Auxin-stimulated ethylene production in fern gametophytes and sporophytes

The auxins indole-3-acetic acid (IAA) and 2,4-dichlorophenoxyacetic acid (2,4-D) stimulated ethylene production from gametophytes of the fern Pteridium aquilinum (L.) Kuhn. var. latiusculum (Desv) underw. ex Heller and sporophytes of the ferns Matteuccia struthiopteris (L.)Todaro and Polystichum munitum (Kaulf.) Presl. Treatment with Co²⁺ or l -α -(2-aminoethoxyvinyl)-glycine (AVG) eleminated or significantly reduced the stimulatory effects of IAA. Treatment with 1-aminocyclopropane-1-carboxylic acid (ACC) resulted in significantly greater rates of ethylene production from all tissues tested. Based on their response to auxin, ACC, AVG and Co²⁺, the ethylene biosynthetic pathway in these three lower vascular plants appears similar to that existing in angiosperms.     

The influence of aggregate size and drannage potential on germination of barley seeds in flooded soil

Emergence and growth of barley was severely decreased by short periods (less than 24 hours) of pre-emergence waterlogging at 20°C. The extent of damage depended on a combination of duration of waterlogging, soil water potential and aggregate size. Potentials of less than—4kPa prevented loss of plants developing in aggregates of less than 2 mm diameter after a transitory period of waterlogging although some shoot and root damage occurred. By comparison seeds growing in soil consisting of aggregates greater than 2 mm in diameter were not damaged by transitory waterlogging even when drainage only occurred at−0.8kPa. The severity of damage increased with the period of waterlogging. A criterion obtained as the product of mean size grade and water potential gave a single value (−4NM⁻¹) below which emergence was satisfactory. Waterlogging halfway through germination gave more severe damage than near sowing date or near emergence.     

Plant-water relations in wheat as influenced by root pruning

Summary A greenhouse study in which 24, 54 and 71 per cent roots of wheat (Triticum aestivum L.) were pruned on the 73rd day from the date of planting (anthesis stage) showed that during a 7-day period following root pruning, total transpiration and leaf water potential were significantly lower (P=0.05) and the stomatal resistance was significantly higher (P=0.05) where 54 and 71 per cent roots were pruned, as compared to no root pruning or 24 per cent root pruning. The leaf relative water content, however, showed no significant differences. Thus about one-fourth root sytem could be reduced without adversely affecting the plant-water status.     

Induction and floral determination in the terminal bud of Nicotiana tabacum L. cv. Maryland Mammoth,a short-day plant

Floral determination in the terminal bud of the short-day plant Nicotiana tabacum cv. Maryland Mammoth has been investigated. Plants grown continuously in short days flowered after producing 31.4±1.6 (SD) nodes while plants grown continuously in long days did not flower and produced 172.5±9.5 nodes after one year. At various ages, expressed as number of leaves that were at least 1.0 cm in length above the most basal 10-cm leaf, one of three treatments was performed on plants grown from seed in short days: 1) whole plants were shifted from short days to long days, 2) the terminal bud was removed and then rooted and grown in long days, and 3) the terminal bud was removed and then rooted and grown in short days. Whole plants flowered only when shifted from short days to long days at age 15 or later. Only rooted terminal buds from plants at age 15 or older produced plants that flowered when grown in long days. Only terminal buds from plants at age 15 or older that were rooted and grown in short days produced the same number of nodes as they would have produced in their original locations while buds from younger plants produced more nodes than they would have in their original locations. Thus, determination for floral development in the terminal bud, as assayed by rooting, is simultaneous with the commitment to flowering as assayed by shifting whole plants to non-inductive conditions.Abbreviations LD long day(s) - SD short day(s) - DN dayneutral     

Basic peroxidases in isolated vacuoles of nicotiana tabacum L.

Vacuoles of tobacco mesophyll and of suspension-cultured cells were isolated in order to study the localization of peroxidase isoenzymes. Only basic peroxidases were detectable by electrophoretic separation of the vacuolar sap. Some of the basic peroxidases have formerly been described as an ionically bound cell-wall fraction. This fraction, however, was found to be an artifact produced by incomplete cell breakage. Reinvestigation of isolated cell walls confirmed that mainly acidic peroxidases are localized in the cell walls where they move freely or are bound. As a consequence of former and present results we think it probable that all of the peroxidase isoenzymes are secretory proteins because they have to be transported from the sites of synthesis in the cytoplasm to the sites of function, the extracytoplasmic spaces, cell wall (acidic peroxidases), and vacuole (basic peroxidases).Abbreviation ER endoplasmic reticulum - PAGE polyacrylamide gel electrophoresis     

Calculation of leaf photosynthetic parameters from light-response curves for ecophysiological applications

