Excised Shoot Apices Research Articles

Anatomical responses to cytokinins of abscised grapevine shoot apices cultured in vitro

Responses of excised shoot apices of V. vinifera L. cv. Chenin blanc to different cytokinin treatments were studied at various intervals (days) after the start of in vitro culture, using light and scanning electron microscopy. Results clearly indicated that in vitro produced shoots were of axillary origin. Shoot clusters were produced by the enhanced release of axillary meristems from apical dominance, due to the application of 6-benzylaminopurine (BAP) singly as well as in combination with zeatin riboside (ZR). Axillary meristems on these axillary shoots were subsequently released from apical dominance, thus giving rise to shoot clusters of high densities. Shoot clusters induced by ZR alone were less dense, probably due to an initial delay in elongation of axillary meristems nearest to the main apical meristem of the shoot. However, elongation of axillary meristems lower down the axes proceeded strongly in the presence of ZR. Application of BAP resulted in more pronounced release of axillary meristems from apical dominance than with ZR.

Crown gall transformation of lentil (Lens culinaris Medik.) with virulent strains of Agrobacterium tumefaciens

Four diverse strains of Agrobacterium tumefaciens (C58, Ach5, GV3111, and A281) were capable of inducing tumors at a high frequency on inoculated stems of lentil (Lens culinaris Medik. cultivar Laird) in vivo, and on excised shoot apices in vitro. GV3111 and Ach5 produced the largest and heaviest tumors in vivo, while A281 produced the heaviest tumors in vitro. Tumor formation and opine production are indicative of plant cell transformation and tumors produced appropriate opines: nopaline (C58), octopine (Ach5 and GV3111), and agropine and mannopine (A281). Southern analysis of DNA from a tumor line produced by strain C58 showed that a T-DNA fragment had been transferred into the lentil genome.

Vernalization in Lolium temulentum L.: Responses of In Vitro Cultures of Mature and Immature Embryos, Shoot Apices and Callus

Response of vernalization to low temperature (2°C) was studied in a winter-annual form of Lolium temulentum L., using imbibed seeds, excised mature and immature embryos, shoot apical meristems and callus tissue. Excised embryos, as early as 5 days after anthesis, and excised shoot apices could be vernalized as effectively as imbibed seeds. Cold treatment of developing embryos within the ear, however, appeared to have no vernalizing effect. Plants derived from callus by somatic embryogenesis showed varying degrees of vernalization response. The vernalization response in L. temulentum, as in winter annual cereals, appears to be located in the shoot apical meristem and the vernalized condition can be transmitted to new axillary meristems formed from it

Tissue culture investigations of bamboo—IV. Organogenesis leading to adventitious shoots and plants in excised shoot apices

Shoot apices cultured in 2,4-D medium developed a creamy-white callus, subcultures of which do not differentiate shoots in response to variations of auxin/cytokinin levels. In contrast, those cultured in combinations of NAA and BA produced a green, partially organized, granular or nodular callus. Further culture of this callus maintained its partially organized state and resulted in the emergence of adventitious shoots. The new shoots were rooted and readily transplanted in soil. The organogenic callus, developed by intense cell division within axillary buds, resulted in irregular swelling and eventual bursting of buds. New shoot primordia differentiated in superficial cell layers of swollen tissues and specifically in regions with an epidermis. The epidermis formed part of the primordium. Older cultures displayed principally an increase of amorphous callus through swelling occurring in newly formed buds, as well as differentiation of super-numerary buds. The granular or nodular texture was due to aggregates of hard callus interspersed with buds in all stages of development. Although adventitious, the buds were not derived from single cells.

Clonal propagation of Lemon Grass (Cymbopogon citratus Stapf) through shoot tip culture.

A tissue culture method for rapid clonal propagation of lemon grass (Cymbopogon citratus) is described. Shoot cultures were induced by culturing small excised shoot apices on the LS basal medium supplemented with 0.1μM NAA and 10μM BA. Multiple shoots were divided and cultured on a basal medium containing 1μM NAA for rooting. The regenerated plantlets were successfully transferred to soil.

Development of maize plants from cultured shoot apices

Excised shoot apices of maize (Zea mays L.), comprising the apical meristem and one or two leaf primordia, have been cultured and can form rooted plantlets. The plantlets, derived from meristems that had previously formed 7-10 nodes, develop into mature, morphologically normal plants with as many nodes as seed-grown plants. These culture-derived plants exhibited the normal pattern of development, with regard to the progression of leaf lengths along the plant and position of axillary buds and aar shoots. Isolation of the meristem from previously formed nodes reinitiates the pattern and number of nodes formed in the new plant. Thus, cells of the meristem of a maize plant at the seedling stage are not determined to form a limited number of nodes.

