Showing papers in "Israel journal of botany in 2013"
TL;DR: A seed ecology syndrome for Cistaceae is postulated, featuring small seed size, hardcoatedness (primary dormancy), short-distance dispersal, long-term persistence in soil seed banks, fire- or heat- induced seed “softening”, an opportunistic strategy of germination (germination at a wide range of temperature and light conditions), and a slow germination rate of “ softened” seeds.
Abstract: An examination of 203 seed lots from 42 Old World species (or 54 taxa), with representatives from all five genera (Cistus, Fumana, Halimium, Heliarthemum, and Tuberaria) and an additional seed lot of the New World Lechea maritima shows that the phenomenon of haidseededness is a prominent characteristic of the entire Cistaceae family. Promotion of seed germination in the laboratory can be obtained by mechanical scarification and thermal pretreatment, while light seems to be totally ineffective. A seed ecology syndrome for Cistaceae is postulated, featuring small seed size, hardcoatedness (primary dormancy), short-distance dispersal, long-term persistence in soil seed banks, fire- or heat- induced seed “softening”, an opportunistic strategy of germination (germination at a wide range of temperature and light conditions), and a slow germination rate of “softened” seeds. This syndrome is suggested to endow Cistaceae, a principally Mediterranean family, with a considerable ecological advantage in the ...
239 citations
TL;DR: The anatomical structure of the secretory hairs of eight species of Labiatae was studied and the main components of their secretory substances identified.
Abstract: The anatomical structure of the secretory hairs of eight species of Labiatae was studied and the main components of their secretory substances identified. Peltate and capitate hairs were found in all species, the latter consisting of three types, differing in structure and mode of secretion. The capitate hairs precede the peltate hairs in their development and secretory activity. In the capitate hairs the secreted material is extruded to the outside, while in the peltate hairs it remains in a subcuticular space. The eight species were divided into groups according to the structure of the volatile compounds they secrete.
205 citations
TL;DR: Four elements are sketched out of a theory which can deal with exceptions to the grazing pressure of rangelands, where which plant growth-forms win competition often depends not only on the growth- forms but also on which is present as established adults, or on which are most abundant.
Abstract: Under grazing pressure the vegetation of rangelands is often altered. Range managers traditionally have thought of these changes as retrogression or disturbance, setting climax vegetation back to a seral stage. Unfortunately, removing the grazing pressure often does not reverse the changes in the way the succession model would predict. Here four elements are sketched out of a theory which can deal with these exceptions. First, which plant growth-forms win competition often depends not only on the growth-forms but also on which is present as established adults, or on which is most abundant. Second, vegetation changes can sometimes induce soil changes. The extent to which reversing a vegetation change depends on soil restoration varies greatly, and the speed with which soil structure can be restored varies from rapid to negligible. Third, the impact of grazing on different life-forms varies greatly in different situations; in particular, the nature of and scope for selectivity is very different in ...
203 citations
TL;DR: It is considered it evident that specific pollinators have a strong selective effect on Ophrys flowers and an indirect proof of this hypothesis is brought by comparing the characters of the Ophreys flowers and of their pollinators.
Abstract: The flowers of the Mediterranean genus Ophrys imitate important specific sexual releasing factors of aculeate hymenopteran females. They attract hymenopteran males who attempt to copulate with the labellum searching for females. During this “pseudocopulation,” the insects perform pollination. As this relation is highly specific, the pollinators serve as prepollinating isolation factors. This is illustrated by many examples. We consider it evident that specific pollinators have a strong selective effect on Ophrys flowers. By comparing the characters of the Ophrys flowers and of their pollinators, we try to bring an indirect proof of this hypothesis1. As a pollinator usually acts as a prepollinating isolation mechanism, speciation in Ophrys is always a consequence of a change in pollinator. We discuss some ideas about how speciation in Ophrys might have occurred and how the attraction and pollination modality of pseudocopulation developed during evolution.
