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Avoiding attacks is clearly better than suffering, or even overcoming attacks. Here we discuss the signalling ways by which galls (i.e., gall-inducers) may defend themselves from damage by avoiding attacks. Many colourful galls that are simultaneously chemically and/or physically defended, and/or omit repelling odours fulfilling the general criteria to be tentatively considered as aposematic. It has been shown experimentally that chemically defended galls also emit volatiles that repel relevant herbivores. Thus, both visual and olfactory gall traits may serve as adaptive signals that have been usually overlooked. It is also highly probable that the conspicuous colours (red, yellow) of many galls may also serve physiological functions, such as defence from reactive-oxygen production, from UV, and from excess visible light, or serve other, unknown functions. The certain role of camouflage (especially by being green), in defence from enemies, thus potentially increasing a gall-inducers’ fitness, was not given the attention it deserves. Detailed comparative and especially experimental studies on the adaptive role of gall shape, colouration and odours can further shed light on these phenomena.

A common idea is that resisting or blocking herbivore attacks by structural, chemical and molecular means after they have commenced is the first line of plant defence. However, these are all secondary defences, operating only when all the various methods of avoiding attack have failed. The real first line of plant defence from herbivory and herbivore-transmitted pathogens is avoiding such attacks altogether. Several visual, chemical and ‘statistical’ methods (and commonly their combined effects) have been proposed to allow avoidance of herbivore attacks. The visual types are camouflage, masquerade, aposematic coloration of toxic or physically defended plants (including Müllerian/Batesian mimicry), undermining herbivorous insect camouflage, delayed greening, dazzle and trickery coloration, heterophylly that undermines host identification, leaf movements, and signalling that colourful autumn leaves are soon to be shed. The mimicry types include: herbivore damage, insects and other animals, fungal infestation, dead/dry leaves or branches, animal droppings, and stones and soil. Olfactory-based tactics include odour aposematism by poisonous plants, various repelling volatiles, mimicry of faeces and carrion odours, and mimicry of aphid alarm pheromones. The ‘statistical’ methods are mast fruiting, flowering only once in many years and being rare. In addition to the theoretical aspects, understanding these mechanisms may have considerable potential for agricultural or forestry applications.

Clonal plants present an interesting example of division of labour among their ramets. Here we elaborated on hydraulic structure in respect to the division of labour among ramets in Arundo donax, a perennial clonal reed. Mature clones have three shoot types: (1) large mostly flowering; (2) medium mostly vegetative and (3) small vegetative. The shoots grow from buds initiating in the upper side of underground rhizomes, and the shoot growth is primary with vasculature produced from the procambium. We tested whether the number of vascular strands in a shoot has a fixed developmental programme or follows a flexible developmental pattern, and we found that the number of vascular strands strongly differs between shoot types. Large shoots on average have 560 vascular strands with both the widest vessels and significantly highest hydraulic conductivity. Medium ones and small shoots have 409 and 102 on average, respectively, with narrower vessels and with low conductivity. Thus, the shoot apices have three alternative developmental programmes. Apparently, a clone is built of functionally different modular units that enable Arundo donax to maximize its potential in a heterogeneous environment. Although the smaller culms do not contribute directly to the sexual reproduction of the clone, under stress their safer hydraulic system offers them a better chance of survival.

We examined the geography of top achievements in weightlifting in the Olympic Games for men (1992-2016), and women (2000-2016). Geographic origins of men are restricted to countries with a salient center around the Balkan and the Caucasus areas. This is especially evident for weightlifters in the upper body weight categories. Top achievements of women are more widely spread geographically, yet with clustering in the south-eastern part of Asia. Data on participation in the Olympic Games suggest that this unbalanced geographical spread of men is unlikely to be explained by cultural preferences but rather by specific physical adaptations. This conclusion receives further support from considering weight to height ratio of athletes winning gold medals relative to the average in the general population.

