Differences among three clones of Gentiana punctata L. hairy root shoot regenerants were investigated in relation to their growth patterns, production of secondary metabolites and 2D protein profiles. Prominent differences in growth parameters were stable thus qualifying regenerant clones as true somaclones. Marked differences in protein spots were registered among the regenerant clones but not in comparison with the non-transformed control. Southern blot hybridization of regenerants showed the absence of rolA, B and C genes, initially present in the main hairy root lines. Orf13 and rolD were present and orf8 was missing in all three regenerant clones whereas orf3 was missing only in clone 2. Although lacking the three major rol genes, plants of regenerant clones retained characteristics of the hairy root phenotype.

Catechin is associated with several functions in animal and plant systems, with little information available regarding its role in plant growth. Low concentrations of catechin (50 and 100 μM) were found to enhance length of primary and lateral roots, number of lateral roots, fresh and dry masses of shoots and roots, leaf area, water potential of leaf and root tissues, the number of vascular bundles in the inflorescence, and leaf thickness in Arabidopsis thaliana ecotype Col-0. A significant increase in net photosynthetic rate, stomatal conductance and concentration of indole-3-acetic acid was also observed in catechin treated plants.

A two-step protocol for improving the frequency of shoot regeneration from oilseed rape (Brassica napus L.) hypocotyl explants was established. The protocol consists of a pre-culture on callus induction medium (CIM) and a subsequent shoot regeneration on shoot induction medium (SIM). The SIM was Murashige and Skoog medium supplemented with different concentrations of 6-benzylaminopurine (BA; 2-5 mg dm^-3) and naphthaleneacetic acid (NAA; 0.05-0.15 mg dm^-3). Maximum frequency of shoot regeneration (13 %) was on the SIM medium containing 4 mg dm^-3 BA and 0.1 mg dm^-3 NAA, but it increased to 24.45 % when 20 μM silver thiosulphate (STS) was added. Strikingly, an extremely high frequency of shoot regeneration up to 96.67 % was reached by a two-step protocol when hypocotyl explants had been pre-cultured for 7 d on a CIM medium containing 1.5 mg dm^-3 2,4-dichlorophenoxyacetic acid. In addition, the shoot emergence was also 7 d earlier than that observed by use of the one-step protocol. The two-step protocol was also applied for regeneration of transgenic plants with cZR-3, a nematode resistance candidate gene. As a result, 43 plants were generated from 270 shoots and from these 6 plants proved to be transgenic.

The possible costs of inducible defences against pests were evaluated in tomato. To activate inducible resistance traits, we used transgenic plants that over-expressed the systemin precursor (prosystemin). The constitutive expression of the prosystemin, which is normally induced by herbivores in tomato, allowed the measurement of the impact of induced defences in a pest-free environment. The results showed that the continuous activation of traits that are normally induced by pests should be costly, affecting the growth, physiology and reproductive success of tomato plants.

Although crosstalk between cytosolic and plastidic terpenoid pathways has been validated in many plant species, we report here for the first time a striking elevation of the nucleus-encoded artemisinin biosynthesis relevant DBR2 mRNA following the incubation of plants with fosmidomycin (FM). FM decreased singlet oxygen (¹O₂) scavengers such as β-carotene and α-tocopherol and subsequently invoked ¹O₂ burst. The treatment of plants with fluridone (FD) neither decreased α-tocopherol content nor triggered ¹O₂ emission. In conclusion, FM can up-regulate ¹O₂-sensitive nuclear genes responsible for artemisinin biogenesis by mitigating the accumulation of plastidic scavenging terpenoids, thereby eliciting ¹O₂ generation and initiating ¹O₂ retrograde signaling.

Sorghum bicolor L. Moench cv. SPV462 was transformed with the mtlD gene encoding for mannitol-1-phosphate dehydrogenase from E. coli with an aim to enhance tolerance to water deficit and NaCl stress. Transgene (pCAM mtlD) integration and expression were successfully confirmed by PCR, Southern, RT-PCR and Western analysis. Segregation analysis based on germination of T0 seed on hygromycin-supplemented medium revealed an expected Mendelian ratio 3:1 in lines 5, 72 and 75. Retention of leaf water content was remarkably higher in transgenic leaf segments when exposed to polyethylene glycol 8000 (-2.0 MPa), as compared to the untransformed controls. Another significant finding is that the transgenics maintained a 1.7 to 2.8 fold higher shoot and root growth, respectively, under NaCl stress (200 mM) when compared to untransformed controls. These results demonstrate that engineering mannitol biosynthetic pathway into sorghum can impart enhanced tolerance to water deficit and salinity.

