Chlorophyll Fluorescence Induction in Leaves of Phaseolus vulgaris Infected with Bean Rust (Uromyces appendiculatus)

To our knowledge, this report describes the first application of video imaging of Chl fluorescence to the study of light utilization in photosystem II of attached leaves of Phaseolus vulgaris infected with the obligate biotrophic fungus Uromyces appendiculatus (race 38). The video-based detection system produced a spatially resolved, quantifiable signal that was highly specific for chlorophyll fluorescence. Video images of spatial variation in the initial stage of the fluorescence induction (dark-light) transient revealed discreet regions of intense emission coinciding with centers of subsequent lesion development and accompanying chlorosis. Incipient lesions were visible by this procedure 3 d following inoculation, fully 3 to 4 d prior to visible symptoms. Fluorescence emission patterns in infected areas during the induction transient were heterogeneous with radial distance from the point of invasion and varied with the length of the time delay between re-illumination and image capture. During later ([greater than or equal to]1 min) stages of the induction transient, fluorescence emission in incipient lesions was quenched compared to surrounding tissue. These essential features of the induction transient observed in video images were also noted when individual lesions were examined using pulse modulation fluorimetry.     

Changes in Auxins in Expanding and Senescent Primary Leaves of Dwarf French Bean (Phaseolus vulgaris)

A bound, unextractable auxin, or auxin precursor, in the primaryleaves of dwarf French bean was converted to a form, probablyindol-3yl-acetic acid, extractable in ethyl acetate, by maceratingleaves in pH 7.5 phosphate buffer and incubating them at 37–38°C for 2 days in the presence of toluene or hibitane. Boilingthe leaves before macerating and incubating them prevented therelease of bound auxin. This bound auxin was also released whenmacerated leaves were hydrolysed with normal potassium hydroxideat 100° C for 2 hours. The amounts of free auxin and tryptophanin senescent primary leaves increased as their bound auxin andchlorophyll decreased. Removing the apical growing region immediatelyabove the node bearing the primary leaves delayed their senescenceand the conversion of their bound to free auxin.     

Mechanism of Zinc Uptake in Bean (Phaseolus vulgaris) Tissues

Uptake of micronutrient zinc by intact leaves, enzymically isolated leaf cells, leaf disks, excised roots, and stem-callus tissue of two field bean cultivars 'Saginaw’ and ‘Sanilac’) was studied using radio-isotope tracer technique. Radio-phosphorus absorption by these tissues was also followed under comparable experimental conditions. A rapid absorption of the micronutrient and strong dependency on external zinc concentration and pH were revealed. Absorption of zinc was not inhibited by respiratory inhibitors (dinitrophenol, azide, cyanide, and amytal), and was not light or temperature dependent. Q₁₀ values for zinc uptake ranged between 1 and 1.2. Uptake of phosphate, on the other hand, was temperature and light dependent and drastically reduced by the presence of metabolic inhibitors. Differences in responses to respiratory inhibitors, temperature, pH, light and darkness, and kinetic data, strongly suggest that zinc uptake in bean tissues occurs primarily by a passive mechanism, involving possibly a physical or physiochemical binding of the micronutrient ions to the cell wall and free space components, and a passive diffusion into the interior of the cell.     

Endogenous Regulation of Photosynthetic Rate in Primary Leaves of Bean (Phaseolus vulgaris L.)

The rate of photosynthesis and/or dry matter production wasstudied in fully-expanded primary leaves of bean (Phaseolusvulgaris cv. Bulgarian) plants which had been subjected to varioussurgical and hormonal treatments. Between 30 and 40 per centof the assimilates produced by the primary leaves, over a 4-dayperiod starting with expansion of the first trifoliate leaf,were diverted to the growing shoot above the insertion of theprimary leaves. In detopped plants (i.e. lacking all leaves,stem and buds above insertion of primary leaves), both the rateof net photosynthesis (NP) of the primary leaves 4 days afterdetopping, and the mean net assimilation rate (NAR) over thisinterval, did not differ significantly from those of intactplants. The assimilate normally diverted to the top in intactplants was distributed between the remaining organs of the detoppedplant. When translocation of assimilates from the primary leaveswas stopped by girdling their petioles, both NAR and NP wereas in untreated control plants after a 2-day period. The assimilatesproduced during that period accumulated in the mesophyll chlorenchymain the form of starch granules. Intact plants supplied withGA₃, or IAA, through the primary leaves as well as detoppedplants supplied with IAA through the stump, differed from untreatedcontrol plants in the pattern of distribution of the assimilatesproduced: IAA favoured dry-matter accumulation in the roots,while GA₃ favoured the tops. Nevertheless, neither NP, nor NARdiffered significantly from the corresponding controls.     