Some plant lineages, such as Araceae and Orchidaceae, have independently evolved deceptive flowers. These exploit the insect's perception and deceive the insects into believing to have located a suitable opportunity for reproduction. The scent compounds emitted by the flowers are the key signals that dupe the insects, guiding them to the right spots that in turn ensure flower pollination. Most species of the genus

Some plant lineages, such as Araceae and Orchidaceae, have independently evolved deceptive flowers. These exploit the insect's perception and deceive the insects into believing to have located a suitable opportunity for reproduction. The scent compounds emitted by the flowers are the key signals that dupe the insects, guiding them to the right spots that in turn ensure flower pollination. Most species of the genus Amorphophallus of the Araceae emit scent compounds that are characteristic of a deceit, suggesting a specific plant pollinator interaction and according odors. However, only a few clear evolutionary trends in regard to inflorescence odors in Amorphophallus could be traced in previous studies - an intriguing result, considered the multitude of characteristic scent compounds expressed in Amorphophallus as well as the key function of scent compounds in deceptive floral systems in general. At least two factors could account for this result. (1) The deceptive pollinator-attraction floral system, including the emitted scent compounds, is less specific than assumed. (2) An evolutionary trend cannot be discerned if the intraspecific scent variation (odor polymorphism) exceeds the interspecific odor variation. Therefore, we discuss the potential deceptive function of the emitted scent compounds, in particular those that are related to cadaveric decomposition. Moreover, we review the data about emitted scent compounds in Amorphophallus with a focus on putative odor polymorphism. Upon examination, it appears that the emitted scent compounds in Amorphophallus are highly mimetic of decomposing organic materials. We show that several species display odor polymorphism, which in turn might constitute an obstacle in the analysis of evolutionary trends. An important odor polymorphism is also indicated by subjective odor perceptions. Odor polymorphism may serve several purposes: it might represent an adaptation to local pollinators or it might assumingly prevent insects from learning to distinguish between a real decomposing substrate and an oviposition-site mimic.

Premise of research. The bark of several Betula and Populus species common in temperate/boreal North America and Eurasia is conspicuously white, and such bark coloration is uncommon in warmer ecolo...

We revisit a case of mimicry in Amorphophallus involving visual mimicry of lichens and colonies of cyanobacteria on their tree-trunk sized petioles. We investigate the entire genus for similar defensive coloration types and report a defensive leaf coloration strategy in several Amorphophallus spp. that involves mimicry, camouflage and plant-mimicking that results in defensive visual masquerade. We propose that the visual expression of lichen and cyanobacteria mimicry enables the huge and fleshy petioles to look like solid non-edible tree trunks, a classic case of masquerade, probably as defence against herbivores. The results are discussed in a phylogenetic and evolutionary context.

Several types of defensive Batesian mimicry seem to be much more common in plants than was historically and is currently considered. It is based either on visual aspects (shape, coloration, and even movement), on odors, and on combinations of both these sensing modalities. Various characters that seem to function as defensive Batesian mimicry, may also simultaneously take part in pollination, physiological functions, or in other defensive mechanisms. The defended models for the visual Batesian mimics in plants belong to several categories: (1) spiny, thorny and prickly plant species, (2) mechanically or chemically defended parts of the same individual plant, or other members of the same species (auto mimicry), (3) colorful and chemically defended plants, (4) dangerous animals (aggressive, toxic), (5) fungal attacks, (6) animal action and animal damage cues, and (7) oozing defensive white latex. Olfactory defended models include: (1) toxic plants, (2) animal alarm pheromones, and (3) animal carrion and feces odors. Many more descriptive, genetic, phylogenetic and experimental studies have to be done in order to better understand the role of defensive Batesian mimicry in plant biology.

SUMMARY The axial and radial derivatives of the cambium showed contrasting wound responses in Melia azedarach L. The vascular rays became larger, less spaced, and their shapes were modified following wounding. As the wound effects vanished with time, ray size, spacing and shape returned to normal patterns. On the other hand, following wounding, vessels became smaller, and fibres were not formed. Vessels returned to normal size, and vessels and fibres reverted to their normal pattern when wound effects vanished. These changes in the patterns of vascular rays, vessels and fibres reflect the nature of the regulatory mechanisms of their formation: axial signal flows, and the involvement of wound effects.

summary Radial fibres differentiate in many aggregate rays of Quercus Calliprinos Webb. The occurrence of radial fibres in rays suggests a radial flow of developmental stimuli for fibre differentiation.

