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Fifteen years of research and development aimed at the production of high-quality early-winter strawberries in the Negev desert, are concluded. This goal required synchronization of seasonal yields with the peaks of the markets\' demand, November−February. For this purpose, selected infra short-day (ISD) cultivars were used. Rooted plug plants with enhanced capacity of simultaneous fast vegetative growth and fruiting were produced. Production was carried out in greenhouses and various protocols aimed at yield enhancement were tested. Currently, drip-fertigated, eye-level hanging soilless system, with plant density at about 200,000 plants ha−1, combined with biological pest management program, are employed. This system brought about a two-fold increase in yield compared to soil culture (80–100 t ha−1), significantly reduced risks of soil- and air-borne diseases, reduced the use of fungicides, and eased extensive labor demands. However, beyond substantial refinements of practices, a significant proportion, 15–25% of the seasonal high-quality yield, was harvested during the earlier two months with no reduction in the total yield or fruit quality. In this chapter, the state of art in early-winter strawberry production is portrayed, including principles, approaches, and methods that have been used and improved during the project. Additionally, ideas for further possible enhancement are discussed.

Balanced fertilizer management promotes plant growth, enhances produce quality, minimizes inputs, and reduces negative environmental impacts. Wax gourd (Benincasa hispida) is an important vegetable crop species in China and in South Asia. Two crop nutrition options, NPK and the natural mineral polyhalite, were tested, separately and combined, with the aim of enhancing wax gourd yield and quality and simultaneously to increase nutrient use efficiency and reducing inputs. The experiments tested the optimization of NPK by reducing the proportion of phosphorus (P), and the effect of enriching the soil with essential macronutrients by the use of the supplementary mineral fertilizer polyhalite containing magnesium (Mg), calcium (Ca) and sulfur (S). Two experiments were carried out in Foshan County, Guangdong, China, in 2018 and 2019. Experiments included four treatments: (1) Conventional NPK (15:15:15); (2) Optimized NPK (16:8:18); (3) Conventional NPK + polyhalite; (4) Optimized NPK + polyhalite. Fertilizers were applied prior to planting. While optimized NPK alone had no effects on fruit yield and quality, supplementary polyhalite resulted in a 10–17% increase in yield and significantly improved produce quality due to increased nutrient uptake from polyhalite, resulting in better foliar biomass. We conclude that the combined crop nutrition options improved yield and quality, enhanced nutrient use efficiency, and reduced risks of nutrient pollution. Inclusion of polyhalite in balanced fertilization practices as a supplementary source of secondary macronutrients seems promising. Nevertheless, plenty of space remains open for further adjustments of NPK application management, focusing on reduced rates, optimized ratio, and accurate timing of application for each nutrient.

Hairy stork’s-bill (Erodium crassifolium) (HSB) is one of the few Geraniaceae species that produce tubers. While HSB tubers were occasionally used as a food source by desert nomads, they have not yet been taken up in the modern kitchen. Recently, HSB tubers were recognized as harboring potential to become an industrial pharmaceutical crop. The objective of this study was to determine a set of agricultural practices that would maximize the yield of the bioactive compounds of the present HSB genetic material. A generous and consistent irrigation regime of about 700 mm season−1 increased tuber yield and size. The optimal plant density on sandy soils was 16–20 plants m−2. Mineral nutrition, applied through fertigation, increased tuber yield from 0.6 to almost 1 kg m−2. Source-sink manipulations (consistent pruning of the reproductive organs) almost doubled the tuber yield. During 10 years of research, the adopted agricultural practices increased yield by an order of magnitude (from about 0.2–2.0 kg m−2) without any dilution of the bioactive compounds. Nevertheless, further research and development are required to achieve HSB potential as an industrial field crop, including selection and breeding of outstanding infertile clones, optimization of fertigation, and development of various concrete pharmaceutical products.

