Effects of solar UV stress on chlorophyll fluorescence kinetics of intertidal macroalgae from southern Spain: a case study in Gelidium species

Photoinhibition and recovery kinetics after short exposure to solar radiation following three different irradiance treatments of irradiances (PAR, PAR+UVA and PAR+UVA+UVB) was assessed in two intertidal species of the genus Gelidium, Gelidium sesquipedale and G. latifolium, collected from Tarifa (southern Spain) using in vivo chlorophyll fluorescence (PAM fluorometry). After 3 h UV radiation exposure, optimal quantum efficiency (Fv/Fm) in G. sesquipedale decreased between 25 and 35% relative to the control. Under PAR alone, values decreased to 60%. In G. latifolium, photoinhibition did not exceed 40%. Similar results were found for the effective quantum yield (ΔF/Fm′), however, no marked differences in relation to light treatments were seen. When plants were shaded for recovery from stress, only in G. latifolium a significant increase in photosynthesis was observed (between 80 and 100% of control). In contrast, photosynthesis of G. sesquipedale suffered a chronic photoinhibition or photodamage under the three light irradiances. Full solar radiation (PAR+UVA+UVB) affected also the electron transport rate in both species. Here, initial slopes of electron transport vs. irradiance curves decreased up to 60% of controls. Although the recovery kinetic under PAR+UVA+UVB conditions was delayed in G. latifolium, after 24 h recovery this species reached significantly higher than G. sesquipedale. PAR impaired electron trasport only in G. sesquipedale. Overall, both species are characterized by different capacity to tolerate enhanced solar radiation. G. latifolium is a sun adapted plant, well suited to intertidal light conditions, whereas G. sesquipedale, growing at shaded sites in the intertidal zone, is more vulnerable to enhanced UV radiation. This revised version was published online in June 2006 with corrections to the Cover Date.     

Physiological responses of resistant and susceptible barley, Hordeum vulgare to the Russian wheat aphid, Diurpahis noxia (Mordvilko)

Knowledge of the physiological responses of barley, Hordeum vulgare L., to the Russian wheat aphid, Diuraphis noxia (Mordvilko) (Hemiptera: Aphididae) is critical to understanding the defense response of barley to aphid injury and identifying resistance mechanisms. This study documented the impact of D. noxia feeding on resistant (‘Sidney’) and susceptible (‘Otis’) barley through chlorophyll fluorescence measurements, chlorophyll content, and carbon assimilation (A–C_i) curves recorded at 1, 3, 6, 10, and 13 days after aphid introduction. All chlorophyll fluorescence parameters evaluated were similar between aphid-infested and control plants for both cultivars. A–C_i curves showed that D. noxia feeding negatively impacts the photosynthetic capacity in both cultivars, but this effect was greater in the susceptible plants. From the A–C_i curves, it is apparent that compensation occurs in resistant barley by day 10, but by the conclusion of the experiment, aphid populations reached levels that overwhelmed the resistant barley seedlings. Differences observed in carbon assimilation curves between control and infested plants show that D. noxia feeding impacts the dark reaction, specifically rubisco activity and RuBP regeneration. It is likely that declines in the photochemical efficiency and chlorophyll content of the plants may be a secondary effect and not the primary trigger of declines in host plant function.     

Chlorophyll content and leaf elongation rate in wheat seedlings as a measure of manganese tolerance