Glandular trichomes are well known to participate in plant chemical and physical defenses against herbivores, especially herbivorous insects. However, little is known about large-scale geographical patterns in glandular trichome occurrence. Herbivory pressure is thought to be higher at low elevations because of warmer and more stable climates. We therefore predicted a higher proportion of species with glandular trichomes at low elevations than at higher elevations. We compiled glandular trichome data (presence/absence) for 6,262 angiosperm species from the Hengduan Mountains (a global biodiversity hotspot in southwest China). We tested the elevational gradient (800–5,000 m a.s.l.) in the occurrence of plant species with glandular trichomes, and its correlations with biotic (occurrence of herbivorous insects) and abiotic factors, potentially shaping the elevational gradient in the occurrence of glandular trichomes. We found a significantly positive relationship between elevation and the occurrence of glandular trichomes, with the proportion of species having glandular trichomes increasing from 11.89% at 800 m a.s.l. to 17.92% at above 4,700 m. This cross-species relationship remained significant after accounting for phylogenetic relationships between species. Herbivorous insect richness peaked at mid-elevations and its association with the incidence of glandular trichomes was weak. Mean annual temperature was the most important factor associated negatively with glandular trichomes. Our results do not support the hypothesis that plant defenses decrease with increasing elevation. In contrast, a higher proportion of plant species with glandular trichome toward higher elevations is observed. Our results also highlight the importance of considering the simultaneous influences of biotic and abiotic factors in testing geographical variation in multifunctional plant defenses.

We present here the earliest evidence for large-scale table olive production from the mid-7th millennium BP inundated site of Hishuley Carmel on the northern Mediterranean coast of Israel. Olive pit size and fragmentation patterns, pollen as well as the architecture of installations associated with pits from this site, were compared to finds from the nearby and slightly earlier submerged Kfar Samir site. Results indicate that at Kfar Samir olive oil was extracted, while at Hishuley Carmel the data showed that large quantities of table olives, the oldest reported to date, were prepared. This process was most probably facilitated by the site’s proximity to the Mediterranean Sea, which served as a source of both sea water and salt required for debittering/pickling/salting the fruit, as experimentally demonstrated in this study. Comparison of pit morphometry from modern cultivars, wild-growing trees and the archaeological sites, intimates that in pit morphology the ancient pits resemble wild olives, but we cannot totally exclude the possibility that they derive from early cultivated trees. Our findings demonstrate that in this region, olive oil production may have predated table olive preparation, with each development serving as a milestone in the early exploitation of the olive.

Cell wall thickening and development of secondary cell walls was a major step in plant terrestrialization that provided the mechanical support, effective functioning of water-conducting elements and fortification of the surface tissues. Despite its importance, the diversity, emergence and evolution of secondary cell walls in early land plants have been characterized quite poorly. Secondary cell walls can be present in different cell types with fibers being among the major ones. The necessity for mechanical support upon increasing plant height is widely recognized; however, identification of fibers in land plants of early taxa is quite limited. In an effort to partially fill this gap, we studied the fibers and the composition of cell walls in stems of the sporophyte of the living fossil Psilotum nudum. Various types of light microscopy, combined with partial tissue maceration demonstrated that this perennial, rootless, fern-like vascular plant, has abundant fibers located in the middle cortex. Extensive immunodetection of cell wall polymers together with various staining and monosaccharide analysis of cell wall constituents revealed that in P. nudum, the secondary cell wall of its cortical fibers is distinct from that of its tracheids. Primary cell walls of all tissues in P. nudum shoots are based on mannan, which is also common in other extant early land plants. Besides, the primary cell wall contains epitope for LM15 specific for xyloglucan and JIM7 that binds methylesterified homogalacturonans, two polymers common in the primary cell walls of higher plants. Xylan and lignin were detected as the major polymers in the secondary cell walls of P. nudum tracheids. However, the secondary cell wall in its cortical fibers is quite similar to their primary cell walls, i.e., enriched in mannan. The innermost secondary cell wall layer of its fibers but not its tracheids has epitope to bind the LM15, LM6, and LM5 antibodies recognizing, respectively, xyloglucan, arabinan and galactan. Together, our data provide the first description of a mannan-based cell wall in sclerenchyma fibers, and demonstrate in detail that the composition and structure of secondary cell wall in early land plants are not uniform in different tissues.