Starch Accumulation and Photosynthetic Activity in Primary Leaves of Bean (Phaseolus vulgaris L.)

The effects of starch accumulation on photosynthesis and chloroplastultrastructure were studied in primary leaves of bean (Phaseolusvulgaris L. cv. Bulgarian). De-topping the shoot above the primaryleaf node, caused over an 8-day period, a considerable increasein the photosynthetic activity of the primary leaves, despitethe fact that a large quantity of starch had accumulated intheir chloroplasts. The accumulation of starch was greater inthe chloroplasts of spongy cells in comparison with that ofthe palisade cells. Initiation of starch grains was observedmainly in the peripheral part of the chloroplast, distant fromthe cell wall. As a result, most of the starch was accumulatedclose to the inner part of the cell, leaving a considerablemass of the chloroplast near the cell wall free of starch. Theaccumulation of starch was accompanied by the destruction, deformationand disorientation of grana and thylakoids. It is concludedthat the accumulation of starch is not inevitably a limitingfactor in photosynthesis and the results cast doubt on the hypothesisthat starch accumulation or dissipation is the main factor involvedin the regulation of photosynthesis. Phaseolus vulgaris L, bean, photosynthesis, starch accumulation, chloroplast ultrastructure     

Cellulase and Abscission in the Red Kidney Bean (Phaseolus vulgaris)

Cellulase (β-1, 4-glucan-glucanohydrolase EC 3.2.1.4) activity in the abscission zone of red kidney bean (Phaseolus vulgaris) was previously shown to exist in at least two different molecular forms. The form of the enzyme which has an isoelectric point of 4.5 is present in both abscising and nonabscising tissue and requires grinding for extraction. Another form of the enzyme which has an isoelectric point of 9.5 is present only in tissue in which the abscission process has been induced. Further, much of this form of cellulase can be removed from the tissue by vacuum infiltration with buffer. Time course studies indicate that while the increase in measurable cellulase activity in tissue which is actively undergoing abscission was due primarily to the appearance of cellulase 9.5, this form of the enzyme cannot be removed by vacuum infiltration until after the breakstrength of the abscission zone has decreased nearly to zero. The intracellular localization of these two forms of cellulase is discussed.     

Uptake Hydrogenase (Hup) in Common Bean (Phaseolus vulgaris) Symbioses

Strains of Rhizobium forming nitrogen-fixing symbioses with common bean were systematically examined for the presence of the uptake hydrogenase (hup) structural genes and expression of uptake hydrogenase (Hup) activity. DNA with homology to the hup structural genes of Bradyrhizobium japonicum was present in 100 of 248 strains examined. EcoRI fragments with molecular sizes of approximately 20.0 and 2.2 kb hybridized with an internal SacI fragment, which contains part of both bradyrhizobial hup structural genes. The DNA with homology to the hup genes was located on pSym of one of the bean rhizobia. Hup activity was observed in bean symbioses with 13 of 30 strains containing DNA homologous with the hup structural genes. However, the Hup activity was not sufficient to eliminate hydrogen evolution from the nodules. Varying the host plant with two of the Hup⁺ strains indicated that expression of Hup activity was host regulated, as has been reported with soybean, pea, and cowpea strains.     

The Effect of Cycloheximide on Absorption of Ions by Bean (Phaseolus vulgaris L) Roots

10^–7 M cycloheximide inhibited bean (Phaseolus vulgaris)root elongation by about 20 per cent but it inhibited absorptionof rubidium, sodium, and phosphate ions to a much greater extent(34–71 per cent). Tips of intact plant roots grown inthe inhibitor showed more inhibition in ion uptake than adjacentproximal portions of the same roots and this is taken to indicatethat 10^–7 M cycloheximide does not exert its effect onion uptake by any uncoupling action. Sodium uptake from 0.5 or 10 mM NaCl solutions by root tipswas inhibited by 10^–7 M cycloheximide to twice the extentthat it was in the elongating region of the root. Assuming thatthe inhibitor affects the plasmalemma more than the tonoplast,Epstein's model of parallel operation of system 1 and system2 at the plasmalemma is supported.     