Salinity affects plant growth due to both osmotic and ionic stress. The root system is essential in defense mechanisms against salinity, particularly involving salt ion avoidance or exclusion. Jojoba (Simmondsia chinensis) displays significant resistance to salinity. In the present study, Jojoba was planted in 60-L plastic buckets containing perlite growth medium and were provided with eight distinct salinity levels using two operating tanks of final irrigation solutions. Response of Jojoba to salinity was measured in above ground parameters and in roots using minirhizotron access tubes and imaging analysis. Leaf phosphorous and potassium concentrations decreased with increasing salinity level while leaf manganese, calcium, sodium and chloride concentrations increased with irrigation salinity level. Jojoba plants were found to have high level of storage of salt minerals in leaves but without effects on photosynthesis or transpiration. Roots exhibited different distribution patterns under different salinity treatments. Root length density increased with increased salinity at each depth. Root number and root length increased over time. During spring, the plant growth was faster than winter. Root diameter decreased over time due to new root development. Time had a more significant effect on root length density than irrigation water salinity or soil depth. Root number and root length were not significantly affected by the salt treatments.

Roots are the first plant organ to encounter, sense, and respond to soil salinity. Like for many moderately salt tolerant species, roots of olive (Olea eurpaea) trees are the principal players in salt tolerance. We studied roots of mature olive trees in order to illuminate the yet vague mechanism(s) of root salt exclusion. Root structural traits were examined in olive trees grown in lysimeters and from a long-term salinity field trial. The distribution of salts was detected in root cross-sections using scanning electron microscopy combined with energy dispersive spectroscopy. Increased soil salinity caused a continuous decline in specific root length and an increase in root diameter, periderm thickness, and specific hydraulic conductivity. While periderm cell number was not modified, cell diameter increased linearly by a total of 50 % as root zone salinity increased nearly eight-fold. Strong compartmentation of Na within the periderm was found, with highest content in the outer periderm layer and lowest content in the stele. Increase in soil salinity was associated with decrease in stele area, yet, hydraulic conductivity was doubled due to higher fraction of large diameter xylem vessels. Our results indicate significant root structural plasticity, which underlies the salt resistance mechanisms. The dominant trait enabling salt tolerance of olive trees is the enlarged periderm serving as an apoplastic barrier that enhances salt compartmentation and exclusion from the vascular tissues.

Emerging needs for diversifying human diet and to explore novel therapeutic procedures have led to increasing attempts to retrieve traditional nourishments and recruit beneficial wild plant species. Species of the genus Erodium (Geraniaceae) harbor medicinal indications and substances known from folklore and scientific research. Hairy stork’s bill (Erodium crassifolium L’Hér), is a small hemicryptophyte that inhabits arid southeast Mediterranean regions. E. crassifolium is among the very few Geraniaceae species known to produce tubers. Traditional knowledge holds that the tubers are edible and used by Bedouin tribes. However, no scientific information was found regarding nutrition or medicinal properties of these tubers. The objectives of our project are to unravel potential nutritional and medicinal benefits of the tubers, conduct initial steps towards domestication and develop agricultural practices enhancing E. crassifolium tuber yield and quality. Tubers show high water content (90%), low caloric value (23 Kcal 100−1 g) and considerable contents of minerals and vitamins. In addition, the tubers contain significant amounts of catechins and epigallocatechin, polyphenolic compounds known for their antioxidative, anti-inflammatory and antiproliferative activities. Furthermore, in vitro experiments demonstrated significant anti-inflammatory effects on human cell cultures. E. crassifolium is highly responsive to environmental changes; fertigation (700 mm) increased tuber yield by 10-fold, compared to simulated wild conditions (50–200 mm). These results indicate a significant potential of E. crassifolium becoming a valuable crop species. Therefore, there is a need for continued efforts in domestication, including ecotype selection, breeding, development of suitable agricultural practices and further exploration of its medicinal benefits.

