Optimizing Cucumis sativus seedling vigor: the role of pistachio wood vinegar and date palm compost in nutrient mobilization.

BACKGROUND: The goal of this research is to enhance the quality of cucumber seedlings grown in greenhouses by experimenting with various soilless culture mediums (CMs) and the application of pistachio wood vinegar (WV). The experimental setup was designed as a factorial experiment within a randomized complete block design (RCBD), in greenhouse conditions featuring three replications to assess the effects of different culture media (CMs) and concentrations of pistachio wood vinegar (WV) on cucumber seedling growth. Cucumber seeds were planted in three CMs: coco peat-peat moss, coco peat-vermicompost, and date palm compost-vermicompost mixed in a 75:25 volume-to-volume ratio. These were then treated with pistachio WV at concentrations of 0, 0.5, and 1%, applied four times during irrigation following the emergence of the third leaf. RESULTS: The study revealed that treating seedlings with 0.5% WV in the date palm compost-vermicompost CM significantly enhanced various growth parameters. Specifically, it resulted in a 90% increase in shoot fresh mass, a 59% increase in shoot dry mass, an 11% increase in root fresh mass, a 36% increase in root dry mass, a 65% increase in shoot length, a 62% increase in leaf area, a 25% increase in stem diameter, a 41% increase in relative water content (RWC), and a 6% improvement in membrane stability index (MSI), all in comparison to untreated seedlings grown in coco peat-peat moss CM. Furthermore, chlorophyll a, b, total chlorophyll, and carotenoid levels were 2.3, 2.7, 2.6, and 2.7 times higher, respectively, in seedlings treated with 0.5% WV and grown in the date palm compost-vermicompost CM, compared to those treated with the same concentration of WV but grown in coco peat-peat moss CM. Additionally, the Fv/Fm ratio saw a 52% increase. When plant nutrition was enhanced with the date palm compost-vermicompost CM and 1% WV, auxin content rose by 130% compared to seedlings grown in coco peat-peat moss CM and treated with 0.5% WV. CONCLUSIONS: The study demonstrates that using 0.5% WV in conjunction with date palm compost-vermicompost CM significantly betters the quality of cucumber seedlings, outperforming other treatment combinations.

Catechin promotes the germination of Pistacia chinensis seeds via GA biosynthesis.

BACKGROUND AND AIMS: Chinese pistachio (Pistacia chinensis), an important horticultural plant species, holds great ornamental value with beautiful leaves and fruits. Seedling propagation of this tree species is restricted by its erratic seed germination; however, the germination mechanism is ambiguous. The aim of this study was to determine the germination mechanism from a novel perspective based on the multi-omics data. METHODS: The multi-omics technique combined with hormone content measurement was applied to seed germination of Chinese pistachio. KEY RESULTS: Due to its great accumulation during seed germination, catechin stood out from the identified metabolites in a broadly targeted metabolomic analysis. Exogenous catechin at 10 mg L-1 significantly improved the germination of Chinese pistachio seeds. An interesting result of hormone analysis was that the improving effect of catechin could be attributed to an increase in gibberellic acid 3 (GA3) content rather than a decrease in abscisic acid (ABA) content before germination. Treatments with paclobutrazol (PAC, a GA biosynthesis inhibitor) and PAC + catechin also showed that the promoting effect of catechin on seed germination depends on GA biosynthesis. Transcriptome analysis and qRT‒PCR further revealed that catechin induced the expression of PcGA20ox5 to activate GA biosynthesis. Several transcription factors were induced by catechin and GA treatments, such as TCP, bZIP and C3H, which may play an important regulatory role in GA biosynthesis in a catechin-mediated way. CONCLUSIONS: Catechin promotes seed germination via GA biosynthesis in Chinese pistachios. This study proposes a novel mechanism by which catechin promotes seed germination via the GA pathway, which provides new insight into a comprehensive understanding of seed dormancy and germination.

Spatial patterns of tree yield explained by endogenous forces through a correspondence between the Ising model and ecology.

