Replicating Arabidopsis Model Leaf Surfaces for Phyllosphere Microbiology

Artificial surfaces are commonly used in place of leaves in phyllosphere microbiology to study microbial behaviour on plant leaf surfaces. These surfaces enable a reductionist approach to be undertaken, to enable individual environmental factors influencing microorganisms to be studied. Commonly used artificial surfaces include nutrient agar, isolated leaf cuticles, and reconstituted leaf waxes. Recently, replica surfaces mimicking the complex topography of leaf surfaces for phyllosphere microbiology studies are appearing in literature. Replica leaf surfaces have been produced in agar, epoxy, polystyrene, and polydimethylsiloxane (PDMS). However, none of these protocols are suitable for replicating fragile leaves such as of the model plant Arabidopsis thaliana. This is of importance, as A. thaliana is a model system for molecular plant genetics, molecular plant biology, and microbial ecology. To overcome this limitation, we introduce a versatile replication protocol for replicating fragile leaf surfaces into PDMS. Here we demonstrate the capacity of our replication process using optical microscopy, atomic force microscopy (AFM), and contact angle measurements to compare living and PDMS replica A. thaliana leaf surfaces. To highlight the use of our replica leaf surfaces for phyllosphere microbiology, we visualise bacteria on the replica leaf surfaces in comparison to living leaf surfaces.

Replicating Arabidopsis Model Leaf Surfaces for Phyllosphere Microbiology

Artificial surfaces are commonly used in place of leaves in phyllosphere microbiology to study microbial behaviour on plant leaf surfaces. Studies looking into individual environmental factors influencing microorganisms are routinely carried out using artificial surfaces. Commonly used artificial surfaces include nutrient agar, isolated leaf cuticles, and reconstituted leaf waxes. However, interest is growing in using microstructured surfaces mimicking the complex topography of leaf surfaces for phyllosphere microbiology. As such replica leaf surfaces, produced by microfabrication, are appearing in literature. Replica leaf surfaces have been produced in agar, epoxy, polystyrene, and polydimethylsiloxane (PDMS). However, these protocols are not suitable for replicating fragile leaves such as of the model plant Arabidopsis thaliana. This is of importance as A. thaliana is a model system for molecular plant genetics, molecular plant biology, and microbial ecology. Here we present a versatile replication protocol for replicating fragile leaf surfaces into PDMS. We display the capacity of our replication process using optical microscopy, atomic force microscopy (AFM), and contact angle measurements to compare living and PDMS replica A. thaliana leaf surfaces. To highlight the use of our replica leaf surfaces for phyllosphere microbiology, we visualised bacteria on the replica leaf surfaces in comparison to living leaf surfaces.

Englerodothis kilimandscharica. [Descriptions of Fungi and Bacteria].

A description is provided for Englerodothis kilimandscharica. Information is included on the disease caused by the organism, its transmission, geographical distribution, and hosts. DISEASE: Parasitic on living leaf blades and petioles, and inflorescences. HOSTS: Mayepea gilgiana (Oleaceae). GEOGRAPHICAL DISTRIBUTION: AFRICA: Tanzania (Kilimanjaro). TRANSMISSION: Presumably by air-borne ascospores.

Effect of plant moisture stress and application surface on uptake and translocation of triclopyr with organosilicone surfactant in red maple seedlings

This study investigated the effect of plant moisture stress and surface of application on the absorption, translocation, and "rainfastness" (short-term ability to retain herbicide) of organosilicone-adjuvated (adjuvant added) [14C]triclopyr amine on greenhouse-grown, 4-month-old red maple (Acerrubrum L.) seedlings. Xylem water potentials were −1.6 and −0.9 MPa and leaf conductances were 0.07 and 0.13 cm s−1 for the stressed and control seedlings, respectively. At 2 h, rainfastness was 13% less for stressed seedlings. Uptake increased with time, and by 72 h no effect of moisture stress treatment was apparent. Abaxial absorption into living leaf tissue was 57% greater at 72 h than was adaxial absorption, but application surface did not significantly affect translocation. Plant moisture stress did, however, reduce translocation of herbicide into the shoots and roots. Organosilicone surfactants may enhance long-term triclopyr uptake in water-stressed seedlings, but do not appear to facilitate translocation in stressed seedlings. Plant moisture status, therefore, should continue to be a concern when scheduling herbicide applications.