163 citations
TL;DR: Theoretical arguments and some evidence indicate that the direct, unidirectional and independent responses of plant and animal populations to environmental variations may be sufficient to explain most ecological phenomena in deserts.
Abstract: Is the concept “ecosystem structure and function,” taken as implying biological interaction and regulation, useful in understanding deserts? Some theoretical arguments and some evidence indicate that the direct, unidirectional and independent responses of plant and animal populations to environmental variations may be sufficient to explain most ecological phenomena in deserts. There is clear evidence to the contrary for some phenomena: competition between shrubs; mutual regulation of granivores and annual plants; local modification of climate and soil around shrubs creating and maintaining biologically distinct micro-ecosystems.
145 citations
TL;DR: The distribution of mucilage cells in vegetative parts of the dicotyledons is reviewed on the basis of an extensive literature study and their systematic and diagnostic value at different levels of the taxonomic hierarchy is discussed.
Abstract: The distribution of mucilage cells in vegetative parts of the dicotyledons is reviewed on the basis of an extensive literature study. Mucilage or slime cells occur in 144 families, belonging to 47 orders as defined in Takhtajan's system of classification. Their systematic and diagnostic value at different levels of the taxonomic hierarchy is discussed. Although mucilage cells are generally diagnostic at the species level, variation within genera and families seriously limits the systematic significance in mostphylads. The core families of the Malvales, which are all mucilaginous, constitute an exception at the ordinal level, while in a number of genera, families, and orders the distribution of mucilage cells tends to be associated with natural groups. In most families and orders of the subclass Asteridae, mucilage cells are absent from the vegetative organs. Development, ultrastructure, histochemistry, and distribution of mucilage cells are briefly reviewed. In almost all well documented cases, m...
139 citations
TL;DR: A nested vegetation sampling method which was developed by R.H. Whittaker for comparison of plant species diversity is described and different plant communities from different regions of the world can be compared.
Abstract: A nested vegetation sampling method which was developed by R.H. Whittaker for comparison of plant species diversity is described. The species richness of an area of 0.1 ha (1 dunam; 20 × 50 m) is analyzed by a special procedure in which different parameters of diversity such as differential diversity, point diversity, equibility and dominance are recorded. Normal supplementary observations such as plant coverage, growth forms, phenology and vertical foliage profile are added to the sample. By standardization of data collection for diversity samples, different plant communities from different regions of the world can be compared.
116 citations
TL;DR: In this paper, the volatiles from whole flowers, petals, sepals plus gynoecium, anthers, and pollen were collected from Rosa rugosa Thunb and analyzed by gas chromatography/mass spectrometry.
Abstract: Fragrances (volatiles) from whole flowers, petals, sepals plus gynoecium, anthers, and pollen were collected from Rosa rugosa Thunb. by headspace adsorption methods and analyzed by gas chromatography/mass spectrometry. Each flower part showed a distinctive volatile profile. Petal volatiles, dominated by terpenoid and benzenoid alcohols, contributed most to the whole-flower fragrance. Sepal odors contained mainly sesquiterpenes, together with several compounds found in the petals. The major volatiles in the androecium were more diverse and overall different from the perianth. Empty anthers shared a high proportion of their volatile profile with pollen. Pollen odor appeared to be self-contained, showing only minor adsorption of volatiles from sepals and petals. Compounds typical of the androecium were present as significant, albeit quantitatively small, components of the whole-flower fragrance, where they may well function as signals to pollen-seeking insects.
97 citations
TL;DR: Under field conditions secondary dormancy is part of cyclic changes in the level of dormancy that often follow a seasonal pattern, and develops when germination is inhibited, e.g. by burial in soil.