After aluminum toxicity, manganese (Mn) toxicity is probably the second most important growth limiting factor in acid soils. The purpose of this study was to determine the feasibility of using chlorophyll content and leaf elongation rate (LER) for regrowth of Mn stressed seedlings as a rapid seedling based screening bioassay for Mn tolerance in segregating populations of wheat (Triticum aestivum L.). In one experiment, chlorophyll was determined for the cultivars Norquay (Mn-tolerant) and Columbus (Mn-sensitive) subjected to twelve Mn levels (2 to 2000 μM) in nutrient solutions. As Mn concentration increased, chlorophyll ‘a’ and ‘b’ contents of the Mn-tolerant cultivar decreased up to 9%, while in the Mn-sensitive cultivar it was reduced by as much as 43%. The chlorophyll ‘a/b’ ratio did not differ among Mn concentrations for either cultivar. In a second experiment, chlorophyll content and LER for regrowth of Mn stressed seedlings (1000 μM) was determined for Columbus and Katepwa (Mn-sensitive), Oslo (Mn-intermediate), and Norquay and Laura (Mn-tolerant). Manganese tolerance as assayed by chlorophyll ‘a’ and ‘b’ and LER was significantly correlated with Mn tolerance as assayed by the relative root weight methodology (RRW). Thus, chlorophyll content of Mn-stressed seedlings and LER of seedling regrowth appear to be suitable techniques for screening unreplicated selections of segregating populations for tolerance to Mn.     

Osmoregulation and osmoprotection in the leaf cells of two olive cultivars subjected to severe water deficit

In this study, we compared the efficacy of defense mechanisms against severe water deficit in the leaves of two olive (Olea europaea L.) cultivars, ‘Chemlali’ and ‘Meski’, reputed drought resistant and drought sensitive, respectively. Two-year old plants growing in sand filled 10-dm³ pots were not watered for 2 months. Changes in chlorophyll fluorescence parameters and malondialdehyde content as leaf relative water content (RWC) decreased showed that ‘Chemlali’ was able to maintain functional and structural cell integrity longer than ‘Meski’. Mannitol started to accumulate later in the leaves of ‘Chemlali’ but reached higher levels than in the leaves of ‘Meski’. The latter accumulated several soluble sugars at lower dehydration. ‘Chemlali’ leaves also accumulated larger quantities of phenolic compounds which can improve its antioxidant response. Furthermore, the activity of three antioxidant enzymes catalase (CAT), peroxidase (POD) and ascorbate peroxidase (APX) increased as leaf RWC decreased. However, differences were observed between the two cultivars for CAT and POD but not for APX. The activity of the first two enzymes increased earlier in ‘Meski’, but reached higher levels in ‘Chemlali’. At low leaf hydration levels, ‘Chemlali’ leaves accumulated mannitol and phenolic compounds and had increased CAT and POD activities. These observations suggest that ‘Chemlali’ was more capable of maintaining its leaf cell integrity under severe water stress because of more efficient osmoprotection and antioxidation mechanisms.     

Chlorophyll <Emphasis Type="Italic">a</Emphasis> fluorescence study revealing effects of flooding in canola hybrids

By generating stress conditions soil flooding can induce alterations in the cell metabolism and thus is detrimental to plant growth. This study was done under the greenhouse conditions to determine the effect of soil flooding on the chlorophyll fluorescence of some hybrids of canola (Brassica napus L.). Fifty five days old plants were subjected to flooding for six days. There was no difference in the parameters modulate chlorophyll fluorescence, in contrast, some the parameters related to the energy flux in photosystem II varied due to flooding stress. At the end of the six days, the performance indexes (PI_total and PI_ABS) decreased, in all hybrids except in ‘Hyola 420’. The difference kinetics of the chlorophyll a fluorescence transient showed different effects on different sites of the photosynthetic machinery. It could be concluded that compared to the other hybrids, ‘Hyola 420’ was less sensitive to flooding.     

Production and molecular characterization of potential seedless cybrid plants between pollen sterile Satsuma mandarin and two seedy <Emphasis Type="Italic">Citrus</Emphasis> cultivars