Olive oil quality has become a foremost revenue-determining parameter for olive growers. While the upper threshold of oil acidity, a major quality standard of extra-virgin olive oil (EVOO), is under pressure of being reduced to below 0.8% of free fatty acids (FFA), excessive oil acidity is a frequent phenomenon, raising considerable economic concerns. Despite the many assumptions regarding the origins of FFA in olive oil, there is no concrete understanding upon which to base practical solutions. The objective of the present study was to identify the major actual reasons for excess oil acidity in a 2-year (2011–2012) countrywide survey that included 25 olive orchards of the Barnea variety. In each location, orchard management and environment were characterized, and the fruit of selected trees with specified fruit loads were sampled. Each sample underwent comprehensive analyses for fruit size, ripening index, oil and water content, incidence of insect damage and fruit rot, tree mineral nutrient status, and parameters of oil quality. Whereas geographic and environmental factors had no significant effects, excessive oil acidity was strongly associated with low fruit load ( −1 ) and advanced ripening index. High N concentration in fruit was also associated with high oil acidity. Further investigations revealed a particular segment of the fruit population accounting for most of the excess FFA values: large, fully ripened, fungus-infected fruit from low-yielding trees. It appears that in-orchard unsynchronized alternate bearing leads to significant diversity of the fruit population. Consequently, mature fruit of low-yielding trees harvested too late in the season are prone to fungal infections that may have adverse effects on oil quality. Keeping this hazardous segment of produce away from the olive press might help maintain oil acidity below the desired threshold.

While the intensification of olive cultivation has brought about increased yields and allowed the expansion of olive production to arid and saline environments, alternate bearing – a significant problem of the olive oil industry – remains unresolved. Developing fruit is a major sink for nutrients, and therefore extreme fruit loads are likely to disturb tree-scale mineral balance. Mineral availability, a prerequisite of plant performance, is largely determined by an intrinsic ability to store and remobilize nutrients timely, according to seasonal supply and demand. Unfavorable environmental conditions (aridity and salinity) might disrupt nutrient uptake and interrupt tree growth and reproduction. The objectives of the present study were: (1) to characterize the effect of fruit load on annual macroelement balance in olive trees under intensive management practices in a saline and arid environment and (2) to identify acute risks of mineral deficiencies occurring along the annual production cycle under the same conditions. Nitrogen, P, K, Na, and Ca concentrations were determined every 2 months during 2006 in the leaves, branches, bark, and roots of corresponding heavily (On) and lightly (Off) yielding ‘Barnea’ trees grown under arid and saline conditions. Nitrogen concentrations in trees were generally unaffected by the fruit load. During fruit development, P and K concentrations were significantly higher in leaves of Off-trees. Potassium concentrations also showed a typical alternate pattern in bark and roots. Sodium concentrations were particularly higher in roots, while Ca accumulated in leaves. An alternating pattern was observed for Na in branches and for Ca in leaves, pointing to a possible mechanism employing Ca to avoid Na-toxic hazards in leaves of fruit-loaded trees. Large quantities of N, P, and K were found in the fruit at harvest. The role of the fruit as an ultimate sink of N, P, K, and Ca, versus the function of leaves or branches as instantaneous sources of these nutrients was demonstrated in a separate fruit removal experiment in ‘Coratina’. Macroelement balance at the whole tree level calculated after harvest indicated that the functional reserves of N and P, but not of K, were sufficient to furnish a successive On-year yield. It is concluded that no risks of acute mineral deficiency occur during the biennial cycle. Consideration of alternate bearing cycles is necessary for optimization of N, P, and K application in olive in order to achieve more efficient production, improved produce quality, and minimized environmental consequences.

A Tuber melanosporum plantation established in 1994/1995 on Kibbutz Bar’am (in the Upper Galilee, Israel) gradually lost its T. melanosporum mycorrhiza. In 1999, T. aestivum inoculated seedlings were inadvertently introduced into the plantation to fill the gaps between trees. A single T. melanosporum fruit body was found in 1999. Although no truffles were found after 1999 and until 2009, in that year and in 2010, truffles were collected. Morphological and molecular analyses proved these to be T. aestivum. Thus, the intentionally introduced T. melanosporum mycorrhiza was replaced by that of another introduced mycorrhizal fungus, T. aestivum. Local oak species produced higher yields compared to introduced host species known to be good T. melanosporum plant symbionts. The yield was comparable to that reported for young commercial orchards, but the fruiting season was earlier than in Europe.