Abstract: Secondary dormancy, is defined as the dormancy developing in seeds after harvest or dispersal. Under field conditions secondary dormancy is part of cyclic changes in the level of dormancy that often follow a seasonal pattern. It develops when germination is inhibited, e.g. by burial in soil. Temperature, absence of light or oxygen, presence of volatile or allelopathic inhibitors and moisture conditions are among the factors which may contribute to inhibition of germination and thus to development of dormancy. Decreasing light sensitivity is part of the development of secondary dormancy. It is partly attributed to photo- or dark-reversion of the far-red absorbing form of phytochrome (Pfr), pre-existing in the seeds or newly formed, to Pr. Changing levels of Pfr at its primary site of action, possibly being a membrane, are also held responsible for the decreasing light-sensitivity. Secondary dormancy is not related to a deterioration of the seeds. A specific relationship with any particular metabol...
96 citations
Journal Article•
TL;DR: Analysis of the demography of six species (Schismus arabicus, Spergularia diandra, Erodium bryoniifolium, Gymnarrhena micrantha, Carrichtera annua, Filago desertorum) in several habitats shows a rather different time-space pattern of germination, survival and seed production in each.
Abstract: Germination, survival and seed production of annuals were observed for two years in 100 permanent quadrats (05 × 05 m), representing the vegetation of the loess plain Sede Zin in the Negev desert (average annual rainfall 90 mm) The first year (1972/73) was extremely dry (48 mm) Significant germination of many species occurred, but in most habitats survival and seed production were very low Thus, germination resulted in considerable net population losses in some species However, 1973/74 was rainy (155 mm), and germination occurred in a wider range of species and habitats Survival and seed production were high and almost all populations recovered their losses or far exceeded them An analysis of the demography of six species (Schismus arabicus, Spergularia diandra, Erodium bryoniifolium, Gymnarrhena micrantha, Carrichtera annua, Filago desertorum) in several habitats shows a rather different time-space pattern of germination, survival and seed production in each This pattern can be related
93 citations
TL;DR: Differences in soil properties were found between north- and south-facing slopes located in a Mediterranean region with an average annual rainfall of 690 mm, and the differences between the aspects in plant species diversity are very great and are expressed mainly in relatively dry winters.
Abstract: Differences in soil properties were found between north- and south-facing slopes located in a Mediterranean region with an average annual rainfall of 690 mm. In general, the differences are small, and in some cases even insignificant. The amount of organic matter, Na, Cl, and K, and available nitrogen (N-NH4 and N-NO3) are higher in the northern aspect than in the southern one. However, pH, CaCO3, and available P are significantly higher in the southern than the northern aspect. The differences between the aspects in plant species diversity are very great and are expressed mainly in relatively dry winters. The higher species diversity in the south-facing slope is due to the presence of herbaceous, mainly annual, plants. The importance of such differences in the Mediterranean region is discussed.
TL;DR: A morphometric estimation of leucoplast development in the cells suggested a quantitative relationship between the expansion of this plastidome and the ratio of monoterpenes in the oil....
Abstract: Analytical and structural studies were performed on 45 species of higher plants containing specialized secretory structures and/or producing essential oils or resins. Significant amounts of volatile compounds, mainly monoterpenes and sesquiterpenes, were recovered from these species. The specialized structures included glandular hairs, resin ducts, secretory cavities and idioblasts. During the ultrastructural investigation, special attention was paid to the plastidome. A number of secretory cells contain true leucoplasts, devoid of thylakoids and ribosomes. The comparison between analytical and structural data showed a very close correlation between the presence of leucoplasts in secretory cells and the significant quantities of monoterpenes (hydrocarbons or oxygenated compounds) in the volatile extract. Moreover, a morphometric estimation of leucoplast development in the cells suggested a quantitative relationship between the expansion of this plastidome and the ratio of monoterpenes in the oil....
TL;DR: Major Mediterranean vegetation types of California and Israel were compared and California matorral is shorter in stature, has a more complete canopy closure, is richer in woody taxa and poorer in herbaceous taxa, has fewer deciduous elements, and exhibits more specialized adaptations to fue.