The Nicotiana tabacum transgenic plants expressing a Cucurbita pepo antisense PHYA RNA were obtained. The seedlings of transgenic tobacco with reduced phytochrome A (PHYA) content displayed decreased sensitivity to continuous broad-band far-red radiation (λ > 680 nm). Under far-red irradiance transgenic seedlings showed less elongation of the hypocotyls, more rapid plastid development, more chlorophyll accumulation, less repression of lightdependent NADPH:protochlorophyllide oxidoreductase than wild-type plants that was in accordance with PHYA control of plant development. Dynamics of the far-red radiation dependent changes in low temperature chlorophyll fluorescence spectra for the transgenic and wild-type seedlings were consistent with the more rapid formation of photosynthetic apparatus in the seedlings with reduced PHYA.

To gain a comprehensive understanding of plant response to Cd, physiological and proteomic changes in wheat (Triticum aestivum L.) leaves exposed to a range of Cd concentrations (10, 100 and 200 μM) were investigated. Leaf elongation was decreased, whereas the H₂O₂ and malondialdehyde content increased significantly at higher Cd concentrations. Changes in protein profiles were analyzed by two-dimensional electrophoresis. Twenty-one proteins which showed 1.5-fold change in protein abundance in response to Cd were identified. These proteins can be functionally grouped into three groups: 1) oxidative stress response, 2) photosynthesis and sugar metabolism and 3) protein metabolism and others. These results provide a new insight into our understanding of the molecular basis of heavy metal response in plants.

A protocol is established for regeneration of the economically important cut flower plant, Gypsophila paniculata L., using shoot tips explants. Multiple shoots were obtained on Murashige and Skoog medium fortified with 0.5 mg dm^-3 each of α-naphthaleneacetic acid and 6-benzyladenine. Addition of 10 g dm^-3 agar promoted shoot proliferation and reduced the degree of shoot vitrification. Transfer to 3 mg dm^-3 indole^-3-butyric acid containing medium produced optimum root initiation and development. The produced plants as well as intact plants were subjected to the random amplified polymorphic DNA (RAPD) analysis. Using 9 primers, the total number of amplification products generated by polymerase chain reaction was 142 bands (15.7 bands per primer), of which 7.74 % showed polymorphism. The analysis of bands recorded, showed 92.25 % similarity. The results indicated that very low variation at the DNA level occurred during in vitro culture of Gypsophila.

Arabidopsis thaliana plants (wild type accessions Col and N1438) were grown in nutrient solution for 34 d with or without 50 mM NaCl. Salt stress inhibited plant growth rate more in Col than in N1438 and a decrease in K⁺, Ca²⁺ and nitrogen contents was observed in both accessions. NaCl diminished accumulation of malate, fumarate and citrate only in Col accession. To measure the effect of NaCl on transcript level of superoxide dismutase (SOD) isoforms and copper chaperone for SOD genes, a semi-quantitative polymerase chain reaction (RT-PCR) method was developed using cDNA normalized against the EF1a gene in parallel with quantitative real time RT-PCR (Q-PCR) technique. Both methods gave the same results. The abundance of transcripts of the three genes coding for Cu/Zn-SOD responded similarly to NaCl in both accessions: CSD1 gene was overexpressed, and CSD2 and CSD3 genes were repressed. However, the genes coding for Fe-SOD (FSD1), Mn-SOD (MSD1) and Cu-chaperone for SOD (CCS) responded to NaCl differently in Col and N1438: the former gene was overexpressed in Col and repressed in N1438, and the opposite behaviour was observed for the latter two genes.

The growth and ion content of salt sensitive Lycopersicon esculentum Mill. cv. M82 and salt tolerant L. pennellii Correll accession LA716 were examined under both control and stress conditions (150 mM NaCl). L. esculentum grew more vigorously than L. pennellii under optimal conditions, however, L. pennellii was able to maintain its growth better than cultivated tomato when the plants were exposed to salinity. Sodium content of both L. esculentum and L. pennellii increased as a result of NaCl stress. In addition, both species showed reduced potassium and calcium content due to salinity. The physiological traits were also measured in a population of 52 L. pennellii introgression lines grown under both normal and stress conditions. A total of 311 quantitative trait loci (QTL) were identified for the studied traits: plant height, stem diameter, leaf number, leaf and root fresh and dry mass, and sodium, potassium and calcium contents. Some of the loci (124) were identified under both control and stress conditions while 86 QTL were identified only under non-stress conditions and 101 loci were identified only under NaCl stress.

