STABILITY OF NUCLEAR DNA CONTENT DURING ADVENTITIOUS SHOOT FORMATION IN PINUS TAEDA L. TISSUE CULTURE

Attempts to preserve selected genotypes through clonal propagation may be hampered by genetic instability produced during the tissue culture phase of the propagation procedure. To investigate the genetic condition of loblolly pine (Pinus taeda L.) tissue cultures, nuclear DNA content in embryos grown in vitro and in regenerated buds were examined using two-wavelength microspectrophotometry. Embryos were grown on chemically defined media containing cytokinin as the sole growth regulator. Nuclear DNA content remained at or between 2 C and 4 C with no evidence of polyploidy during nearly 3 months of continuous culture. Benzylaminopurine, even at concentrations which were supraoptimal for shoot regeneration, had no effect on nuclear DNA content. Regenerated shoots also had stable nuclear DNA contents which correspond to a diploid condition. These results are of significance for the development of mass propagation techniques for this commercially valuable species.     

SOME ASPECTS OF SIEVE CELL ULTRASTRUCTURE IN PINUS STROBUS

The immature sieve cell of Pinus strobus contains all of the protoplasmic components commonly encountered in young cell types. In addition, it contains slime bodies with distinct double-layered limiting membranes. The mature sieve cell is lined by a narrow layer of cytoplasm consisting of a plasmalemma, one or more layers of anastomosing tubules of endoplasmic reticulum, numerous mitochondria, starch granules and crystal-like bodies. Each mature cell contains a necrotic nucleus. Ribosomes and dictyosomes are lacking. Strands derived ontogenetically from the slime bodies of the immature cell traverse the central cavity and are continuous with those of neighboring sieve cells through the plasmalemma-lined pores of the sieve areas. Sieve-area pores are also traversed by numerous endoplasmic membranes. A membrane was not found separating the parietal layer of cytoplasm from the large central cavity.     

SEASONAL SECONDARY GROWTH IN NEEDLE LEAVES OF PINUS STROBUS AND PINUS BRUTIA

Mature needles and elongating current year's needles of Pinus strobus growing in Massachusetts and P. brutia growing in Israel were collected monthly or bimonthly for seasonal analysis of leaf cambial activity. Mature needles produced secondary phloem but no xylem, and, regardless of the season, had a cambial zone from 2 to 3 cell layers wide. In the current year's needles maturation was basipetal and the procambium differentiated into primary xylem, primary phloem, and the phloem-producing vascular cambium before needle maturity. One- and 2-year-old needles of Pinus strobus produced slightly over 4 cell layers of phloem between April 15 and September 1 of 1983, with a peak production rate of about 2 cell layers per month in May and early June. One-year-old needles of P. brutia produced about 6 phloem cell layers in 1983, with phloem being produced throughout the year except in midsummer. This was contrasted by fall and winter dormancy in needles of P. strobus.     

FORMATION OF BONE TISSUE IN CULTURE FROM ISOLATED BONE CELLS

A system is described for the formation of bone tissue in culture from isolated rat bone cells. The isolated bone cells were obtained from embryonic rat calvarium and periosteum or from traumatized, lifted periosteum of young rats. The cells were cultured for a period of up to 8 wk, during which time the morphological, biochemical, and functional properties of the cultures were studied. Formation of bone tissue by these isolated bone cells was shown, in that the cells demonstrated osteoblastic morphology in light and electron microscopy, the collagen formed was similar to bone collagen, there was mineralization specific for bone, and the cells reacted to the hormone calcitonin by increased calcium ion uptake. Calcification of the fine structure of the cells and the matrix is described. Three stages in the calcification process were observed by electron microscopy. It is concluded that these bone cells growing in vitro are able to function in a way similar to such cells in vivo. This tissue culture system starting from isolated bone cells is therefore suitable for studies on the structure and function of bone.     

MITOTIC ACTIVITY IN THE CAMBIAL ZONE OF PINUS STROBUS

Mitotic activity in the cambial zone of 20-year-old Pinus strobus L. trees was determined quantitatively, using mitotic counts from serial tangential sections of sample pieces. Counts from nine cores 1.6 mm in diameter from each sample piece were averaged and expressed as the number of mitoses per core with the sampling error. Estimation of the number of cambial zone cells per core permitted calculation of mitotic indices. In the fourth internode from the ground the first mitoses were observed on April 15 and the last on September 15. The number of mitoses per sample piece was comparable throughout each internode at any one sampling, but the number was higher in internodes within the crown than in those below it. Mitotic index was not appreciably higher within the crown, but it decreased from 3.7 in spring to 2.0 in fall. An internode in the crown sampled May 11–13 showed afternoon peaks in mitotic activity, but an internode below the crown showed no peaks, nor did other internodes sampled later in the season.     

