjected to lethal level of salinity stress EC of 12 dS m^?1 for 21 days, followed by irrigation with tap water till maturity. Non-acclimated plants were irrigated with tap water from emergence to 65 days, then directly irrigated with lethal level of salinity for 21 days, followed by irrigation with tap water till maturity. The control plants were continuously irrigated with tap water from emergence until maturity. The non-acclimated plants had decreased electron transport rates at the donor and acceptor side of PSII and PSI in Giza 168, and decreased electron transport rates at PSII acceptor side in Sakha 8 compared to control plants. In both genotypes, the non-acclimated plants had decreased chlorophyll a, b, carotenoid, proline and total soluble sugar concentration, relative water content, membrane stability index, yield and yield components compared with acclimated plants. While, osmotic potential and lipid peroxidation showed an opposite trend. Overall, acclimation treatment (EC of 2.09 dS m^?1) during vegetative stage alleviated the inhibitory effects of lethal level of salinity stress at booting stage through enhanced photosynthetic efficiency and osmotic adjustment, resulting in increased membrane integrity, biomass production and grain yield than in non-acclimated plants.     

Organelle DNA polymorphism in apple cultivars and rootstocks

Summary Restriction fragment length polymorphisms (RFLPs) have been used to detect chloroplast (cp) and mitochondrial (mt) DNA variation among 18 apple cultivars and three rootstocks. The distribution of RFLP patterns allowed the assignment of these genotypes into three groups of cytoplasmic relatedness. Our results also demonstrate maternal inheritance of cp- and mtDNAs in apple. Thus, the organelle DNA assay provides a convenient and reliable method to assess cytoplasmic diversity within the apple germ-plasm collection and to trace the maternal lineages involved in the evolution of apple.     

不同砧木对西瓜嫁接苗耐寒性的影响

以西瓜(Citrullus vulgarris)郑抗1号为接穗,日本南瓜（C. moschata）、黑籽南瓜（C. ficifolia）、葫芦（Lagenaria siceraia）为砧木,研究了嫁接苗和自根苗在（7.5±0.5）℃低温胁迫下叶片相关耐寒性指标的变化。结果表明：低温处理后嫁接苗丙二醛（MDA）含量、电解质渗透率显著低于自根苗;叶绿素、脯氨酸（Pro）、可溶性糖含量以及超氧化物歧化酶（SOD）、过氧化物酶（POD）、过氧化氢酶（CAT）活性显著高于自根苗。与处理前相比,12 d时日本南瓜砧、黑籽南瓜砧和葫芦砧嫁接苗叶绿素含量分别降低了30.48%、28.48%和52.69%;葫芦砧嫁接苗MDA含量6 d时较处理前增加了313.16%;3～12 d日本南瓜砧和黑籽南瓜砧嫁接苗电解质渗透率显著低于葫芦砧嫁接苗;低温处理期间,日本南瓜砧嫁接苗可溶性糖含量分别比黑籽南瓜砧和葫芦砧嫁接苗高出24.71%和31.17%,SOD、POD、CAT酶活性高于另外2个组合。综合各项指标显示：3种砧木均能提高接穗对低温的忍耐能力,其顺序为日本南瓜砧＞黑籽南瓜砧＞葫芦砧。     

Tissue water relations and leaf growth of tropical corn cultivars under water deficits

Abstract This study reports on the effect of water deficit on the tissue water relations and leaf growth of six corn cultivars, growing in glasshouse conditions, in order to understand growth responses to drought of tropical corn. A mild water-stress treatment was imposed slowly; plants reached a minimum pre-dawn leaf water potential of about –1.5 MPa by day 12 after watering was withheld. Analysis of the water relation characteristics of growing leaves using the pressure–volume technique demonstrated that under water deficits all the cultivars changed their moisture-release curves compared with irrigated plants. Osmotic potential at full turgor was lowered in water-stressed plants of all the genotypes and the degree of such change was between 0.34 MPa and 0.58 MPa. Thus, turgor pressure was lost at a lower water potential in water-stressed plants than in irrigated plants of all the varieties. Volumetric elastic moduli were also increased under water deficits and the increase ranged between 10% and 141% among the cultivars. In all the genotypes, the stress imposed led to a reduction of leaf area and dry matter accumulation. Leaf expansion was very sensitive to low turgor pressure and it ceased when turgor reached 0.2 MPa. Thus, varieties able to maintain a higher degree of turgor pressure (i.e. by osmotic adjustment) under water deficits may be able to prolong leaf growth.     

Possible involvement of polyphenols and polyamines in salt tolerance of almond rootstocks

Leaf physiological and biochemical adaptive strategies and more particularly the possible involvement of polyamines and polyphenols in salt stress tolerance were investigated. Three almond rootstocks (GN15, GF677 and bitter almond) were subjected to 0, 25, 50 and 75 mM NaCl for 30 days. The dry mass of leaves, stems and roots decreased with increasing salt concentration in the irrigation solution regardless of genotype. Photosynthetic assimilation rate decreased in the three almond rootstocks, but more so in GF677 and bitter almond. The accumulation of toxic ions was greater in the leaves than in the roots in all genotypes. GN15 accumulated less Na⁺ and Cl⁻ than GF677 and bitter almond. GF677 accumulated polyphenols, but had less anthocyanin and antioxidant activity in its leaves compared to bitter almond. It seems that GN15 was more able to tolerate the excess of toxic ions using anthocyanins which are abundant in its red leaves and free polyamines for a more efficient response to stress. However, most of the antioxidant activity was found in the leaves and was lower in the roots. Given that the upper part of the tree will be of a different cultivar after grafting, this advantage may not be relevant for the tree’s survival. GF677 showed a different antioxidant strategy; it maintained a stable carotenoids content and accumulated polyphenols in its leaves. The three rootstocks used different strategies to deal with the excess of salt in the growth medium.     