Cucumis sativus L. seedlings were pretreated 1 h with 10 μM paraquat (PQ) and then were subjected to normal (25/18 °C) or elevated (42/38 °C) temperature to investigate whether PQ can protect plants against heat stress. Heat stress inhibited fresh and dry masses of the second leaf, root dry mass and shoot fresh mass. In leaves, the stress disintegrated membranes of 84.97 % chloroplasts and elevated contents of malondialdehyde, superoxide radical and hydrogen peroxide. In contrast, PQ pretreatment altered antioxidant activities in leaves, even after PQ was rinsed off before seedlings were exposed to different temperatures. Under heat stress, PQ pretreatment improved plant growth, decreased percentage of abnormal chloroplasts (53.03 %) and reduced contents of malonaldehyde, superoxide radical and hydrogen peroxide due to increased activities of antioxidant enzymes such as superoxide dismutase, catalase, guaiacol peroxidase, glutathione peroxidase, ascorbate peroxidase, monodehydroascorbate reductase, dehydroascorbate reductase and glutathione reductase.

A simple and efficient protocol for the micropropagation of Drosera intermedia, using cultures initiated from in vitro produced seedlings, is described. Shoot proliferation was significantly influenced by Murashige and Skoog (MS) macronutrient concentration, showing higher multiplication rates for 1/4 MS (the lowest concentration), but was not affected by the addition of 0.1 mg dm^-3 kinetin. In all cases a multiplication percentage above 90 % was recorded. High rooting percentages (up to 100 %) were obtained in multiplication phase on 1/4 MS medium without growth regulators. In average 15.8 plantlets per initial shoot was produced after 8 weeks of culture. All plantlets were successfully acclimatized to ex vitro conditions, exhibiting normal development.

To identify genes that are up and down-regulated by water deficit in sugarcane we used the macroarray methodology and the expression level of 3 575 independent sugarcane cDNAs was measured by hybridization with RNA extracted from plants submitted to mild, moderate and severe water deficit. We identified approximately 1 670 differentially expressed genes from which 62 % were up-regulated by different stress-conditions, whereas many repressed genes were exclusive for each time-point. Analysis of similarity showed that approximately 24 % of the differentially expressed genes shared homology with proteins involved in different processes such as signal transduction, hormone metabolism, photosynthesis, transcription and stress response. Transcripts with no known function accounted for approximately 39 % and those without similarity represented 36 % of the sequences. Five genes analyzed by RT-PCR confirmed the macroarray results.

Methylglyoxal (MG) is a highly reactive α-oxoaldehyde, demonstrating anticancer effect on plant neoplastic tumours. In in vivo studies it was observed that MG destroyed crown gall tumours in Nicotiana tabacum produced by Agrobacterium tumefaciens, without any adverse effect on the host. The efficacy of MG in comparison to other anticancer drugs viz. cisplatin and ellagic acid in the treatment of crown gall was investigated. A slight degeneration of galls was noted in plants treated with cisplatin and ellagic acid but the plants died subsequently. With MG however, crown galls were completely cured and the plants completed their usual life cycle by flowering and producing seeds. MG inhibited the respiration of crown gall calluses suggesting that energy depletion resulted in tumour destruction.

The root system of potato (Solanum tuberosum L. cv. Favorita) plants was treated with different O₂ and CO₂ concentrations for 35 d in aeroponic culture. Under 21 or 5 % O₂ in the root zones, the thickness of leaves and palisade parenchyma significantly increased at 3 600 μmol(CO₂) mol^-1 in the root zone, compared with CO₂ concentration 380 μmol mol^-1 or low CO₂ concentration (100 μmol mol^-1). In addition, smaller cells of palisade tissue, more intercellular air spaces and partially two layers of palisade cells were observed in the leaves with root-zone CO₂ enrichment. Furthermore, there was a significant increase in the size of chloroplasts and starch grains, and the number of starch grains per chloroplast due to elevated CO₂ only under 21 % O₂. In addition, a significant decline in the thickness of grana and the number of lamellas, but no significant differences in the number of grana per chloroplast were observed under elevated CO₂ concentration. The accumulation of starch grains in the chloroplast under elevated CO₂ concentration could change the arrangement of grana thylakoids and consequently inhibited the absorption of sun radiation and photosynthesis of potato plants.

