Germination and Growth of Potamogeton pectinatus (L.) at Different Water Depths in Lake Nainital,Uttar Pradesh,India

Data on germination of tubers and subsequent growth of young plants of Potamogeton pectinatus were recorded at different depths of the water column in Lake Nainital. The depth of euphotic zone is about 5 m. Tubers were placed at 1, 2.5, 5.0, 7.5 and 10 m water depth in brass net bags. A highly significant negative correlation was found between depth on one hand and germination percentage of tubers, length of shoots and number of leaves on the other hand. Germination of tubers was positively related to pH, dissolved oxygen and temperature of water.     

The Translocation of Lead and Copper in Two Submerged Aquatic Angiosperm Species

The translocation of lead and copper was studied in two speciesof submerged aquatic angiosperm, Potamogeton crispus L. andPotamogeton pectinatus L. A perspex container incorporatinga potters' clay seal around the stems of intact plants was designedfor the chemical separation of the shoot and root environmentsduring 11–21 d treatment periods. Metal solutions wereadded to the root or shoot environments and concentrations weremonitored in waters and sediments. A technique was developedfor the direct quantitative analysis of metals in small (0.02–0.2mg) segments of water plant tissue, using the graphite rod attachmentto an atomic absorption spectrophotometer. Experimental resultsindicated minimal translocation of lead, but extensive acropetaltranslocation of copper to particular sites of accumulation.     

Involvement of calcium ion in the stimulated shoot elongation of arrowhead tubers under anaerobic conditions

Shoot elongation of arrowhead (Sagittaria pygmaea Miq.) tubers was stimulated in anaerobic conditions. The anaerobic elongation was attributed to stimulation of cell elongation in the middle of the shoots. The anaerobic elongation of the shoots was severely inhibited by ethylene glycol bis(beta-aminoethylether)-N,N,N',N'-tetraacetic acid (EGTA). The EGTA inhibition was completely nullified by exogenous CaCl2, which acts as an enhancer of anaerobic elongation. Moreover, calcium channel blockers, verapamil, diltiazem and LaCl3, inhibited the anaerobic elongation enhanced by CaCl2. These results showed that calcium plays an important role in stimulating the elongation in anaerobic conditions. Incorporation of 45Ca into the shoot tissues was measured to determine the involvement of calcium uptake in anaerobic elongation. Incorporation of 45Ca into the cell sap, which was collected from frozen and thawed shoots after thorough washing with LaCl3, was significantly stimulated in anaerobic conditions. Verapamil and diltiazem prevented the stimulation of 45Ca incorporation in anaerobic conditions. These results suggest that calcium uptake from the medium serves to enhance shoot elongation of arrowhead tubers under anaerobic conditions.     

Growth dynamics of Potamogeton pectinatus L. in Lake Burullus,Egypt: a modelling approach

In this study, we used a macrophyte model to describe the growth production and the interaction between above‐ and below‐ground organs of Potamogeton pectinatus in Lake Burullus, Egypt. Above‐ and below‐ground biomass of P. pectinatus was sampled on a monthly basis from April to December 2011 at three sites of Lake Burullus. Shoots started to grow in April, reached the maximum biomass in September and then rapidly decreased in October when they moved into the senescence stage. Tubers biomass reduced in August due to the upward translocation to shoots, but sharply increased to the maximum in October by downward translocation from shoots and roots. Potamogeton pectinatus allocated approximately 82.3% of its total biomass to shoots, 15.5% to tubers and 2.2% to roots.     

Cryopreservation of Shoot Tips of Tetraploid Potato (Solanum tuberosumL.) Clones by Vitrification

