Isolation, culture and plant regeneration from mesophyll protoplasts of Digitalis obscura

High yields of protoplasts were obtained from mesophyll tissue of Digitalis obscura L. Osmotic potential of the isolation medium and Ca²⁺ were important in obtaining a high viability of the preparations. In different culture techniques employed, liquid-over-agar-solidified medium was superior to liquid medium alone. Agar plating technique was ineffective. On Murashige and Skoog modified medium with casein hydrolysate and several indoleacetic acid and benzyladenine combinations, isolated protoplasts underwent sustained mitotic division and produced calli. The calli formed shoots when transferred to regeneration media. Regenerated shoots could be easily rooted and developed into whole plants on half-strength Murashige and Skoog hormone-free medium.     

Hormonal control of cambial activity and vessel differentiation in Quercus robur

Cambial activity and vessel differentiation of the Quercus robur stem were investigated in relation to concentration of growth regulators and sucrose, seasonal changes in the sensitivity of cambial cells, and axial polarity of the stem. Basipetal efflux of natural auxin was measured in the oak stem cambial region. IAA, GA₃, kinetin and sucrose affected cambial activity and/or initiation of vessel differentiation differently, depending upon concentration. Depending upon the season, kinetin increased or reduced the stimulation of cambial activity caused by IAA and GA₃, but it did not affect the differentiation of vessels. Supply of sucrose in higher concentrations reduced the number of differentiated vessels but did not decrease the stimulation of cambial divisions.Unlike stimulation of cambial activity by GA₃, auxin stimulation of cambial divisions and differentiation of vessels were highly dependent upon stem polarity, 2,3,5-triiodobenzoic acid (TIBA) inhibited formation of vessels, but not cambial activity. The oscillations in basipetal efflux of natural auxin from the cambial stem region of successive 6 mm long sections substantiate the hypothesis that the histogenesis of xylem tissue in ring-porous species is under control of the vectoriat field that is associated with oscillatory phenomena in polar auxin transport.     

A GLC procedure for determining sub-nanogram levels of indol-3-yl acetic acid

Mono-, di- and tri-chloroethyl esters of indol-3-yl-acctic acid were synthesized and analysed by a gas-liquid chromatography using an electron capture     

Physiological effects of betalains upon higher plants

Red and yellow betalains isolated from red beetroots by means of gel filtration were strong inhibitors of indole-3-acetic acid oxidase; 50% inhibition was obtained at 5 × 10^?7 M and 3 × 10^?7 M respectively. Concentrations of 10^?4 M betanin had no effect upon ATP production in mitochondria. The red pigment relieved the inhibitory effects upon wheat root elongation caused by indole-3-acetic acid but not the inhibition caused by 2,4-dichlorophenoxyacetic acid.     

Nitrate reductase activity in corn seedlings as influenced byArthrobacter sp.

Summary Nitrate reductase activity has been assayed in corn seedlings grown in a nutrient solution containing different concentrations of nitrate and inoculated withArthrobacter sp. The enzymatic activity was greatly enhanced especially at the levels of NO₃-ions suboptimal for the maximum induction. The ability of synthetic phytohormones (IAA, IPA and GA₃) in inducting nitrate reductase activity has been also texted.     

Free tryptophan and indole-3-acetic acid levels in the leaves and vascular pathways of Ricinus communis L.

Levels of free tryptophan in the leaves, phloem and xylem saps of Ricinus communis L. were determined by colorimetric assay. Values of 0.38 g ml^-1 in root pressure sap and 96.0 g ml^-1 in phloem sap were recorded. Tryptophan levels were highest in mature and senescing leaves. Levels of indoleacetic acid (IAA) in the phloem sap and leaves were determined by gas chromatography—mass spectrometry using a deuterated internal standard. A mean value of 13.0 ng ml^-1 was recorded in phloem sap. The distribution in the leaves showed an inverse relationship to that of tryptophan, being highest in young leaves.Abbreviations IAA indoleacetic acid - GC-MS Gas chromatography-mass spectrometry - PFP-derivative pentafluoropropionyl-derivative - TLC thin layer chromatography     

Determination of 5-hydroxytryptamine metabolites in isolated perfused rabbit lung by high-performance liquid chromatography.

An analytical procedure, utilizing high-performance liquid chromatography (HPLC) hasbeen developed for the separation of radiolabeled metabolites of 5-hydroxytryptamine (5-HT) in biological fluids. Four different chromatographic systems are described, which enable the separation of groups of metabolites possessing similar organic functionality to be achieved. As an example of this general analytical method, it is demonstrated that no methylation of 5-HT occurs in perfused rabbit lung, the principal metabolites being 5-hydroxyindoleacetic acid and 5-hydroxytryptophol.     

