Abscisic acid in shoots and roots of Scots pine (Pinus sylvestris L.) seedlings grown in controlled long-day and short-day environments.

Scots pine (Pinus sylvestris L.) seedlings grown in nutrient solution in controlled-environment chambers were used. The effects of a shortday (SD, early autumn) treatment on growth and the content of "free" and alkaline hydrolysable abscisic acid (ABA) in shoots and roots were investigated. The weekly relative growth rates of seedlings grown continuously under long-day (LD, summer) conditions were stable at approx. 0.08 g g(-1) d(-1) between weeks four and eight from germination. Weekly relative growth rates of seedlings transferred to SD conditions decreased rapidly to a then stable level of approx. 0.04 g g(-1) d(01). Shoot elongation ceased within two weeks of SD treatment. The content of both "free" and alkaline hydrolysable ABA was approx. 40-50% higher in shoots of seedlings grown for five weeks in LD plus one week in SD than in shoots of seedlings grown for five or six weeks in LD. Two additional weeks of SD did not change the "free" ABA content. Three weeks in simulated late autumn (SD but decreased temperatures) and three weeks in simulated winter (lower light intensity and temperature) further increased the content of "free" ABA in the shoots. A transfer back to LD conditions reduced the ABA content to a level equal to the level found during the first LD period. The recovery of radioactive ABA at certain times after application ofr[(3)H] ABA was the same in shoots and roots of LD-grown and SD-treated seedlings.

Metabolism of Tritiated Gibberellins A(4) and A(9) in Norway Spruce, Picea abies (L.) Karst. : Effects of a Cultural Treatment Known to Enhance Flowering.

Shoots of mature grafted propagules of Picea abies (L.) Karst. metabolized [(3)H]gibberellin A(4) (GA(4)) to at least 14 acidic substances, two of which were tentatively identified by gas-liquid radiochromatography as GA(2) (possibly an artifact) and GA(34). [(3)H]GA(9) was converted into a number of metabolites, one of which was chromatographically similar to, but not identical with, GA(4). Metabolism was maximally 61 and 57% over 48 hours for GA(4) and GA(9), respectively, and was correlated with the rate of change (i.e. increase followed by decrease) in endogenous GA-like substances as shoot elongation progressed. Propagules covered with a clear plastic film, a treatment which promotes flowering, metabolized [(3)H]GA(4) more slowly than did control plants in the open. Inasmuch as a GA(4/7) mixture can also promote flowering in P. abies, the retarded metabolism of [(3)H]GA(4) may reflect the manner in which trees under plastic metabolize endogenous GA-like substances. If so, then the stimulating effect of this cultural treatment on flowering may come about through an increased level of endogenous, less polar GA-like substances.