In vitro-grown shoot tips of five tetraploid potato (SolanumtuberosumL.) clones were cryopreserved by vitrification. Excisedshoot tips (0.5–0.7 mm) were pre-cultured on filter paperdiscs over half strength liquid Murashige and Skoog (MS) mediumsupplemented with 8.7 µMGA₃and different combinationsof sucrose (0.3, 0.5 and 0.7M) plus mannitol (0, 0.2 and 0.4M)for 2 d under a 16 h photoperiod at 24 °C. The pre-culturedshoot tips were either successively loaded with 20 and 60% PVS2 solutions or directly exposed to concentrated vitrificationsolution before physical vitrification during liquid nitrogentreatment. The vitrified shoot tips were warmed rapidly andtreated with dilution mixture (MS+1.2Msucrose) for 30 min beforeplating on regrowth medium. Addition of mannitol to the pre-culturemedium improved survival of vitrified shoot tips. Direct dehydrationof pre-cultured shoot tips with concentrated PVS 2 was detrimentalto survival of vitrified shoot tips. Shoot tips pre-culturedon medium containing 0.3Msucrose plus 0.2Mmannitol, and loadedwith 20% PVS 2 for 30 min followed by 15 min incubation in 60%PVS 2 and 5 min incubation in 100% PVS 2 at 0 °C resultedin up to 54% survival after vitrification. About 50% of vitrifiedand warmed shoot tips formed shoots directly. Post-thaw culturingof vitrified shoot tips on medium containing an elevated levelof sucrose (0.2M) under diffuse light for the first week enhancedthe survival rate. Continuous culturing of vitrified shoot tipson high-sucrose medium induced multiple shoot formation.Copyright1998 Annals of Botany Company Solanum tuberosumL., potato, cryopreservation, germplasm conservation,in vitroconservation, meristems, shoot tips, tissue culture, vitrification.     

Some Effects of Low-velocity Currents on the Metabolism of Aquatic Macrophytes

A prototype apparatus for making determinations of oxygen exchangesunder controlled conditions of water flow is briefly describedand some problems of technique are discussed in detail. Theresults include determinations of the photosynthesis and respirationof Ranunculus pseudofluitans and Potamogeton pectinatus in naturalwaters at velocities between 0.02 and 0.5 cm/sec, and some examinationof effects of changes in irradiance and oxygen concentration.Flow was laminar at all velocities. At low velocities photosynthesisincreased rapidly with velocity, but the rate of increase becameless at higher velocities. The size of the effects varied withthe metabolic capacity of the plant. For healthy shoots of R.pseudofluitans the maximum rate of photosynthesis was six timesthe probable static rate. These velocities are smaller thanthose in open water in streams, or even in the littoral of lakes,but may be comparable with the velocities within weed-beds.     

Modulated Degradation of Ribulose Bisphosphate Carboxylase in Leaves on Top-Pruned Shoots of the Mulberry Tree (Morus alba L.)

Yamashita, T. 1987. Modulated degradation of ribulose ftisphosphatecarboxylase in leaves on top-pruned shoots of the mulberry tree(Morus alba L.).—J. exp. Bot. 38: 1957–1964. The effects of pruning shoot tops on the synthesis and degradationof ribulose 1,5–Wsphosphate carboxylase (RuBPCase) inleaves on remaining shoots were investigated in mulberry trees.Leucine labelled with ¹⁴C was fed to leaf discs from field-grownmulberry trees and ¹⁴C incorporation into RuBPCase was examined.Proportion of ¹⁴C in RuBPCase to leucine–¹⁴C absorbedby leaf discs was remarkably lowered by top-pruning, thoughoccasionally a slight increase was observed soon after pruning.Yet RuBPCase content in leaves on top-pruned shoots became progressivelyhigher than that in leaves on intact shoots. Changes in ¹⁴Cin Ru1BPCase in leaves of mulberry saplings previously fed ¹⁴CO₂were followed. Following ¹⁴CO₂ feeding, the attainment of themaximal level of ₁₄C in RuBPCase was retarded by top-pruning.The highest level of ₁₄C in RuBPCase was maintained in leaveson top-pruned shoots but decreased in leaves on intact shoots.Specific radioactivity in RuBPCase continued to increase inleaves on top-pruned shoots even after attaining a maximum levelin the control leaves. These facts suggest that the increasein RuBPCase by top-pruning results from a cessation of its degradationfor the remobilization of nitrogen for newly developing leaveson shoot tops. Key words: RuBP carboxylase, shoot pruning, mulberry (Morus alba)     

Growth and energy status of arrowhead tubers,pondweed turions and rice seedlings under anoxic conditions