Leucoanthocyanidin reductase (LAR) converts leucoanthocyanidin to (+)-catechin, a precursor of proanthocyanidins abundant in Japanese persimmon (Diospyros kaki Thunb.) fruits. A putative LAR gene (DkLAR) was isolated by rapid amplification of cDNA ends from young fruits. The full-length cDNA of DkLAR gene was 1 356 bp long and encoded an open reading frame of 349 residues. The deduced DkLAR protein was closely related to the homolog in other plant species. The expression of the DkLAR gene in Chinese pollination-constant non-astringent (PCNA) genotype was coincident with the tannin cell development, but was not in Japanese PCNA and Chinese pollination-variant astringent (PCA) genotypes.

The effects of two-day dark treatment, applied to whole plants or to individual organs, on the photosynthetic apparatus in cotyledons and first rosette leaves of young Arabidopsis thaliana plants were studied. Darkness affected the individually darkened pair of cotyledons as well as the cotyledons of whole darkened plants (DP) in a similar manner as revealed by the significant decrease in the actual yield of photosystem 2 electron transport and the down-regulation of the psaB and rbcL transcript levels. However, cotyledons and rosette leaves responded differently to darkness with respect to the non-photochemical quenching (NPQ) and the non-regulated energy dissipation (Φ_NO), indicating different capacity for photoprotection depending on the type of the applied dark treatment. Besides, the expression of the genes for the two plastid proteases FtsH5 and Deg1 involved in D₁ protein degradation was inhibited in both leaf organs, suggesting that these proteases function mainly under irradiance. Upon re-irradiation, dark-treated cotyledons recovered from the applied stress and during further senescence the changes in the photosynthetic parameters and the mRNA levels of psaB, rbcL and SAG12 were similar as in the control plants. However, in the course of recovery typical chloroplast senescence symptoms were observed only in individually darkened leaves while re-irradiated DP leaves maintained high photosynthetic capacity.

The function of SNF2 ATPases, the major catalytic subunits of chromatin remodeling complexes, in plants is not sufficiently understood. Here we identified 39 putative SNF2 genes of rice (Oryza sativa L.) by homology analyses and analyzed the expression profiles of eight of them in response to phytohormones and abiotic stresses. Our results indicated that expression of the SNF2 genes was affected by auxin, gibberellin, cytokinin, abscisic acid, ethylene, and some abiotic stresses such as heat, chilling, darkness, drought and salinity. It suggests that, like Arabidopsis SNF2s, rice SNF2 proteins may function in phytohormone signaling pathways and/or be associated with the resistance to abiotic stresses, but in distinct manners from their Arabidopsis orthologs. Some SNF2 proteins in rice may be involved in cross-talk of the signaling pathways between phytohormones and abiotic stresses.

Exposure of pea plants to high irradiance (HI) for 60 min caused a reversible photoinhibition as shown by changes in variable to maximum fluorescence ratio (F_v/F_m). A significant decline in F_m was observed in leaves from both pea cultivars subjected to HI, the decrease being higher in JI281 than in JI399 plants. The values recovered during the post-stress period in both cultivars. In both cultivars, minimal fluorescence (F₀) increased under HI, but in cultivar JI399 F₀ recovered to initial value during the post-stress period. The expression of antioxidant enzyme genes was higher in JI399 than in JI281, both in control and stressed plants. In JI281, after 60 min of HI, an induction of the transcripts of CAT, chlMDHAR, cytAPX and cytCu,Zn-SOD was observed, whereas there was a slight increase in PHGPX, stAPX and chlCu,Zn-SOD mRNAs. After 24 h of the recovery period, the induction of some transcripts was not maintained (CAT, cytAPX and cytCu,Zn-SOD), whereas the induction of others was maintained (PHGPX and chlCu,ZnSOD) or even increased (cytGR, stAPX and chlMDHAR). In JI399, CAT and cytAPX were increased strongly after 60 min of HI, and slight increases were observed in cytGR, chlGR and chlMDHAR. In the post-stress period the expression of stAPX, cytGR and chlMDHAR was even slightly higher than after 60 min of HI, however, expression of CAT, cytAPX, cytCu,ZnSOD, chlCu,ZnSOD and chlGR decreased.