Abstract: Major Mediterranean vegetation types of California and Israel were compared. These included woodland, matorral, phrygana, montane belts, riparian, and ecotones with the desert. Major differences in life form spectra, physiognomy, species richness, fire adaptations, leaf traits, the altitudinal sequence of montane belts and floras were summarized. In some cases it was possible to speculate that differences in the above traits are correlated with differences in climate, soil, fire frequency and human history. The matorral (chaparral, maquis) was emphasized. In comparison to Israel, California matorral is shorter in stature, has a more complete canopy closure, is richer in woody taxa and poorer in herbaceous taxa, has fewer deciduous elements, exhibits more specialized adaptations to fue, is under-represented in retamoid species and has a more spinescent overstorey but a less spinescent understorey of associated chamaephytes and hemi-cryptophytes. In California, the matorral continues through the mo...
TL;DR: Freshly harvested sunflower seeds germinated poorly, with a temperature optimum close to 25 °C, while dry storage greatly improved germination at temperatures ranging from 5 to 40°C, by eliminating both the seed-coat imposed and the embryo dormancy.
Abstract: Freshly harvested sunflower (Heliarthus annuus L) seeds germinated poorly, with a temperature optimum close to 25 °C The inability to germinate at high temperatures (25 to 40°C) resulted principally from a seed-coat imposed dormancy, whereas poor germination at temperatures below 25 °C was mainly due to an embryo dormancy Dry storage greatly improved germination at temperatures ranging from 5 to 40°C, by eliminating both the seed-coat imposed and the embryo dormancy A too high temperature (45°C) always completely inhibited germination and rapidly induced a secondary dormancy which was broken by redrying and dry storage of the seeds The depth of embryo dormancy varied during the development of the seeds It was low in very immature embryos, but increased and then decreased during desiccation of the seeds on the mother plants Ethylene and its immediate precursor (1-aminocyclopropane-l-car- boxylic acid) strongly stimulated germination of primary dormant seeds On the contrary, inhibitors of e
TL;DR: Environmental factors that determine seed germinability, such as day length and temperature, seed position in the capsule, in the dispersal unit, inThe inflorescences and in different inflorescence of the same plant are discussed.
Abstract: Survival of annual plants, and desert annuals in particular, seems to be dependent on three mechanisms: (1) seed dispersal or topochoric behavior for determining suitable microhabitats; (2) germination at the right time; (3) germination of only part of the seeds at one time, even under optimal conditions (heteroblasty). Environmental factors that determine seed germinability, such as day length and temperature, seed position in the capsule, in the dispersal unit, in the inflorescences and in different inflorescences of the same plant are discussed. These factors affect heteroblasty even during the last days of seed maturation. In plants of different taxa the photoperiodic induction that influences germination is absorbed by the leaves or even by the post-harvested fruit and is transferred to the seeds. Flowers along the same branch produce seeds that differ in their germinability according to the day length during the last few days of their maturation.
TL;DR: Most species in the scrublands of Andalucia (southern Spain) either secrete no nectar or are insignificant nectar producers, but the nectar secretion pattern is largely determined by three families: Cistaceae, Labiatae and Leguminosae.
Abstract: Most species in the scrublands of Andalucia (southern Spain) either secrete no nectar or are insignificant nectar producers. Although the 122 species studied belong to 23 families, the nectar secretion pattern is largely determined by three families: Cistaceae, Labiatae and Leguminosae. The amount of sugar secreted by nectariferous species is positively related to flower dry weight. The amount of sugar produced, for a given floral dry weight, is significantly higher for species with tubular corollas than for species with non-tubular ones.
TL;DR: The ability of plants to synthesize rubber is based on a single enzyme, rubber transferase, which causes the cis-polymerization of isoprene units, as isopentenyl pyrophosphate, into long, single stranded hydrocarbons.