The responses of two aquatic plants, arrowhead (Sagittaria pygmaea Miq.) and pondweed (Potamogeton distinctus A. Benn), to anoxia were compared with those of rice (Oryza sativa L.). Shoot elongation of arrowhead tubers was enhanced at around 1 kPa O₂, whereas that of pondweed turions was slight in air and reached a maximum in the absence of O₂. Anaerobic enhancement of alcohol dehydrogenase (ADH) activity took place in rice coleoptiles but not in arrowhead and pondweed shoots. Shoots of both arrowhead and pondweed maintained a more stable energy status than did the rice coleoptile under anaerobic conditions. Total adenylate nucleotide contents of arrowhead and pondweed shoots were constant under anaerobic conditions. Adenylate energy charge in both shoots remained at a high and stable level of more than 0·8 for at least 8 d. Three forms of ADH from arrowhead shoots were separated by starch gel electrophoresis, showing that the activity of each ADH form was different under aerobic and anaerobic conditions. The incorporation of ³⁵S-labelled Cys and Met into soluble proteins in arrowhead shoots showed active protein biosynthesis and an involvement of a special set of polypeptides in the anaerobiosis.     

Antagonistic and Synergistic Interactions between Ancymidol and Gibberellins in Shoot Growth of Cucumber (Cucumis sativus L. )

Effects of the plant growth retardant, ancymidol, on the growthand morphology of the shoot system of cucumber (Cucumis sativusL. ) were investigated. Ancymidol inhibited stem elongation,reducing both number and length of internodes. Reduction inleaf area, attributable to a reduction in both cell size andnumber, was accompanied by an increase in chlorophyll per unitarea. The retardant decreased apical dominance and delayed anthesis.Gibberellic acid fully reversed ancymidol-induced inhibitionof stem elongation, internode length and production, and leafexpansion. GA_4/7 and ancymidol gave a synergistic promotionof stem elongation by increasing elongation of younger internodesand increasing internode production. Synergistic promotion ofpetiole elongation by this combination was also observed. Ancymidol,applied 7 d previously either to the shoot or root, severelyreduced the level of gibberellin-like activity in bleeding sapcollected from decapitated plants.     

Effects of Gibberellin on Shoot Development in the dgt Mutant of Tomato

The morphological effects of gibberellin A₃ (GA₃) on the dgtmutant of tomato were investigated. The mutant effectively showedthe normal range of responses, including a promotion of stemlength due to an increased number of longer internodes, a dramaticincrease in apical dominance, and effects on leaf shape andcolour. In the case of stem elongation, the quantitative responseof the mutant was greater than normal. The morphological abnormalitiescharacteristic of the dgt mutant, such as horizontal growth,a thin stem and hyponastic leaves, were not normalized by GA₃. It is concluded that the demonstrated lack of response to auxinof the dgt mutant does not impair its gibberellin responses. Tomato, gibberellin, auxin, mutant, shoot development     

The Combined Effects of Salinity and Root Anoxia on Growth and Net Na+ and K+-accumulation in Zea mays Grown in Solution Culture

The effects of excess salinity and oxygen deficiency on growthand solute relations in Zea mays L. cv. Pioneer 3906 were examinedin greenhouse experiments. The roots of plants 14 d old growingin nutrient solution containing additions of NaCl in the range1.0–200 mol m^–3 were either exposed to a severedeficiency of O₂ by bubbling with nitrogen gas (N₂ treatment),or maintained with a supply of air (controls), for a periodof 1–7 d. The threshold NaCl concentration resulting inappreciable inhibition of leaf extension, and shoot f. wt gainin controls was between 10 and 25 mol m^–3. At 25 mol m^–3NaCl the ratio of Na+/K+ transported to shoots was about 20times greater than in plants in 1.0 mol m^–3 NaCl. Theeffect of addition of NaCl to the nutrient solution was to enhanceNa+ movement but simultaneously depress the rate of K+ transportto shoots (per g f. wt roots). Interactions between NaCl levels and aeration treatment wereshown by analyses of variance to be statistically significantfor leaf extension, shoot and root f. wt gains, Na+ and K+ concentrationsin shoots and roots. When roots were N₂-treated, shoot and rootgrowth were depressed, the effect of aeration treatment beinggreatest at NaCl concentrations of 50 mol m^–3 or less.Additionally, N₂-treatment greatly accelerated Na- transportto shoots while depressing K+ transport still further, so thatat 10 mol m^–3 NaCl the ratio Na+/K+ acquired by the shootswas 230 times greater than in controls. Over the concentrationrange 1.0 to 50 mol m^–3 NaCl, the ratio Na+/K+ transportedto shoots by anoxic roots increased by a factor of 860. Mechanisms controlling changes in solute flux to the shoot,and the significance in relation to plant tolerance of excesssalts or oxygen deficiency are discussed. Anaerobic, corn, flooding, maize, oxygen-deficiency, salinity     