Cytoplasmic male sterility (CMS) is known to be controlled by mitochondrial genome in higher plants including Satsuma mandarin (Citrus unshiu Marc.). Citrus symmetric fusion experiments often produce diploid cybrids possessing nuclear DNA from the mesophyll parent and mitochondrial DNA (mtDNA) from the embryogenic callus parent. Therefore, it is possible to transfer CMS from Satsuma mandarin as callus parent to seedy citrus cultivars as leaf one by somatic cybridization. Herein, symmetric fusion technique was adopted to create cybrids for potential seedlessness by transferring CMS from Citrus unshiu Marc. cv. Guoqing No. 1 (G1) to two traditional Chinese seedy citrus cultivars, ‘Shatian’ pummelo (C. grandis (L) Osbeck) and ‘Bingtang’ orange (C. sinensis (L) Osbeck). Flow cytometry analysis showed that 19 plants recovered from G1 + ‘Bingtang’ orange and 17 of 35 plants regenerated from G1 + ‘Shatian’ pummelo were diploid. The remaining plants from G1 + ‘Shatian’ pummelo were tetraploid. The diploid plants from the two combinations were confirmed as true cybrids by simple sequence repeat (SSR) and cleaved amplified polymorphic sequence (CAPS) analysis, with nuclear DNA from their corresponding leaf parent and mtDNA from their common suspension parent, G1 Satsuma mandarin. The remaining plants from G1 + ‘Shatian’ pummelo were identified as somatic hybrids with mtDNA from G1. The chloroplast simple sequence repeat (cp-SSR) analysis revealed somatic hybrid/cybrid plants from the two combinations in most cases possessed either of their parental chloroplast type, and two plants from G1 +‘Shatian’ pummelo and all embryoids analyzed from G1 + ‘Bingtang’ orange possessed chloroplast DNA (cpDNA) from both parents. These results demonstrated that we succeeded in introducing mtDNA from G1 Satsuma mandarin into the two target seedy citrus cultivars for potential seedlessness through symmetric fusion.     

A comparison of the three isoforms of the light-harvesting complex II using transient absorption and time-resolved fluorescence measurements

In this article we report the characterization of the energy transfer process in the reconstituted isoforms of the plant light-harvesting complex II. Homotrimers of recombinant Lhcb1 and Lhcb2 and monomers of Lhcb3 were compared to native trimeric complexes. We used low-intensity femtosecond transient absorption (TA) and time-resolved fluorescence measurements at 77 K and at room temperature, respectively, to excite the complexes selectively in the chlorophyll b absorption band at 650 nm with 80 fs pulses and on the high-energy side of the chlorophyll a absorption band at 662 nm with 180 fs pulses. The subsequent kinetics was probed at 30–35 different wavelengths in the region from 635 to 700 nm. The rate constants for energy transfer were very similar, indicating that structurally the three isoforms are highly homologous and that probably none of them play a more significant role in light-harvesting and energy transfer. No signature has been found in the transient absorption measurements at 77 K for Lhcb3 which might suggest that this protein acts as a relative energy sink of the excitations in heterotrimers of Lhcb1/Lhcb2/Lhcb3. Minor differences in the amplitudes of some of the rate constants and in the absorption and fluorescence properties of some pigments were observed, which are ascribed to slight variations in the environment surrounding some of the chromophores depending on the isoform. The decay of the fluorescence was also similar for the three isoforms and multi-exponential, characterized by two major components in the ns regime and a minor one in the ps regime. In agreement with previous transient absorption measurements on native LHC II complexes, Chl b → Chl a energy transfer exhibited very fast channels but at the same time a slow component (ps). The Chls absorbing at around 660 nm exhibited both fast energy transfer which we ascribe to transfer from ‘red’ Chl b towards ‘red’ Chl a and slow transfer from ‘blue’ Chl a towards ‘red’ Chl a. The results are discussed in the context of the new available atomic models for LHC II.     

Mapping QTL, epistasis and genotype?×?environment interaction of antioxidant activity, chlorophyll content and head formation in domesticated lettuce (Lactuca sativa)

