Yoav Waisel

Allergy to cypress pollen

Although Cupressus sempervirens has been spread over southern Europe since antiquity, cypress pollen allergy has not been reported until 1945 ( 1 ). In France, the very first case reports were published in 1962 ( 2 ). Since then, the prevalence of cypress pollinosis seems to demonstrate an upward trend, concomitantly with the increased use of cypress trees as ornamental plants, as wind breaks and as hedges. Hyposensitization, using improved pollen extracts, is increasingly prescribed. Besides, prevention measures begin to be implemented. Such measures include avoidance of planting new cypress trees, especially near human populations’ centres, trimming of cypress hedges before the pollination season and agronomical research for hypoallergenic trees. Altogether, such new developments in cypress allergy deserve an update review.

Photosynthetic pathways and the ecological distribution of the chenopodiaceae in Isreal

SummaryFifty-four species of the Chenopodiaceae in Israel were examined for their anatomical features, δ13C values, habitat and phytogeographical distribution. 17 species have δ13C values between -20‰ and -30‰and non-Kranz anatomy (NK) and are therefore considered as C3 plants. 37 species have δ13C values between -10‰ and -18‰ and Kranz or C4-Suaeda type anatomy and are therefore considered as C4 plants. Some C4 plants have leaf structure which seems to be intermediate between the Kranz and the C4-Suaeda type of leaf anatomy.The segregation of the species into photosynthetic groups shows tribal and phytogeographical grouping. Most of the C3 Chenopods are either mesoruderal plants or coastal halophytes, with a distribution area which covers the Euro-Siberian as well as the Mediterranean phytogeographical regions. The C4 Chenopods are mainly desert or steppe xerohalophytes with a distribution area which includes the Saharo-Arabian and/or Irano-Turanian phytogeographical regions.

Climatic effects on the δ18O and δ13C of cellulose in the desert tree Tamarix jordanis

Abstract The 13 C 12 C and 18 O 16 O ratios of stem cellulose of Tamarix jordanis (a tree common in wadis of rid regions) increased with decreasing relative humidity (RH) in individual trees growing along a climatic gradient in Israel. The response to RH observed in the δ18O of the wood cellulose was strongly similar to that observed in leaf water over a diurnal cycle. Most of the data for δ13C and all of the data for δ18O could be fitted to two independent linear equations that, combined, allowed the reconstruction of RH and the δ18O of source water from the isotopic composition of ancient T. jordanis wood previously reported from the ancient fortress of Masada. Since the Roman period, RH at Masada decreased by about 17%, while the δ18O value of local groundwater remained similar to present-day values, suggesting that changing atmospheric circulation has played a role in climate change in the Middle East over the past two millennia.

Adaptation of plants to saline environments: salt excretion and glandular structure

Excretion of ions by special salt glands is a well known mechanism for regulating the mineral content of many halophytic plants.

Patterns of Water Movement in Trees and Shrubs

Paths of water flow in trees and shrubs of different sizes and chorotypes were investigated with injected dyes. Aged shrubs possessed a sectorial ascent. Young specimens of these species showed a sectorial turning into a ring ascent. Differences in pattern of water flow were observed among various tree species. Species with large and tall crowns showed either a spiral pattern or a sectorial straight pattern turning into a ring pattern of ascent. Other species exhibited a sectorial straight pattern. Since independence of branches or trunk segments is characteristic of shrubs, it is suggested that woody species exhibiting a sectorial pattern of water movement should be considered as chamaephytes. See full-text article at JSTOR

The role of fish in distribution and germination of seeds of the submerged macrophytes Najas marina L. and Ruppia maritima L.

SummaryThe effects of three species of fish (tilapia, grass carp and common carp) on the seeds of Najas marina L. and of Ruppia maritima L. were investigated. Practically all the seeds that were injested by the common carp were digested. The two other fish were less affective: they digested seeds with soft seed-coats but excreted a good portion of the hard ones. Germination of the excreted seeds was improved. Seeds have been retained in the digestion tracts of the fish for up to 65 h. It is thus suggested that tilapias and grass-carps play a role in the distribution and the improvement of reproduction of Najas and Ruppia.