Anaerobic promotion of stem extension in Potamogeton pectinatus. Roles for carbon dioxide, acidification and hormones

Dark-grown shoots of tubers of the aquatic monocot Potamogön pectinatus L. elongated more strongly in anaerobic than aerobic solutions over 5 days. The response was located in the stem rather than the leaf. Anaerobic carbon dioxide (CO₂) production was similar to that in aerobic conditions. Approximately half the anaerobic stem extension was attributed to acidification of the submerging medium by respiratory CO₂. Sparging with an anaerobic gas mixture of nitrogen and hydrogen to remove dissolved CO₂ inhibited stem elongation and prevented acidification of the medium. Similarly, supplying CO₂ anaerobically promoted stem elongation while acidifying the medium. Carbon dioxide was also active on aerobic shoots. The effect of CO₂ on anaerobic stem extension could be mimicked with an acidic buffer. Anaerobic stem extension was inhibited by exogenous abscisic acid (ABA), while gibberellic acid and the gibberellin-biosynthesis inhibitor paclobutrazol proved inactive. Exogenous indole-3-acetic acid promoted stem extension in the absence of oxygen. A strong gravitropic response by anaerobic stems of P. pectinatus was inhibited by the auxin-efflux inhibitor naphthylphthalamic acid.     

Zinc Mobility in Wheat: Uptake and Distribution of Zinc Applied to Leaves or Roots

Little is known about transport of Zn from leaves to other plantorgans. The present study tested a range of Zn forms appliedfoliarly for their suitability to provide adequate Zn nutritionto wheat (Triticum aestivum L.). Transport of⁶⁵Zn applied eitherto leaves or to one side of the root system was also studied.Inorganic (ZnO, ZnSO₄) and chelated sources of Zn (ZnEDTA, glycine-chelatedBiomin Zn) applied foliarly provided sufficient Zn for vigorousgrowth. Zinc concentrations in roots and shoots were in thesufficiency range, except in the -Zn control. Foliar treatmentswith ZnSO₄and chelated Zn forms resulted in shoot Zn concentrationsin 7-week-old plants being about two-fold greater than thosein plants supplied with Zn in the root environment or via foliarspray of ZnO. Adding surfactant to foliar sprays containingchelated forms of Zn did not cause negative growth effects,but surfactant added to ZnO or ZnSO₄foliar sprays decreasedshoot growth. Adding urea to the ZnO foliar spray had no effecton shoot growth. Foliarly-applied⁶⁵Zn was translocated to leavesabove and below the treated leaf as well as to the root tips.Stem girdling confirmed that⁶⁵Zn transport toward lower leavesand roots was via the phloem. Split-root experiments showedintensive accumulation of⁶⁵Zn in the stem and transport to allleaves as well as to the root tips in the non-labelled sideof the root system. Foliar application of Zn in inorganic ororganic form is equally suitable for providing adequate Zn nutritionto wheat. Phloem transport of Zn from leaves to roots was demonstrated.Copyright 2001 Annals of Botany Company Foliar spraying, phloem, surfactant, urea, xylem, wheat, zinc     

The Role of Roots in Control of Bean Shoot Growth

Restriction of root growth by growing bean plants (Phaseolusvulgaris L.) in very small pots led to the development of dwarfplants. The leaves of those plants were smaller and their internodesshorter than those of control plants which were grown in largerpots and had developed a more extensive root system. A largequantity of starch—much more than in control plants —accumulated in the leaves and shoots of the dwarf plants. Increasingthe amount of minerals which was supplied to the roots, enhancedleaf growth of the control plants but failed to affect the dwarfones, in spite of the fact that in both cases the treatmentincreased the content of N, P and K in all the plant organs.The leaf water content was similar in both treatments, but theleaf water potential was higher in the dwarf plants. Exogenousapplication of gibberellic acid (GA₃) to the dwarf plants overcamethe reduction of stem growth completely, and that of the leavespartially. Application of the cytokinin, benzyladenine (BA)did not affect stem growth, but increased that of the primaryleaves. A combined supply of GA₂ + BA restored completely thegrowth of the stem and the primary leaves, and partially thatof the trifoliate leaves. It is concluded that a limited rootsystem restricts shoot growth through an hormonal system inwhich at least gibberellins and cytokinins are involved, andthat the dwarfing is not a consequence of mineral or assimilatedeficiency, or due to water stress. Phaseolus vulgaris L., leaf growth, stem growth, root restriction, gibberellic acid, benzyladenine, cytokinin     