Fruits and vegetables are rich sources of antioxidants in human diets and their intake is associated with chronic disease prevention. Lettuce (Lactuca sativa L.) is a common vegetable in diets worldwide, but its nutritional content is relatively low. To elucidate the genetic basis of antioxidant content in lettuce, we measured the oxygen radical absorbance capacity (ORAC) and chlorophyll (Chl) content as a proxy of β-carotene in an F₈ recombinant inbred line (RIL) in multiple production cycles at two different production sites. Plants were phenotyped at the open-leaf stage to measure genetic potential (GP) or at market maturity (MM) to measure the influence of head architecture (‘head’ or ‘open’). Main effect quantitative trait loci (QTL) were identified at MM (three Chl and one ORAC QTL) and GP (two ORAC QTL). No main effect QTL for Chl was detected at GP, but epistatic interaction was identified in one pair of marker intervals for each trait at GP. Interactions with environment were also detected for both main and epistatic effects (two for main effect, and one for epistatic effect). Main effect QTL for plant architecture and nutritional traits at MM colocated to a single genomic region. Chlorophyll contents and ORAC values at MM were significantly higher and Chl a to Chl b ratios were lower in ‘open’ types compared to ‘head’ types. The nutritional traits assessed for GP showed a significant association with plant architecture suggesting pleiotropic effects or closely linked genes. Taken together, the antioxidant and chlorophyll content of lettuce is controlled by complex mechanisms and participating alleles change depending on growth stage and production environment.     

Differences in abscisic acid concentration in roots and leaves of two young Olive (<Emphasis Type="Italic">Olea europaea</Emphasis> L.) cultivars in response to water deficit

Differences in abscisic acid (ABA) accumulation between two olive cultivars were studied by enzyme-linked immunosorbent assay in roots and leaves, leaf water potential (Ψ_l), stomatal conductance (g _s) as well as photosynthetic rate (A) were also determined in well-watered (WW) and water-stressed (WS) plants of two olive cultivars ‘Chemlali’ and ‘Chetoui’. ‘Chemlali’ was able to maintain higher leaf CO₂ assimilation rate and leaf stomatal conductance throughout the drought cycle when compared with ‘Chetoui’. Furthermore, leaf water potential of ‘Chemlali’ decreased in lower extent than in Chetoui in response to water deficit. Interestingly, significant differences in water-stress-induced ABA accumulation were observed between the two olive cultivars and reflect the degree of stress experienced. Chemlali, a drought tolerant cultivar, accumulated lower levels of ABA in their leaves to regulate stomatal control in response to water stress compared to the drought sensitive olive cultivar ‘Chetoui’ which accumulated ABA in large amount.     

Seasonal studies on alginate and its composition II: Turbinaria conoides (J.Ag.) Kütz. (Fucales, Phaeophyceae)

The alginates extracted from ‘leaf’, ‘stem’ and entire thallus of Turbinaria conoides (J.Ag.) Kütz. were investigated for their viscosity and biochemical constituents namely, β-D-mannuronic acid (M-block}), α-L-guluronic acid (G-Block) and alternating sequences of β–D-mannuronic acid and α-L-guluronic acid (MG-block). Substantial seasonal variation was recorded with high yield of alginate during premonsoon. The yield of alginate was maximum in ‘leaf’ region. In contrast to this, viscosity and G-block were maximum in the ‘stem’ region. A significant positive correlation was observed between viscosity and G-block}. The ratio of guluronic: mannuronic acid was also assessed. Low levels of M/G ratio were recorded in the ‘stem’ region followed by ‘leaf’ and entire thallus.     

Cold-hardening of winter triticale (<Emphasis Type="Italic">x Triticosecale</Emphasis> Wittm.) results in increased resistance to pink snow mould <Emphasis Type="Italic">Microdochium nivale</Emphasis> (Fr., Samuels &; Hallett) and genotype-dependent chlorophyll fluorescence modulations

The resistance of triticale (x Triticosecale Wittm.) to infection of snow mould Microdochium nivale (Fr., Samuels & Hallett) was examined under different temperature pre-treatment regimes. The results of laboratory “cold chamber” resistance tests correlated with the breeders’ report from field experiments. Studied genotypes differed substantially in their resistance to infection. Two cultivars: ‘Magnat’ (susceptible) and ‘Hewo’ (relatively resistant) were further studied as a plant model to test the role of pre-hardening and cold-hardening induction of resistance expression. Both model cultivars were susceptible to M. nivale infection without cold pre-treatment and gained genotype-depended level of resistance after 4 weeks treatment at 4°C, moreover the resistance grew gradually. Simultaneously to the resistance tests, the measurements of chlorophyll fluorescence parameters were taken. The results showed that higher vitality index Rfd of cold-hardened triticale seedlings correlated with increased pink snow mould resistance while differences in other parameters of fluorescence were not distinctly significant. Establishment of Rfd in 4 weeks hardened triticale seedlings could be used for a large scale screening of breeding material in order to select potentially resistant genotypes. Such analyses have not been reported for triticale before.     

