Site of photo-reception to opening response in Mimosa leaflets

A pair of leaflets excised from Mimosa pinna and floated onwater for a day, responded to light and mechanical stimuli.Only when a small spot of light was shone on the abaxial surfaceof pulvinule, did the opening response of the leaflets occur.No translocatable effect from suchirradiation was observed. ¹ Present address: Biological Institute, Faculty of Science,Kobe University, Kobe 657, Japan. (Received May 17, 1973; )     

Calcium Involvement In the IAA-induced Leaflet Opening of Cassia fasciculata

Opening of Cassia fasciculata leaflets was induced in darknessafter application of indole-3-acetic acid (IAA). This movementwas obtained with concentrations from 10^–6 M to 10^–4M, after a corresponding time-lag ranging from 120 to 30 min.IAA (5x10^–5 M) allowed leaflet opening at all the pH valuestested (from 3·5 to 7·5), the largest aperturebeing obtained at pH 60 in MES 2·5 mM. Our data suggesta functional involvement of calcium in the regulation of theturgor variations occurring in the pulvinar motor cells duringIAA-induced leaflet opening which occurs in darkness: indeed,this movement was inhibited by the Ca²⁺ chelator EGTA (thisinhibition was reversed by CaCl²) or by antagonists (LaCl³,TMB-8); on the contrary, the IAA-opening was enhanced by ionophoreA 23187. Calcium mobilization through specific channels was tested usingantagonists such as verapamil and nifedipine: at physiologicaldoses, these compounds did not significantly affect leafletresponse. The possibility that calcium could originate frominternal stores was checked using lithium chloride which isknown to block the phosphatidylinositol cycle in animal cells.This compound hindered auxin-induced opening for concentrationshigher than 5x10^–4 M. The calcium-binding protein calmodulinwas shown to be implicated in the IAA-induced response sinceopening was inhibited in a concentration-dependent manner aftertreatment with compound 48/80 and with W-7. Key words: Cassia fasciculata, auxin, calcium, second messenger, turgor regulation     

Role of pulvinar chloroplasts in light-driven leaf movements of the trifoliate leaf of bean (Phaseolus vulgaris L.)

Laminar pulvini of bean (Phaseolus vulgaris L.) contain numerouschloroplasts in cells of their motor tissue. The quantitativerelationships of the chloroplast pigments, chlorophyll a andb, ß-carotene, lutein, neoxanthin as well as the xanthophyllcycle carotenoids (violaxanthin, antheraxanthin and zeaxanthin)were similar to those of mesophyll chloroplasts from leafletlaminae. Exposure of pulvinules to light caused deepoxidationof violaxanthin to zeaxanthin, showing that the xanthophyllcycle is functioning. Chlorophyll fluorescence analysis of pulvinulesconfirmed that their chloroplasts are capable of both photosyntheticelectron transport and non-photochemical fluorescence quenching,showing that they build up a considerable transthylakoid protongradient in the light. Application of DCMU to excised pulvinulesand laminar discs, as well as to pulvinules of intact, attachedterminal leaflets blocked electron transport and fluorescencequenching. Application of the uncoupler CCCP to intact pulvinulesalso prevented non-photochemical fluorescence quenching. Therate of movement of the low-light-adapted terminal leaflet inresponse to exposure of its pulvinule to overhead red light(500 µmol m^–2 s^–1) was reduced when the pulvinulewas pretreated with DCMU. The pulvinar response to overheadblue light (50 µmol ^–2 s^–1), which is morepronounced than to red light, was not affected by similar pretreatmentwith DCMU. Pretreatment with CCCP caused a short lag in theresponse to red light, but did not affect its subsequent rate.The results suggest that the pulvinar response to red, but notto blue light, requires non-cyclic electron transport and theresulting generation of ATP Key words: Leaf movements, light, non-cyclic electron transport, Phaseolus, pulvinar chloroplasts     