Abstract: The ability of plants to synthesize rubber is based on a single enzyme, rubber transferase, which causes the cis-polymerization of isoprene units, as isopentenyl pyrophosphate, into long, single stranded hydrocarbons. These are assembled and accumulated in the cell as rubber particles which range in size from 0.01 to 15 μm and are bounded by an osmiophilic film. Parthenium argentatimi (guayule) and Hevea brasiliensis represent two species which accumulate large quantities of high molecular weight rubber by different intercellular routes. Rubber synthesis takes place in parenchyma cells in guayule and in specialized latex vessels in Hevea. Biochemical questions concerning rubber synthesis are discussed.
TL;DR: The effectiveness of external seed transport on sheep, goats and man was studied experimentally in open, grazed chaparral in Israel and high abundances on the animals and long retention times were observed in diaspores of Gramineae having characters most often interpreted as adaptations for burro adaptation.
Abstract: The effectiveness of external seed transport (epizoochory) on sheep, goats and man was studied experimentally in open, grazed chaparral in Israel. The animals were introduced into a permanent study area of known floristic composition, and the numbers of diaspores attached to their fur were recorded. Dyed diaspores of twenty species were attached to the fur of sheep and goats, and the numbers of diaspores remaining were monitored for several days. Significantly higher abundances on the animals (relative to abundance in the study area) were observed for diaspores having well-developed morphological characters (such as barbs and hooks) conventionally regarded as adaptations for attachment to animals. These diaspores also had significantly longer retention times on sheep and goats and could remain attached for periods of days to months. High abundances on the animals and long retention times were also observed in diaspores of Gramineae having characters most often interpreted as adaptations for burro...
Journal Article•
TL;DR: The intensity of flowering and the leaf NH3–NH4 + content increased with the severity of the stress, and the foliar application of low biuret urea to trees ...
Abstract: Changes in the leaf NH3-NH4 + content were monitored during floral induction in Citrus. Five-year-old rooted cuttings of ‘Washington’ navel orange (Citrus sinensis) were induced to flower by subjecting the trees to 8 weeks of low temperature, 8-h day (500 μE m−2 s−1) at 15–18°C/16-h night at 10–13°C and by transferring them afterwards to 12-h day (500 μE m−2 s−1) at 24°C/12-h night at 19°C. Maximum bloom occurred 4 weeks after the transfer to the warmer temperature. The number of flowers and the NH3–NH4 + content of leaves increased significantly (p < 0.05 and P < 0.01, respectively) with the length of the low temperature treatment. Sixteen-year-old ‘Frost Lisbon’ lemon trees (Citrus limon) on ‘Troyer’ citrange rootstocks (C. sinensis × Poncirus trifoliata) under commercial production were subjected to water-deficit stress of increasing severity. The intensity of flowering and the leaf NH3–NH4 + content increased with the severity of the stress. The foliar application of low biuret urea to trees ...
TL;DR: Experimental evidence is presented to show that single-stranded breaks occur in nuclear DNA during ageing of rye embryos in the dry state, which can be attributed to DNA repair before the onset of semi-conservative DNA replication.
Abstract: Experimental evidence is presented to show that single-stranded breaks occur in nuclear DNA during ageing of rye embryos in the dry state. Total DNA is retained and on imbibition unscheduled DNA synthesis occurs which can be attributed to DNA repair before the onset of semi-conservative DNA replication.
TL;DR: This work investigated the interactive effects of salinity and calcium on hydraulic conductivities and osmotic potential gradients in roots of maize seedlings to better define the biophysical mechanisms involved in these growth responses.
