The effects of resource availability and environmental conditions on genetic rankings for carbon isotope discrimination during growth in tomato and rice.

Carbon isotope discrimination (Δ) is frequently used as an index of leaf intercellular CO concentration (c) and variation in photosynthetic water use efficiency. In this study, the stability of Δ was evaluated in greenhouse-grown tomato and rice with respect to variable growth conditions including temperature, nutrient availability, soil flooding (in rice), irradiance, and root constriction in small soil volumes. Δ exhibited several characteristics indicative of contrasting set-point behaviour among genotypes of both crops.

A baculovirus enhancin alters the permeability of a mucosal midgut peritrophic matrix from lepidopteran larvae.

The peritrophic matrix (PM) in lepidopterous larvae may function as a defensive barrier against ingested viral pathogens. PMs isolated from Trichoplusia ni and Pseudaletia unipuncta larvae, were treated with a baculovirus-encoded metalloprotease (enhancin) from Trichoplusia ni granulosis virus (TnGV) and their in vitro permeability to blue dextran and fluorescent-labelled Autographa californica nuclear polyhedrosis virus (AcMNPV) was determined using a dual chamber permeability apparatus. Incubation of T.

Estimating water use by sugar maple trees: considerations when using heat-pulse methods in trees with deep functional sapwood.

Accurate estimates of sapwood properties (including radial depth of functional xylem and wood water content) are critical when using the heat pulse velocity (HPV) technique to estimate tree water use. Errors in estimating the volumetric water content (V(h)) of the sapwood, especially in tree species with a large proportion of sapwood, can cause significant errors in the calculations ofsap velocity and sap flow through tree boles. Scaling to the whole-stand level greatly inflates these errors.

Study of tobacco transformants to assess the role of chloroplastic NAD(P)H dehydrogenase in photoprotection of photosystems I and II.

Nicotiana tabacum L. wild-type plants and transformants (DeltandhCKJ), deficient in functional NAD(P)H dehydrogenase (NDH), were subjected to high light at 20 degrees C and 4 degrees C for 2 h to examine a possible role of NDH-mediated cyclic electron flow in protecting photosystems I and II from photoinhibition. Photochemical activity of photosystem I (PSI) was assessed by means of P700 absorbance changes at 810 nm.

BIOSYNTHESIS OF ASCORBIC ACID IN PLANTS: A Renaissance.

The structure of the familiar antioxidant L-ascorbic acid (vitamin C) was described in 1933 yet remarkably, its biosynthesis in plants remained elusive until only recently. It became clear from radioisotopic labeling studies in the 1950s that plant ascorbic acid biosynthesis does not proceed in toto via a route similar to that in mammals. The description in 1996 of an Arabidopsis thaliana mutant deficient in ascorbic acid prompted renewed research effort in this area, and subsequently in 1998 a new pathway was discovered that is backed by strong biochemical and molecular genetic evidence.

A nucleus-encoded suppressor defines a new factor which can promote petD mRNA stability in the chloroplast of Chlamydomonas reinhardtii.

Mutations in the Chlamydomonas reinhardtii nuclear gene MCD1 specifically destabilize the chloroplast petD mRNA, which encodes subunit IV of the cytochrome b6/f complex. The MCD1 gene product is thought to interact with the mRNA 5' end to protect it from degradation by a 5' --> 3' exoribonuclease and may also have a role in translation initiation. Here we report the isolation and characterization of a semidominant, allele-specific, nucleus-encoded suppressor of the mcd1-2 mutation.

Identification of ascorbic acid-deficient Arabidopsis thaliana mutants.

Vitamin C (l-ascorbic acid) is a potent antioxidant and cellular reductant present at millimolar concentrations in plants. This small molecule has roles in the reduction of prosthetic metal ions, cell wall expansion, cell division, and in the detoxification of reactive oxygen generated by photosynthesis and adverse environmental conditions. However, unlike in animals, the biosynthesis of ascorbic acid (AsA) in plants is only beginning to be unraveled.

Transgenic Plants Created for Oral Immunization Against Diarrheal Diseases.

We have created transgenic plants that express subunit antigens of infectious bacteria and viruses. These proteins have been isolated and characterized to demonstrate that they retain immunogenic properties. When raw potatoes containing the recombinant immunogens were fed to mice, the animals were orally immunized.

petD mRNA maturation in Chlamydomonas reinhardtii chloroplasts: role of 5' endonucleolytic processing.

Complex processing of primary transcripts occurs during the expression of higher-plant chloroplast genes. In Chlamydomonas reinhardtii, most chloroplast genes appear to possess their own promoters, rather than being transcribed as part of multicistronic operons. By generating specific deletion mutants, we show that petD, which encodes subunit IV of the cytochrome b6/f complex, has an RNA processing site that is required for accumulation of monocistronic petD mRNA in petD promoter deletion mutants; in such mutants, transcription of petD originates from the upstream petA promoter.

The petD gene is transcribed by functionally redundant promoters in Chlamydomonas reinhardtii chloroplasts.

FUD6, a nonphotosynthetic mutant of Chlamydomonas reinhardtii, was previously found to be deficient in the synthesis of subunit IV of the cytochrome b6/f complex, the chloroplast petD gene product (C. Lemaire, J. Girard-Bascou, F.

Isoforms of the cuticle-degrading Pr1 proteinase and production of a metalloproteinase by Metarhizium anisopliae.

The entomopathogenic fungus, Metarhizium anisopliae, produces three distinct types of proteinases during growth on cockroach cuticle. These were separated by analytical isoelectric focusing and characterized according to their substrate specificity and inhibition patterns as Pr1 subtilisin-like proteinases (four isoforms pI range approximately 9.3-10.

