Clifford E. Lamotte

Plant regeneration in vitro from primary leaf nodes of soybean (Glycine max) seedlings.

Summary A simple and reproducible protocol for regeneration of soybean plants from explants derived from 7-day-old seedlings has been developed.Explants, each consisting of the primary leaf node (the unifoliate leaf node), the cotyledonary node, the internode between them, and one cotyledon, were cultured in vitro on a modified Murashige and Skoog (MS) agar medium containing 3% sucrose, four times the MS inorganic micronutrient level, the vitamins of B 5 medium, 2g L -1 L-proline,2mgL -1 N 6 -benzyladenine (BA), and 0.02mgL -1 α-naphthalene acetic acid (NAA) to induce the formation of adventitious shoots at the primary leaf node.In inducing shoot formation, this medium was superior to MS and B5 media even when all were supplemented with the same BA, NAA and proline levels.Explants from seedlings of the cultivar Peking produced an average of ca.20 shoots per explant after 4–5 weeks on this medium.Shoot formation was greater when a cotyledon remained attached to the explant.Shoot formation was also influenced by medium composition, explant orientation, age of donor seedling, and cultivar.Exogenous cytokinin (BA) was essential for shoot formation; proline and the fourfold-raised level of MS inorganic micronutrients caused a large increase in shoot number.

Abscisic acid is present in liverworts

Abstract Gametophytes of the liverwort Marchantia polymorpha contain both abscisic acid and 2- trans -abscisic acid in a 1.2: 1 ratio. Abscisic acid is present in concentrations similar to those in higher plants. Indole-3-acetic acid was also detected. This is the first chemical demonstration that ABA and its 2- trans -isomer occur in the Hepatophyta.

Synergistic Effects of Proline and Inorganic Micronutrients and Effects of Individual Micronutrients on Soybean (Glycine max) Shoot Regeneration In Vitro

Summary We reported earlier that adding 2g·L -1 L-proline and raising fourfold the level of inorganic micronutrients in a modified Murashige and Skoog (MS) medium enhances shoot regeneration from primary-leafnode explants of 7-d-old soybean ( Glycine max [L.] Merr.) seedlings. These findings are here extended to regeneration from explants consisting of a cotyledon cut from a 7-d-old soybean seedling. For both kinds of explant, a synergistic, approximately threefold stimulation of shoot regeneration by these two supplements in combination is documented. Proline increased number but decreased length of regenerated shoots, whereas raising micronutrient level generally increased both shoot number and length and, thus, partly overcame the effect of proline on length. Examining the effects of singly including, omitting, raising the levels of, and lowering the levels of the seven different micronutrient elements of the original MS medium provides evidence that the supply of cobalt is near-optimal at the original MS concentration but the other six elements are in less than optimal supply. Altering the zinc supply had the strongest effects overall.

Quantitative relationship between indole-3-acetic acid and abscisic acid during leaf growth in Coleus blumei

Quantitative determinations by gas chromatography-mass spectrometry ofindole-3-acetic acid (IAA) and abscisic acid (ABA) in growing leaves ofColeusblumei plants show parallel declines in leaf concentrations of bothhormones,except in leaf number 3 (about three-fourths of full size) where IAA level wasthe lowest of those measured. Expansion of the most recently unfurled leaf tofull size serves, in effect, to dilute both IAA and ABA about 1.7 to 1.Althoughabsolute levels of leaf IAA varied as much as an order of magnitude from onebatch of plants to another, ABA levels were proportional to the IAA level withan overall correlation coefficient of 0.91. Evidence, both correlative andcausal, for the determination of ABA status by IAA—and of IAA status byABA—in leaves and other developing organs is summarized.

Identification of the cytokinins in red pine seedlings

Zeatin-9-riboside was identified in shoots and roots of Pinus resinosa by GC-MS analysis of its permethyl derivative. Based on their chromatographic properties on Sephadex LH-20 and C18 HPLC, and their susceptibility to enzymatic degradation, several other cytokinins have been tentatively identified. The basic fraction of both the roots and shoots contained zeatin, whereas the shoots contained dihydrozeatin-O-glucoside and the roots contained zeatin-O-glucoside. Zeatin-9-riboside monophosphate, isopentenyladenosine monophosphate ([9R-5′P]iP) and glucosyl phosphate derivatives were detected in the acidic fractions from both roots and shoots. There were equivalent amounts of [9R-5′P]iP in both roots and shoots. The presence of equivalent amounts of [9R-5′P]iP in both the roots and shots suggests that cytokinin biosynthesis may be occurring in both locations.

Definitive identification of indole-3-acetic acid and abscisic acid in shoots of Coleus blumei by gas chromatography-mass spectrometry

Mass spectra provide definitive identification of indole-3-acetic acid and abscisic acid in shoots of Coleus blumei, a species used for studying the hormone control of plant development since the early 1930s.

Effects of photoperiod, light intensity, and stage of development on flower initiation in Sagittaria graminea Michx. (Alismataceae)

Heterophyllous plants of Sagittaria graminea Michx. do not normally flower until non-phyllodial leaves have emerged from the water. Effects of photoperiod, light intensity, and excision of non-phyllodial leaves on growth and flower initiation by plants developing from submerged seedlings were tested in controlled environments. Light quality and irradiance were measured as function of water depth. Plants flowered at all tested daylengths (7–15 hours per day). In light of high irradiance (ca. 3000 μW cm−2 at soil surface) plants without emergent leaves (i.e. bearing only phyllodia) flowered when grown in shallow water (5 cm). When grown in deeper water (17.5 cm), they flowered only after leaves had emerged. A low irradiance (ca. 600 μW cm−2) sufficed for leaf emergence and flower formation at this depth; higher irradiances resulted in faster growth and earlier flowering. An hypothesis involving phytochrome is presented to explain the depth-dependence of the morphogenetic sequence.

Comparison of Cytokinin-habituated and Normal Callus Strains of Psychotria punctata (Rubiaceae)

Summary During routine subculture of Psychotria punctata stem callus, white nodular protuberances develop occasionally on the normal, cream-colored callus. Such variant callus has been isolated on three occasions, subcultured, and compared with the original strain. Unlike the cytokinin-requiring original strain, the variant callus is cytokinin-habituated, unpigmented, and has never formed roots. It grows more rapidly and for longer duration on the normal medium, and has higher relative water content than the original strain. It exhibits an unusual longevity in response to high IAA concentration even though neither strain requires auxin for growth in vitro.