Effect of rootstocks on floral nectar composition in apple cultivars

 Insect attraction of flowers in apple cultivars is an essential question from the viewpoint of fruit yield, since apple flowers are autosterile and entomogamous. Therefore, it is important to study the two most significant factors of primary attraction, pollen and nectar production. The composition of nectar in apple cultivars on different rootstocks was investigated, putting an emphasis on sugar components. It was stated that the composition of nectar and the ratio of mono- and disaccharides was almost identical and constant in trees on rootstock M.4, whereas on other rootstocks the effects of the season were more pronounced. In triploid cultivars on rootstocks M.9 and M.26 nectar can be characterised by the dominance of sucrose. Relationship was found between free fertilisation rate of cultivars and sugar amount of nectar. In triploid cultivars nectar sugar content was usually lower than in diploid ones, and reached the bee visitation threshold only in some years, influenced also by the effect of rootstocks. Received August 27, 2002; accepted November 16, 2002 Published online: June 2, 2003     

Relationships between stomatal behavior,xylem vulnerability to cavitation and leaf water relations in two cultivars of Vitis vinifera

Current understanding of physiological mechanisms governing stomatal behavior under water stress conditions is still incomplete and controversial. It has been proposed that coordination of stomatal kinetics with xylem vulnerability to cavitation [vulnerability curve (VC)] leads to different levels of isohydry/anisohydry in different plant species/cultivars. In this study, this hypothesis is tested in Vitis vinifera cultivars displaying contrasting stomatal behavior under drought stress. The cv Montepulciano (MP, near‐isohydric) and Sangiovese (SG, anisohydric) were compared in terms of stomatal response to leaf and stem water potential, as possibly correlated to different petiole hydraulic conductivity (k_petiole) and VC, as well as to leaf water relations parameters. MP leaves showed almost complete stomatal closure at higher leaf and stem water potentials than SG leaves. Moreover, MP petioles had higher maximum k_petiole and were more vulnerable to cavitation than SG. Water potential at the turgor loss point was higher in MP than in SG. In SG, the percentage reduction of stomatal conductance (PLg_s) under water stress was almost linearly correlated with corresponding percentage loss of k_petiole (PLC), while in MP PLg_s was less influenced by PLC. Our results suggest that V. vinifera near‐isohydric and anisohydric genotypes differ in terms of xylem vulnerability to cavitation as well as in terms of k_petiole, and that the coordination of these traits leads to their different stomatal responses under water stress conditions.     

Effect of genotype and graft type on the hydraulic characteristics and water relations of grafted melon

Abstract

From the measurements of the profiles of hydraulic conductance and water potential from soil through to the leaf system in fully established melon plants, the limits to water flow set by coupling of hydraulic conductance (k) with water relation parameters was evaluated in the laboratory using high pressure flow device (HPFM) and evaporative flux method (EF). The rootstock Arava was grafted onto self, and onto two genotypes (AR57 and AR82) using side and V graft types, and there was an ungrafted control. Hydraulic transport efficiency was estimated from measurements of evaporative flux (transpiration rate) and leaf water potential (ψL) measured between pre-dawn and sunset during the growth cycle. Measured parameters to characterize the hydraulic efficiency (architecture) of the vascular system of melon were normalized to areas of leaves and stem cross section; this enabled the examination of their physiological and ecological functions. The effects of rootstock genotype were more marked on graft union and scion water relations. Differences in the magnitudes of water relation parameters of hydraulic conductance, water potential (lwp) and evaporative water loss (EF) were detected. AR/RS82 side grafted exhibited high EF and Kh despite its lower leaf water potential compared to AR/RS57 V grafted. Self grafting (Arava/Arava grafts) in melon seems to improve water relations and xylem water transport efficiency. Parameters describing the hydraulic efficiency (architecture) of vascular system of melon plants were described in relation to plant attributes. The expression of hydraulic conductance of the root and shoot system relative to plant attributes did not eliminate differences in the magnitudes of conductance elements in tomato and melon. Differences obtained among the different melon grafts in whole plant leaf and stem area specific hydraulic conductance (Kl) indicate the carbon efficiency and hence the cost of resource allocation to areas of root surface and leaves. The role of plant water relations in root-shoot communications and whole plant regulation of water flux are inferred from this study.     

Drought stress effects on three cultivars of Eragrostis curvula: photosynthesis and water relations

Water stress effects were studied on three cultivars ofEragrostis curvula. Leaf water potential, RWC, total plantleaf area, green dry weight mass percentage and CO₂ gas-exchangeweremeasured during the onset of stress and after recovery. After 3 days of waterstress, RWC of cv Tanganyika plants was around 30–40% of controls,while RWC of cvs Ermelo and Consol was around 50–60% of controls.However midday and predawn water potentials were lower in cvs Tanganyka andErmelo than in cv Consol. After re-watering, RWC and water potentials recoveredonly in Consol plants. A strong decrease of leaf area was recorded in cvsErmeloand Consol during water stress (about 91–94% less than the leafarea of controls). Photosynthesis decreased as a function of the degree ofwaterstress severity in all cultivars. Also, light saturated photosynthesis,CO₂ quantum yield and light at which saturated photosynthesisoccurred, were strongly reduced by water stress. Recovery of photosynthesis wasfound in cv Consol after five days re-watering. Cv Consol showed a betterconservation of water and higher resistance to water stress than the other twocvs.