Chickpea shows a distinct domestication trajectory vis‐a‐vis pod dehiscence and growth cycle mediated by vernalization insensitivity compared with its companion Near Eastern legumes. Our objectives were: (i) to map the quantitative trait loci (QTLs) associated with vernalization response and seed free tryptophan in domesticated × wild chickpea progeny and (ii) estimate the genetic correlation between vernalization response and free tryptophan content. A domesticated × wild chickpea cross was used to document phenotypic segregation in both traits and to construct a skeletal genetic map for QTL detection. A number of vernalization response and seed free tryptophan content QTLs were documented in both F₂ and F₃ generations. No significant genetic correlation between these two traits was observed. Epistatic relationship between two free tryptophan loci was documented. It is evident that selection for high seed tryptophan is easier to accomplish relative to selection for vernalization insensitivity. This suggests that the two traits were selected independently in antiquity, thereby corroborating earlier claims for conscious selection processes associated with chickpea domestication.

Variation in flowering color among plant species is widely documented, but its ecological function is often unknown. Comparing phylogenetically related species that differ in ecology can help identify factors that select for flower colors. We compared the distribution of inflorescence colors of the 98 spiny versus the 189 non-spiny species of the Asteraceae in the flora of Israel, and found significant differences between the two groups. Yellow/white inflorescences dominate the non-spiny species, while pink/purple/blue flowers dominate the spiny plants. We hypothesize that the pink/purple/blue flowering of the spiny species may advertise their deterring spines to mammalian herbivores. This putative aposematic signal is particularly conspicuous in summer, when the surrounding landscape turns yellow and grazing pressure is highest. Additional potential adaptive functions for pink/purple/blue flowering in summer-blooming species include increased visibility to pollinators, and improved protection from radiation damage due to the flowers’ high anthocyanin content. The pollinator attraction and radiation defense hypotheses, however, do not account for the observation that the spiny species that flower in yellow/white and in pink/purple/blue have overlapping blooming periods, as do yellow/white and pink/purple/blue flowers of non-spiny species. Phylogenetic constraints may further influence Asteracean flowering colors, a hypothesis that is partially consistent with our data. Spine colors differ significantly from flower color in the spiny species, suggesting that spine and flower colors may have evolved in response to different selective agents. Proximately, the different colors of flowers and spines may reflect the cellular location of pigments in different cell types (anthocyanic red parenchyma versus yellow carotenized lignified hard cells).

A “cultivation prior to domestication”, or a “pre-domestication cultivation” phase features in many reconstructions of Near Eastern plant domestication. Archaeobotanists who accept this notion search for evidence to support the assumption regarding a wild plant’s cultivation phase, which in their view, preceded and eventually led to plant domestication. The presence of non-crop plant remains in the archaeobotanical record interpreted as arable weeds, i.e., weeds of cultivation, is viewed as a strong argument in support of the pre-domestication cultivation phase. Herein, we show that the simple practice of harvest by hand-pulling (uprooting) has the potential to secure an almost weed-free harvest. Indeed, rather clean (weed-free) Neolithic seed caches from a range of relevant sites were documented in archaeobotanical reports. These reports, alongside ethnographic observations suggest that (in certain cases) ancient harvest may have been carried out by selective hand-pulling. Hence, one has no reason to view archaeobotanical assemblages from occupation sites as fully representative of cultivated fields. Therefore, the concept of “arable—pre-domestication weeds”, its logic, and its potential contribution to the prevailing reconstructions of Near Eastern plant domestication need be reconsidered.

