Juvenile Needles Research Articles

Seasonal variation in the monoterpenes in needles of Picea abies (L.) Karst.

This investigation was conducted to obtain information about the fluctuations in composition and amount of needle monoterpenes during the development of spruce needles. Studies conducted with two Norway spruce clones clearly revealed the existence of fluctuations. In juvenile needles, the amounts of the oxygenated terpenes increase constantly with age during the first 2 months of needle growth. The hydrocarbon terpenes dominate within the first weeks, some of them even showing a very distinct first maximum within the first 3 weeks after bud burst. All terpenes, including the oxygenated ones, have a maximum in June/July, which favours the hypothesis of a substitution of the hydrocarbons later on. There are significant changes even in mature needles of Norway spruce. The terpene level of 1-year-old needles of the clonal trees increased from spring to early summer and then dropped again towards winter. In addition, fluctuations in mature needles were shown for a set of ten wild trees. Needles of the same age class, which emerged in 1986, were sampled 4 times from 1986 to 1988. The needle terpene concentrations of the 1 -year-old needles were considerably lower in spring at the time of bud burst than in autumn. The terpene level of older needles thus seems to be influenced by biosynthetic and catabolic activities.

Regeneration of calabrian pine from juvenile needles

Cytokinins applied in an agar medium induced adventitious buds on cultured needles from seedling of Pinus brutia Ten. Cytokinins applied as pulses to the explants prior to culture were less effective. Irrespective of the mode of cytokinin application, 8 weeks was the time required to bring about bud formation. Organogenetic potential of the cultured needles decreased with chronological age of the explanted seedlings. The induced buds grew into elongated shoots on culture medium without cytokinins, but the inclusion of activated charcoal (1%) doubled the elongation rate. There was an indication that mixtures of cytokinins were more effective than separate cytokinins in producing buds on explants, but the difference between treatments did not achieve statistical significance. Parenchyma cells in mesophyll layers were evidently the target cells responding to the culture conditions. After a period of activity and division in these cells, meristematic zones developed which later led to formation of bud primordia, and subsequently these primordia developed into well-formed adventitious buds. Subsequent rooting (64%) of shoots was achieved using a combination of two auxins and a low level of cytokinin.

Variation of the Pinus ponderosa needle oil with season and needle age

Influence of season and needle age on the yield and composition of the Pinus ponderosa needle oil was investigated. Oil yields throughout the year averaged 0·13% on the basis of tissue green weight. The average composition was 11·9% α-pinene, 70·2% β-pinene, 8·0% 3-carene, 5·0% myrcene, 1·8% limonene, 2·2% β-phellandrene and 6·4% methyl chavicol (total monoterpenes = 100%). The amount of methyl chavicol and total monoterpenoids was highest in summer, lower in juvenile than in mature firstyear needles, and decreasing thereafter with needle age. A significant increase in 3-carene and decrease in β-pinene was apparent in juvenile needles. The most important step towards decreasing the seasonal and age variability of needle samples in ecological or chemotaxonomic studies was found to involve exclusion of sample collections during a period between the initial appearance of young needles and the time that they reach maximum length.

EXPERIMENTS ON THE PRECOCIOUS FLOWERING OF WESTERN RED CEDAR AND FOUR SPECIES OF CUPRESSUS WITH GIBBERELLINS A3 AND A4/A7 MIXTURE

Induction of staminate and ovulate strobili was obtained on western red cedar (Thuja plicata Donn) by foliar application of gibberellin A3. Staminate strobili could be induced as early as age 4 months after 3.5 months of treatment under long-day conditions, but further development of the strobilus required a photoperiodic sequence of long-day — short-day — long-day. Induction of the ovulate strobilus may also have occurred under long-day conditions at an early age, but development did not become apparent until the above photoperiodic sequence had been given. Age at this time was 12 months. It is concluded that induction and development of the strobilus is under photoperiodic as well as hormonal control.Foliar application of gibberellin A3 and a gibberellin A4/A7 mixture to pygmy cypress (Cupressus pygmaea Sarg.), Portuguese cypress (Cupressus lusitanica Mill.), and Arizona cypress (Cupressus arizonica Greene) at age 7–9 months resulted in induction of staminate strobili on all plants. Length of time to flowering varied both with species of plant and gibberellin. Application of gibberellin A3 to Arizona and Portuguese cypress seedlings resulted in production of ovulate as well as staminate strobili at ages 21 and 10 months respectively. Mourning cypress (Cupressus funebris Endl.) still in a juvenile needle stage at age 9 months has proved unresponsive to foliar application of gibberellin A3 for at least 100 days.