Estimation of available potassium for cotton by soil analysis

Measurements of exchangeable K, percentage of exchangeable K of the total exchange capacity (EPP), K extracted in a CaCl₂ solution, and the change in free-energy of exchange of K for Ca+Mg (F), were compared as methods for estimation of available K in soil for growing irrigated cotton. A significant correlation was found between each of the methods and the response to K fertilizer. The different methods are discussed; the advantages of extraction with CaCl₂ solution are that it reflects the change in free energy and is easy to operate. For sandy soils, it is suggested that determination of exchangeable K be added.Contribution from the Agricultural Research Organization, The Volcani Center, Bet Dagan, Israel. 1975 Series, No. 202-E Contribution from the Agricultural Research Organization, The Volcani Center, Bet Dagan, Israel. 1975 Series, No. 202-E     

Overexpressed Monomeric Human Acetylcholinesterase Induces Subtle Ultrastructural Modifications in Developing Neuromuscular Junctions of Xenopus laevis Embryos

Abstract: Formation of a functional neuromuscular junction (NMJ) involves the biosynthesis and transport of numerous muscle-specific proteins, among them the acetylcholine-hydrolyzing enzyme acetylcholinesterase (AChE). To study the mechanisms underlying this process, we have expressed DMA encoding human AChE downstream of the cytomegalovirus promoter in oocytes and developing embryos of Xenopus laevis. Recombinant human AChE (rHAChE) produced in Xenopus was biochemically and immunochemically indistinguishable from native human AChE but clearly distinguished from the endogenous frog enzyme. In microinjected embryos, high levels of catalytically active rHAChE induced a transient state of over-expression that persisted for at least 4 days postfertilization. rHAChE appeared exclusively as nonassembled monomers in embryos at times when endogenous Xenopus AChE displayed complex oligomeric assembly. Nonetheless, cell-associated rHAChE accumulated in myotomes of 2-and 3-day-old embryos within the same sub-cellular compartments as native Xenopus AChE. NMJs from 3-day-old DNA-injected embryos displayed fourfold or greater overexpression of AChE, a 30% increase in postsynaptic membrane length, and increased folding of the postsynaptic membrane. These findings indicate that an evolutionarily conserved property directs the intracellular trafficking and synaptic targeting of AChE in muscle and support a role for AChE in vertebrate synaptogenesis.     

Senescence inhibition and respiration induced by growth retardants and N-benzyladenine

Senescence of Grand Rapids leaf lettuce was greatly reduced at 3 storage temperatures by post-harvest treatment with N,N-dimethylaminosuccinamic acid (Alar) and 2-chloroethyltrimethylammonium chloride (CCC), but not with ⁶N-benzyladenine (BA). Conversely, Alar and CCC were inactive on broccoli while BA was markedly effective. The deterioration and discoloration of mushrooms was inhibited by Alar with no effect observed from BA or CCC.     

Stamens and Gibberellic Acid in the Regulation of Flavonoid Gene Expression in the Corolla of Petunia hybrida

Stamen removal at an early stage of flower development inhibits anthocyanin synthesis and chalcone flavanon isomerase (CHI) enzyme activity in corollas of Petunia hybrida. The inhibition can be overcome by gibberellic acid (GA₃) application. Gibberellin also induces anthocyanin synthesis in detached, young green corollas, grown in vitro in a sucrose medium and promotes CHI enzyme activity. Western blot analysis indicates an increase in chalcone synthase (CHS) and CHI protein levels following GA₃ treatment in both the in vivo and the in vitro systems. Northern blot analysis shows a higher level of steady-state mRNAs for CHS and CHI 24 hours after GA₃ application. In corollas from a transgenic plant containing a β-glucuronidase gene driven by a CHI promoter, a sixfold increase of β-glucuronidase activity was measured following GA₃ application. The mode of action of stamens and GA₃ control over flavonoid gene expression is discussed.     