Olive (Olea europaea) has a very high tendency for year-to-year deviation in yield (alternate bearing), which has a negative economic impact on the olive oil industry. Among possible reasons for alternate bearing, depletion of stored carbohydrates (CHO) during the On-year (high yield) has often been mentioned. The objective of the present study was to verify the role of CHO reserves, as a cause or effect, in the alternate bearing of intensively cultivated olives. A monthly survey of soluble sugar and starch concentrations in the leaves, branches, bark and roots of On- and Off-trees (cv. Barnea) was carried out during a complete reproductive cycle from November 2005 to October 2006. Carbohydrate concentration in the sapwood was determined in January, as well as an estimate of whole-tree biomass. The trunk and limbs possess the largest portion of CHO reserves. The influence of reduced fruit load on CHO reserves was also investigated. Starch, mannitol and sucrose concentra tions increased from December to March in all tissues, and then declined along with fruit development. Leaves, branches and bark have a significant role in CHO storage, whereas roots accumulated the lowest CHO concentrations. However, fluctuations in reserve content suggested considerable involvement of roots in the CHO budget. Nevertheless, there were no meaningful differences in the annual pattern of CHO concentration between On- and Off-trees. Even a 75–100% reduction in fruit number brought about only a minor, sluggish increase in CHO content, though this was more pronounced in the roots. Carbohydrate reserves were not depleted, even under maximum demands for fruit and oil production. It is concluded that in olives, the status of CHO reserves is not a yield determinant. However, they may play a significant role in the olive’s survival strategy, ensuring tree recovery in the unpredictable semiarid Mediterranean environment. This suggests that CHO reserves in olive act like an active sink, challenging the common concept regarding the regulation of CHO reserves in plants.

Studying the composition of olive oil requires cold-press olive oil extraction. One of the most common laboratorial mills is the Abencor system. However, its operation protocol was formulated decades ago for Spanish olive varieties from traditionally rain-fed orchards. We modified this protocol for use with “Barnea” and “Picual” olives from irrigated orchards that are characterized by high water content. Independent effects of malaxation time, temperature, water addition and talc addition on extraction efficiency, and major quality indices of virgin olive oil were studied. Overall, addition of talc to the fruit paste was the most significant treatment in terms of yield and quality of the oil although its effect was cultivar dependent. Improved oil yield was particularly significant for “Picual.” Extended malaxation time was also effective in improving oil extractability. Addition of talc generally improved oil-quality parameters, while water addition had the opposite effect. Yet, quality parameters remained within the extra virgin level. Temperature increments reduced oil quality. The need to adapt a modified protocol for use with fruits from irrigated orchards that will facilitate critical comparison of results obtained from different agronomic theses and different laboratories is highlighted. It is recommended that each laboratory develops an appropriate protocol for the operation of the Abencor system in accordance to the characteristics of the olive fruit they are working with. Practical applications: Abencor system serves as the major laboratorial mill world-wide. Those mills allow the researchers to characterize olive oil in accordance to the treatments received by the trees. This cannot be done in commercial mills. The system operation protocol was established decades ago for fruits from rain-fed orchards. In the past decade there was a rapid increase in the use of irrigation in olive orchards and therefore it is crucial to optimize the operation protocol for fruit with relatively high water content. In the current work we have evaluated the influence of a series of technological parameters (i.e., talc and water addition, malaxation time, and temperature) on the extraction efficiency and quality indices of olive oil. This allowed us to present a modified protocol for the Abencor system operation suitable for olive fruit of irrigated orchards that will facilitate a reliable representation of the influence of different treatments on the yield and characteristics of the olive oil.

