A Cytophotometric Study of Nucleic Acids and Proteins in the Shoot Apex of White Spruce

Abstract

During the annual three‐phase growth cycle of white spruce [Picea glauca (Moench) Voss] the vegetative shoot apex changed in anatomical configuration. Relative amounts of DNA, histones, RNA, and proteins were measured in three cytohistological zones and were related to the anatomical changes during ontogeny. An extended period of DNA synthesis (S) and G2 preceded an increase in the number of apical initial cells which were part of the mammillary apex. While DNA and histones were generally synchronous during ontogeny, the ratio of DNA to histone increased on June 20. This loss of histone and subsequent increases in RNA and cytoplasmic proteins preceded the appearance of needle primordia on next year's apex. We propose that induction of the apex to reorganize and form needle primordia occurred when the DNA was in a 2C condition, following the loss of histone on June 20.

An Ultrastructural and Microspectrophotometric Study of the Shoot Apex During the Initiation of the First Leaf in Germinating Pinus Banksiana

“…An increase in mitosis just before the appearance of leaf primordia has been reported previously (Chouinard, 1959;Cecich et al, 1972;Owens and Molder, 1973). In this study, the appearance of the primordia at about 72 hr was probably caused by enlargement of the daughter cells which originated from the abundant mitoses at 68 hr.…”

“…Our cytophotometric measurements of RNA from single cells of squashed meristems had standard errors of approximately 5 % (Table 1), which indicated that cells from different regions of the meristem appeared to be in similar metabolic states. This is supported by previous work on meristems of germinating jack pine (Durzan, Mia, and Ramaiah, 1973;Mia and Durzan, 1974) and on other plants (West and Gunckel, 1968;Lyndon, 1970;Cecich, Lersten, and Miksche, 1972). Mia and Durzan (1974) labelled apices of germinating jack pine with uracil-5-3H and, at 96 hr post-imbibition, showed that heavy labelling due to RNA synthesis occurred in most cells of the meristem, with only lesser amounts in the subapical region.…”

Bud development in Sitka spruce. I. Annual growth cycle of vegetative buds and shoots

“…Maximum development occurs ment for 1st-and 2nd-year seedlings from 47 on the 0lympic peninsula of and on different provenances and showed that vegetative the Queen Charlotte Islands of British Columbia bud burst in the spring was (Fowel]s 1965). Anatomical studies of vegetative bud development have been made for some species of Picea (Lewis and Dowding 1924;Korody 1937 ;Camefort 1956;Fraser 1962Fraser , 1966Romberger 1966;Cecich et al 1972). Burley (19666) showed that when from northern provenances.…”

“…Burley (19666) showed that when from northern provenances. Histochemical studies of P. glauca vegetative apices were made by Vanden Born (1963) and Cecich et al (1972). Anatomical studies of vegetative bud development have been made for some species of Picea (Lewis and Dowding 1924;Korody 1937 ;Camefort 1956;Fraser 1962Fraser , 1966Romberger 1966;Cecich et al 1972).…”

“…No observations were made of lateral shoot development in mature trees. Cecich et al (1972) used cytophotometric methods to measure nucleic acids and proteins within the vegetative apex during the growth cycle. Burley (19666) described zonation in the terminal shoot aDex of Sitka spruce seedlings, but no descriptions have been given for reproductively mature trees.…”