In Vitro Phosphorylation of Proteins in IAA-Treated Mesocotyls in Zea mays

Five-mm sections of elongation zones of Zea mesocotyls wereincubated for designated periods with various concentrationsof IAA. In vitro protein phosphorylation in the soluble fraction(85,000 x g supernatant) prepared from the sections was analyzedby sodium dodecyl sulfate-polyacrylamide gel electrophoresis.The phosphorylation of proteins in the soluble fraction thathad been prepared from sections incubated for 20 min in thepresence of 10{small tilde}^s M IAA was greater than that inthe sections incubated for 20 min without IAA. The amount ofphosphorylation of proteins per protein became higher when higherconcentrations increased (10{small tilde}⁸—10{small tilde}⁵M).The growth of sections incubated in the presence of 10{smalltilde}⁸ M IAA or higher concentrations was greater than thatof sections incubated in the absence of IAA. The promotion ofgrowth by IAA was greater at higher concentrations of IAA. Proteinsin the soluble fraction, prepared from sections incubated for20 min in the presence of 10{small tilde}⁵ M IAA, were phosphorylatedin the presence of either 10 fM cAMP, 10 µM cGMP, 100µM W-7, 100 µM W-5, 20 µM H-7 or 20 µMHA1004. The calmodulin antagonist, W-7, and the inhibitor ofprotein kinase C, H-7, inhibited the phosphorylation of proteinsstimulated by incubation with IAA. These results suggest thatIAA promotes cell elongation via protein phosphorylation thatdepends on calmodulin-dependent protein kinase and protein kinaseC. (Received November 29, 1995; Accepted May 20, 1996)     

Role ofLLD, a new locus for leaflet/pinna morphogenesis inPisum sativum

Properties of a mutant at theLLD (LEAF-LET DEVELOPMENT) locus in peaPisum sativum L. are reported in this paper. Plants homozygous for the Mendelian recessive mutationlld bear leaves in which a few to many leaflets are incompletely developed. Opposite pinnae of rachis nodes often formed fused incompletely developed leaflets. Thelld mutation was observed to abort pinna development at almost all morphogenetic stages. Thelld mutation demonstrated high penetrance and low expressivity. The phenotypes oflld plants intl, tac, tl tac, tl af andtl af tac backgrounds suggested that LLD function is involved in the separation of lateral adjacent blastozones differentiated on primary, secondary and tertiary rachides and lamina development in leaflets. The aborted development of tendrils and leaflets inlld mutants was related to deficiency in vascular tissue growth. The morphological and anatomical features of the leaflets formed on atl lld double mutant permitted a model of basipetal leaflet development. The key steps of leaflet morphogenesis include origin of the lamina by splitting of a radially symmetrical growing pinna having abaxial outer surface, opposite to the vascular cylinder, through an invaginational groove, differentiation of adaxial surface along the outer boundary of split tissue in the groove and expansion of the lamina ridges so formed into lamina spans.     

Mobilization of Nitrogen in Fruiting Plants of a Cultivar of Cowpea

Patterns of flow of nitrogen were constructed for the post-anthesisdevelopment of symbiotically-dependent cowpea (Vigna unguiculataWalp. cv. Vita 3-Rhizobium CB756). Nitrogen fixed after floweringcontributed 40% of the fruits' total intake of N, mobilizationof N fixed before flowering the remaining 60%. Leaflets, nodulatedroot, stem plus petioles, and peduncles contributed mobilizedN in the approximate proportions 5: 2: 1: 1 respectively. Eachfruit drew on all available current sources of N, but N fromleaves was distributed preferentially to closest fruit(s), andlower fruits monopolized the N exported from nodulated rootsduring late fruiting. Rates of nitrogen fixation declined parallel with decreasingnet photosynthesis of shoots. Leaflets at upper reproductivenodes mobilized 70–77% of their N and declined steeplyin net photosynthesis rate per unit chlorophyll or per unitribulose-l, 5-bisphosphate carboxylase (RuBPCase)² before abscisingduring mid- to late fruiting, whereas leaflets at lower vegetativenodes (1–3) mostly failed to abscise, lost 44–57%of their N and maintained photosynthetic activity throughoutfruiting. Peptide hydrolase activity was examined in extracts of leaflets,roots and nodules, by autodigestion of extracts, or in assaysusing bovine haemoglobin and purified RuBPCase isolated fromcowpea as substrates. Hydrolase activities during fruiting werebroadly related to N loss from plant organs, but asynchronyin peaks of activity against different protein substrates indicateddistinct groups of hydrolases within single organs. Hydrolaseactivity of leaflet extracts against RuBPCase was highly andpositively correlated with in vivo rates of loss of RuBPCasefrom the same leaflets, and preferential degradation of thisprotein occurred during leaflet senescence. Key words: Nitrogen, Mobilization: Cowpea     

Further Studies of Electro-Osmosis in Nitella in Relation to Pores in Membranes

By measuring the number of water molecules per ion which weremoved electro-osmotically through cells of Nitella translucensand N. flexilis it has been shown that a significant differenceexisted between samples of these species in 1965. In each speciesthe electro-osmotic efficiency was greater with Na⁺ than withK⁺⁺. Also 10^-4 to 10^-5 M IAA tended to decrease electro-osmoticefficiencies while IAA, after 30 min. treatment, produced asignificant increase in water flow into the treated end of aliving cell. Calculations based on this work suggest that about10⁸–10⁹ pore sites per cm² exist on the surface membranesfor Na⁺ or K⁺ ion transport.     