Effect of Chloramphenicol on Formation of Chloroplast Structure and Protein During Greening of Etiolated Leaves of Phaseolus vulgaris

Greening of leaves of Phaseolus vulgaris in the presence of chloramphenicol inhibits formation of A) total chloroplast protein, B) an easily extractable fraction removed during isolation of chloroplasts in isotonic media by differential centrifugation, and C) the insoluble lamellar fraction which remains after extracting osmotically shocked freeze-dried plastids. The inhibition of insoluble chloroplast protein formation is correlated with decreased formation of lamellae and increased formation of vesicular structures. In contrast, chloramphenicol increases the formation of a fraction not removed during differential centrifugation, but removed by water extraction after osmotic shock and freeze-drying of chloroplasts. Analysis of this fraction by electrophoresis and column chromatography, indicates that the increased accumulation of this protein fraction is largely due to accumulation of a protein which is normally present in this fraction in small quantities. It was suggested that this protein may be a precursor which is normally incorporated into the lamellae. The protein extracted from freeze-dried chloroplasts of chloramphenicol treated chloroplasts contains a smaller proportion of one or more proteins than a similar extract of untreated plastids. However, per plastid, no such difference exists.     

Yield-Respiration Relationships at Different Bean (Phaseolus vulgaris) Plant Densities

Bean (Phaseolus vulgaris L.) plants were grown, one to fiveplants per pot, with a non-limiting supply of mineral nutrients.As plant density increased, seed and N yield per plant decreased,but those per pot remained fairly constant. The shoot: rootratio and the contribution of roots to total plant respirationwere also almost constant with changing density; the Q₁₀ forshoot respiration was higher at maximal densities. However,growth respiratory C losses per plant over the growth periodon a seed dry matter of N yield basis were not dependent onplant densities tested. Phaseolus vulgaris L., yield, respiration, plant density     

Effect of Removing Cotyledons, Apical Growing Region, or Trifoliate Leaves on the Growth and Growth-substance Content of Dwarf French Bean (Phaseolus vulgaris)

The growth of the primary leaf on intact plants was comparedwith that on plants from which the cotyledons, apical growingregion, or trifoliate leaves had been removed. Removing thecotyledons early decreased the final area of the primary leaves,this response being partially accounted for by a decrease intheir cell number, and increased the concentration (but notthe quantity) of gibberellin and auxin in them. This responsewas not altered by applying any of several growth substances.Early removal of the apical growing region increased the finalarea of the primary leaves; it also increased the gibberellincontent and concentration at Day 10 but did not influence theauxin content and concentration. Primary leaf expansion wasaffected less by detaching young trifoliate leaves than by removingthe entire apical growing region.     

Selenate and Selenite Uptake and Translocation in Bean Plants (Phaseolus vulgaris)

After 3 h, selenate uptake by roots of Phaseolus vulgaris L.cv. Contender resulted in more than 50% of the Se absorbed beingconveyed to the aerial organs. This distribution was sensitiveto respiratory inhibitors and when roots were soaked in a solutionsupplied with hydroxylamine, the level of Se decreased by about80% in the whole plant, suggesting that selenate uptake requiresenergy. Addition of glucose to the nutrient medium resultedin slightly decreased uptake and distribution. Under the same growth conditions and 3 h incubation with selenite,a major part of the Se had accumulated in the roots, while asmall fraction was conveyed towards the aerial organs. Thispercentage was decreased by about 20% when plants were transferredto a solution supplied with hydroxylamine, suggesting that partof the selenite entered the roots passively. Addition of glucoseto the nutrient solution, resulted in enhanced levels of Sein the whole plant. Application of plant growth substances affected Se transport.When roots were incubated in abscisic acid (ABA), selenate uptakewas affected, while foliar spraying of gibberellin A₃ (GA₃)enhanced selenite uptake and translocation. Key words: Phaseolus vulgaris, selenate, transport, selenite, glucose, harmones     

Influence of Light on the Bioelectric Potential of the Bean (Phaseolus vulgaris) Hypocotyl Hook

By use of surface electrodes electropotenlial measurements were carried out on hypocotyl hooks of Phaseolus vulgaris seedlings. The hooks were illuminated with a small spot of white, blue, red or far red light. The potential changes in bean hypocotyl hooks do not show the red-far red reversible characteristics of phytochrome-mediated processes. By experimenting with inhibitors of photosynthesis we could demonstrate that the light-triggered potential changes in green bean hooks are correlated to photosynthetic electron transport phenomena. The red-light-induced transient is a depolarization, whereas blue light induces a hyperpolarization. Etiolated beans exhibit no bioelectric potential changes when subjected to red or far red irradiations. Blue light and white light induce a strong hyperpolarization in etiolated hooks cells. This transient seems to be an action potential induced by light. The action potential is influenced by inhibitors of electron transport and oxidative phosphorylation. By comparing the action spectrum of the action potential induced by light with the absorption spectra of extracted carotenoids and xanthophylls from etiolated bean hypocotyl hooks, we observed similarities.     

