No abstract

Maxie and Crane (37) pointed out that "Before CMH can be established as a growth regulator in figs, it must be verified that production of the gas is correlated with the onset of renewed growth (Period III)." Evidence indicating the existence of such a correlation is presented here. MATERIALS AND METHODSCurves of growth in diameter were developed for both firstand second-crop fruits and were used for reference in timing of ethylene treatment and in fruit sampling. Diameters of 10 basal-most fruits on each of five 10-year-old trees were measured periodically with a vernier caliper. Sampling of treated fruits as well as controls was confined to the basalmost fruits. Average fresh and dry weights were determined by weighing triplicate five-fruit samples before and after drying at 60 C until weights remained constant.Ethylene (5 1ul/l in an air mixture) was applied to fruitbearing branches in the orchard. For this purpose, a 1900-liter tank was evaculated, a predetermined volume of ethylene gas was injected, and the tank was compressed to the appropriate pressure (about 110 kg/ cm2). Whole branches were enclosed in large polyethylene bags provided with an inlet and an outlet, and ethylene was introduced into them through Tygon tubing at the rate of 100 ml/min, as regulated by a flow meter (8). Other branches that were similarly treated with compressed air served as controls.Rate of respiration at different stages of fruit development was monitored using triplicate fruit samples, each consisting of 200 to 300 g. The samples were placed in 4-liter glass jars, the lids of which were tight and provided with two glass tubes that served as inlets and outlets. Respiration rate, measured as mg C02/kg fruit hr, was determined by the colorimetric method of Claypool and Keefer (8). The fruits were kept at 20 C, and the first measurement was made 24 hr after harvest, followed by daily measurement for the following 6 days.Changes were monitored in the concentration of endogenous C2H4, CO2, and 02 in the internal atmosphere of the fruits during development and following treatment. The gases were extracted from the fruits by the vacuum method described by Maxie et al. (38). Their concentrations were determined by gas chromatography (31,38).

An inhibitor of seed germination was isolated from the integuments of Lovell peach seeds. Evidence from chromatographic analysis, from studies of its absorption of ultraviolet light and from assays on its effects on plant growth, indicate that the inhibitor is, if not identical with, dormin. Termination of rest in peach seeds is correlated with the disappearance of the inhibitor. The effects of the inhibitor are antagonistic to those of gibberellic acid on sections of wheat coleoptiles.

Development of both floral and vegetative buds was inhibited by application of gibberellin to branches of Prunus species. The development of the lateral meristem was blocked, in general, through inhibition of mitosis, while, concurrently, the growth of certain other plant organs was stimulated in some cases. That higher dosages were required to block vegetattive than floral bud growth suggests that gibberellin also exerts the more specific effect of inhibiting floral initiation.

The biosynthesis of Mg protoporphyrin monoester, protochlorophyll and chlorophyll a and b by crude homogenates, isolated etioplasts, and differentiating chloroplasts has recently been described by . In the present communication we wish to report briefly on the capacity of subchloroplastic fractions to form free porphyrins and metal porphyrins. MATERIALS AND METHODSCucumber seeds (Cucumis sativus L. cv. Alpha Green) were germinated in vermiculite (Terra Lite) at 24 C in complete darkness for 4 days (7,8). Cotyledons were harvested with full hypocotyl hook as previously described (2). They were placed in beakers with enough distilled H20 to keep them moist and were irradiated with white fluorescent light for 4 hr (8). De The reaction was stopped by the addition of 15.0 ml of acetone:0.1 N NH4OH (9:1 v/v) and centrifuged at 39,000g for 10 min. The pellet was saved for the extraction of free porphyrins and the acetone: NH4OH supernatant containing metal porphyrins and free porphyrins was extracted with an equal volume of hexane. The hexane extracted most of the ,8-carotene and chlorophyll. The metal porphyrins remaining in the hexane-extracted acetone: NH4OH supernatant were transferred to ether as previously described (6). The proteinaceous pellet and the aqueous acetone phase that was left after metal porphyrins extraction were pooled and used for the extraction of free porphyrins as described previously (6).Free porphyrins were separated by ascending paper chromatography on Whatman No. 3 MM paper in 2,6-lutidine:0.05 N NH4OH (5:3.5 v/v). Metal porphyrins, in ether, were separated on thin layers of Silica Gel H in benzene-ethyl acetateethanol (8:2:2 v/v). All fractions were routinely monitored by their absorption spectra and recorded with a Beckman double beam spectrophotometer Model DK-2A. All absorbancies used in quantitative determinations were derived from the appropriate spectra.The amount of uroporphyrin in acidified, saturated sodium acetate (pH 2.5) was estimated from absorbancy at 402 nm using the molar extinction coefficient (5.41 X 106) and the correction factors reported by Rimington and Sveinsson (10) for uroporphyrin in 0.5 N HCI.The copro + protoporphyrin fraction in ether containing mostly coproporphyrin was estimated from its absorbancy at 401 nm and a molar extinction coefficient of 1.8 X 105 (6). When protoporphyrin was predominant in this fraction, its absorbancy at 404 nm and a molar extinction coefficient of 1.5 X 105 were used instead (6).