Growth of bean and tomato plants as affected by root absorbed growth substances and atmospheric carbon dioxide

Summary Bean and tomato plants were grown in solution culture root media containing pre-determined concentrations of gibberellin A₃ (GA), 1-naphthaleneacetic acid (NAA), N⁶-benzyladenine (BA), (2-chloroethyl)trimethylammonium chloride (CCC), and at atmospheric levels of 300 and 1000 ppm of CO₂. Net assimilation rates (NAR), relative growth rates (RGR), leaf area ratios (LAR), root to top dry weight ratios (R/T) and changes in dry weight, size, and form of each organ were recorded.Gibberellin had no effect on RGR of either plant species but increased the NAR of tomatoes at 1000 ppm CO₂. Total dry weight was only slightly affected by GA but root growth and R/T were markedly depressed. CCC had no effect on NAR, but decreased RCR and LAR. Root growth of beans and R/T in both plants were promoted by CCC. NAR and RGR were strongly inhibited by BA and NAA. Inhibition of stem and leaf growth by CCC and NAA was greater than that for roots; thus, R/T ratios were increased. Root branching was promoted by NAA.High (1000 ppm), compared to the low (300 ppm), atmospheric levels of CO₂ generally promoted root growth and produced an increase in the R/T, both in the absence and presence of chemical treatment. The multiplicity of effects of the rootabsorbed chemical growth substances and CO₂ on growth and photosynthesis is discussed.Journal article No 3883 of the Michigan Agricultural Experiment Station.NATO Fellow, University of Pisa, Italy.     

Involvement of signal transduction pathway components in photoperiodic flower induction in Pharbitis nil

The possible participation of several major components of the signal transduction pathway in photoperiodic flower induction was examined in Pharbitis cotyledons. Exogenous applications of GTP-γ-S (1–10 μ M ) or of the phorbol ester, phorbol 12-myristate-13-acetate (PMA, 0.1–5.0 μ M ) to Pharbitis plants held under a marginal inductive period (11.5 h dark) significantly increased their flowering response. Membrane lipid fluidity, GTP-binding and protein kinase activity were increased following a single flowering-inducing dark period of 16 h; however, a light-break of 10 min that abolished flower induction failed to reverse the dark-induced increase in these processes. Photo-inductive dark conditions significantly increased the content of diacylglycerol (DAG) and phosphoinositides in the cotyledon membranes, together with the activities of their kinases, and a light break decreased them to control levels and below. In addition, a single spraying with GTP-γ-S or PMA at 1 μ M significantly increased both the lipid content and the kinase activities. These compounds also enhanced the kinase activities in vitro. It is concluded that DAG and phosphoinositide metabolism play a role in the linking of the photoperiodic induction of the phytochrome with the flowering response in Pharbitis nil .     

Molecular imaging of cell death in vivo by a novel small molecule probe

Apoptosis has a role in many medical disorders, therefore assessment of apoptosis in vivo can be highly useful for diagnosis, follow-up and evaluation of treatment efficacy. ApoSense is a novel technology, comprising low molecular-weight probes, specifically designed for imaging of cell death in vivo. In the current study we present targeting and imaging of cell death both in vitro and in vivo, utilizing NST-732, a member of the ApoSense family, comprising a fluorophore and a fluorine atom, for both fluorescent and future positron emission tomography (PET) studies using an ¹⁸F label, respectively. In vitro, NST-732 manifested selective and rapid accumulation within various cell types undergoing apoptosis. Its uptake was blocked by caspase inhibition, and occurred from the early stages of the apoptotic process, in parallel to binding of Annexin-V, caspase activation and alterations in mitochondrial membrane potential. In vivo, NST-732 manifested selective uptake into cells undergoing cell-death in several clinically-relevant models in rodents: (i) Cell-death induced in lymphoma by irradiation; (ii) Renal ischemia/reperfusion; (iii) Cerebral stroke. Uptake of NST-732 was well-correlated with histopathological assessment of cell-death. NST-732 therefore represents a novel class of small-molecule detectors of apoptosis, with potential useful applications in imaging of the cell death process both in vitro and in vivo. Revital Aloya and Anat Shirvan are equal contribution to the paper