Studies on Trypsin Inhibitor in Bean (Phaseolus vulgaris L) Cultivars of Himalayan Region

Eight Phaseolus vulgaris L cultivars of Himalayan region were analyzed for trypsin inhibitor activity and inhibition of gut trypsin enzyme extracted from Spodoptera littoralis larvae. Trypsin unit inhibited per gram seed weight was maximum in local yellow cultivar. The trypsin inhibitor was purified to 65.9-fold with 55.6% recovery from seeds of selected cultivar. The purified protein had a molecular weight of 14,130 Daltons and was found to be a monomer by SIDS-PAGE. It was heat stable at 100°C for 10 minutes and had a pH optimum of 7.5. Hence, the purified inhibitor appears to be of Bowman-Birk type. It lost its activity on exposure to 0.2M 2-mercaptoethanol. The inhibition pattern was of non-competitive type and the Ki value was 0.8μM. The KM value of trypsin enzyme for the substrate BApMA was 2.2mM.     

Effect of Glyphosate on Intact Bean Plants (Phaseolus vulgaris L.) and Isolated Cells

Whole bean (var. “Eastern Butterwax”) plants and isolated cells were used to investigate possible mechanisms of action of glyphosate [N-(phosphonomethyl)glycine]. Results showed that glyphosate was quickly absorbed by the whole plant but not by individual cells and that it caused a rapid reduction in leaf dry matter accumulation, leaf expansion, leaf angle, and stomatal aperture without affecting the water status of the plant. Glyphosate also caused a rapid reduction in cellular uptake of ⁸⁶Rb and ³²P which preceded its detrimental effects on photosynthesis, RNA and protein synthesis, and respiration of isolated cells. This reduction in ion absorption was not due to a loss of membrane integrity, decrease in energy supply or chelation of ions. It was concluded that glyphosate was directly inhibiting the ion absorption process of bean leaf cells.     

The Effect of Growth Regulators, CCC and B9, on Protein and Total Nitrogen of Bean Leaves (Phaseolus vulgaris) during Development

Total-N and protein-N were greatest in developing primary leavesof intact plants of Phaseolus vulgaris before the leaves werefully expanded. Treating plants with CCC or B9 delayed the timewhen total-N and protein-N diminished. Removing the growingpoint made nitrogen accumulate in the leaves and the total-Ndid not diminish until they were fully expanded. Treatment withCCC did not affect the amount of total-N or protein-N in decapitatedplants. Apparently nitrogen moves more slowly from primary leavesof CCC-treated plants because the shoot grows more slowly anddemands less nitrogen. Similarly, leaves of decapitated plantshave more nitrogen because there is no shoot. When primary leaveswere detached and rooted, protein continued to increase in themalthough they were fully expanded before they developed roots,again probably because the demand for nitrogen was small. Changesin protein were correlated with changes in chlorophyll duringdevelopment. Maximum photosynthesis per leaf probably occurs before leavesare fully expanded, and the protein changes in the leaf maybe closely related to the trend of photosynthesis during thelife of a leaf.     

Variation of Protein among Eleven Varieties of Common Bean (Phaseolus vulgaris)

The acylated, amidated and esterified derivatives of N-acetylglucosaminyl-α(1 → 4)-N-acetylmuramyl tri- and tetrapeptide were synthesized and examined as to their protective effect on pseudomonal infection in the mouse and pyrogenicity in the rabbit. Modifications of the terminal end function of the peptide moieties in their molecules caused enhancement of resistance to pseudomonal infection and reduction of pyrogenicity. Among the compounds tested, sodium N-acetylglucosaminyl-β(1 → 4)-N-acetylmuramyl-l-alanyl-d-isoglutaminyl-(l)-stearoyl-(d)-meso-2,6-diaminopimelic acid-(d)-amide and sodium N-acetylglucosaminyl-β(1 → 4)-N-acetylmuramyl-l-alanyl-d-isoglutaminyl-(l)-stearoyl-(d)-meso-2,6-diaminopimelic acid-(d)-amide-(l)-d-alanine were found to be advantageous and conceivably worthwhile for further investigation as immunobiologically active compounds.     

Thigmotropism in Organs of the Bean Plant (Phaseolus vulgaris L.)

When each vegetative aerial organ of the young bean plant isunilaterally mechanically perturbed by gentle rubbing, it exhibitspositive thigmotropism. The internodes undergo only moderatethigmotropism, but leaves and petioles bend much more, especiallywhen they are rubbed on their abaxial surfaces. When the abaxialsurface of one petiole is rubbed, it bends down, but the oppositepetiole bends upward at the stem-petiole pulvinus. These observationsare interpreted in terms of the vining habit of bean plants. Bean, Phaseolus vulgaris, thigmotropism, mechanical perturbation