Effects of Light and Growth Substances on the Diurnal Movements of the Leaflets of Mimosa pudica

The leaflets of Mimosa pudica show diurnal opening and closingmovements for some days when they are removed in pairs fromthe parent plant along with the pulvini and a small sectionof the rachis, and floated in water. The movements can be measuredfrom changes in the angle of the blades. When the leaflets arekept in darkness they show a diurnal movement of opening inthe morning at the same time as opening occurs in light. Light,however, is necessary to prevent the leaflets from closing duringthe day after an initial opening. Blue light was most effectivein maintaining the open condition throughout the day. Low concentrationsof indole-3-acetic acid (IAA) and gibberellic acid (GA) promotedopening of the leaflets while higher concentrations preventedtheir closure at night. IAA and GA acted synergistically inreducing dark-closure. Growth substances also prevented daylightclosure of the leaflets in the dark. The results arre discussedin relation to the changes in the osmotic relations of pulvinarcells regulating leaf movements.     

Stomatal responses of Vicia faba L. to indole acetic acid and abscisic acid

Evidence is presented that stomata in isolated epidermal peelsof Vicia faba L. open in darkness in response to the externalpresence of indole acetic acid (IAA) in the incubation medium.The effect of IAA is found to be overcome completely in thepresence of either TRIS or MES buffers. In the absence of buffer,V. faba stomata are shown to be influenced by IAA in a concentration-dependenttrend which reached a maximum at an [IAA] of 10^–3 molm^–3. Further investigations reveal that stomata in thisspecies can be shown to respond to the presence of IAA and anotherphytohormone, abscisic acid (ABA). IAA and ABA are demonstratedto be antagonistic in their effects provided the incubationconditions are suitable. The data are discussed in relationto stomatal responses of other species in different treatmentconditions. Recommendations are made with respect to standardizationof incubation media during epidermal peel experiments. Key words: Vicia faba, stomata, indole acetic acid, abscisic acid, buffers     

The Uptake of Growth Substances: XIII. DIFFERENTIAL UPTAKE OF INDOL-3YL-ACETIC ACID THROUGH THE EPIDERMAL AND CUT SURFACES OF ETIOLATED STEM SEGMENTS

The patterns of uptake of indol-3yl-acetic acid (IAA-2-¹⁴C)by etiolated stem segments of varying lengths have been examined,employing tissues excised from (a) the first and third internodesof Pisum sativum, (b) the top and base of the hypocotyl of Gossypiumhirsutum, and (c) the mesocotyl of Avena sativa. For all species,concentrations (10^–5–10^–3 M) and times upto 24 h, there is a steady accumulation of radioactivity inthe segments. For equal volumes of tissue uptake is inverselycorrelated with segment length but for extending tissues theinitial enhanced extension growth is independent of length;that is there is no direct linkage between the rate of extensionand auxin content. Comparisons between segments with free andsealed ends established that over 24 h some 57–73 percent of the IAA enters via the cut surfaces. Initially, thepercentage is greater; expressed as a rate per unit of surfacethe differences between cut and epidermal surfaces can reach28-fold. The rate of entry through the epidermal surface islinearly proportional to the external concentration but thisdoes not hold for cut surfaces. The addition of streptomycin,synthalin, cetyltrimethylammoniumbromide (CTAB), and chitosanto the external medium does not promote uptake of IAA by Pisumsegments; indeed synthalin is markedly inhibitory. With Gossypiumsynthalin causes little inhibition. Larger depressive effectswere induced for entry via the cut surfaces. On entry the IAAis rapidly metabolized and the rate of conversion is higherfor segments with sealed ends. These findings are discussedin relation to (a) differences in the mechanisms determiningthe uptake of IAA and other auxins, (b) cell extension and thedistribution of auxin in the tissues.     