Selection of Highly Informative Microsatellite Markers to Identify Pollen Donors in ‘Hass’ Avocado Orchards

‘Hass’ is the most popular avocado (Persea americana Mill.) cultivar in the world. It has been characterized as a crop requiring cross-pollination. However, the potential extent of self-pollination and the most effective pollen donors (best cross-pollinizing cultivars) have not been determined. In this study, 56 markers were screened against ‘Hass’ and nine commonly used pollinizing cultivars grown in southern California: ‘Bacon,’ ‘Ettinger,’ ‘Fuerte,’ ‘Harvest,’ ‘Lamb Hass,’ ‘Marvel,’ ‘Nobel,’ ‘Sir Prize,’ and ‘Zutano.’ Seventeen microsatellite, i.e., simple sequence repeat (SSR) markers, were found to be very promising for paternity analysis. Four highly informative SSR markers were selected to accurately and unequivocally identify pollen parents of ‘Hass’ fruit from an orchard interplanted with these pollinizing cultivars. From 2003 to 2006, 7,984 ‘Hass’ fruit were analyzed for their paternity. Overall, the pollen parents of 99.55% of the analyzed fruit could be unequivocally identified with a single multiplex polymerase chain reaction (PCR). Only 36 fruits (<0.45%) required a second PCR reaction to reach unequivocal identification of the pollen parents.     

Isoenzyme markers in varietal identification of banana

Summary Salt-soluble polypeptide and a few isozymes were profiled to identify banana cultivars available in Andamans, India. Salt-soluble polypeptide profile was found to be inappropriate in cultivar identification However, isozymes such as peroxidase could differentiate ‘Jungli kela’, ‘Tissue Cultured Dwarf Cavendish’ (TCDC), ‘Lal kela’, ‘Rajbel’, and ‘Baratang wild’, while esterase identified all the cultivars except ‘Rajbel’ and ‘Tarkari kela’. The latter two cultivars could be identified with the use of malate dehydrogenase (MDH) and peroxidase profiles, MDH portrayed cultivar-specific distinct banding pattern in ‘Khatta Champa’, ‘Tarkari kela’, and ‘Baratang wild’, ‘China kela’ could be identified easily by superoxide dismutase (SOD). Amongst four isozymes, esterase was found to be most efficient in identifying eight cultivars amongst 10; bence this isozyme may be used often as a marker for cultivar identification of banana.     

Effects of drought and salinity on some growth-contributing parameters in wheat and barley

Summary This study is mainly concerned with some parameters contributing to growth as indicators of difference in drought resistance and salt tolerance of wheat and barley cultivars. Parameters made use of are: transpiration efficiency (‘dry matter/transpiration’ ratio), ‘leaf/root’ ratio, chlorophyll content, chlorophyll stability to heat and anatomical modifications. The results revealed that transpiration efficiency is much higher in mexican ‘super-x’ wheat than in the egyptian ‘Giza-155’ cultivar under reduced soil water matric- or osmotic potentials. Chlorophyll content increased in super-x with decreasing soil water potential while chlorophyll heat stability decreased. The reverse is true in Giza-155 cultivar. Decreased leaf/root ratio in super-x is interpretted in favour of more beneficial water balance in this cultivar. Development of more sclerenchyma in its stems supports this judgement. Of barley cultivars tested, Borg El-Arab is favoured for drought resistance and Giza-117 for salt tolerance. re]19751014     

History of the word photosynthesis and evolution of its definition

In 1893, Charles Barnes (1858–1910) proposed that the biological process for ‘synthesis of complex carbon compounds out of carbonic acid, in the presence of chlorophyll, under the influence of light’ should be designated as either ‘photosyntax’ or ‘photosynthesis.’ He preferred the word ‘photosyntax,’ but ‘photosynthesis’ came into common usage as the term of choice. Later discovery of anoxygenic photosynthetic bacteria and photophosphorylation necessitated redefinition of the term. This essay examines the history of changes in the meaning of photosynthesis. This revised version was published online in June 2006 with corrections to the Cover Date.     