Foliar Sprays for Insect Control in Tomatoes, 1993

Tomatoes were transplanted on 23 Jul at the Eastern Shore Agricultural Experiment Station, Painter, VA. Each plot consisted of a 25 ft. row, bordered on each side by an untreated guard row, and replicated 4 times in a randomized, complete block design. Spacing was 5 ft. between rows. Sprays were applied weekly beginning 20 Aug through 23 Sep using a 3 nozzle hollow cone boom backpack sprayer delivering 45 gal water/acre at 40 psi. Evaluation criteria consisted of counts of new or living leaf mines present on five marked plants/plot on the dates indicated in the table, and number of marketable fruit from the same five plants harvested on 8 and 22 Sep.

Effect of sodium chloride on leaf succulence and area of Atriplex hastata L.

The effect of NaCl in water cultures on morphology and histology are studied with A. hastata, a semisucculent halophyte with a mesomorphic leaf structure. NaCl is shown to extend the ontogeny of the living leaf, and to produce an accelerated rate of leaf thickening, which has its main emphasis in the extended ontogenetic period. The most rapid thickening rate occurred when a high salt concentration (0.6 m) was applied to only part of the root system, so as not to impede a rapid general growth rate in the plant. Maximum leaf areas occurred in 0.1m NaCl cultures, minimum areas in 0.6 m. Epidermal cell areas in a 0. m treatment were double those of the treatment devoid of NaCl and those in the 0.6 m treatment. Numbers of epidermal cells per leaf decreased progressively with increasing concentrations of NaCl. The salt-induced thickening rate is looked upon as a process superimposed on a rather similar light and moisture-sensitive process. Differences in timing between salt effects on leaf area and succulence are explained by differential vacuolation of epidermis and palisade tissue. The high-salt cultures (0.4–0.6 m, which greatly reduced growth, apparently did not reduce turgor pressures necessary for succulence. It is considered that the data required to explain differences noted in epidermal cell size are relationships between their rates of expansion and the rates of maturation of structural limiting factors.

The photosynthesis of naturally occurring compounds.—III. Photosynthesis in vivo and in vitro

The evidence adduced in the two preceding communications leads to the belief that the direct photosynthesis of complex carbohydrates in a single operation from carbonic acid has now been achieved in the laboratory. There still remains, however, the question as to how far the results take us in the explanation of the natural process as it occurs in the living leaf. It must be admitted that the natural process has ever presented many difficulties, and in view of the foregoing results the problem of its explanation is one of peculiar interest. In the first place, we may refer to the difficulty arising from the complete absence of ordinary formaldehyde in the living leaf. The elegant work of Willstätter, proving that the molecular ratio of the carbon dioxide assimilated and the oxygen transpired is unity, offers a very definite proof that the first product in the photosynthesis is formaldehyde, and, in consequence, the fact of its entire absence from the leaf during photoassimilation of carbon dioxide was very difficult to understand. This difficulty has been completely eliminated by our results. Theoretical considerations based on the formation of activated carbonic acid as the initial stage in the process lead to the view that activated formaldehyde is then produced, which at once undergoes polymerisation to give the hexoses. De-activated or ordinary formaldehyde should not, therefore, take part in the reaction and, in consequence, should not be found at any stage. These theoretical deductions have been proved to be correct, since in the photosynthetic production of carbohydrates in vitro the complete absence of ordinary formaldehyde has been proved. So far as this fact is concerned there is agreement between the laboratory and living processes.