Abstract: Increasing the calcium ion activity in salinized root media has often been shown to ameliorate the inhibitory effect of salinity on plant growth. In order to better define the biophysical mechanisms involved in these growth responses, we investigated the interactive effects of salinity and calcium on hydraulic conductivities and osmotic potential gradients in roots of maize seedlings. The length of the primary roots was reduced by 54% after 4 days of growth in 0.1-strength Hoagland solution salinized with 100 mM NaCl and by 20% when 10 mM calcium was also added to the salinized root medium. Roots showed 69% osmotic adjustment in response to salinization, with or without extra calcium in the root medium. The mean hydraulic conductivity, L, of the apical 4 cm of maize seedling roots was determined by assaying osmotically-induced backflow. The assay was sensitive enough to detect reductions in L induced by lowering the assay temperature from 27 to 14°C. These reductions in L exceeded those caused by...
Journal Article•
TL;DR: The glandular hairs and the essential oils of various vegetative and reproductive organs of Salvia sclarea and S. dominica were studied, suggesting different functions for different hair types.
Abstract: The glandular hairs and the essential oils of various vegetative and reproductive organs of Salvia sclarea and S. dominica were studied. Both species have peltate hairs and capitate hairs of various shapes, sizes and modes of secretion. Certain types are predominant on different organs, suggesting different functions for different hair types. The main components of the oils from calyces, bracts and peduncles of S. sclarea and of the oils from the calyces and corollas of S. dominica were linalool and linalyl acetate. The leaves of S. sclarea contained an unidentified sesquiterpene as their major component while the main components in the leaves of S. dominica were neryl acetate, α-terpinyl acetate and linalool. Correlations between the chemical analysis of various plant parts and the types of glandular hairs are discussed.
TL;DR: (1982).
Abstract: (1982). AZOSPIRILLUM: PHYSIOLOGICAL PROPERTIES, MODE OF ASSOCIATION WITH ROOTS AND ITS APPLICATION FOR THE BENEFIT OF CEREAL AND FORAGE GRASS CROPS. Israel Journal of Botany: Vol. 31, BAT-SHEVA SEMINAR ON BIOLOGICAL NITROGEN FIXATION, pp. 214-220.
TL;DR: The myrosin cells were characterized morphologically and compared to other idioblasts in the tissue, and changes in ultrastructure take place during development and light has a negative effect on the extent of cellular differentiation.
Abstract: The occurrence and distribution of myrosin cells and myrosinases has been followed in different organs during development of 7 species of the Brassicaceae. Using light and electron microscopy the myrosin cells were characterized morphologically and compared to other idioblasts in the tissue. Myrosin grains stain specifically with toluidine blue, methylene blue azur-II, lactophenol aniline blue and fuchsin. At the ultrastructural level myrosin grains were seen to contain proteins, and oleosomes occupy most of the myrosin cells at an early stage of development in young seedlings, together with precursors for mitochondria, plastids and microbodies. Changes in ultrastructure take place during development and light has a negative effect on the extent of cellular differentiation. Myrosin cells are generally found distributed in differentiated tissue, from the imbibition stage up to 192 h after germination. The relative area occupied by the myrosin cells has been calculated by morphometrical analyses an...
TL;DR: The physiological, biochemical, morphological and ultrastructural studies which support a current hypothesis of host-symbiont interactions and structure-function relationships are described and are largely based on recent studies of the ontogenetic sequence of leaf development and associated events in the symbiotic cyanobacterium.
Abstract: Heterosporous ferns of the genus Azolla contain an N2-fixing cyanobacterium, designated Anabaena azollae, in specialized leaf chambers. Our studies of the symbiosis per se have been primarily restricted to A. caroliniana. However, comparative studies have encompassed four of the six known Azolla species: A flliculoides, A. mexicana and A. pinnata, in addition to A. caroliniana. The physiological, biochemical, morphological and ultrastructural studies which support a current hypothesis of host-symbiont interactions and structure-function relationships are described. The latter is largely based on recent studies of the ontogenetic sequence of leaf development and associated events in the symbiotic cyanobacterium. Under optimal growth conditions the four Azolla species double their biomass within two days and maintain an N content of 5–6% of the dry weight with N2 as the only N source. Results of subsequent comparative studies of photosynthesis, respiration, nitrogen fixation and associated processe...