Microsatellite diversity in tetraploid <Emphasis Type="Italic">Gossypium</Emphasis> germplasm: assembling a highly informative genotyping set of cotton SSRs

A series of 320 mapped simple sequence repeats (SSRs) have been used to screen the allelic diversity of tetraploid Gossypium species. Fourty-seven genotypes were analyzed representing (i) the wide spectrum of diversity of the cultivated pool and of the primitive landraces of species G. hirsutum (‘marie-galante’, ‘punctatum’, ‘richmondi’, ‘morrilli’, ‘palmeri’, and ‘latifolium’, and ‘yucatanense’), and (ii) species G. barbadense, G. darwinii and G. tomentosum. The polymorphism of 201 SSR loci revealed 1128 allelic variants ranging from 3 to 17 per locus. Neighbor-joining (NJ) method based on genetic dissimilarities produced groupings consistent with the assignments of accessions both at species and at race level. Our data confirmed the proximity of the Galapagos endemic species G. darwinii to species G. barbadense. Within species G. hirsutum, and as compared to the other 6 races, race yucatanense appeared as the most distant from cultivated genotypes. Race yucatanense also exhibited the highest number of unique alleles. The important informative heterogeneity of the 201 SSR loci was exploited to select the most polymorphic ones that were assembled into three series of genome-wide (i.e. each homoeologous AD chromosome pair being equally represented) and mutliplexable (× 3) SSRs. Using one of these ‘genotyping set’, consisting of 39 SSRs (one 3-plex for each of the 13 AD chromosomes pairs) or 45 loci, we were able to assess the relationships between accessions and the topology in the genetic diversity sampled. Such genotyping set of highly informative SSR markers assembled in PCR-multiplex, while increasing genotyping throughput, will be applicable for molecular genetic diversity studies of large germplasm collections. Electronic Supplementary Material Supplementary material is available in the online version of this article at and is accessible for authorized users.     

Oxygen Consumption and Respiration During and After two Yoga Relaxation Techniques

Cyclic meditation (CM) is a technique which combines ‘stimulating’ and ‘calming’ practices, based on a statement in ancient yoga texts suggesting that such a combination may be especially helpful to reach a state of mental equilibrium. The oxygen consumption, breath rate and breath volume of 50 male volunteers (group mean age±SD, 27±6.3 years) were assessed before, during, and after sessions of CM and sessions of supine rest in the corpse posture (shavasana, SH). The sessions were one day apart and the order was alternated. The oxygen consumption, breath rate and breath volume increased during the ‘stimulating’ practices of CM, returned to the baseline during the ‘calming’ practices, and the oxygen consumption decreased by 19.3 percent below baseline values after CM. During the SH session the oxygen consumption, breath rate and breath volume reduced; however the decrease in oxygen consumption after SH was less than after CM (i.e., 4.8 percent). The results support the idea that a combination of yoga postures with supine rest (in CM) reduces the oxygen consumption more than resting supine alone does.     