We are grateful to Ben-Yosefet al. (above) for their thorough critical evaluation of our recent paper. We identified a group of modified wooden shafts originating in two large complex caves with Late Chalcolithic (Ghassulian) burials in the Negev Desert (Israel) as the earliest Levantine wooden spinning implements (Langgutet al. 2016). Their detailed assessment culminated in the alternative hypothesis that the wooden objects functioned as sticks that carried metal maceheads during rituals. This raises several issues that merit serious consideration. Our response to Ben-Yosefet al.'s suggestions is divided into two sections, each concentrating on one of the two main technologies under discussion: spinning and metallurgy.

It is widely accepted that quite a number of invertebrate and vertebrate animal species visually mimic or masquerade as plant parts and by this gain protection from predators or crypsis from their unaware prey (Cott 1940; Wickler 1968; Edmunds 1974; Ruxton et al. 2004; Purser 2003; Stevens 2016). Classic examples listed in Cott (1940) include: several species of fish and crabs that resemble algae; geckos and moths that look like lichens; many insects, amphibians and reptiles that masquerade as leaves; tree bark mimicked by spiders, moths, beetles, amphibians, lizards and birds; stick-insects (Phasmida) that resemble branches, and flower masquerade by thomisid spiders and bugs.

The question of the spread of an aposematic or of an otherwise visually defended plant type within a non-aposematic or a visually non-defended population is a long-standing enigma that has received considerable theoretical attention. However, the spreading of aposematic or otherwise visually defended plant genotypes within a non-aposematic or a non-visually-defended population has never, as far as is known, been shown or studied in nature in wild plant populations. This study investigates the loss of the various simultaneous types of defensive coloration in the spiny thistle Silybum marianum by a mutation that occurred independently and found in 13 wild populations in Israel. Mutant plants have plain leaves rather than leaves of the zebra-like wild-type, which has a white network of stripes on the upper leaf surface. The mutants never spread beyond several dozen meters and usually only over several meters. The mutation has a simple developmental origin, since the white variegation is the result of...

Leaf variegation, the outcome of various genetic, developmental and physiological factors, is a well-known phenomenon proposed and even shown experimentally to defend plants from herbivory. A visually similar phenomenon that we define as pseudo-variegation is induced in plants by various external biological agents. We propose that pseudo-variegation may defend leaves and other plant organs (and also some of the organisms that induce them) from herbivory by several visual and chemical mechanisms: camouflage, aposematism and by indicating via olfactory cues/signals that the plants are damaged or occupied by herbivores or pathogens. From an evolutionary point of view, because of the common reduced quality as food and in many cases even toxicity for herbivores of leaves expressing pseudo-variegation, as well as because of competition with pathogens and herbivores that arrived earlier, or because of cannibalistic or predatory herbivores, such leaves were probably the defended models that were later mimicked by plants with mutations that caused various variegated phenotypes. Pseudo-variegation types induced by various pathogens and herbivores that actually defend plants from herbivory should be considered the extended phenotypes of both these plants and of the inducers that in this way defend their plant habitat.

Diet is central for understanding hominin evolution, adaptation, and environmental exploitation, but Paleolithic plant remains are scarce. A unique macrobotanical assemblage of 55 food plant taxa from the Acheulian site of Gesher Benot Ya'aqov, Israel includes seeds, fruits, nuts, vegetables, and plants producing underground storage organs. The food plant remains were part of a diet that also included aquatic and terrestrial fauna. This diverse assemblage, 780,000 y old, reflects a varied plant diet, staple plant foods, environmental knowledge, seasonality, and the use of fire in food processing. It provides insight into the wide spectrum of the diet of mid-Pleistocene hominins, enhancing our understanding of their adaptation from the perspective of subsistence. Our results shed light on hominin abilities to adjust to new environments, facilitating population diffusion and colonization beyond Africa. We reconstruct the major vegetal foodstuffs, while considering the possibility of some detoxification by fire. The site, located in the Levantine Corridor through which several hominin waves dispersed out of Africa, provides a unique opportunity to study mid-Pleistocene vegetal diet and is crucial for understanding subsistence aspects of hominin dispersal and the transition from an African-based to a Eurasian diet.