The effects of shading on lisianthus (Eustoma grandiflorum) floral transition, plant development, flower yield and quality, and content of starch and soluble sugars were assessed in three cultivars, over two consecutive years. Shading nets affording 67% or 88% reduction in light intensity, were fitted at planting in the greenhouse for periods ranging from 3 to 8 weeks. Meristem morphology at floral transition was characterized by apical meristem widening and the appearance of two bract primordia. Floral transition time was affected by cultivars, but in general, longer and heavier shade treatments delayed floral transition; the longest delay (6 weeks) being recorded in Mariachi White under 88% shade for 7 weeks or under a combined shade treatment of 88% for 3 weeks followed by 67% for 5 weeks. Despite interactions between cultivar and shade treatment, consistent trends were discerned: the heaviest and most prolonged shading reduced yield (up to 40%), cut stem length (up to 15%), and number of flower buds/stem (up to 26%), within cultivar. Total carbohydrates levels were very low, and it is questionable whether changes observed in carbohydrate quantity following shade treatments had any effect on plant growth or flower yield. Rather, it appears that lisianthus is very dependent on current photosynthesis, so that even a brief shading interlude could reduce branching and flower quality. It may be concluded that the intensive shading usually applied is detrimental for lisianthus.

Olive (Olea europaea) demonstrates a high tendency toward alternate fruit production, with significant negative consequences on the industry. Fruit load is one of the main cause-and-effect factors in the phenomenon of biennial bearing, often disrupting the balance between reproductive and vegetative processes. The objectives of the present study were to identify the time range during which heavy fruit load reversibly interrupts the reproductive processes of the following year. The linkage between timing of fruit removal, vegetative growth, return bloom, and fruit yield was studied. Complete fruit removal in cv. Coratina until about 120 days after full bloom (August 15) caused an immediate resumption of vegetative growth. The new shoots grew to twice the length of those on trees that underwent later fruit removal. Moreover, a full return bloom, corresponding with high subsequent yields, was obtained by early fruit removal, while poor or no bloom developed on late-defruited or control trees. Thus, the critical time to affect flowering and subsequent fruiting in the following year by fruit thinning occurs in olive trees even weeks after pit hardening—much later than previously suggested. Furthermore, the data indicate that flowering-site limitation, due to insufficient or immature vegetative growth during the On-year, is a primary factor inducing alternate bearing in olive.

A Tuber melanosporum plantation established in 1994/5 on Kibbutz Bar’am (in the Upper Galilee, Israel, Fig. 1) gradually lost its T. melanosporum mycorrhiza. When checked in 1998, only about 70% of the trees maintained their original mycorrhiza (Kagan-Zur et al. 2001) and was deteriorating constantly. A number of trees perished. Several different tree species were initially introduced. These included both ACTA MYCOLOGICA Vol. 47 (2): 169–171 2012

We tested the hypothesis that whole-tree water consumption of olives (Olea europaea L.) is fruit load-dependent and investigated the driving physiological mechanisms. Fruit load was manipulated in mature olives grown in weighing-drainage lysimeters. Fruit was thinned or entirely removed from trees at three separate stages of growth: early, mid and late in the season. Tree-scale transpiration, calculated from lysimeter water balance, was found to be a function of fruit load, canopy size and weather conditions. Fruit removal caused an immediate decline in water consumption, measured as whole-plant transpiration normalized to tree size, which persisted until the end of the season. The later the execution of fruit removal, the greater was the response. The amount of water transpired by a fruit-loaded tree was found to be roughly 30% greater than that of an equivalent low- or nonyielding tree. The tree-scale response to fruit was reflected in stem water potential but was not mirrored in leaf-scale physiological measurements of stomatal conductance or photosynthesis. Trees with low or no fruit load had higher vegetative growth rates. However, no significant difference was observed in the overall aboveground dry biomass among groups, when fruit was included. This case, where carbon sources and sinks were both not limiting, suggests that the role of fruit on water consumption involves signaling and alterations in hydraulic properties of vascular tissues and tree organs.

