Greenhouse-grown Bean Research Articles

Frequency, Size, and Localization of Bacterial Aggregates on Bean Leaf Surfaces

Using epifluorescence microscopy and image analysis, we have quantitatively described the frequency, size, and spatial distribution of bacterial aggregates on leaf surfaces of greenhouse-grown bean plants inoculated with the plant-pathogenic bacterium Pseudomonas syringae pv. syringae strain B728a. Bacterial cells were not randomly distributed on the leaf surface but occurred in a wide range of cluster sizes, ranging from single cells to over 10(4) cells per aggregate. The average cluster size increased through time, and aggregates were more numerous and larger when plants were maintained under conditions of high relative humidity levels than under dry conditions. The large majority of aggregates observed were small (less than 100 cells), and aggregate sizes exhibited a strong right-hand-skewed frequency distribution. While large aggregates are not frequent on a given leaf, they often accounted for the majority of cells present. We observed that up to 50% of cells present on a leaf were located in aggregates containing 10(3) cells or more. Aggregates were associated with several different anatomical features of the leaf surface but not with stomates. Aggregates were preferentially associated with glandular trichomes and veins. The biological and ecological significance of aggregate formation by epiphytic bacteria is discussed.

A passive two-band sensor of sunlight-excited plant fluorescence

We have designed and built a passive remote sensor of sunlight-excited chlorophyll fluorescence (U.S. Patent No. 5,567,947, Oct. 22, 1996) which provides for the real-time, in situ sensing of photosynthetic activity in plants. This sensor, which operates as a Fraunhofer line discriminator, detects light at the cores of the lines comprising the atmospheric oxygen A and B bands, centered at 762 and 688 nm, respectively. These bands also correspond to wavelengths in the far-red and red chlorophyll fluorescence bands. The sensor is based on an induced fluorescence approach; as light collected from fluorescing plants is passed through a low-pressure cell containing oxygen, the oxygen absorbs the energy and subsequently reemits photons which are then detected by a photomultiplier tube. Since the oxygen in the cell absorbs light at the same wavelengths that have been strongly absorbed by the oxygen in the atmosphere, the response to incident sunlight is minimal. This mode of measurement is limited to target plants sufficiently close in range that the plants’ fluorescence is not itself appreciably absorbed by atmospheric oxygen (∼200 m). In vivo measurements of fluorescence in the 760 and 690 nm bands of vegetation in full sunlight are also presented. Measurements of plant fluorescence at the single-plant canopy level were obtained from greenhouse-grown bean plants subjected to a range of nitrogen treatments. The ratio of the fluorescence obtained from the two measurement bands showed statistically significant variation with respect to nitrogen treatments.

Homobotcinolide: a biologically active natural homolog of botcinolide from Botrytis cinerea.

A novel natural product exhibiting biological activity was isolated from a strain of Botrytis cinerea that had infected raspberry fruit (Rubus ideaus). Liquid fermentation and bioassay-directed fractionation of the organism yielded a compound with molecular formula C22H38O8 that is trivially named homobotcinolide. It significantly inhibited etiolated wheat coleoptile growth. Greenhouse-grown bean, corn, and tobacco plants were also affected by exogenous application of homobotcinolide, severe chlorosis and necrosis being exhibited in corn. The compound is a polyhydroxylated nonalactone esterified with 4-hydroxy-2-decenoic acid.

Botcinolide: A Biologically Active Natural Product fromBotrytis cinerea

A novel biologically active natural product was isolated from a strain of Botrytis cinerea found on cultivated raspberry fruit (Rubus ideaus) upon fermentation in a liquid medium. Following a bioassay-directed purification process, the final product was an amorphous solid with the molecular formula C20H34O8, and is trivially named botcinolide. It significantly inhibited etiolated wheat coleoptile growth at 10−3 and 10−4 M by 100 and 82% respectively, relative to the controls. Greenhouse-grown bean, corn, and tobacco plants were affected by treating with botcinolide, and exhibited chlorosis and severe necrosis at 10−2 and 10−3 M. The structure is a new hydroxylated nonalactone that is esterified with 4-hydroxy-2-octenoic acid.

Cinereain. A novel metabolite with plant growth regulating properties from Botrytis cinerea.

Botrytis cinerea, which was isolated from the surface of stored sunflower seed, produced a novel biologically active natural product when cultured on shredded wheat medium. The metabolite, trivially named cinereain, was a ruby red crystalline product with the molecular formula C18H21N3O3 and melting point 201-203°C. The structure was unequivocally established by single crystal X-ray diffraction; UV, IR, NMR (1H and 13C) and mass spectrometry supported the crystallographic data. Cinereain significantly inhibited the growth of etiolated wheat coleoptiles (p<0.01) at 10-3 and 10-4M in bioassays. No effects were noted on treated intact greenhouse-grown bean and tobacco plants, but there was mild necrosis and chlorosis in corn.

FROST PROTECTION OF CROPS BY SPRINKLER IRRIGATION

The effectiveness of sprinkler irrigation in the Yukon Territory as a means of frost protection on peas (Pisum sativum L.), potatoes (Solanum tuberosum L.) and excised bean plants (Phaseolus vulgaris L.), and the effect of rate of applying water were investigated. Bean plants were protected from serious injury when plant temperature was maintained above −0.8 °C. Potato foliage and peas were not injured seriously when maintained above −1.1 °C. To maintain plant temperatures above −1.1 °C required 0.9 mm/hr of water when air temperature was down to −2.8 °C, 1.2 mm/hr down to −3.3 °C, 1.6 mm/hr down to −4.4 °C, 2.2 mm/hr down to −5.5 °C, and 2.9 mm/hr down to −7.2 °C. Excised, greenhouse-grown bean plants served as a useful indicator of frost injury.