Spatial patterning of periodic dynamics is a dramatic and ubiquitous ecological phenomenon arising in systems ranging from diseases to plants to mammals. The degree to which spatial correlations in cyclic dynamics are the result of endogenous factors related to local dynamics vs. exogenous forcing has been one of the central questions in ecology for nearly a century. With the goal of obtaining a robust explanation for correlations over space and time in dynamics that would apply to many systems, we base our analysis on the Ising model of statistical physics, which provides a fundamental mechanism of spatial patterning. We show, using 5 y of data on over 6,500 trees in a pistachio orchard, that annual nut production, in different years, exhibits both large-scale synchrony and self-similar, power-law decaying correlations consistent with the Ising model near criticality. Our approach demonstrates the possibility that short-range interactions can lead to long-range correlations over space and time of cyclic dynamics even in the presence of large environmental variability. We propose that root grafting could be the common mechanism leading to positive short-range interactions that explains the ubiquity of masting, correlated seed production over space through time, by trees.

Assessment of changes in physiological and biochemical traits in four pistachio rootstocks under drought, salinity and drought + salinity stresses.

In this study, 7-month-old UCB-1, Badami, Ghazvini and Kale-Ghouchi pistachio rootstocks were exposed to control, drought, salinity and drought + salinity environments for 60 d. Total chlorophyll and total carotenoid contents decreased in all cultivars under drought, salinity and drought + salinity stresses. Under drought and salinity stresses, alone or in combination, Na+ and Cl- ions increased in all four pistachio rootstocks, while K+ ion decreased only in Ghazvini and Kaleh-Ghouchi cultivars. The enzyme activities of ascorbate peroxidase, polyphenol oxidase, catalase and guaiacol peroxidase increased in all cultivars when subjected to all three stresses with the exception of the ascorbate peroxidase activity in Kale-Ghouchi cultivar during drought stress. Oxidative stress parameters including electrolyte leakage, malondialdehyde, other aldehydes and hydrogen peroxide increased under all three stress conditions in all genotypes. The content of proline, total free amino acids and total soluble carbohydrates were enhanced under drought, salinity and drought + salinity stresses, whereas the protein content decreased in all pistachio rootstocks. In all evaluated traits, except for the K+ ion content and APX activity, the highest impacts was seen for drought + salinity > salinity > drought stresses, respectively. For the first time, we have proven that K+ ion content has a positive correlation with the ascorbate peroxidase, polyphenol oxidase, catalase and guaiacol peroxidase enzymes activities under drought + salinity stress. Finally, based on the bi-plot and cluster analyses, we have selected the UCB-1 > Badami > Ghazvini > Kale-Ghouchi cultivars as the most tolerant pistachio rootstocks under drought + salinity stress, respectively.

Climate change threatens central Tunisian nut orchards.

Temperate deciduous trees can only be productive where winters are cold enough to meet their chilling needs. In the Mediterranean region, chill has traditionally been sufficient for many species, but this may change as temperatures increase. We explored the region's present and future suitability for temperate trees by quantifying chill for the Sfax region in central Tunisia, one of the warmest regions where temperate nuts are commercially grown. We assessed climatic risk by calculating historic chill (since 1973) and using a weather generator calibrated with local weather data (1973-2015) to produce 101 years of chill estimates (computed with the Dynamic Model) and 3 past and 72 future scenarios (for 2041-2070 and 2071-2100, using two representative concentration pathways: RCP4.5 and RCP8.5). For almonds and pistachios, we compared available chill during the chilling period with the species' estimated chilling requirements, and we computed the date by which sufficient chill was expected to have accumulated. Our findings indicated severe chill losses for all future scenarios. For all species, the current chill period is no longer expected to be sufficient for meeting chilling requirements in the future. Chill needs may still be fulfilled later in the year, especially for low-chill almonds, but this would result in delayed phenology, with possible adverse effects on productivity. Temperate nut production is thus unlikely to remain viable at this site, highlighting an urgent need to identify locally appropriate adaptation options. This challenge is likely shared by other warm production regions of temperate fruits and nuts around the world.

A genome-wide transcriptome map of pistachio (Pistacia vera L.) provides novel insights into salinity-related genes and marker discovery.