Differences in Architecture and Shoot Growth during Stagnant and Extension Growth Phases of Acanthopanax sciadophylloides(Araliaceae)

The shoot growth of a deciduous tree, Acanthopanax sciadophylloidesFranch. et Savat. shows inter-annual intermittent repetitionof two distinctive phases, a stagnant growth phase (S-phase)and vigorous extension-growth (E-phase). To help understandthe differentiation mechanism, shoot development was studiedover time in both shoot phases. S-phase and E-phase shoots weredistinguished from each other by morphological traits: S-phaseshoots are characterized by higher allocation to leaves anda shorter period of stem growth, while E-phase shoots show continuousstem extension over the growing season. Specific leaf area didnot differ between the two phases. This shoot differentiationwas similar to the morphological differentiation of shoots betweenlong vs. short shoots found in some temperate trees. Leavesof both phases were well-dispersed through adjustment of petiolelength and leaf-blade size to reduce mutual shading within ashoot. Stem-wood density of current-year shoots was lower inE-phase compared with S-phase shoots. Leaves produced earlyin the season affected the growth phase of the following year.These results suggest that annual shoot differentiation of A.sciadophylloides was determined during the previous season andreflects leaf productivity in a given habitat during that growingseason. Copyright 2001 Annals of Botany Company Acanthopanax sciadophylloides, Araliaceae, biomass allocation, intermittent shoot growth, leaf display, shoot architecture, shoot differentiation     

Short-Term Fixation of 14Carbon by the Submerged Aquatic Angiosperm Potamogeton pectinatus

In ¹⁴C fixation experiments, 3-phosphoglyceric acid was thefirst product of carbon assimilation in the light in Potamogetonpectinatus. The pattern of early ¹⁴C-labelled compounds wasthe same over a range of pH values of the medium from 3.5 to8.1. Rates of ¹⁴C incorporation declined with increasing pHof the medium indicating that free CO₂ is the major exogenoussource of carbon for photosynthesis in Potamogeton pectinatus.     

A Quantitative Analysis of the Uptake of Carbon and of the Supply of 14C-labelled Assimilates to Areas of Meristematic Growth in Lolium temulentum

A quantitative analysis of the ¹⁴C-labelled assimilate suppliedby leaves on the main shoot to terminal meristem, stem, tillers,and roots was conducted during parallel periods of reproductiveand vegetative development in Lolium temulentum. The initial rate of entry of carbon into the shoot varied withthe area and photosynthetic efficiency of the assimilating leaf.Subsequently, respiratory losses of carbon during translocationand incorporation of assimilate at the site of utilization alsovaried. The combined effect of these differences resulted inthe supply of recently assimilated carbon being twofold greaterin reproductive shoots than in vegetative shoots, while withinshoots the carbon supply of the youngest fully expanded leafranged from four-or five-fold greater than the oldest leaf inyoung shoots, to two-or three-fold greater in older shoots.In both reproductive and vegetative shoots, the two or threeyoungest leaves thus dominated the supply of carbon for meristematicgrowth. Meristematic tissue in expanding leaves and leaf primordia atthe terminal meristem of the vegetative shoot received 18–27per cent of the total shoot carbon. This meristem utilized aboutthe same proportion of shoot carbon when it developed into aninflorescence, indicating no major change in the level of meristematicactivity. The proportion of shoot carbon utilized in stem growthincreased as both reproductive and vegetative shoots aged; thisincreased meristematic activity in stem internodes was accompaniedby reduced export of carbon to roots, which received less than10 per cent of the shoot carbon when the experiments ended.The main shoot translocated 20–30 per cent of its recentlyassimilated carbon to developing and rooted tillers, which assinks for carbon were thus as important as the terminal meristemand stem. This outward flow of carbon continued relatively uncheckedwhen donor and receptor shoots developed inflorescences.     