TL;DR: Wild relatives of the main food crops that occur in Israel are surveyed and available information on wild progenitors of the different crops is assessed.
Abstract: Wild relatives of the main food crops that occur in Israel are surveyed and available information on wild progenitors of the different crops is assessed. The following crops are examined: wheat, barley, oat, pea, lentil, flax, safflower, beet, radish, cabbage, carrot, celery, globe artichoke, lettuce, leek, eggplant, watermelon, melon, olive, fig, date palm, almond, plum and pear.
TL;DR: VAM fungi indigenous in the soil of the semi arid northern Negev of Israel greatly enhanced phosphorus uptake of mycorrhizal pepper plants in three out of four soils tested and at four P levels.
Abstract: Vesicular-arbuscular mycorrhizal (VAM) fungi indigenous in the soil of the semi arid northern Negev of Israel greatly enhanced phosphorus (P) uptake of mycorrhizal pepper plants in three out of four soils tested and at four P levels. In a calcareous loess soil, additions of superphosphate equivalent to 3,000 kg ha−1 could not alleviate the absence of the VAM association. Increasing internal leaf P levels were correlated closely with a stimulation of flower bud production in pepper. Subsequent planting of onion in the same soils with no further P addition revealed the total dependency of this species on the VAM symbiosis. Mycorrhizal infection reduced by half the R/S ratios of onion plants, mainly by the enhancement of shoot growth. Results indicate the presence of a highly efficient VAM population in the loess soil. These findings are considered with regard to the evolution of the mycorrhizal association and its effect on plant morphology and physiological processes.
TL;DR: The various requirements necessary for the successful osmo-conditioning of different species are discussed, as are the biochemical changes associated with it.
Abstract: Osmotic seed treatment is an effective physiological method for improving seed performance, and is of particular significance in increasing the agricultural productivity of a number of crop plants. The various requirements necessary for the successful osmo-conditioning of different species are discussed, as are the biochemical changes associated with it.
TL;DR: The sprouting rate was enhanced or reduced by shallow planting in the field, depending on the prevailing climatic conditions, and the number of sprouting buds and hence that of daughter corms decreased with the planting depth.
Abstract: The developmental processes in Crocus sativus L. were studied with the aim of improving cultivation methods. The effects of planting depth on rooting, sprouting, flowering, leaf development, and corn production were investigated. Total rooting and flowering capacities were not affected by planting depth. In the case of shallow planting, contractile roots, whose function is to lower the daughter corms into the ground, formed singly at die base of daughter corms. The sprouting rate was enhanced or reduced by shallow planting in the field, depending on the prevailing climatic conditions. Leaf elongation increased markedly with the planting depth. The number of sprouting buds and hence that of daughter corms decreased with the planting depth. The average size of the daughter corms was inversely related to their number. In the saffron crocus, the fibrous roots are situated at the base of the mother corm. During the growing season, mother corms shrink and their vitality is lost; assimilate translocatio...
TL;DR: Germination tests revealed an annual rhythm in seed germinability which ensures that germination is restricted to winter, the normal rainy season of this ombrohydrochoric plant.
Abstract: Mesembryanthemum nodiflorum L. is an annual plant that inhabits the hottest and driest parts of Israel's deserts. This ombrohydrochoric plant requires only extremely small amounts of rain for seed release and dispersal near the dead mother plant (topochory). There is no relationship between rainfall required for seed dispersal and that needed for germination. Dry closed capsules were collected in 1972 and 1974 between Jericho and the Dead Sea, and stored in the laboratory. Germination tests during the summer of 1976 and the years 1978, 1979/80, revealed an annual rhythm in seed germinability which ensures that germination is restricted to winter, the normal rainy season. Within a capsule the outer seeds are released first and have higher germination percentages than the inner seeds. This position effect (heteroblasty), together with the topochory and annual rhythm, are related to the life cycle of this plant in its desert habitat.