BACKGROUND: Pistachio (Pistacia vera L.) is one of the most important commercial nut crops worldwide. It is a salt-tolerant and long-lived tree, with the largest cultivation area in Iran. Climate change and subsequent increased soil salt content have adversely affected the pistachio yield in recent years. However, the lack of genomic/global transcriptomic sequences on P. vera impedes comprehensive researches at the molecular level. Hence, whole transcriptome sequencing is required to gain insight into functional genes and pathways in response to salt stress. RESULTS: RNA sequencing of a pooled sample representing 24 different tissues of two pistachio cultivars with contrasting salinity tolerance under control and salt treatment by Illumina Hiseq 2000 platform resulted in 368,953,262 clean 100 bp paired-ends reads (90 Gb). Following creating several assemblies and assessing their quality from multiple perspectives, we found that using the annotation-based metrics together with the length-based parameters allows an improved assessment of the transcriptome assembly quality, compared to the solely use of the length-based parameters. The generated assembly by Trinity was adopted for functional annotation and subsequent analyses. In total, 29,119 contigs annotated against all of five public databases, including NR, UniProt, TAIR10, KOG and InterProScan. Among 279 KEGG pathways supported by our assembly, we further examined the pathways involved in the plant hormone biosynthesis and signaling as well as those to be contributed to secondary metabolite biosynthesis due to their importance under salinity stress. In total, 11,337 SSRs were also identified, which the most abundant being dinucleotide repeats. Besides, 13,097 transcripts as candidate stress-responsive genes were identified. Expression of some of these genes experimentally validated through quantitative real-time PCR (qRT-PCR) that further confirmed the accuracy of the assembly. From this analysis, the contrasting expression pattern of NCED3 and SOS1 genes were observed between salt-sensitive and salt-tolerant cultivars. CONCLUSION: This study, as the first report on the whole transcriptome survey of P. vera, provides important resources and paves the way for functional and comparative genomic studies on this major tree to discover the salinity tolerance-related markers and stress response mechanisms for breeding of new pistachio cultivars with more salinity tolerance.

Acclimation of Pistacia integerrima trees to frost in semi-arid environments depends on autumn's drought.

Main conclusion Cold acclimation is revealed through induced stem respiration during pre-winter frost of native Pistacia integerrima trees in continental semi-arid environments. Semi-arid environments challenge vegetation by simultaneous abiotic stresses. In this study, we examine the combined effects of water stress and frost on the physiology of Pistacia integerrima stems. This species is native to semi-arid environments where drought and frost frequently co-occur. We quantified carbohydrates and proline in P. integerrima stems responding to frost and experiencing water potentials between -0.2 and -1.8 MPa. We report that dehydrated trees (i.e., Ψstem <=-1 MPa) had more soluble sugars and proline than the well-watered trees (-0.2 MPa). The dehydrated trees also froze at lower temperatures and were less damaged by freezing. Interestingly, we observed a significant increase in stem CO2 efflux at near-freezing temperatures that could be linked to frost protection. This novel finding challenges current paradigm of plant respiration-kinetics which predicts, according to Arrhenius equation, lower respiration rates during frost. Our results support the notion that drought and frost are analogous stresses that can independently activate corresponding physiological processes in trees and amplify protection. This inevitable stress response 'collaboration' may be the key to understanding how non-dormant perennial plants survive the highly variable weather patterns of early winters in semi-arid environments.

Sex-related differences in lipid peroxidation and photoprotection in Pistacia lentiscus.