The determination of pea leaves,leaflets, and tendrils

Pea leaf determination was examined by culturing excised leaf, leaflet, and tendril primordia of different ages on a nutrient medium. Pinna primordia were designated as 1) determined, if they grew normally in culture; 2) undetermined, if they grew into differentiated structures that were morphologically and anatomically different from either leaflet or tendril; or 3) partially determined, if the two pinnae of an opposite pair developed unequally in isolation, or for leaflet pinnae only, if laminae were initiated but did not develop completely. The compound pea leaf as a whole is determined over four plastochrons of development. Proximal pinnae are determined during the second leaf plastochron, approximately 0.8 plastochron after their initiation. The second most proximal pair of pinnae is determined during the third plastochron, and the terminal portion of the rachis is determined last, during the fourth plastochron. Determination of leaflet dorsiventrality is gradual, requiring a critical minimum period with the leaf in physiological contact with the shoot system. The rachis primordium, when isolated from the shoot, does not affect determination of its pinnae as leaflets or tendrils. Afila and tendril-less homeotic mutations do not alter the timing of pinna determination.     

Transport of 14C-lableled indoleacetic acid in Vicia root segments

IAA transport in Vicia root segments was investigated for comparisonwith that in intact roots. Lanolin paste (1-mm-wide ring) oragar blocks (3?3?1.5mm), both containing IAA-2-¹⁴C were appliedto the surface or a cut end of the root segments, respectively;transported ¹⁴C was collected in receiver agar blocks placedon the cut end of the segments. When lanolin paste was appliedto 5-mm segments, basipetal transport of IAA predominated overacropetal transport. When agar blocks were applied to 1- and2-mm segments, the same was true; in longer segments (3 and5 mm long), however, basipetal movement occurred predominantlyat first but was surpassed by acropetal movement after 2–3hr. Among the segments tested (regions 2–4, 4–6and 8–10 mm from the tip), the most apical one showedthe distinctest predominancy of basipetal movement. The velocitiesof the acropetal and basipetal movement of the ¹⁴C were estimatedat 3–3.8 and 8–12 mm/hr, respectively. Autoradiographicstudy and the experiment in which wire was inserted longitudinallythrough the central part of the segments showed that basipetalmovement occurred mainly through the outer part of the rootsand acropetal movement mainly through the central cylinder.The present results were compatible with those obtained previouslywith intact roots. Some properties of polar movement, such asits specificity, inhibition by TIBA, and dependency on terneprature are described. (Received March 22, 1978; )     

Epidermal Growth Factor Interacts with Indole-3-Acetic Acid and Promotes Coleoptile Growth

We used coleoptile sections of Avena sativa, Sorghum bicolor,and Zea mays seedlings to examine interactions between epidermalgrowth factor (EGF) and indole-3-acetic acid (IAA) that mayaffect plant growth and development. Our 24-h bioassays employedthree controls ranging in dilution from 10^–4 to 10^–8g ml^–1: (1) 50 mM potassium-phosphate buffer solution(pH=6.0), (2) bovine serum albumin, a nonspecific protein; and(3) IAA; plus two treatments: (1) mouse epidermal growth factor(EGF) ranging from 10^–6 to 10^–10gml^–1, and(2) EGF + IAA. In all three species growth in IAA, EGF, andEGF + IAA treatments showed significant increases over controls;EGF+IAA showed significant increases in growth over IAA alone.As the concentrations of IAA decreased, the EGF and IAA interactionbecame more pronounced. At the highest IAA concentrations, EGF+ IAA increased growth rates ca. 2% to 39%, whereas at lowerIAA concentrations EGF + IAA promoted growth as much as 121%,thereby lowering the normal IAA physiological set point up tothree or four orders of magnitude. Our data suggest that aninteraction between EGF and IAA may allow plants to recognizeand respond to animal biochemical messengers, resulting in changesin plant cell elongation that ultimately may alter plant growthpatterns. (Received April 27, 1994; Accepted September 5, 1994)     

Morphology and Hormone Levels of Tobacco and Carrot Tissues Transformed by Agrobacterium tumefaciens II. IAA Biosynthetic Activity of Cultured Carrot Tissues Transformed with Wild-Type and Mutant Ti Plasmids