Measurement of the light response of photosynthetic CO₂ uptake is often used as an implement in ecophysiological studies. A method is described to calculate photosynthetic parameters, such as the maximum rate of whole electron transport and dissimilative respiration in the light, from the light response of CO₂ uptake. Examples of the light-response curves of flag leaves and ears of wheat (Triticum aestivum cv. ARKAS) are shown.Abbreviations and symbols A net photosynthesis rate - D ¹ rate of dissimilative respiration occurring in the light - f loss factor - I incident PPFD - I effective absorbed PPFD - J rate of whole electron transport - J _m maximum rate of whole electron transport - p ^c intercellular CO₂ partial pressure - PPFD photosynthetic photon flux density - q effectivity factor for the use of light (electrons/quanta) - absorption coefficient - I ^* CO₂ compensation point in the absence of dissimilative respiration (bar) - II conversion factor for calculation of CO₂ uptake from the rate of whole electron transport - convexity factor Gas-exchange rates relate to the projective area and are given in mol·m^-2·s^-1. Electron-transport rates are given in mol electrons·m^-2·s^-1; PPFD is given in mol quanta·m^-2·s^-1.     

Identification of somatic hybrids in plant protoplast fusions with monoclonal antibodies to plasma-membrane antigens

Monoclonal antibodies generated by immunization with a plasma-membrane preparation from suspension-cultured cells of Nicotiana glutinosa L. were used in combination with fluoresceinor rhodamine-labeled goat anti-mouse immunoglobulins to identify heterokaryons in protoplast fusion procedures. Antibody labeling did not inhibit callus formation nor plantlet regeneration. The antibodies are non-invasive and surface labeling provides clear optical discrimination of true heterokaryons from unfused aggregates as well as from parental protoplasts and homokaryons. Labeling is stable throughout fusion and hence by pre-labeling parental protoplast populations the strategy is both versatile and of general applicability.     

Spinach ferredoxin is a calcium-binding protein

Spinach-leaf ferredoxin was identified as a calcium-binding protein by ⁴⁵Ca autoradiography on nitrocellulose membranes and with the cationic carbocyanine dye 1-ethyl-2-[3-(1-ethylnaphtho[1,2-d]thiazolin-2-ylidene)-2-methylpropenyl] naphtho[1,2-d]thiazolium bromide (stains-all). Binding of ⁴⁵Ca was observed at pH 6.8 and pH 7.8 and in the presence of 5 mM and 20 mM MgCl₂. At the higher MgCl₂ concentration the Ca²⁺-binding capacity is reduced. Only micromolar concentrations of LaCl₃, however, are required to achieve a similar effect. Both the oxidized and reduced forms of ferredoxin bind calcium.Abbreviations PAGE polyacrylamide gel electrophoresis - SDS sodium dodecyl sulfate - stains-all 1-ethyl-2-[3-(1-ethylnaphtho[1,2-d]thiazolin-2-ylidene)-2-methylpropenyl] naptho[1,2-d]thiazolium bromide     

Expression of the β-subunit of β-conglycinin in seeds of transgenic plants

Soybean (Glycine max (L.) Merr.) seeds contain the storage protein -conglycinin, encoded by a multigene family. -Conglycinin consists of three subunits; , , and . A genomic clone for a -subunit of -conglycinin has been characterized by restriction-enzyme mapping and hybrid selected in-vitro translation followed by immunoprecipitation. In order to determine the developmental regulation of this -subunit gene, its expression was studied in seeds of transgenic petunia (Petunia hybrida) and tobacco (Nicotiana tabacum L.) plants. The -subunit expressed in seeds of petunia and tobacco was recognized by anti--conglycinin serum at a relative molecular mass of 53 000, equivalent to that of the native protein. Separation of the petunia-seed proteins by isoelectric focusing followed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and immunoblot analysis showed that multiple isoelectric forms of the -subunit were produced. There was approximately a twofold variation in the accumulation of the -subunit protein in the mature seeds of transgenic petunia plants, each containing a single -subunit gene. However, the level of protein accumulation in mature seeds and the amount of -subunit mRNA in developing seeds was not correlated. Accumulation of the -subunit protein in transgenic seeds was less than the -subunit protein that accumulated in transgenic petunia seeds containing a single -subunit gene and less than the amount of the -subunit in mature soybean seeds which contain 8–13 -subunit genes. In transgenic tobacco plants, the accumulation of the -subunit protein in seeds was generally well correlated with the number of genes that were incorporated in the different transformants.Abbreviations kb kilobase - kDa kilodalton - M_r relative molecular mass - SDS-PAGE sodium dodecyl sulfate polyacrylamide gel electrophoresis