Sex-related differences in the response of dioecious plants to abiotic stress have been poorly studied to date. This work explored to what extent sex may affect plant stress responses in Pistacia lentiscus L. (Anacardiaceae), a tree well adapted to Mediterranean climatic conditions. It was hypothesized that a greater reproductive effort in females may increase oxidative stress in leaves, particularly when plants are exposed to abiotic stress. Measurements of oxidative stress markers throughout the year revealed increased lipid peroxidation in females, but only during the winter. Enhanced lipid peroxidation in females was associated with reduced photoprotection, as indicated by reduced tocopherol levels and nonphotochemical quenching (NPQ) of chlorophyll fluorescence. Enhanced lipid peroxidation in females was also observed at predawn, which was associated with increased lipoxygenase activity and reduced cytokinin levels. An analysis of the differences between reproductive (R) and nonreproductive (NR) shoots showed an enhanced photoprotective capacity in R shoots compared to NR shoots in females. This capacity was characterized by an increased NPQ and a better antioxidant protection (increased carotenoid and tocopherol levels per unit of chlorophyll) in R compared to NR shoots. It is concluded that (i) females exhibit higher lipid peroxidation in leaves than males, but only during the winter (when sex-related differences in reproductive effort are the highest), (ii) this is associated with a lower photoprotective capacity at midday, as well as enhanced lipoxygenase activity and reduced cytokinin levels at predawn, and (iii) photoprotection capacity is higher in R relative to NR shoots in females.

Gall volatiles defend aphids against a browsing mammal.

BACKGROUND: Plants have evolved an astonishing array of survival strategies. To defend against insects, for example, damaged plants emit volatile organic compounds that attract the herbivore's natural enemies. So far, plant volatile responses have been studied extensively in conjunction with leaf chewing and sap sucking insects, yet little is known about the relationship between plant volatiles and gall-inducers, the most sophisticated herbivores. Here we describe a new role for volatiles as gall-insects were found to benefit from this plant defence. RESULTS: Chemical analyses of galls triggered by the gregarious aphid Slavum wertheimae on wild pistachio trees showed that these structures contained and emitted considerably higher quantities of plant terpenes than neighbouring leaves and fruits. Behavioural assays using goats as a generalist herbivore confirmed that the accumulated terpenes acted as olfactory signals and feeding deterrents, thus enabling the gall-inducers to escape from inadvertent predation by mammals. CONCLUSIONS: Increased emission of plant volatiles in response to insect activity is commonly looked upon as a "cry for help" by the plant to attract the insect's natural enemies. In contrast, we show that such volatiles can serve as a first line of insect defences that extends the 'extended phenotype' represented by galls, beyond physical boundaries. Our data support the Enemy hypothesis insofar that high levels of gall secondary metabolites confer protection against natural enemies.

Root architecture and hydraulic conductance in nutrient deprived Pistacia lentiscus L. seedlings.

Plants respond to low nutrient availability by modifying root morphology and root system topology. Root responses to nitrogen (N) and phosphorus (P) limitation may affect plant capacity to withstand water stress. But studies on the effect of nutrient availability on plant ability to uptake and transport water are scarce. In this study, we assess the effect of nitrogen and phosphorus limitation on root morphology and root system topology in Pistacia lentiscus L seedlings, a common Mediterranean shrub, and relate these changes to hydraulic conductivity of the whole root system. Nitrogen and phosphorus deprivation had no effect on root biomass, but root systems were more branched in nutrient limited seedlings. Total root length was higher in seedlings subjected to phosphorus deprivation. Root hydraulic conductance decreased in nutrient-deprived seedlings, and was related to the number of root junctions but not to other architectural traits. Our study shows that changes in nutrient availability affect seedling water use by modifying root architecture. Changes in nutrient availability should be taken into account when evaluating seedling response to drought.

Ephedra alte (joint pine): an invasive, problematic weedy species in forestry and fruit tree orchards in Jordan.

A field survey was carried out to record plant species climbed by Ephedra alte in certain parts of Jordan during 2008-2010. Forty species of shrubs, ornamental, fruit, and forest trees belonging to 24 plant families suffered from the climbing habit of E. alte. Growth of host plants was adversely affected by E. alte growth that extended over their vegetation. In addition to its possible competition for water and nutrients, the extensive growth it forms over host species prevents photosynthesis, smothers growth and makes plants die underneath the extensive cover. However, E. alte did not climb all plant species, indicating a host preference range. Damaged fruit trees included Amygdalus communis, Citrus aurantifolia, Ficus carica, Olea europaea, Opuntia ficus-indica, and Punica granatum. Forestry species that were adversely affected included Acacia cyanophylla, Ceratonia siliqua, Crataegus azarolus, Cupressus sempervirens, Pinus halepensis, Pistacia atlantica, Pistacia palaestina, Quercus coccifera, Quercus infectoria, Retama raetam, Rhamnus palaestina, Rhus tripartita, and Zizyphus spina-christi. Woody ornamentals attacked were Ailanthus altissima, Hedera helix, Jasminum fruticans, Jasminum grandiflorum, Nerium oleander, and Pyracantha coccinea. Results indicated that E. alte is a strong competitive for light and can completely smother plants supporting its growth. A. communis, F. carica, R. palaestina, and C. azarolus were most frequently attacked.