IAA biosynthetic activity was examined in cultured carrot tissuestransformed with Agrobacterium tumefaciens harboring wild-type,aux^– or cyt^– Ti plasmids. In vitro IAAM hydrolaseactivities in tissues transformed with wild-type, and cyt^–Ti plasmids were 3.09 and 19.82 nmol/g proteins/30 min, respectively,but not detectable when aux^– Ti plasmids were used. Theactivity of IAA biosynthesis, determined by the incorporationof radioactivity into IAA in tissues fed with [¹⁴C]-tryptophan,was 34.13, 10.92 and 32.47 pmol/g fr wt/30 min in tissues transformedwith wild type, aux^– and cyt^– Ti plasmids, respectively.The incorporation of radioactivity into the IAAM fraction wasdetected only in the tissues transformed with wild type andcyt^– Ti plasmids. These results showed that the T-DNAencoded pathway of IAA biosynthesis was active in tissues transformedwith wild-type and cyt^h Ti plasmids, and that the activity ofIAA biosynthesis in those tissues was higher than that in tissuestransformed with the aux^– Ti plasmid. (Received March 16, 1988; Accepted July 31, 1988)     

Photosynthetic Oxygen Production Facilitates Translocation of 11C-Labelled Photoassimilates from Tendrils and Leaflets of Pisum sativum L

The translocation profiles of ¹¹C-photoassimilates from eithertendrils or leaflets of the compound leaf of Pisum sativum weresimilar in shape, speed and susceptibility to blockage by chillingand heat girdling. When the feed leaf component was exposedto an anaerobic gas stream consisting of N₂ gas supplementedwith 40 Pa CO₂, the export of previously-fixed ¹¹C-photoassimilatesfrom both leaflets and tendrils continued in the light, butstopped in the dark. However, in the light, translocation of¹¹C-assimilates from the leaflet was rapidly blocked by a flowof pure N₂ (i.e. anoxia). Movement of ¹¹C-assimilates from theleaf of another C₃ plant, sunflower, was similar to that fromthe pea leaflet. In contrast to both laminar leaf components,export from the tendrils was stopped under pure N₂ only in thedark. Taken together the data suggest that photosynthetic O₂production facilitated the movement of ¹¹C-assimilates in theabsence of exogenous O₂. The differences observed between thetendrils and the leaflets exposed to pure N₂ could be attributedto the greater capacity of tendrils to produce and recycle CO₂to support photosynthetic O₂ production in the light. Key words: Pea, ¹¹C-translocation, anoxia, tendril, leaflet     

Movements of K+ during Shutting and Opening of the Trap-Lobes in Aldrovanda vesiculosa

K⁺ movements during the shutting and subsequent opening of trap-lobesin Aldrovanda vesiculosa were measured using ⁸⁶Rb as a tracerfor K⁺. Immediately after the shutting, a large amount of ⁸⁶Rbpre-loaded in the trap-lobes was detected in the hollow spaceinside the shut trap. This may indicate that much of the K⁺in the active motor cells leaks out during the shutting, resultingin turgor loss in the cells. ⁸⁶Rb(K⁺) uptake in the trap wasactive. During the opening process, enhanced ⁸⁶Rb uptake wasobserved. The time course of this uptake was similar to thatof the opening of the trap-lobes, and both courses were acceleratedby IAA. Enhanced K⁺ uptake may restore the turgor in activemotor cells. The quantity of K⁺ that moved during the shuttingor opening was estimated as 20% of that in the active motorcells in the open state of the trap-lobes. The K⁺ efflux acrossthe membranes of the active motor cells may be caused by a largeincrease in bulk flow triggered by an action potential, andwas estimated as 6,200 pmol.cm^–2. ¹ This paper is dedicated to the memory of Professor Joji Ashidawho established the physiology of rapid movement in Aldrovandavesiculosa. (Received July 22, 1982; Accepted November 11, 1982)     

The Polarity of Movement of Endogenously Produced IAA in Relation to a Gravity Perception Mechanism

The polarity of radioactive IAA transport in segments of theleaf sheath base of Avena fatua L. is reversed upon their inversionthrough 180° transport towards the apex being greater thantowards the base. Changes in rates of transport leading to thisreversal can be detected within 10–20 min, correlatingwith the timing of statolith movements from the base to theapex of statocyte cells and conforming to a proposed model forthe gravity control of auxin transport. Transport of H³-trytophan-derived H³-IAA was found to undergosimilar changes in polarity upon re-orientation as did exogenouslyapplied H³ or C¹⁴ IAA. It is concluded that the proposed modelalso relates to the movement of endogenously produced IAA.