The effect of plant water deficit on ethylene production by intact plants was tested in three species, beans (Phaseolus vulgaris L.), cotton (Gossypium hirsutum L.) and miniature rose (Rosa hybrida L., cv Bluesette). Compressed air was passed through glass, plant-containing cuvettes, ethylene collected on chilled columns, and subsequently assayed by gas chromatography. The usual result was that low water potential did not promote ethylene production. When plants were subjected to cessation of irrigation, ethylene production decreased on a per plant or dry weight basis of calculation. No significant promotion of ethylene production above control levels was detected when water deficit-treated bean or cotton plants were rewatered. The one exception to this was for cotton subjected to a range of water deficits, plants subjected to deficits of -1.4 to -1.6 MPa exhibited a transient increase of ethylene production of 40 to 50% above control levels at 24 or 48 hours. Ethylene was collected from intact leaves while plants developed a water deficit stress of -2.9 megapascals after rewatering, and no significant promotion of ethylene production was detected. The shoots of fruited, flowering cotton plants produced less ethylene when subjected to cessation of irrigation. In contrast, the ability of bench drying of detached leaves to increase ethylene production several-fold was verified for both beans and cotton. The data indicate that detached leaves react differently to rapid drying than intact plants react to drying of the soil with regard to ethylene production. This result suggests the need for additional attention to ethylene as a complicating factor in experiments employing excised plant parts and the need to verify the relevance of shock stresses in model systems.interest because the ethylene could be responsible for senescence and abscission induced by water deficits (13,25,26).Although the promotion of ethylene synthesis by water deficits appears firmly established, there are a number of concerns. First, to have a convenient experimental system, water deficits have often been imposed rapidly by drying detached leaves or fruits (3-6, 16, 18, 24, 31). In contrast, under natural drought the soil water is depleted slowly and plants progress through a series of drying cycles during which #w3 falls during the day and rises at night as plants recover due to reduced evaporative demand (30). Second, the experimental measurement of ethylene has usually required that detached plant parts be concentrated in a sealed container from which air samples are withdrawn and analyzed for ethylene. The air supply in these containers has often been static which is of some concern because oxygen is needed for the conversion of ACC to ethylene (2) and CO2 can either promote or reduce the production of ethylene (33). Finally, there are a few reports in the literature where investigators failed to observe a promotion of ethylene release with water deficit treatment of intact plants (6,9,13,19).With the development of flowing air sys...

The ipt gene of Agrobacterium tumefaciens T-DNA encodes an isopentenyltransferase which causes cytokinin overproduction and developmental alterations in transformed plants. A chimaeric gene constructed by positioning the ipt coding region under the control of the hsp70 gene from Drosophila melanogaster allows heat-regulated expression in transgenic plant tissue. Heat-shock treatment of tobacco calli transgenic for the chimaeric hsipt gene increases the endogenous cytokinin concentration and enables these calli to grow on cytokinin-free medium. Transgenic plants regenerated from calli transformed with the hsipt gene and grown at normal temperature are phenotypically normal.

Eight-day-old dark-grown bean leaves were greened by prolonged irradiation with far red light. Growth, chlorophyll content, oxygen-evolving capacity, photophosphorylation capacity, chloroplast structure (by electron microscopy), and in vivo forms of chlorophyll (by low temperature absorption and derivative spectroscopy on intact leaves) were followed during the greening process. Chlorophyll a accumulated slowly but continuously during the 7 days of the experiment (each day consisted of 12 hours of far red light and 12 hours of darkness). Chlorophyll b was not detected until the 5th day. The capacity for oxygen evolution and photophosphorylation began at about the 2nd day. Electron microscopy showed little formation of grana during the 7 days but rather unfused stacks of primary thylakoids. The thylakoids would fuse to give grana if the leaves were placed subsequently in white light.The low temperature spectroscopy of intact leaves showed that the chlorophyll a was differentiated into three forms with absorption maxima near 670, 677, and 683 nanometers at -196 C during the first few hours and that these forms accumulated throughout the greening process. Small amounts of two longer wavelength forms with maxima near 690 and 698 nanometers appeared at about the same time as photosynthetic activity.The development of etiolated tissue of higher plants in the light involves phototransformations of both phytochrome and protochlorophyll. Phytochrome controls a number of developmental processes from the synthesis of specific proteins (14) to the gross morphological characteristics such as leaf expansion (15). The development of photosynthetically active plastids, however, requires the phototransformation of protochlorophyll and the accumulation of chlorophyll. Even though both pigment systems play decisive roles in directing the development of the plant, there appears to be little interaction between the two systems with the exception that the rate of protochlorophyll synthesis after the initial transformation is influenced by phytochrome (16). Long before the discovery of phytochrome as the photomorphogenic pigment (5) of California, San Diego, La Jolla, California 92037 sources of different spectral quality and red and blue sources of low intensity, that protochlorophyll and chlorophyll did not participate in the photomorphogenic growth responses.Phytochrome in dark-grown seedlings is entirely in the Pr' form (3). It was shown, however, that a low level of Pfr is established as a photostationary state by far red light (because of the long wavelength absorption tail of Pr), and it was suggested that the photomorphogenic responses obtained with prolonged far red irradiation were due to the maintenance of the low level of Pfr over a long period of time (in darkness Pfr reverts to Pr) (3). Mohr and his co-workers (13) have shown in a number of cases that prolonged irradiation with far red light activates the phytochrome system. Hicker (9) illuminated etiolated mustard seedlings with continuous far red light (740 nm ...

The composition and characteristics of b-type cytochromes from higher plant plasma membranes, purified using aqueous two-phase partitioning, were investigated. At least three different cytochromes were identified by their wavelength maxima and redox midpoint potentials (Eo'). Cytochrome b-560.7 (Eo' from +110 to +160 millivolts) was present in zucchini (Cucurbita pepo) hypocotyls and bean (Phaseolus vulgaris L.) hooks, although in different concentrations. The main component in cauliflower (Brassica oleracea L.) inflorescences (cytochrome b-558.8) is probably functionally similar to this cytochrome. The plasma membrane generally contains two to three cytochrome species. However, the occurrence and concentrations were species dependent. The high potential cytochrome can be reduced by ascorbate but not NADH, and may be involved in blue light perception.

Abstract— Kalanchoë blossfeldiana seeds are light‐requiring for seed germination. On water or KNO3 solution and irradiated with several daily red (R) irradiations, the seeds show a low‐fluence (LF) response which is far‐red (FR) reversible. Incubated on gibberellic acid (GA3) the seeds show a very‐low‐fluence (VLF) response which can be saturated with red as well as with far red light. As germination is a quantal response, the sub‐optimal segments of the dose‐response curves are analysed by means of probit analysis in order to calculate the seed population parameters. There is a linear relation between the probit of the germination response and the logarithm of the fluence. Moreover, the slope for the VLF as well as for the LF response is the same. The VLF requires about 8 × 104 times less fluence than the LF. VLF saturation with FR requires about 200 times more fluence than with R. Although, GA3 and KNO3 modulate VLF and LF, respectively, there is no direct influence on the phytochrome‐phototransformations. Once Pfr is formed (in VLF or LF, or preserved in dry seeds) germination is proportional to the GAS concentration (for VLF and dark germination) or proportional to the KNO, concentration (for LF). The non‐photochemical events leading to germination seem to be triggered by a similar action mechanism for both GA, and KNO3.