Leaves of field-grown mastic trees suffer oxidative stress at the two extremes of their lifespan.

Leaf senescence is a complex phenomenon occurring in all plant species, but it is still poorly understood in plants grown in Mediterranean field conditions and well-adapted to harsh climatic conditions. To better understand the physiological processes underlying leaf senescence in mastic trees (Pistacia lentiscus L.), we evaluated leaf growth, water and N content, photosystem II (PSII) photochemistry, lipid peroxidation and levels of photosynthetic pigments, antioxidants, abscisic acid, and salicylic acid and jasmonic acid during the complete leaf lifespan, from early expansion to late senescence in relation to natural climatic conditions in the field. While mature leaves suffered from water and N deficit during late spring and summer, both young (emerging) and old (senescing) leaves were most sensitive to photo-oxidative stress, as indicated by reductions in the F(v)/F(m) ratio and enhanced lipid peroxidation during late autumn and winter. Reductions in the F(v)/F(m) ratio were associated with low α-tocopherol (vitamin E) levels, while very old, senescing leaves additionally showed severe anthocyanin losses. We have concluded that both young (emerging) and old (senescing) leaves suffer oxidative stress in mastic trees, which may be linked in part to suboptimal temperatures during late autumn and winter as well as to low vitamin E levels.

A genome-wide identification, characterization and functional analysis of salt-related long non-coding RNAs in non-model plant Pistacia vera L. using transcriptome high throughput sequencing.

Long non-coding RNAs (lncRNAs) play crucial roles in regulating gene expression in response to plant stresses. Given the importance regulatory roles of lncRNAs, providing methods for predicting the function of these molecules, especially in non-model plants, is strongly demanded by researchers. Here, we constructed a reference sequence for lncRNAs in P. vera (Pistacia vera L.) with 53220 transcripts. In total, we identified 1909 and 2802 salt responsive lncRNAs in Ghazvini, a salt tolerant cultivar, after 6 and 24 h salt treatment, respectively and 1820 lncRNAs in Sarakhs, a salt sensitive cultivar, after 6 h salt treatment. Functional analysis of these lncRNAs by several hybrid methods, revealed that salt responsive NAT-related lncRNAs associated with transcription factors, CERK1, LEA, Laccase genes and several genes involved in the hormone signaling pathways. Moreover, gene ontology (GO) enrichment analysis of salt responsive target genes related to top five selected lncRNAs showed their involvement in the regulation of ATPase, cation transporter, kinase and UDP-glycosyltransferases genes. Quantitative real-time PCR (qRT-PCR) experiment results of lncRNAs, pre-miRNAs and mature miRNAs were in accordance with our RNA-seq analysis. In the present study, a comparative analysis of differentially expressed lncRNAs and microRNA precursors between salt tolerant and sensitive pistachio cultivars provides valuable knowledge on gene expression regulation under salt stress condition.

The role of large environmental noise in masting: general model and example from pistachio trees.

Masting is synchronous, highly variable reproduction in a plant population, or synchronized boom-bust cycles of reproduction. These pulses of resources have cascading effects through ecosystems, and thus it is important to understand where they come from. How does masting happen and synchronize? In this paper, we suggest a mechanism for this. The mechanism is inspired by data from a pistachio orchard, which suggest that large environmental noise may play a crucial role in inducing masting in plant populations such as pistachio. We test this idea through development and analysis of a mathematical model of plant reproduction. We start with a very simple model, and generalize it based on the current models of plant reproduction and masting. Our results suggest that large environmental noise may indeed be a crucial part of the mechanism of masting in certain types of plant populations, including pistachio. This is a specific example of an important functional consequence of the interactions between stochasticity and nonlinearity.

