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Mung bean cuttings were dipped in solutions of wild type and mutant forms of the plant growth-promoting rhizobacterium Pseudomonas putida GR12-2 and then incubated for several days until roots formed. The bacteria P. putida GR12-2 and P. putida GR12-2/aux1 mutant do not produce detectable levels of the enzyme 1-aminocyclopropane-1-carboxylate (ACC) deaminase, whereas P. putida GR12-2/acd36 is an ACC deaminase minus mutant. All bacteria produce the phytohormone indole-3-acetic acid (IAA), and P. putida GR12-2/aux1 overproduces it. Treatment of cuttings with the above-mentioned bacteria affected the rates of ethylene production in the cuttings in a way that can be explained by the combined effects of the activity of ACC deaminase localized in the bacteria and bacterial produced IAA. P. putida GR12-2 and P. putida GR12-2/acd36-treated cuttings had a significantly higher number of roots compared with cuttings rooted in water. In addition, the wild type influenced the development of longer roots. P. putida GR12-2/aux1 stimulated the highest rates of ethylene production but did not influence the number of roots. These results are consistent with the notion that ethylene is involved in the initiation and elongation of adventitious roots in mung bean cuttings.

Leafless cut Superstar roses (Rosa hyb.) were kept in a 1% sucrose solution. During the first few days of treatment, the abscisic acid content and the water deficit in the petals was higher in treated flowers than in controls kept in water. Later and up (3,7,10). Sucrose is the main transport form of the products of photosynthesis. When flowers are cut, they are severed from their sucrose supply and this no doubt is one of the reasons for imperfect development and the shorter life span of the cut flower (17). Sucrose supplied exogenously, promotes normal development of the cut flower, lengthens its life span, diminishes the change in petal color, and reduces proteolytic breakdown (1,3,16 flower stems were graded to a uniform length of 40 cm and before placing in 500-ml vases containing the treatment solutions, all leaves were removed from the stem. The flowers were kept under controlled conditions of 20 t 1 C, 55 t 10% relative humidity, and continuous illumination from cool white fluorescent light at a light energy flux density of 650 MAw/cm2. The base of the flower stalk was recut every other day and the solutions in the vases was brought up to a volume of 500 ml. The environment was not changed in experiments involving water stress, but flowers were removed from the solutions for specified periods of times (Fig. 3, Table I). At the end of the stress treatment the stems were recut. Some of the flowers which had been subjected to water stress conditions for 4 hr were given a recovery treatment. This consisted of wrapping the flower bud with wet blotting paper after the flower had been returned to its vase containing the treatment solution. This treatment raised the humidity around the flower to 90 to 100%. All treatment solutions contained 300 ,ug/ml A12(SO4)3 16 H20 to prevent development of bacteria.Extraction and Determination of ABA in Petals. Extraction, separation, and identification methods were adapted from those described in previous reports (10,15,18,19). Details of certain changes follow. Extraction and Purification. Each sample consisted of all the petals from five flowers. Samples were weighed (12 to 30 g fresh weight) and blended in 80% methanol (10 ml/g) for 2 min in a Waring Blendor. The resulting suspension was shaken for 18 hr at 4 C in the dark. After filtering, the solids were further extracted by shaking in the dark for 1 hr at 4 C with 3 ml/g 100% methanol. The combined methanol fractions were evaporated down to the aqueous phase at 38 C under vacuum. After centrifugation for 20 min at 500g, the supernatant was brought to pH 8.3 with NH40H and washed three times with methylene chloride (v/v) which was then discarded. After acidifying the aqueous phase to pH 3 with HCI, it was washed six times with methylene chloride (v/v), after which the aqueous phase was discarded. The methylene chloride fraction was evaporated to dryness at 38 C under vacuum.Preparative TLC. Samples were dissolved in 1 ml methylene chloride and these were loaded as a band on glass plates (20 x 20 cm) coated w...

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