589 PS 132 TISSUE PROLIFERATION IN ELEPIDOTE RHODODENDRONS

Experiments were conducted on tissue proliferation (TP) development and in vitro and ex vitro growth of tissues from plants with (TP+) and without TP (TP-). In 1993 the increase in TP in one-, two-, and three-yr-old `Holden' and `Besse Howells' was 3%, 52%. and 32% and 10%, 26% and 21%, respectively. No differential mortality was observed. Shoot tip cultures initated from TP+ and TP- `Montego' showed 10-12 mo were required for miniaturiziation and multiplication in TP- shoot tips and 4 mo in TP+ shoot tips. TP- cultures require 10 uM 2-iP for normal shoot proliferation; whereas TP+ cultures had to be transferred to hormone-free medium after 6 mo to maintain normal shoot morphology. Cutting propagation from TP- and TP+ plants older than 5 yr, showed persistence of morphological aberrations associated with TP+ plants.

Copper deficiency in young Eucalyptusmaculata plantations

Copper deficiency has been identified as the cause of distorted growth symptoms in 2- to 3-year-old stands of Eucalyptusmaculata Hook, established on a disturbed laterite-pallid zone profile in southwestern Australia. The main symptoms of Cu deficiency were undulate leaf margins, shoot dieback, enlarged nodes giving rise to numerous short-lived axillary shoots, and reduced lignification of wood. Visible symptoms were associated with depressed foliar Cu concentrations (mean 1.1 μg•g−1 compared with mean 1.9 μg•g−1 for healthy trees). Normal shoot growth in affected trees was restored by the addition of CuSO4 to the soil or as a foliar spray.

A Vegetative Propagation System for Tamarack

Greenwood cuttings from greenhouse-produced tamarack seedlings and 3- to 10-year-old tamarack wildlings transplanted from natural stands in north-western Ontario were rooted under mist in peat-vermiculite. Eighty-five percent of cuttings from seedlings rooted; treatment with indolebutyric acid increased number of roots per cutting, but not rooting percent. At 6 weeks after planting, rooting of cuttings from wildlings averaged 66%, and at 12 weeks, 91%. Twelve-week rooting percent of cuttings from individual ortets ranged from 12 to 100, but cuttings from the majority of ortets exhibited 100% rooting. Nearly all rooted cuttings survived overwintering outdoors and initiated normal shoot growth after forcing in mid-winter. The described propagation system is recommended for production of container stock for tamarack plantations. North. J. Appl. For. 3:91-93, Sept. 1986.

XVII.—The Endodermis in Light-grown and Etiolated Shoots of the Leguminosæ: A Contribution to the Causal Study of Differentiation in the Plant

Twelve years ago Priestley and Ewing (1923) reported that in certain plants, normally showing but little development of stem-endodermis, an extensive formation of this layer could be induced by etiolation. (Note: In this paper the term endodermis is used only when the layer shows characteristic structural features—in the present case the Casparian strip.) A later paper by Priestley (1926) dealt with the same subject. The specified plants with which this result was obtained consisted of four closely related species, namely, Vicia Faba, V. sativa*, Pisum sativum, and Lens esculenta*, and also Solanum tuberosum. (The statements relating to the species marked with an asterisk are based on unpublished work carried out at Leeds, kindly placed at the author's disposal by Professor J. H. Priestley.) In these plants a primary endodermis, though present only at the base of the normal shoot, was described as extending to a considerable height in the etiolated shoot. It was concluded that the absence of endodermis from the greater part of the shoot of these plants, when grown under normal conditions, arises from the inoperation, in the presence of light, of the mechanism forming the Casparian strip.