Motivated by the increasing interest in the black Perigord truffle (Tuber melanosporum), we have been seeking to develop a controlled cultivation method for this celebrated fungus. Our strategy is based on establishing optimal conditions for mycorrhizal development in detached media by mimicking natural productive truffle beds. Cistus incanus, a Mediterranean shrub, was used as host. The components of the growth medium—polystyrene foam flakes, Perlite, peat, and dolomite powder—provided the coarse and fine porosity required for adequate drainage, appropriate balance between aeration and moisture, the desired pH (7.5-8.2), and support of mycorrhizal development. Optimum rhizosphere temperatures for inoculation and continued mycorrhizal development were 20-25 °C. Inoculation with mycorrhized root fragments proceeded more rapidly than traditional inoculation with a carpophore suspension, particularly at suboptimal growth medium temperatures. A keystone of our system is to determine the optimum root volume re...

Progress was made towards a reliable in vitro system for mycorrhizing Cistus incanus seedlings with Tuber melanosporum. A rich growth medium favored extensive growth of mycorrhized Ri-transformed roots (MTR) but inhibited mycelial outgrowth into the medium. A minimal medium, on the other hand, inhibited MTR growth but supported considerable mycelial outgrowth into the medium. While the presence of a C.␣incanus propagule clearly enhanced mycelial growth into the minimal medium, a highly significant factor appeared to be the use of MTR inoculant, which supported mycorrhizal development to the Hartig net stage. The advantages of MTR for in vitro mycorrhization of host plant seedlings are discussed.

Brackish water (7 dS m−1) is frequently utilized to drip-irrigate crops in the Negev desert of Israel, the practice being to use deep sandy soils (96% sand) to avoid soil salinization. When muskmelon (Cucumis melo L.), a moderately salt-sensitive crop species, was grown using brackish irrigation under these conditions, yields declined due to a significant reduction in fruit size, but fruit quality parameters improved markedly. In the present study, we tested the hypothesis that the use of fresh irrigation water during the early vegetative phase would increase canopy size and leaf area index (LAI) and hence the potential productivity of the melon plant. The application of brackish water during the reproductive phase, on the other hand, would improve fruit quality. Using multiple irrigations within a 24-h period, applied with drip irrigation, we examined the timing, the duration, and the concentration of brackish irrigation water as tools to optimize fruit yield and quality in late-summer melons. Indeed, the combination of fresh (1.2 dS m−1) and brackish (7 dS m−1) irrigation water increased the yield level to that of fresh water plants whereas it brought about the improvement of fruit quality typical to brackish water plants, thus providing an attractive approach to optimize late-summer melon production. Our results demonstrate the trade-off between fruit size and fruit quality as related to the timing and the duration of brackish irrigation water. The use of a milder (

Farmland salinization due to unsustainable agricultural practices has become a worldwide problem. Salt-resistant forage crops, introduced at the primary stages of land reclamation, can provide fodder for livestock, thus adding economic benefit to the process. Saltgrass (Distichlis spicata), a wild halophytic grass species distributed in salt marshes in America, is occasionally grazed by livestock and wild animals. In attempts to domesticate this species, we evaluated and ranked the fodder potential of groups of accessions from several sites in North and South America. Ash content never exceeded 110 g kg−1, even when plants were grown with salty water. Crude protein content was variable and averaged 116 g kg−1 of DM. Mean yield of metabolizable energy was 6.30 and 5.61 kJ g−1 DM for sheep and goats, respectively. Organic matter digestibility (in vitro) was higher in sheep than in goats (506 g kg−1 and 478 g kg−1, respectively) for all saltgrass accessions. Differences in quality parameters were usually larger within than among groups of accession when sorted according to country of origin or ecosystem. Accessions from the South Atlantic coast of North America and from South America were superior in several parameters. South Atlantic coast accessions were relatively vigorous and were productive under saline conditions, as indicated by their relative growth rate (RGR) in small-scale experiments. Six outstanding saltgrass accessions were chosen for further examination. The results of the present study indicate that saltgrass holds considerable promise for selection and suggest that efforts should continue to identify and characterize additional saltgrass ecotypes. Copyright © 2005 Society of Chemical Industry