Flower-color polymorphisms are well-documented, but how color morph frequencies change over time is usually unknown. We studied this question using the milk thistle, Silybum marianum (Asteraceae). Purple flowers commonly occur in Israel, but an infrequent white morph has been recorded since the 1920s, at first from the south of the country. Over seven years, we recorded the frequencies of the two color morphs in 17 populations along a 156 km south-north transect with a steep rainfall gradient. The proportion of white inflorescences per population consistently decreased from south to north, and their mean proportion decreased from 24% to 12% over the study period. Four of the populations went extinct, but two were recolonized, and two additional populations decreased to

International audience; Dioecy, the specialization of individuals into either male-only or female-only sexual function, has multiple evolutionary origins in plants. One proposed ancestral mating system is heterodichogamy, two morphs of cross-fertilizing hermaphrodite flowers that differ in their timing of flowering. Previous research suggested that small specializations in these morphs’ functional genders could facilitate their evolution into separate sexes. We tested the possible role of pollinators in driving such specializations. Ziziphus spina-christi is an insect-pollinated heterodichogamous tree with self-incompatible flowers and two sympatric flowering morphs. We compared the flower development patterns, floral food rewards, pollinator visits, and fruit production between the two morphs. Male-phase flowers of Z. spina-christi’s “Early” and “Late” morphs open before dawn and around noon, respectively, and transition into female-phase 7–8 h later. Flowers of both morphs contain similar nectar and pollen rewards, and receive visits by flies (their ancestral pollinators) at similar rates, mostly during the morning. Consequently, the Early morph functions largely as pollen donor. The Late morph, functioning as female in the morning, produces more fruit. We developed an evolutionary probabilistic model, inspired by Z. spina-christi’s reproductive system, to test whether pollinator visit patterns could potentially play a role in an evolutionary transition from heterodichogamy towards dioecy. The model predicts that reproductive incompatibility within flowering morphs promotes their evolution into different sexes. Furthermore, the pollinators’ morning activity drives the Early and Late morphs’ specialization into male and female functions, respectively. Thus, while not required for transitioning from heterodichogamy to dioecy, pollinator-mediated selection is expected to influence which sexual specialization evolves in each of the flowering morphs.

Leaves of the spiny winter annual Silybum marianum express white patches (variegation) that can cover significant surface areas, the outcome of air spaces formed between the epidermis and the green chlorenchyma. We asked: (1) what characterizes the white patches in S. marianum and what differs them from green patches? (2) Do white patches differ from green patches in photosynthetic efficiency under lower temperatures? We predicted that the air spaces in white patches have physiological benefits, elevating photosynthetic rates under low temperatures. To test our hypotheses we used both a variegated wild type and entirely green mutants. We grew the plants under moderate temperatures (20°C/10°C d/n) and compared them to plants grown under lower temperatures (15°C/5°C d/n). The developed plants were exposed to different temperatures for 1 h and their photosynthetic activity was measured. In addition, we compared in green vs. white patches, the reflectance spectra, patch structure, chlorophyll and dehydrin content, stomatal structure, plant growth, and leaf temperature. White patches were not significantly different from green patches in their biochemistry and photosynthesis. However, under lower temperatures, variegated wild-type leaves were significantly warmer than all-green mutants – possible explanations for that are discussed These findings support our hypothesis, that white variegation of S. marianum leaves has a physiological role, elevating leaf temperature during cold winter days.

