The transport of radiolabeled indoleacetic acid and its conjugates in nodal stem segments of Phaseolus vulgaris L.

The transport of radiolabeled indoleacetic acid (IAA), and some of its conjugates, was investigated in nodal stem segments of Phaseolus vulgaris L. Donor agar blocks containing either [2-acetyl-¹⁴C]-IAA; [2-acetyl-¹⁴C]-indole-3-acetyl-L-aspartate (IAAsp); [2-acetyl-¹⁴C]-indole-3-acetyl-L-glycine (IAGly); or [2-acetyl-¹⁴C]-indole-3-acetyl-L-alanine (IAAla) were placed on either the apical or basal cut surface of stem segments each bearing an axillary bud at the midline. In some experiments, a receiver block was placed on the end opposite to the donor. After transport was terminated, the segments were divided into five equal sections plus the bud, and the radioactivity of donors, receivers and each part of the stem segment was counted.For all four substances tested, the amount of ¹⁴C transported to the axillary bud from the base was the same or greater than that from the apical end. After basipetal transport, the distribution of ¹⁴C in the segment declined sharply from apex to base. The inverse was true for acropetal transport. Transport for the three IAA conjugates did not differ substantially from each other.The IAA transport inhibitor, N-1-naphthylphthalamic acid (NPA), inhibited basipetal ¹⁴C-IAA transport to the base of the stem segment but did not alter substantially the amount of ¹⁴C-IAA recovered from the bud. Transport of ¹⁴C-IAA from the apical end to all parts of the stem segment declined when the base of the section was treated with nonradioactive IAA. Taken together with data presented in the accompanying article [Tamas et al. (1989) Plant Growth Regul 8: 165–183], these results suggest that the transport of IAA plays a role in axillary bud growth regulation, but its effect does not depend on the accumulation of IAA in the axillary bud itself.     

The Role of Meristematic Activities in the Formation of Leaf Blades

Arabidopsis thaliana (L.) Heynh. Leaf primordia also have their own meristematic regions and meristematic activity is maintained in part of the leaf blade, in some case, even after maturation. Transgenic plants have been generated that have proved to be useful tools in the analysis of the behavior of meristematic regions in leaf blades of A. thaliana. This review, based on our present understanding of molecular mechanisms for the maintenance and development of shoot apical meristems in A. thaliana, summarizes the variations in patterns and functions of meristematic regions in leaf blades focusing, in particular, on the case of indeterminate leaves. Received 5 April 2000/ Accepted in revised form 12 April 2000     

Experimental and genetic analysis of root development inArabidopsis thaliana

The cellular organisation of theArabidopsis thaliana root is remarkably regular. A fate map of the primary root and root meristem that predicts the developmental destinies of cells within the embryonic root primordium has been constructed. Nevertheless, laser ablation experiments demonstrate that root meristem cells develop according to position and not according to lineage. Mutational analysis has identified genes required for cell specification in the radial as well as in the apical-basal dimension. The corresponding gene functions appear to be necessary during embryogenesis for the formation of a correctly patterned primary root. H Lambers Section editor     

Centrifugal ovule inception

Nine samples from Sattler (1973) were found to exhibit a remarkable correlation between the sequence of ovule inception and ovary structure. In every case, the sequence of ovule inception is centrifugal from its supposed final position of the floral apex. Thus, it is hypothesized that ovules are initiated centrifugally from their floral apex and that this is regulated in some mechanical way. To prove this hypothesis, ontogenetical development of the ovary was reexamined inSilene cucubalus, where the sequence of ovule inception was expected to be not simply basipetal but basipetal on the central column and acropetal on the septal protuberances. The results appear to support the hypothesis. A basipetal sequence is clearly visible on the central column. Although the ovule number is very small on the septal placenta, an acropetal sequence can be recognized, i.e., the distal primordia are obviously initiated later than the proximal ones. Two possible mechanisms for centrifugal ovule inception are suggested: (1) that it is regulated by chemical information diffusing from the floral apex or (2) that it is dependent on gradation of cell age in the placenta. The second mechanism is discussed and supporting evidence is suggested in the epidermal cell arrangement of the septal wall. Contribution from the Osaka Museum of Natural History No. 275.     

The marginal band, a new structural component of the developing angiosperm leaf

The marginal band, a newly described structure of the dicot leaf, plays an essential role in the formation of this organ. It arises along the two edges of a leaf as several files of adaxial epidermal cells during the peg stage of ontogeny. Functionally, it appears to serve as the prepattern for a number of secondary features including (i) the marginal growth meristem present in all leaves as seen in mountain laurel, (ii) rows of lobes and spines as in Salvia and Ilex , (iii) pigmentation as in some cultivars of Hydrangea , (iv) propagation as in the plantlets of Kalanchoe pinnata , (v) marginal ridges for support in a few varieties of Viburnum and Ilex , and (vi) marginal necrosis as in Strelitzia for blade partitioning.  © 2003 The Linnean Society of London, Botanical Journal of the Linnean Society , 2003, 143 , 21–28.     