Production of spring potato ( Solanum tuberosum L. cv. Desiree) on a deep sandy soil in the central highland of the Negev desert of Israel under drip irrigation with saline water (up to 6.2 dS m −1 ) was studied in the years 1992–1997. The objective of the study was to determine the effects of saline water irrigation on potato production in an arid environment with special focus on the interactions with weather conditions. Although yields were often high, salinity effects were evident in some years. Thus 1992 and 1996 yields were 6–7 kg m −2 and showed no significant effect of salinity, while a pronounced drop in yield with increasing salinity was observed in 1993 and 1994. Analysis of weather data for 1993–1994 suggests that the decline in yield was due to interactions between saline irrigation and prolonged heat wave events occurring during crop development. Further experimental work (1997) revealed that tuber yield was most sensitive to combined salt and heat stress when heat waves occurred at 40–60 days after emergence. The combined stress apparently leads to the collapse of mechanisms for avoiding salt accumulation in young expanding leaves, resulting in failure of vegetative growth recovery and a consequent reduction in the leaf area index and canopy functioning. The relationship between tuber sink demand and available photoassimilate supply at certain stages of plant development is discussed with reference to the ability of the potato plant to recover from the combined stress.

Morphological and genetic analyses were applied on 37 saltgrass (Distichlis spicata) accessions collected from distant locations throughout the American continent in order to: 1) develop and identify morphologic and genetic profiles for the saltgrass genotypes; 2) characterize the genetic distance among saltgrass accessions within the given germplasm collection; and 3) identify a possible linkage between patterns of genetic and eco-geographical parameters. Analysis based on 70 RAPD markers revealed broad polymorphism among the genotypes and enabled their individual characterization. A UPGMA dendrogram clustered the genotypes into groups according to a general pattern of their geographical origin. Yet, only the group of Californian accessions was significantly distinct from other groups, as determined by χ2 tests. Various statistical analyses indicated that only minor genetic differences existed between seashore and desert saltgrass genotypes, supporting that these two eco-geographical types belong to the same species, Distichlis spicata. Our results suggest that genetic interactions exist between geographically distant saltgrass populations, in spite of the dominance of clonal reproduction in this species. The contribution of dioecy, seed production, and epizoochory to the distribution patterns of saltgrass is discussed at the geographic and at the genetic levels.

The objective of the present study is to evaluate a Citrus tree's investment in the flowering process in relation to its photoassimilate resources, as a part of its annual reproductive effort. The overall requirement for carbohydrate of a single flower of grapefruit (Citrus paradisi Macf. cv. 'Marsb seedless') is evaluated as 8.33 x 10 -3 mol C over 3 weeks. The direct cost of production of a single flower is estimated to be 5.75 x 10 -3 mol C, most of which is allocated to the petals, anthers and style - organs designated to abscise. About 2.58 x 10 -3 mol C is consumed by respiration not associated with growth processes. Growth respiration (R g ) occurs mostly during early stages of flower growth and development. However, the total respiration rate increases sharply during anthesis, when growth processes have almost ceased. Ethylene evolution also reaches remarkably high rates during anthesis. High temperatures increase the rate of flower respiration (Q 10 = 2.12) but shorten the duration of flowering. A grapefruit tree may bear each year 20 000-50 000 flowers, only 0.5-2.5% of which develop into mature fruit. The amount of carbohydrate invested each year in bloom at the whole-tree level is 166-400 mol C per tree (depending on the number of flowers), amounting to 10-20% of the carbohydrate consumed for fruit growth. The overall daily demand for carbohydrate by the flowers of a grapefruit tree during anthesis may exceed the daily carbohydrate production by the leaves. High temperatures lead to a further increase in the daily demand for carbohydrate. In such cases, the management of flowering must rely on carbohydrate reserves recruited from other tree organs. The ecophysiological and evolutionary aspects of Citrus flowering are discussed.