Spinescence has been thought to have evolved mainly as a defense against herbivores. Thus, studying its evolution in a whole flora is an excellent approach for understanding long-term plant–herbivore interactions. In this study, we characterized the spinescent plant species of Jiaozi Snow Mountain, Southwestern China, in order to explore the effects of life forms, plant organs, phylogenetic position, and phytogeographical origin on spinescence occurrence. The Jiaozi Snow Mountain flora includes 137 spinescent species (9.2%) out of 1488 angiosperm species. We found that in these spinescent species, vegetative organs (70.0%) were significantly more defended than reproductive organs (43.8%). Life form had a significant effect on spinescence occurrence. Woody species (18.6%) were more likely to be spiny than non-woody species (6.4%); moreover, woody species mostly defend their vegetative organs (92.2%), whereas herbaceous species mostly defend their reproductive organs (73.3%). For woody plants, leaf habit has a significant effect on spinescence. Specifically, spinescence was more common on the reproductive organs of deciduous woody species than on those of evergreen woody species; furthermore, spinescence was more common on the leaf blades of evergreens than on those of deciduous species; however, the proportion of spinescent petioles in deciduous species was significantly higher than in evergreens. The most common spine color was yellow (40.8%), followed by white (16.8%), red (15.8%), and brown (14.3%); furthermore, 74.4% of spinescence that showed aposematic color was a different color than the plant organ on which grown. These findings suggest that spinescence is visually aposematic in the Jiaozi Snow Mountain flora. Phylogenetically, more families tended to have spines on vegetative organs (83.3% in vegetative organs, 50.0% in reproductive organs), but the phylogenetic signals were weak. The proportion of spinescence was not significantly different between tropical (9.8% of genera, 7.6% of species) and temperate (13.2% of genera, 9.5% of species) elements. These results indicate that in the Jiaozi Snow Mountain flora spinescence evolved differently in various life forms and plant organs, but that these differences were not influenced by phylogenetic position or phytogeographical origin. Keywords: Herbivory, Life form, Physical defense, Trade-off, Plant apparency, Spinescence

Leaves of the spiny winter annual Silybum marianum express white patches (variegation) that can cover significant surface areas, the outcome of air spaces formed between the epidermis and the green chlorenchyma. We asked: (1) what characterizes the white patches in S. marianum and what differs them from green patches? (2) Do white patches differ from green patches in photosynthetic efficiency under lower temperatures? We predicted that the air spaces in white patches have physiological benefits, elevating photosynthetic rates under low temperatures. To test our hypotheses we used both a variegated wild type and entirely green mutants. We grew the plants under moderate temperatures (20°C/10°C d/n) and compared them to plants grown under lower temperatures (15°C/5°C d/n). The developed plants were exposed to different temperatures for 1 h and their photosynthetic activity was measured. In addition, we compared in green vs. white patches, the reflectance spectra, patch structure, chlorophyll and dehydrin content, stomatal structure, plant growth, and leaf temperature. White patches were not significantly different from green patches in their biochemistry and photosynthesis. However, under lower temperatures, variegated wild-type leaves were significantly warmer than all-green mutants – possible explanations for that are discussed These findings support our hypothesis, that white variegation of S. marianum leaves has a physiological role, elevating leaf temperature during cold winter days.

A protracted domestication time-frame for cereals in the Near East is widely endorsed by the plant domestication research community. This occurs in tandem with the pre-domestication cultivation concept, which rests on the assumption that human husbandry operations (namely cultivation) exerted selection pressures in favor of domesticated phenotypes (e.g., non-shattering spikes) at the expense of the wild type (WT) shattering phenotype. The protracted domestication model rests on a long series of assumptions of which we address only two: (1) that the archeobotanical assemblages found in Neolithic occupation sites are representative of the managed plant populations from the cultivated fields; (2) that WT (shattering, brittle spikes) and domesticated (non-shattering, non-brittle spikes) stocks were grown for millennia as admixed populations across the Near East before the domesticated (non-shattering) morphotype slowly came to dominate the managed cereal populations. Scrutinizing these assumptions, and their derivatives, we suggest that the proportion of wild vs. domesticated cereal remains in archeobotanical assemblages cannot possibly represent the presumed cultivated plant populations. Moreover, agronomic considerations expose severe methodological and theoretical drawbacks in the protracted domestication reconstruction vis-a-vis the proportions of shattering vs. non-shattering spikelets in archeobotanical assemblages.