How do Mediterranean shrub species cope with shade? Ecophysiological response to different light intensities.

Under natural conditions, light exposure for Mediterranean shrubs can be highly variable, especially during cloudy days or under a canopy, and can interfere with other environmental factors such as temperature and water availability. With the aim of decoupling the effect of radiation and temperature from water availability, we conducted an experiment where two perennial and three summer semi-deciduous shrub species were subjected to different levels of irradiation. In order to follow plant responses to light exposure, we measured gas exchange, photosystem II photochemical efficiency, photosynthetic pigments and leaf mass area in spring and summer. Results showed that all study species presented a plastic response to different light conditions, and that light-related traits varied in a coordinated manner. Summer semi-deciduous species exhibited a more opportunistic response, with higher photosynthesis rates in full sun, but under shade conditions, the two strategies presented similar assimilation rates. Stomatal conductance did not show such a drastic response as photosynthetsis, being related to changes in WUE. Daily cycles of Fv /Fm revealed a slight photoinhibitory response during summer, mainly in perennial species. In all cases photosynthetic pigments adjusted to the radiation level; leaves had lower chlorophyll content, higher pool of xanthophylls and higher proportion of the de-epoxydaded state of xanthophylls under sun conditions. Lutein content increased in relation to the xanthophyll pool under shade conditions. Our results evidenced that radiation is an important driving factor controlling morphological and physiological status of Mediterranean shrub species, independently of water availability. Summer semi-deciduous species exhibit a set of traits with higher response variability, maximising their photosynthetic assimilation under different sun conditions.

Ion homeostasis, osmoregulation, and physiological changes in the roots and leaves of pistachio rootstocks in response to salinity.

Pistachio, one of the important tree nuts, is cultivated in arid and semi-arid regions where salinity is the most common abiotic stress encountered by this tree. However, the mechanisms underlying salinity tolerance in this plant are not well understood. In the present study, five 1-year-old pistachio rootstocks (namely Akbari, Badami, Ghazvini, Kale-Ghouchi, and UCB-1) were treated with four saline water regimes (control, 8, 12, and 16 dS m-1) for 100 days. At high salinity level, all rootstocks showed decreased relative water content (RWC), total chlorophyll content (TCHC), and carotenoids in the leaf, while ascorbic acid (AsA) and total soluble proteins (TSP) were reduced in both leaf and root organs. In addition, the total phenolic compounds (TPC), proline, glycine betaine, total soluble carbohydrate (TSC), and H2O2 content increased under salinity stress in all studied rootstocks. Three different ion exclusion strategies were observed in the studied rootstocks: (i) Na+ exclusion in UCB-1, because most of its Na+ is retained in the roots; (ii) Cl- exclusion in Badami, in which most of its Cl- remained in the roots; and (iii) similar concentrations of Na+ and Cl- were observed in the leaves and roots of Ghazvini, Akbari, and Kale-Ghouchi. Transport capacity (ST value) of K+ over Na+ from the roots to the leaves was more observable in UCB-1 and Ghazvini. Overall, the root system cooperated more effectively in UCB-1 and Badami for retaining and detoxifying an excessive amount of Na+ and Cl-. The results presented here provide important inputs to better understand the salt tolerance mechanism in a tree species for developing more salt-tolerant genotypes. Based on the results obtained here, the studied rootstocks from tolerant to susceptible are arranged as follows: UCB-1 > Badami > Ghazvini > Kale-Ghouchi > Akbari.

Monitoring of pistachio (Pistacia Vera) ripening by high field nuclear magnetic resonance spectroscopy.

The metabolic profiling of pistachio (Pistacia vera) aqueous extracts from two different cultivars, namely 'Bianca' and 'Gloria', was monitored over the months from May to September employing high field NMR spectroscopy. A large number of water-soluble metabolites were assigned by means of 1D and 2D NMR experiments. The change in the metabolic profiles monitored over time allowed the pistachio development to be investigated. Specific temporal trends of amino acids, sugars, organic acids and other metabolites were observed and analysed by multivariate Partial Least Squares (PLS) analysis. Statistical analysis showed that while in the period from May to September there were few differences between the two cultivars, the ripening rate was different.