The developing fruit is a strong sink, which demands large amounts of assimilates. A correlation between grapefruit (Citrus Paradisi Macf., var. Marsh seedless) fruit size and its pedicel cross sectional area (CSA) can be demonstrated, suggesting a close interaction between them. The presence of fruits seems to determine the developmental pattern of the vascular tissues within the branches on which the fruits are borne. The pedicel normally terminates its diametric growth prior to the linear phase of fruit growth. Fruit thinning (90%) and trunk girdling, performed in order to minimize carbohydrate limitations, result in dramatic increases in fruit growth rate and pedicel CSA. Partial girdling of the pedicel causes a transient decrease in fruit growth. An increase in specific mass transport (SMT) through the existing vascular routes is the immediate response, due to the instantaneous upsurge of carbohydrate supply to individual fruit. Nevertheless, the rapid development of new vascular tissues has been the major factor responsible for the long term enhancement, or recovery, of fruit growth, suggesting that limitation in transport capacity does occur. The cause and effect relationships between fruit and vascular development are discussed.

Almost 1 billion hectares of land in the world is affected by salinity and over 50% of irrigated lands have salinity problems (Flowers and Yeo, 1995). Salinization has been identified as a major process leading to desertification of agricultural lands. The process of salinization of arable lands is mostly (but not solely) caused by human activities, and it is associated with malpractices in irrigation projects, mostly in arid and semiarid countries. Soil salinization can also result from natural processes, such as inland intrusion of seawater (i.e. coastal areas of West Africa and northeast China) or due to continuous evaporation from shallow aquifers in desert environments (i.e. coastal regions of north Africa and the Pampas del Tamarugal in Chile).

Salinity is an escalating problem in agriculture worldwide (Szabolics, 1989; Hamdy, 1996; Choukr-Allah, 1996). The use of recycled and saline waters to replace fresh water in agriculture contributes, among other factors, to the aggravation of salinity problems. Most crop plants are sensitive to salinity and poorly equipped to cope with salt stress without suffering from impaired growth and development, and even injury (Lauchli and Epstein, 1990; Maas, 1990). The adverse effects of salinity cause considerable reduction in yields, far below the economic threshold of most crops in present use. It can be stated quite confidently that the prevalent future environment of agricultural crops will be much more saline than today. Therefore, improving salt resistance of crop plants is of major interest in agricultural research. Halophytes are the ultimate candidates to serve as a genetic source for this purpose.

Biennial bearing is a major horticultural and economic drawback of olive (Olea europaea L.) cultivation, which particularly affects the olive oil industry under intensive production systems. The number of fruits per tree in an on-year is a primary determinant of the biennial cycle. While fruit thinning using NAA shortly after full bloom is commonly practiced to increase fruit size in table olives, the extent of its influence on biennial bearing is unknown. In the present study, the ability of that common naphthaleneacetic acid (NAA) treatment (100 mg/L, 10 days after full bloom) to alleviate biennial bearing in two oil olive cultivars, Picual and Barnea, was poor, although significant influence on the number of fruit was evident solely in Barnea. Picual seemed less susceptible than Barnea to biennial bearing. Consequently, the effect of a broad range of NAA concentrations (0–320 mg/L, 10 days after full bloom) on various yield parameters was investigated during a biennial cycle of Barnea trees. There was a gradual proportional decline in the on-year number of fruits from ~50 000 to 10 000/tree in response to increasing NAA concentrations. The number of return fruits in the off-year was reciprocal to the on-year fruit load, but remained relatively small, below 15 000/tree. The dynamic relationship between fruit load and fruit size in both on- and off-years was a significant compensation factor in fruit and oil yields. In both cultivars, an on-year fruit load smaller than 20 000/tree is likely to provide consistent yearly oil yields ranging from 10 to 12 kg/tree. The results demonstrate the possibility of using NAA post-bloom spraying to balance biennial bearing in oil olives.