A reproducible in vitro regeneration system for Nepalese kutki (Picrorhiza scrophulariiflora Pennell) was developed from in vitro leaf derived callus. Induction of more than seven shoot buds per explant was achieved on Woody plant medium (WPM) supplemented with 0.53 μM α-napthaleneacetic acid (NAA) and 0.23 μM kinetin (KIN). The shoots were elongated on WPM supplemented with 0.44 μM 6-benzylaminopurine (BAP) and rooted on WPM supplemented with 5.3 μM NAA within 2 weeks. The random amplified polymorphic DNA (RAPD) analysis indicated genetic uniformity of the micropropagated plants with its donor plants.

Lettuce plants were treated with gibberellic acid (GA₃) and uniconazole (UZ; a gibberellin synthesis inhibitor) to investigate the influence of GA₃ on cell division frequency in the shoot apical meristem (SAM) during stem elongation and flower initiation in lettuce (Lactuca sativa) grown in a greenhouse. GA₃ (0.1 mM) was sprayed on the surface of outer leaves and uniconazole solution (0.86 mM) was applied to the soil. GA₃ increased cell division frequency in the peripheral zone and the rib meristem of shoot apices, and this was associated with the stimulation of stem elongation. UZ treatment decreased cell division frequency in the peripheral zone, rib meristem and subapical pith, and this was associated with restricted stem elongation. Treatment with UZ and GA₃ together induced minor stem elongation. Flower induction occurred 3 d earlier in the GA₃ and UZ+GA₃ treatments than in the control, while the UZ treatment delayed flower initiation for more than 9 d relative to the control.

Strawberry (Fragaria ananassa Duch.) seedlings were pretreated with hexanoic acid 2-(diethylamino)ethyl ester (DA-6) in concentrations of 0, 10, 20 and 40 mg dm^-3 and then subjected to chilling and rewarming. The effects of applied DA-6 on the generation of reactive oxygen species (O₂ ^-, H₂O₂), lipid peroxidation, proline accumulation and photosynthesis were evaluated. Pretreatment with DA-6 alleviated the inhibition of superoxide dismutase (SOD), catalase (CAT) and ascorbate peroxidase (APX) activities caused by chilling stress thus reducing O₂ ^- and H₂O₂ production and lipid peroxidation in pretreated plants. DA-6 pretreatment also accelerated accumulation of proline and reduce the decrease in proline content after rewarming. DA-6 pretreatment increases maximum quantum yield of photosystem 2 (F_v/F_m), actual photochemical efficiency of photosystem 2 (Φ_PS2), photochemical quenching coefficient (qP) and net photosynthetic rate (P_N) and decreases non-photochemical quenching coefficient (qNP) of the seedlings under chilling stress. DA-6 pretreatment also increased the recovery rate of photosynthesis after rewarming.

Supply of aqueous solution of triadimefon (20 mg dm^-3) to unstressed green gram plants increased the contents of soluble proteins, amino acids, nitrate and nitrite, and the activity of nitrate reductase in the leaves and nitrate reductase in nodules. The nitrogenase activity in nodules and roots was also increased. Number and fresh mass of nodules and their nitrate and nitrite contents were also higher than those of the controls. In contrast, the UV-B stress (12.2 kJ m^-2 d^-1) suppressed nodulation and nitrogen metabolism in leaves and roots compared to plants under natural UV-B (10 kJ m^-2 d^-1). Triadimefon-treated plants did not show such severe inhibitions after exposure to elevated UV-B. Thus triadimefon increased their tolerance to UV-B stress.

A full-length cDNA clone encoding cytosolic glutamine synthetase (GS1; EC 6.3.1.2) was isolated from melon (Cucumis melo L.) for the first time by RT-PCR and RACE approach. The clone, designated as M-GS1 (accession No. DQ851867), contains 1494 nucleotides with an open reading frame (ORF) of 1068 nucleotides. The deduced 356 amino acid sequence showed high similarity with previously reported GS1s from various plant species. Sequence analysis revealed that the predicted protein contains a GS β-Grasp domain, a GS catalytic domain, and the main conserved motifs characteristic of a plant GS1. The phylogenetic analysis displayed that M-GS1 is related most closely to the GS1 from Datisca glomerata. Southern blot analysis indicated that M-GS1 belongs to a small gene family of 2 or 3 members. M-GS1 was expressed in all plant tissues without evident tissue specificity, but with different patterns when the melon plants were fed in hydroponic culture with different forms and concentration of nitrogen. Ammonium dramatically enhanced the contents of M-GS1 transcripts in all tested tissues, while nitrate stimulated M-GS1 transcription only in the roots and leaves, but not in the stems; glutamate, however, depressed M-GS1 transcripts in the roots, but resulted in no significant change to the levels of M-GS1 transcripts in the stems and leaves. Moreover, the same effects were observed at the GS enzyme activity level. These results indicated that melons respond to changes of N nutrition by regulating M-GS1 expression.