Growth and Survival Responses of Rumex Species to Flooded and Submerged Conditions: The Importance of Shoot Elongation, Underwater Photosynthesis and Reserve Carbohydrates

Plants of Rumex thyrsiflorus Fingerh., R. crispus L. and R.maritimus L., which are zoned along a gradient of elevationin a river foreland ecosystem, and differ in their flood-tolerance,were subjected to different flooding levels. Under conditionsof soil flooding, the growth rates of the flood-tolerant R.crispus and R. maritimus were as high as under drained conditions,but that of the flood-intolerant R. thyrsiflorus was halved.Upon submergence, the low elevation species R. maritimus showedrapid shoot elongation; when elongation resulted in a protrusionof leaves above the water surface, the plants survived. Alternatively,underwater photosynthesis also led to a 100% survival of submergedR. maritimus plants, provided that enough inorganic carbon wasmade available in the water. This could be attributed in partto the use of photosynthetically-derived oxygen for root respiration;in a hydroculture experiment, with 5.0 mM CO₂ in the water inthe shoot environment, photosynthetically-derived oxygen contributedmore than 50% to root oxygen consumption at low oxygen concentrationsin the root environment. The intermediately elevated species R. crispus appeared to bemuch more tolerant towards conditions of prolonged total submergence:older plants survived eight weeks submergence in the dark. Thisresponse was explicable in terms of a dormancy-strategy, whichis characterized by a slow consumption of carbohydrates storedin the tap-root. The differential responses of R. maritimusand R. crispus to total submergence reveal the limitations offlood-tolerance and reflect the different life-histories ofthe species. Key words: Photosynthesis, Rumex, submergence, carbohydrates, growth rate, shoot elongation     

Root Water Uptake, Leaf Water Storage and Gas Exchange of a Desert Succulent: Implications for Root System Redundancy

A technique used for hydroponics was adapted to measure instantaneousroot water uptake from the soil for a leaf succulent CAM species,Agave deserti. Comparisons were made to previously modelledwater fluxes for A. deserti and to Encelia farinosa, a non-succulentC₃species. Net CO₂uptake and transpiration forA. deserti underwell-watered conditions occurred primarily at night whereasroot water uptake was relatively constant over 24 h. Leaf thicknessdecreased when transpiration commenced and then increased whenrecharge from the stem and soil occurred, consistent with previousmodels. A drought of 90 d eliminated net CO₂uptake and transpirationand reduced the water content of leaves by 62%. Rewetting theentire root system for 7 d led to a full recovery of leaf waterstorage but only 56% of maximal net CO₂uptake. Root water uptakewas maximal immediately after rewetting, which replenished rootwater content, and decreased to a steady rate by 14 d. Whenonly the distal 50% of the root system was rewetted, the timefor net CO₂uptake and leaf water storage to recover increased,but by 30 d gas exchange and leaf water storage were similarto 100% rewetting. Rewetting 10 or 20% of the root system resultedin much less water uptake; these plants did not recover leafwater storage or gas exchange by 30 d after rewetting. A redundancyin the root system of A. deserti apparently exists for dailywater uptake requirements under wet conditions but the entireroot system is required for rapid recovery from drought.Copyright1999 Annals of Botany Company Agave deserti Engelm., desert, drought, gas exchange, rewetting, roots, succulent, water uptake.     

Some Effects of Daylength, Temperature and Exogenous Growth Regulator Application on the Growth of Actinidia chinensis Planch

The growth responses of Actinidia chinensis raised from cuttingswere compared in 8 h short days (SD) and 16 h long days (LD)at 15, 20 and 25 °C, as well as under varying day and nighttemperatures The data obtained reveal effects on stem elongation,apparent plastochrons, leaf area and shape, as well as dry matteraccumulation and water contents of different plant parts Theseinvestigations were supplemented by studies on the effects ofapplied GA₃ and ethephon Alternating day/night temperatures(thermoperiodicity) increased leaf area and d wt accumulationin LD Effects on sugar and starch contents, are described anddiscussed Unexpected effects such as very high petiole watercontents and their continuous growth, increased twisting ofthe climbing stem in SD and other findings are also reportedand discussed Actinidia chinensis, Kiwi fruit, gibberellic acid, ethephon, temperature, photoperiod, themoperiodicity