A tissue culture technique for rapid clonal propagation and storage under minimal growth conditions of Musa (Banana and plantain)

A tissue culture technique for rapid clonal propagation and storage under minimal growth conditions is presented in this paper. Shoot-tip cultures of Musa cultivars (both banana and plantain) are induced by culturing small excised shoot apices on modified MS semisolid medium supplemented with various concentrations and combinations of auxins and cytokinins. The effects of cytokinin concentration in the medium as well as the genotypic configuration of the cultivars on the rate of shoot-bud proliferation have been tested. The established shoot-tip cultures grown on modified MS semisolid medium supplemented with IAA (0.18 mg/l) and BA (2.30 mg/l) have been successfully stored at 15°C with 1000 lux light intensity up to 13-17 months depending on the cultivar. The cultivars tested in the present investigation seem to vary in their ability to withstand minimal growth temperature.

Fasciation d'extrémités caulinaires du Celosia cristata (Amarantacées) cultivées in vitro

In vitro development of fasciation was achieved from the excised shoot apices of Celosia cristata in a 16-h photoperiod. An 8-h photoperiod produced no development. The explants consisted of the meristematic dome with two leaf primordia. The best results were obtained with a nutrient medium composed of Murashige and Skoog salt mixture, 30 g/L sucrose, 5 g/L agar, and 1 mg/L indoleacetic acid (IAA). Isolated shoot apices developed callus at the bases of the explants and numerous leaves on one, two, or three flattened and fasciated meristems. Root initiation occurred sometimes but only after a long period of culture.

The Effect of Arachidonic Acid, Prostaglandins and Inhibitors of Prostaglandin Synthetase, on the Flowering of Excised Pharbitis nil Shoot Apices under Different Photoperiods

Arachidonic acid and PGE1 (10-4 M) hastened the time to flowering of Pharbitis nil plantlets which developed from excised shoot apices under inductive conditions (short days). Gentisic acid, acetylsalicylic acid, salicylic acid and oleic acid, all known inhibitors of prostaglandin synthetase, inhibited flowering of plantlets under inductive conditions. Arachidonic acid and PGE1, PGE2, PGF1a, PGF2a, PGA1, PGA2, PGB1, and PGB2, (10-4 M, 10-5 M and 10-6 M) did not induce flowering in plantlets which were kept under long days. However, leaf blade growth was reduced by the treatments. A hypothetical scheme is presented for the possible regulation of flowering by prostaglandins and phenolic acids (salicylic acid).

Shoot Initiation from Carnation Shoot Apices Frozen to -196°C

Aseptically excised shoot apices from Dianthus caryophyllus were frozen to -196 degrees C and subsequently thawed to room temperature. Survival rates as high as 33 percent, determined by callus formation, growth, or chlorophyll formation, are reported; plant formation has been observed.

Axenic culture of meristem tips of Rosa multiflora

Excised shoot apices (0.6 or 1.0 mm long) of Rosa multiflora were grown in axenic culture on defined media including auxins, gibberellic acid and cytokinins. In the presence of zeatin (10(-8)-10(-7)M) and 6-benzylaminopurine (10(-7)-10(-6) M) apices grew into plantlets but two other cytokinins, kinetin and 6-(3-methylbut-2-enyl)aminopurien, were ineffective. Auxins or gibberellic acid were either inhibitory or had no effect on differentiation.

APPLICATION OF THE 22.5 MEV DEUTERON MICROBEAM TO THE STUDY OF MORPHOGENETIC PROBLEMS WITHIN THE SHOOT APEX OF OSMUNDA CLAYTONIANA

Excised shoot apices of Osmunda claytoniana were grown under controlled sterile conditions. Histological examination of the normal shoot apex shows that it is comprised of: (1) a promeristem, which possesses 1 or more apical initiating cells at its center; (2) a prestelar tissue consisting of an incipient vascular tissue which flanks the pith‐mother‐cell zone; the pith‐mother‐cell zone gives rise to the pith rib meristem and subsequently to the fundamental parenchyma of the pith; (3) the fundamental parenchyma of the cortex and the fundamental parenchyma of the dermal system both arising from flank cells of the promeristem. Apical initial cells of meristems irradiated with a 127,000 rad acute exposure of a deuteron beam having a diameter of 25μ, histologically examined at 7‐day intervals for a 12‐week period, as early as 3 weeks’ postirradiation, showed the apical initiating cell(s) together with certain of the cells of the pith‐mother‐cell zone to be destroyed. A wound response develops peripherally to the destroyed initials. In addition, an isolated, organized growth center is observed to develop from normal promeristem cells. Incipient vascular tissue and a new pith‐mother‐cell zone are also observed to develop in association with the new center of growth. Implications of the role of the interrelationships between apical initiating cell(s) and other cells of the meristem and the role they may play in maintenance of meristematic integrity within the shoot meristem are discussed.