Effects of light and pressure on photosynthesis in two seagrasses

Photosynthetic responses to light and pressure (up to 4 atm) were measured for two seagrass species abundant in the Gulf of Eilat (Red Sea). In Halodule uninervis (Forssk.) Aschers. pressure decreased net photosynthetic rates, while in Halophila stipulacea (Forssk.) Aschers. pressure had no effect on net photosynthetic rates. In both species, light saturation was reached at 300 μE (400–700 nm) m−2 s−1 and the compensation point was at 20–40 μE (400–700 nm) m−2 s−1. Comparing these results to in situ light measurements, neither species should be light limited to a depth of about 15 m, and Halophila stipulacea should reach compensation light intensities at about 50 m. The latter depth corresponds well to the natural depth penetration of this species. Halodule uninervis is never found deeper than 5 m in the Gulf of Eilat, and it appears that pressure rather than light is one of the factors limiting the depth penetration of this species. The differential pressure response of the two species may be related to aspects of leaf morphology and gas diffusion.

The role of mallard ducks (Anas platyrhynchos) in distribution and germination of seeds of the submerged hydrophyteNajas marina L.

SummaryThe effect of passage ofNajas marina L. seeds through the digestive system of the common mallard duck (Anas platyrhynchos) on their germinability was investigated. Most of the seeds (∼70%), which were consumed by the birds were digested. However, germination of the remaining seeds was remarkably improved. Germination of seeds whose seed coats were mechanically cracked was also higher than that of the controls and equalled the germination percentage of the mallard-treated seeds. Seeds ofNajas are retained in the diegestive tracts of mallards for over 10 hours. Thus, as mallards are strong flyers, the seeds ofNajas may be distributed over long distances.

A plant root system architectural taxonomy: A framework for root nomenclature

Abstract Research into root system morphology over the last two centuries has developed a diverse set of terminologies that are difficult to apply consistently across species and research specialties. In response to a need for better communication, a workshop held by the International Society for Root Research established some nomenclature standards for root research. These standards and their justification are presented in this study. A framework for a root system architectural taxonomy is created by defining four main classes of root: the tap root, that is, the first root to emerge from the seed; lateral roots, which are branches of other roots; shoot‐borne roots, which arise from shoot tissues; and basal roots, which develop from the hypocotyl, that is, the organ which is between the base of the shoot and the base of the tap root. It is concluded that adherence to the presented taxonomy will reduce confusion and eliminate some of the current confounding of results.

Allergic responses to pollen of ornamental plants: High incidence in the general atopic population and especially among flower growers

BACKGROUND The incidence of allergy to pollen of ornamental plants has not been deeply investigated, and its extent has remained obscure. Most of such studies have concentrated only on pollen of ornamental plants from the Asteraceae family (Compositae). In this study an attempt was made to clarify whether various other ornamental plants may also cause skin responses and allergic symptoms among allergic urban dwellers and among rural flower growers. METHODS Two hundred ninety-two patients were referred for allergic evaluation by their primary physicians; 75 flower growers and 44 university students were evaluated. For all participants, a detailed health record was obtained, and skin prick tests (SPTs) were performed. Extracts for SPTs included commercial common airborne allergens and autochthonous pollen extracts of 11 species of plants belonging to the Asteraceae, Ranunculaceae, Liliaceae, Scrophulariaceae, and Genetianaceae families. RESULTS Fifty-one of the 292 patients (17%) referred for allergic evaluation had positive SPT responses to pollen of various ornamental plants. A similar incidence was found among the students (23%). However, the incidence among flower growers was significantly higher, reaching 52%. Higher incidence (83%) of positive SPT responses to ornamental plants was found among flower growers also sensitive to the common allergens. All the tested plants, not only those belonging to the Asteraceae family, provoked positive SPT responses in all 3 groups of participants. None of the participants from the general population or the group of students reported exacerbation of allergic symptoms on exposure to the tested plants. In contrast, almost half of the flower growers (45%) described nasal, ocular, or respiratory symptoms associated with occupational exposure to the tested plants. Some 15% of the growers were eventually compelled to change their profession. CONCLUSIONS The incidence of positive SPT responses to ornamental plants was 17% to 23% among the general public but 52% among flower growers. Thus the effects of ornamental plant pollen on atopic patients should be seriously contemplated.