PEROXIDASE DISTRIBUTION IN THE LEADERS OF ERECT AND INCLINED PINUS STROBUS SEEDLINGS

Westing , A. H. (Purdue U., Lafayette, Indiana.) Peroxidase distribution in the leaders of erect and inclined Pinus strobus seedlings. Amer. Jour. Bot. 47(8) : 609–612. 1960.—A longitudinal gradient of peroxidase activity, decreasing basipetally, which was independent of stem inclination, was found in the leaders of Pinus strobus L. Inclination of intact leaders also had no effect on the transverse distribution of peroxidase activity, but when such leaders were decapitated and defoliated a transverse gradient, increasing from upper side to lower, did develop. Applications of α-naphthaleneacetic acid prevented this transverse redistribution from occurring. Mutilation also resulted in an increase of the overall level of peroxidase activity in the leaders.     

STRUCTURE AND ONTOGENY OF THE STOMATAL COMPLEX IN PINUS STROBUS L. AND PINUS BANKSIANA LAMB.

The morphology of the stomatal complex in Pinus strobus L. and P. banksiana Lamb, is described and it is proposed that the stomatal complex should be considered an eight-celled complex consisting of two guard cells, and two polar, two lateral, and two hypodermal subsidiary cells. An ontogenetic study found these cells closely related developmentally. It was also found that the stomatal complex in these two pines could not readily be classified as haplocheilic because a polar subsidiary cell arises from the same protodermal cell as does the guard cell mother cell. A modification of the classical concept of stomatal development was necessary to describe the stomata as eumesoperigenous.     

诸葛菜组织培养中的器官形成

植物组织和细胞培养技术已在农作物的改良及园艺植物的快速繁殖方面得到广泛的应用。在这方面,十字花科植物正在受到相当多的注意。新近,为了建立十字花科植物的细胞转化系统,我们试验了多种十字花科植物,发现诸葛菜的叶和叶柄等外植体具有极强的器官分化能力,现将结果报告如下。本文取材植物诸葛菜,又名二月兰(Oryc-hophragmus violaceus/Moricandia sonchifolia),     

CAVITY FORMATION IN WINTER BUDS OF PINUS BANKSIANA

The formation of a cavity between the rib meristem and the pith in winter buds of Pinus banksiana is described. Necrosis of cells at the juncture of the rib meristem and pith begins in November, and by mid-March the necrotic region enlarges, forming a cavity that separates the rib meristem from the pith. The cavity appears to be formed by autolysis, rather than a pulling apart of the cells. The function of the cavity remains speculative.     

COLLAGEN BIOSYNTHESIS : TISSUE CULTURE EXPERIMENTS TO ASCERTAIN THE ROLE OF ASCORBIC ACID IN COLLAGEN FORMATION

Quantitative studies of collagen formation by chick embryonic lung tissue grown in media deficient in, or completely lacking, ascorbic acid have been carried out. Cell growth and collagen formation in such cultures can proceed almost normally in media lacking ascorbic acid. Ascorbic acid in combination with whole embryo extract, dialyzed media, or synthetic mixture number 703 was found to have no appreciable effect on cell growth or total collagen formation. This is in marked contrast to the almost total failure of collagen formation in scorbutic animals and suggests that for slow collagen biosynthesis as distinct from more prolific collagen-producing systems, ascorbic acid plays an indirect role.     

IN VITRO CULTURE OF SOMATIC WHEAT CALLUS TISSUE

Sterile culture of excised wheat tissue, Triticum vulgare Vill., was attempted on 20 different media. Most tissue explants did not grow. Endosperm tissue did not grow on any of the media. Callus tissue from intercalary meristems grew for several weeks but gradually became necrotic. Callus tissue derived from the cotyledonary node grew well and produced branching and enlarging root systems when placed on different media. Shoot primordia were not observed. Callus tissue derived from 13 varieties of wheat was cultured. These unique somatic tissues are interesting experimental materials for a study of the developmental biology of wheat.     

MUCOPOLYSACCHARIDES PRODUCED IN TISSUE CULTURE

1. A method of mass tissue culture has been devised by which, in a relatively short period of time, samples large enough for chemical isolation of mucopolysaccharides can be obtained. 2. Chemical isolation of acid mucopolysaccharides from mass cultures of human fetal skin, human fetal bone, bovine fetal skin, and rat subcutaneous tissue has been carried out. It has been found that the fibroblasts of each of these tissues produce in tissue culture more than one mucopolysaccharide, namely, hyaluronic acid, and a chondroitin sulfate. 3. The chondroitin sulfate produced by fibroblasts of the above tissues in tissue culture was not fully sulfated. The possible significance of this finding is discussed.