In vitro proliferation of shoots and regeneration of cotton

Shoot proliferation from different explants of several Indian cultivars of cotton was studied in culture. Cotyledonary nodes taken along with the shoot apex of seedlings produced multiple shoots on modified MS nutrient agar supplemented with cytokinins. 6-Benzyladenine was most effective in inducing growth of multiple shoots. Explants of several genotypes formed organogenic masses that differentiated to secondary shoots on repeated subculture. The isolated shoots were rooted on basal medium supplemented with naphthaleneacetic acid and were transferred to soil after acclimatization. This revised version was published online in June 2006 with corrections to the Cover Date.     

Changes in the pattern of cell arrangement at the surface of the shoot apical meristem in Hedera helix L. following gibberellin treatment

The changes in the pattern of cell arrangement and surface topography at the shoot apical meristem of Hedera helix L., which occur during gibberellic acid (GA₃)-induced transition from spiral to distichous phyllotaxis, were examined by scanning electron microscopy of rapidly frozen tissue. The technique preserves the original shape of the cells in their turgid state. It reveals distinct sets of radially oriented cell files, about four to eight cells wide, which extend from the central region of the meristem toward leaf primordia on the meristem flanks. In apices with spiral phyllotaxis, a new emerging primordium (0) appears as an acropetal bulge between the radial files adjacent to the third (3) and the second (2) older primordia. The bulging is associated with radial or oblique cell divisions while those located at the meristem flanks and in the radial files are oriented tangentially. As the displacement of existing primordia away from the central region increases following the GA₃ treatment, radial and oblique divisions as well as acropetal bulging invade the radial files adjacent to the primordium 2; consequently the angular divergence of the emerging primordium from the youngest existing primordium (1) increases. In apices with distichous phyllotaxis, the earliest bulging appears on both sides of the radial files facing primordium 2, with a slight depression at the files. The radial files therefore correspond to regions of the meristem where acropetal bulging is generally delayed, although this effect apparently diminishes with increasing distance of existing primordia from the meristem center.Abbreviations GA₃ gibberellic acid We thank Mr. Gilbert Ahlstrand, University of Minnesota, for his advice and assistance with the scanning electron microscopy. Contribution of the University of Minnesota Agricultural Experimental Station No. 19032.     

The effect of light quality on the morphogenesis of in vitro cultures of Azorina vidalii (Wats.) Feer

In the present study, the possibility to improve the multiplication rate and quality of in vitro cultured plants of Azorina vidalii (Wats.) Feer was investigated. For these purposes the influence of high and low ratios of blue/red light (2.3 and 0.9, respectively) and red/far red light (1.1 and 0.6, respectively) on the development of shoot cultures of Azorina vidalii (Wats.) Feer was evaluated. Maximum plant length (87.9 ± 5.3 mm) (p ≤ 0.05) and internode length (6.6 ± 0.5 mm) (p ≤ 0.05) were obtained for the plants cultured under the low ratio of red/far red light. In contrast, when blue light was supplemented, plant height was reduced, due to shorter internodes. Highest number of axillary shoots per plant (2.4 ± 0.5) was obtained in the plants growing under a high level of red/far red light, while the lowest number (0.7 ± 0.2) was obtained in the plants cultured under the low level of red/far red light. Leaf area was increased in plants cultured under a low level of red/far red (1,522.5 ± 129.5 mm²) while blue/red light treatments inhibited leaf expansion. For chlorophyll a and total carotenoid contents, statistical differences (p ≤ 0.05) were observed between the plants exposed to the red/far red light treatments and the plants from the control. This revised version was published online in June 2006 with corrections to the Cover Date.     

Chemical and environmental growth regulation of sweetpotato (Ipomoea batatas (L.) Lam.) in vitro

The need for conservation of biotic diversity is well recognized. However, improved techniques for the efficient, cost effective-preservation of plant germplasm are needed. The conservation and distribution of plant germplasm in vitro is gaining acceptance. However, increased usage is dependent upon the ability of curators to minimize culture maintenance requirements. This report examines the effect of various levels of sucrose, photoperiod, temperature, sorbitol and mannitol on minimal growth storage of Ipomoea batatas (L.) Lam. Growth was reduced 50% with a temperature reduction of from 21.1 to 15.6°C. Sucrose concentrations of 15 and 20 g l^-1 resulted in reduced plant stature with few adverse effects on plantlet viability or morphology. Reduction of photoperiod from 16 to 4 h produced smaller, slightly chlorotic, but otherwise normal plants. The addition of sorbitol or mannitol to culture media generally produced undesirable effects on gross plant morphology and loss of apical dominance. Genotype x growth retarding treatment interactions were observed for all variables examined.Abbreviations PL plant introduction - f.w. fresh weight - SE standard error