Induction of embryogenic mango cultures as affected by genotype,explanting, 2,4-D and embryogenic nurse culture

The nucellus was removed from immature seeds of 4 mango genotypes, andcultured under different induction conditions. The mango genotypes includedpolyembryonic ‘Hindi’ and ‘Nam Doc Mai’ and monoembryonic ‘Lippens’ and’Tommy Atkins‘. Nucellar explants were cultured on modified B5 basal mediumunder the following inductive conditions: 1) 4.52 μM 2,4-D; 2) nogrowth regulator (control); 3) 4.52 μM 2,4-D + embryogenic ‘Parris‘nurse culture; 4) no growth regulator + embryogenic ‘Parris’ nurse culture.Induction of embryogenic competence was mediated by 4 factors: genotype,explanting, 2,4-D and the presence of a highly embryogenic nurse culture,although there was considerable difference in genotype response. ‘Hindi’ hadthe greatest embryogenic potential, followed by ‘Lippens’, ‘Tommy Atkins‘and ‘Nam Doc Mai’, respectively. Induction of embryogenic cultures of allgenotypes at low frequency occurred as a result of explanting excisednucellus onto control medium. The most effective treatment for inducingembryogenic cultures was 2,4-D + embryogenic ‘Parris’ nurse culture with’Hindi’, ‘Lippens’ and ‘Nam doc Mai’, with the exception of ‘Tommy Atkins’,in which the treatment with 2,4-D alone was most effective. This revised version was published online in June 2006 with corrections to the Cover Date.     

Determination of self-locompatibility genotypes of Korean apple cultivars based on S-RNase PCR

To prevent self-fertilization, apple has a gametophytic self-incompatibility mechanism, part of a widespread intraspecific system, that is controlled by a multi-allelic locus. This attribute has been exploited in breeding programs for new cultivars. Likewise, many apple orchards depend on artificial pollination. Therefore, molecular analysis and early identification of the self-incompatibility (S) genotype could greatly improve breeding schemes and pollen donors selection. Here, we PCR-amplified the S-RNase PCR fragments from a total of 14 cultivars and parents, using new primers (ASPF3+ASPR3) common to 23 S-alleles in apple. The S-genotypes were determined for the following: ‘Hongro’ (S₁S₃), ‘Gamhong’ (S₁S₉), ‘Saenara’ (S₁S₃), ‘Chukwang’ (S₃S₉), ‘Hwahong’ (S₃S₉), ‘Seokwang’ (S₃S₃), ‘Hwarang’ (S₁S₉), ‘Sunhong’ (S₃S₉), ‘S.E.B.’ (S₁S₁₉), ‘S.G.D.’ (S₂S₃), and ‘Mollie’s Delicious’ (S₃S₇). We also confirmed the characteristics of the S-genotypes for eight Korean apple cultivars by PCR-Southern blot analysis, using seven S-RNases as probes.     

Photosynthesis parameters and activities of enzymes of oxidative stress in two young ‘Chemlali’ and ‘Chetoui’ olive trees under water deficit

The effects of water deficit on photochemical parameters and activities of superoxide dismutase, catalase, ascorbate peroxidase and glutathione reductase were investigated in two olive cultivars differing in drought tolerance — ‘Chemlali’ and ‘Chetoui’. After 30 days without irrigation, leaf water potential fell to −5.5 MPa that was accompanied by a marked decrease in net photosynthesis in ‘Chetoui’ olive cultivar. Maximal efficiency of PSII photochemistry (F_v/F_m) decreased slightly in ‘Chemlali’ (28 %) and substantially in ‘Chétoui’ (47 %). Both cultivars showed a similar decline (about 25 %) in the photochemical quenching coefficient, but only the drought-sensitive olive cultivar exhibited an enhancement (31 %) of non-photochemical fluorescence quenching under water deficit conditions. The quantum yield of electron transport decreased in both olive cultivars. ‘Chemlali’ showed a higher protection against oxidative stress, as judged from the lower levels of the malondialdehyde production. Catalase activity was higher in ‘Chetoui’. Glutathione reductase activity was increased similarly in both olive cultivars under water stress. Ascorbate peroxidase activity was enhanced in ‘Chemlali’ under water stress, but was unaffected in ‘Chetoui’. While, superoxide dismutase activity was inhibited in both cultivars under water stress, but higher activity was detected in ‘Chemlali’. Thus, the ability to increase ascorbate peroxidase and a higher superoxide dismutase activity might be an important attribute linked to the drought tolerance in ‘Chemlali’ olive cultivar.