Association between radionuclides (210Po and 210Pb) and antioxidant enzymes in oak (Quercus coccifera) and mastic tree (Pistacia lentiscus).

The activity levels of naturally occurring radionuclides Polonium-210 and lead-210 in different subjects including plant species have direct or indirect impact on human beings. High levels of ionising radiation cause oxidative stress and the interaction between antioxidative defense and radionuclides is not well established in plant systems. In this study, we aimed to understand the impact of oxidative stress caused by 210Po and 210Pb in two Mediterranean plants; Quercus coccifera and Pistacia lentiscus. We analysed the constitutive and seasonal levels of 210Po, 210Pb, lipid peroxidation levels, superoxide dismutase (SOD) and ascorbate peroxidase (APX) activities in the field-collected samples. The highest activity concentrations of 210Po and 210Pb were detected in both plants in summer and Q. coccifera had higher levels than that of P. lentiscus. SOD and APX activity trends were different between oak and mastic; as compared to P. lentiscus, Q. coccifera efficiently used the two major components of antioxidative defense. Lipid peroxidation levels were low in both plants in all seasons except that of spring which were in good agreement with high antioxidant enzyme activities. In conclusion, we found that high 210Po and 210Pb activity concentrations in oak and mastic did not interfere with their growth and life cycles. The ability of both plants for survival and adaptation to Mediterranean environmental constraints provided an additional advantage for coping radionuclide induced oxidative stress as well.

Costs of reproduction as related to the timing of phenological phases in the dioecious Shrub Pistacia lentiscus L.

Females of woody dioecious species usually devote more resources to reproduction than males. This may lead to a decrease in female survival and growth. The costs of reproduction, however, can be lightened through a number of mechanisms, as for example avoiding the temporal coincidence of reproduction and vegetative growth. The aim of this study was to evaluate whether males and females of P. lentiscus differ in the timing of their vegetative growth, and to assess whether the sequencing of vegetative growth and reproduction reduces reproductive costs. We monitored phenology in males and females. We also compared male and female allocation of nutrients and biomass in the branch, and the developmental stability of the growing shoots. We did this both prior to and at the end of the fruiting period. Males and females showed similar vegetative and flowering phenologies. Males invested more biomass in flowering, but the sexes showed equal vegetative biomass and nutrient content prior to the fruiting period. In female branches, no trade-off was found between fruit load and current-year vegetative growth. In P. lentiscus, avoiding the overlap of flowering, vegetative growth and fruiting probably contributes to reduce the immediate costs of reproductive efforts, both in males and females.

Regulated deficit irrigation and the recovery of water relations in pistachio trees.

Recovery of water status in water-stressed pistachio trees (Pistacia vera L. cv. Kerman) was investigated by subjecting trees to regulated deficit irrigation (RDI) (60% of crop evapotranspiration rate, ET(c)) during stages I and II of fruit development (FD) followed by full irrigation during FD stage III (kernel-filling). Trees irrigated at 100% ET(c) throughout FD stages I, II and III served as controls. Water-stress severity was characterized by changes in soil water content and midday stem water potential (Psi(md)). Midday leaf conductance (g(1)) and trunk diameter variation (TDV) were also measured. In RDI trees, the lowest Psi(md) value, -1.8 MPa, occurred at the end of the RDI period. The corresponding value for the control trees was around -1.1 MPa. Although the RDI treatment affected gas exchange later than Psi(md), the greatest reductions in gas exchange (60% of control values) also appeared at the end of the RDI period. There were significant differences in TDV between control and RDI trees at the end of the RDI period. Although plant water status recovered within 20 days of resuming irrigation, the TDV values indicated a longer period might be necessary for complete recovery. Recovery of g(1) was faster than that of Psi(md), although differences in TDV between control and RDI trees indicated that gas exchange recovered later than Psi(md). The slow recovery of pistachio trees during FD stage III from water stress imposed during FD stages I and II suggests that irrigation should exceed 100% ET(c) during FD stage III or that more extensive irrigation should commence before the end of FD stage II.