Israel Journal of Plant Sciences 

About: Israel Journal of Plant Sciences is an academic journal published by Taylor & Francis. The journal publishes majorly in the area(s): Germination & Population. It has an ISSN identifier of 0792-9978. Over the lifetime, 982 publications have been published receiving 12171 citations.

Why red flowers are not invisible to bees

Abstract: A pervasive idea among pollination biologists is that bees cannot see red flowers. This idea has led many workers to assume that red coloration is an adaptation by which flowers exclude bees as visitors. However, recent empirical and theoretical evidence strongly supports the alternative view, that red flowers are visible to bees. Our purpose is to marshal this evidence from physiology, behavior, and ecology. First, we define the spectral boundary between orange and red, and show that the visual spectrum of all bee species studied to date extends enough into long wavelengths to provide sensitivity to red light. Such sensitivity differs from the ability to discriminate different monochromatic lights, and we argue that bees will be unable to discriminate such lights above about 550 nm. Second, we point out that flowers do not reflect monochromatic lights. Instead many of them, particularly those that appear red, orange, yellow, and white to humans, have reflectance patterns that are essentially ste...

Root elongation in various agronomic crops by the plant growth promoting rhizobacterium pseudomonas putida gr12–2

Abstract: Seeds of canola, lettuce, tomato, barley, wheat, and oats were inoculated with either the wild-type plant growth promoting rhizobacterium (PGPR), Pseudomonas putida GR12–2, or the mutant P. putida GR 12–2lacd68 (deficient in the activity of the enzyme 1-aminocyclopropane-1-carboxylate deaminase) alone and in conjunction with either an inhibitor of ethylene biosynthesis, L-α-(aminoethoxyvinyl)-glycine (AVG), or the chemical ethylene generator, (2-chloroethyl) phosphonic acid (ethophon). For the different treatments, variations in root length under gnotobiotic conditions were compared. Canola, lettuce, tomato, and wheat responded to all of the treatments in a similar manner: The root lengths increased when seeds were treated with P. putida GR 12–2 and/or AVG but not with the mutant strain, in comparison with a MgSO4 control treatment, while the ethophon treatment inhibited root elongation. With barley and oat, none of the treatments had any effect on root lengths; however, when the ethophon concent...

Domestication of emmer wheat and evolution of free-threshing tetraploid wheat

Abstract: We describe here the initial steps of cultivation of wild emmer in the Levant, i.e., the western part of the Fertile Crescent, as well as genetic changes caused by spontaneous mutations, leading to its domestication and to the development of free-threshing tetraploid wheat, Triticum turgidum. Review of archaeological findings from the Pre-Pottery Neolithic A (PPNA) (10,300-9,500 BP; uncalibrated) indicates that wild emmer was first cultivated in the southern Levant. Domesticated emmer (with a nonbrittle spike) appeared several hundred years later in the early PPNB (9,500-9,000 BP), and for a millennium or more was grown in a mixture with wild emmer in many Levantine sites. After the appearance of domesticated emmer, types with naked, free-threshing grains emerged in the late PPNB (9,000-7,500 BP). We support the model in which domestication occurred independently in several sites across the Levant. According to this view, the genes for non-brittleness were transferred to numerous wild emmer genotypes thro...

Core and Peripheral-Populations and Global Climate-Change

Abstract: Environmental conditions outside the periphery of a species' distribution prevent population persistence, hence peripheral populations live under conditions different from those of core populations. Peripheral areas are characterized by variable and unstable conditions, relative to core areas. Peripheral populations are expected to be genetically more variable, since the variable conditions induce fluctuating selection, which maintains high genetic diversity. Alternatively, due to marginal ecological conditions at the periphery, populations there are small and isolated; the within-population diversity is low, but the between-population genetic diversity is high due to genetic drift. It is also likely that peripheral populations evolve resistance to extreme conditions. Thus, peripheral populations rather than core ones may be resistant to environmental extremes and changes, such as global climate change induced by the anthropogenically emitted ''greenhouse gases''. They should be treated as a biogenetic resource used for rehabilitation and restoration of damaged ecosystems. Climatic transition zones are characterized by a high incidence of species represented by peripheral populations, and therefore should be conserved now as repositories of these resources, to be used in the future for mitigating undesirable effects of global climate change. Preliminary research revealed high phenotypic variability and high genetic diversity in peripheral populations relative to core populations of wild barley and the chukar partridge, respectively.

Facultative and constitutive pigment effects on the Photochemical Reflectance Index (PRI) in sun and shade conifer needles

Abstract: Leaf pigment content and spectral reflectance were examined in four conifer species from the Pacific Northwest and Canadian boreal forest. Our goal was to evaluate the causes of within- and between-stand variation in the Photochemical Reflectance Index (PRI), an indicator of xanthophyll cycle activity and carotenoid pigment content that often scales with photosynthetic light-use efficiency. Both the dark-state PRI values and the change in PRI upon dark-light transition (ΔPRI) were measured in situ in leaves from different canopy positions (top vs. bottom) having contrasting light histories (sun vs. shade). PRI varied with species, canopy position, and with the pool sizes of several photoprotective carotenoid pigments (relative to chlorophyll). Upper-canopy leaves had a greater Δ PRI than their shaded counterparts lower in the canopy, reflecting a higher investment of the photoprotective xanthophyll cycle pigments for sun-exposed top-canopy leaves. These results indicate that the relative concentration of ...