We isolated and characterized a novel Ran GTPase homologous gene, FaRan from tall fescue (Festuca arundinacea Schreb.). Reverse transcriptase polymerase chain reaction (RT-PCR) analysis indicated that FaRan is broadly expressed in old mature leaves, young leaves, plumules, stems, infloresence meristems, but at different levels. Transcript of FaRan is higher in young meristems than in old ones. Ectopic expression of FaRan resulted in increased number of axillary buds and reduced apical dominance in transgenic Arabidopsis plants. These results suggest that FaRan in F. arundinacea may be involved in the initiation of meristem and subsequent growth as well as development. In addition, it also suggests that FaRan can be used potentially to improve turfgrass quality.

In this study, we selected two known pathogen-inducible cis-acting elements, F and E17, to construct synthetic pathogen-inducible promoters for analysis in transformed canola (Brassica napus L.). The synthetic promoter approach was used, which involved the insertion of dimers and combining two cis-acting elements (E17 and F) upstream of the minimal CaMV 35S promoter. Canola plants were transformed by three constructs, pGEE, pGFF, pGFFEE containing synthetic promoters (SP), SP-EE, SP-FF and SP-FFEE, respectively. Analyses of histochemical and fluorometric GUS expression indicated that synthetic promoters responded to fungal elicitors and phytohormone treatments. The SP-FF promoter showed high responses against methyl jasmonate and Sclerotinia sclerotiorum, while SP-EE demonstrated inducibility only in response to salicylic acid and Rhizoctonia solani. The SP-EE promoter similar to SP-FFEE, did not respond to S. sclerotiorum and methyl jasmonate. However, SP-FFEE was highly induced by R. solani elicitors and showed that the level of GUS expression was greater than that by either of E17 or F elements alone. These three synthetic promoters did not activate the expression of the reporter gene in response to cold, heat, UV and wounding.

Embryogenic cell suspension cultures of Santalum album were transformed with Agrobacterium tumefaciens harboring pD35SHER plant expression vector having hepatitis B small surface antigen (HBsAg) with a C-terminal ER retention signal. The transformed colonies were selected on culture medium supplemented with kanamycin and subsequently the transgenic nature of these colonies was confirmed by PCR analysis. The expression of HBsAg was confirmed by RT-PCR analysis and Western blot analysis and the expression was quantified using monoclonal antibody-based ELISA. Cell suspension cultures were initiated from the colony with expression of 11.09 μg(HBsAg) g^-1(f.m.). To further increase the expression of HBsAg, transgenic S. album suspensions were cultured on media with various medium additives and cells growing in medium with 30 mM trehalose showed the expression of 19.95 μg(HBsAg) g^-1(f.m.).

Changes in plant growth, photosynthetic gas exchange, chlorophyll fluorescence and stem diameter of soybean [Glycine max (L.) Merr.] plants under drought stress were studied. Total plant dry mass was reduced by 30 % compared to well-watered control plants. Leaf water potential was slightly decreased by water stress. Water stress induced daytime shrinkage and reduced night-time expansion of stem. Photosynthetic rate, stomatal conductance and transpiration rate were significantly declined by water stress, while the intercellular CO₂ concentration was changed only slightly at the initiation of stress treatment. The maximum photochemical efficiency of photosystem 2 and apparent photosynthetic electron transport rate were not changed by water stress.

Cucumber plants were either self-grafted or grafted onto two salt-tolerant pumpkin rootstocks Chaojiquanwang (Cucurbita moschata Duch), and Figleaf Gourd (Cucurbita ficifolia Bouche). Plants were grown hydroponically in 0, 30, 60, or 90 mM NaCl for 16 d in greenhouse. Salinity induced a smaller decrease in plant shoot dry mass, leaf area, net photosynthetic rate, and stomatal conductance in the two rootstock-grafted plants compared to the self-grafted plants. In addition, a significant increase in intercellular CO₂ concentration, as well as a significant decrease in the initial and total ribulose-1,5-bisphosphate carboxylase/oxygenase activities were observed only in the self-grafted plants under 90 mM NaCl treatment. These results suggest that the use of salt tolerant rootstock can improve cucumber photosynthetic capacity under salt stress through both stomatal and non-stomatal pathways.