Influence of ozone air pollution on plant-herbivore interactions. Part 2: Effects of ozone on feeding preference, growth and consumption rates of monarch butterflies (Danaus plexippus).

Effects of ozone fumigation of Asclepias curassavica L. and A. syriaca L.

Responses of plants to simulated saline drift as affected by species and conditions of exposure.

In exposures to simulated saline drift generated from a 0.6% (w/w) chloride (Cl)-solution, under controlled environmental conditions, the median effective doses for the occurrence of any salt-induced foliar injury (expressed as microgCl cm(-2) deposited in six hours) were: 2.9 for Canada hemlock (Tsuga canadensis [L.

Influence of ozone air pollution on plant-herbivore interactions. Part 1: Biochemical changes in ornamental milkweed (Asclepias curassavica L.; asclepiadaceae) induced by ozone.

A series of fumigation experiments was conducted with bloodflower (Asclepias curassavica L.) in continuous-flow stirred reactors (CSTRs) to elucidate the effects of ozone on foliar concentrations of several primary and secondary plant metabolites relevant to herbivores. Plants 8 weeks of age were subjected to different ozone levels ranging from 0 to 134 nl liter(-1) for exposure periods up to 16 days.

Effects of airborne saline particles on vegetation in relation to variables of exposure and other factors.

Saline particles are a heterogeneous group of chloride(Cl)-containing airborne materials of natural as well as anthropogenic origins. They are usually a local problem of air pollution in terms of source and dispersion, but within these areas their effects on agricultural, ornamental or natural species of plants can be of substantial practical concern. These effects include the accumulation of Cl, the production of foliar lesions, and changes in the plant's levels of mineral nutrients and metabolites, physiological processes, and growth and reproduction.

Design and performance of an acidic precipitation delivery system for field investigations with plants.

An acidic precipitation delivery system is described that was designed and constructed for use in a field investigation of the response of red spruce saplings (Picea rubens Sarg.) to the interactive stresses of ozone and acid rain. The system utilizes hydraulic, solid-cone spray nozzles to produce simulated rainfall with droplet size distributions approximating natural rain events, which are of low intensity, i.

Alteration of a lepidopteran peritrophic membrane by baculoviruses and enhancement of viral infectivity.

The peritrophic membrane (PM), which lines the midgut of many insect species, has several functions. In particular, it may serve as a mechanical barrier to invading microorganisms. The protein composition of the PM from healthy and baculovirus-treated Trichoplusia ni (cabbage looper) larvae was analyzed by polyacrylamide gel electrophoresis.

Flash-Induced Delayed Light Emission Patterns of Red Kidney Bean Leaves: Evidence of a New Component Dependent upon Tissue Integrity.

Studies of flash-induced delayed light emission profiles of dark-adapted intact plant tissues revealed a previously unreported component of plant luminescence. Only partially evident in intact chloroplasts and totally absent in broken chloroplasts, this peak may reflect the interaction of one or more light-activated enzyme systems with photosynthetic electron transport.

Isolation and characterization of nodulation genes from Bradyrhizobium sp. (Vigna) strain IRc 78.

An 11.76-kilobase-pair (kb) segment of DNA from Bradyrhizobium sp. (Vigna) strain IRc 78 that hybridizes to nodulation genes of Rhizobium meliloti strain 41 was isolated.

A light-enhanced metabolism of sulfite in cells of Cucumis sativus L. cotyledons.

The effects of light and several photosynthetic inhibitors on the rate of sulfite metabolism in cells obtained from Cucumis sativus L. cotyledons was studied. The cells were treated with 200 μM Na2SO3 and the disappearance of sulfite was monitored using either dithiobisnitrobenzoic acid or fuchsin.

Phytoluminographic detection of dynamic variations in leaf gaseous conductivity.

Gas exchange and plant luminescence (delayed light emission) of a single red kidney bean leaf undergoing synchronous oscillations in gas exchange were recorded and analyzed. Introduction of 1.1 microliter per liter SO(2) during these oscillations produced increases in plant luminescence that, when averaged over a portion of the leaf, oscillated in phase with the gas exchange oscillations.

Inositol and sugars in adaptation of tomato to salt.

Tomato (Lycopersicon esculentum Mill. cv New Yorker) plants subjected to 100 millimolar NaCl plus Hoagland nutrients exhibited a pattern of wilting, recovery of turgor, and finally recovery of growth at a reduced level, which required 3 days. During the nongrowing, adaptation phase there were immediate increases in free hexoses and sucrose which declined to near control levels as growth resumed.

Imbibitional chilling injury in pollen: involvement of the respiratory chain.

Chilling injury is sustained by dry pollen of Typha latifolia L. upon hydration in germination medium at 0 degrees C. This injury is evidenced as poor germination, low vigor, and depressed respiration.

Gas Exchange and Phytoluminography of Single Red Kidney Bean Leaves during Periods of Induced Stomatal Oscillations: A Demonstration of an Integrated, Spatially Resolving Physiometric Technique.

This report examines the capabilities of a new approach to the study of gas exchange and electron transport properties of single, intact leaves. The method combines conventional aspects of analysis with an image intensification system that records the spatial distribution of delayed light emission (DLE) over single leaf surfaces. The combined system was used to investigate physiological perturbations induced by exposure of single leaves of Phaseolus vulgaris cv ;California Light Red' to a combination of SO(2) (0.

Heterotrophic n(2) fixation and distribution of newly fixed nitrogen in a rice-flooded soil system.

Rice (Oryza sativa L.) plants growing in pots of flooded soil were exposed to a (15)N(2)-enriched atmosphere for 3 to 13 days in a gas-tight chamber. The floodwater and soil surface were shaded with a black cloth to reduce the activity of phototrophic N(2)-fixing micro-organisms.