Changes in photosynthetic rates and growth following root treatments of tomato plants with phytohormones

The effects of root applications of kinetin, gibberellic acid (GA₃) and indoleacetic acid (IAA) on photosynthesis was measured using an open infrared CO₂ gas-exchange system. There was a 30–35% increase in the photosynthetic rates (mg CO₂/dm²/hr) of attached leaves within 8 hr following root treatment with 0.47 M kinetin. On a short-term basis (up to 2 days) 0.47 M kinetin was shown to have the optimal stimulatory effect on photosynthesis, relative growth rate (RGR) and total plant dry weight. If the roots were in contact with 0.47 M kinetin for longer than two days there was severe branching of the root system and growth was severely decreased. When plants were left in contact with the kinetin treatment for up to 7 days the optimal stimulatory concentration was considerably lower (0.0047 M) . Plants receiving a 4, 8, or 12 hr pulse with 0.47 M kinetin to the roots exhibited higher leaf photosynthetic rates than the control. Plants receiving an 8 or 12 hr pulse with 0.47 M kinetin maintained photosynthetic rates higher than the control for the duration of the experiment (8 days) while the 4 hr pulse remained higher than the control for only 5 days. A sharp decrease in the photosynthetic rate, RGR and total plant dry weight was observed two days following continual treatments with 0.47 M kinetin to the roots. At low light levels there was approximately a 100% increase in the photosynthetic rate two days following treatment with 0.47 M kinetin while at a saturating irradiance there was a 30 to 35% increase. Indoleacetic acid either showed no effect on the photosynthetic rate, RGR and total plant dry weight or an inhibitory effect was observed. Either GA₃ or kinetin alone were shown to stimulate photosynthesis, RGR and total plant dry weight, however, when GA₃ at a 1.4 M concentration was applied in combination with kinetin at a 0.0047 M concentration to the roots of tomato plants there was no additive effect. In all cases kinetin dramatically reduced leaf resistance whereas GA₃ had no effect.By supplying either GA₃ or kinetin to the roots of tomato plants a highly reproducible stimulation in the photosynthetic rate, RGR and total plant dry weight can be achieved at physiologically relevant concentrations, whereas IAA appears to have an inhibitory effect.Approved for publication on July 29, 1981 as paper number 6281 in the journal series of the Pennsylvania Agricultural Experiment Station.Research Assistant and Assistant Professor, respectively.     

The effect of assimilate supply on fruit growth and hormone levels in tomato plants

Rates of dry matter accumulation and contents of starch, sugars and abscisic acid (ABA) of tomato fruits differed significantly during development at three positions (proximal, middle and distal) on a truss. Proximal fruits, which accumulated dry matter most rapidly during early development, generally had least ABA (per g DW).Partial defoliation reduced carbon accumulation by all fruits but increased ABA, especially in distal fruit, and indoleacetic acid (IAA), particularly in proximal fruits. The ABA content of leaves in partially defoliated plants was similar to that of leaves on non-defoliated plants.Removal of distal fruits on a truss enhanced carbon movement to the remaining proximal fruits and also increased their ABA content early in development but did not affect their IAA content. On the other hand, when proximal fruit were removed there was no large or lasting increased accumulation of carbon by the remaining distal fruits and they contained less ABA and IAA than fruits on plants without fruit thinning. Leaf carbon and ABA levels showed no marked trend in response to fruit thinning.The amount of carbon in the stems was increased by fruit thinning but decreased by partial defoliation.The possible roles of ABA and IAA in regulating fruit growth are discussed.Part of this work has been presented to a Symposium on Phloem loading and related processes at Bad Grund/Oberhar, W. Germany, July 1979.     

Immunocytochemical localization of indole-3-acetic acid in primary roots of Zea mays

Colloidal gold-labelled antibody was used to localize indole-3-acetic acid in caps of primary roots of Z. mays cv. Kys. Gold particles accumulated on the nucleus, vacuoles, mitochondria, and some dictyosomes and dictyosome-derived vesicles. This is the first localization of indole-3-acetic acid in dictyosomes and dictyosome-derived vesicles and indicates that dictyosomes and vesicles constitute a pathway for indole-3-acetic acid movement in and secretion from root cap cells. Our findings provide cytochemical evidence to support the hypothesis that indole-3-acetic acid plays an important role in root gravitropism.