Endogenous Gibberellins in Elongating Shoots of Clones of Salix dasyclados and Salix viminalis

Abstract

Elongating shoots of rapidly growing clones of Salix viminalis L. (clone and Salix dasyclados Wimm. (clone 908) harvested in early August were analyzed for endogenous gibberellins (GA). Distribution of GA-like activity, determined by Tan-ginbozu dwarf rice microdrop bioassay after reverse phase C,I high performance chromatography, was similar for both species. For S. dasyclados, combined gas chromatography-selected ion monotoring (GC-SIM) yielded identifications of GA,, GAS, GA,9, GA20, and GA29. Identifications of GA4 and GA, were also made using coinjections of known amounts of [17,. By bioassay, the main activity was GA,9-like in both species. Gibbereilin Al, GA,,, and GA2.concentrations were approximated by GC-SIM using co-injections of known amounts of [17,17-2H2]GAs. Both bioassay and GC-SIM results indicated very high concentrations of GA,, and GA20 (about 6000 nanograms per kilogram fresh weight shoot tissue using GC-SIM: 800 ng using bioassay), compared to the concentration of GA, (about 130 nanograms per kilogram fresh weight using either GC-SIM or bioassay).Various species of Salix and Populus have been extensively studied in recent years in connection with short rotation forestry or energy forestry (26). Studies with Salix pentandra have shown that cessation of apical elongation growth can be prevented by exogenous GAs4 (10), and further studies have indicated that endogenous GAs may have a significant function in regulation of shoot elongation in Salix (4,11,12). Gibberellins Al, A19, A20, and A29 have recently been identified as endogenous components in S. pentandra (4). Salix viminalis and Salix dasyclados are rapidly growing willow species with an obvious potential for biomass production. In willow, the biomass production is closely related to shoot elongation and in this connection knowledge of GA metabolism is especially interesting. Identification of endogenous GAs is a prerequisite for further studies, and in this paper we report identification of several endogenous GAs from two selected clones of S. viminalis and S. dasyclados. [8]), filtered, and partitioned three times against onethird volumes of toluene to remove Chl and other nonpolar compounds. The aqueous phase was then adjusted to pH 2.5 with 6 N HCl and extracted three times with EtOAc. The acidic EtOAc fraction was taken to dryness in vacuo at 35°C, dissolved in 2 ml MeOH, and further purified on a combined Sephadex LH 20/PVP column (25). The fraction containing free GAs (from 35-159 ml) was collected, adjusted to pH 2.5, and partitioned three times against EtOAc. The EtOAc fraction was purified further by DEAE Sephadex A25 anion exchange chromatography (2). The fraction containing free GAs (from 90-140 ml) was collected and taken to the aqueous phase in vacuo at 35°C, adjusted to pH 2.5, and extracted with EtOAc. The EtOAc fraction was taken to dryness, dissolved in MeOH, adsorbed onto Celite 545, and applied to a silicic acid partition column (5 g silicic acid) saturated with 0.5 M formic acid (5, 22), and GAlike substa...

Genetic Improvement of Willow for Bioenergy and BiofuelsFree Access

“…Studies of bud flush in S. viminalis have shown that an early start in spring is more important than delaying growth cessation in the autumn (Raven 1992; Rönnberg‐Wastljung and Gullberg 1999). Changes in thermal time (Cannell et al 1987) together with altering levels of cytokinins, abscisic acid (Alvim et al 1976, 1978, 1979) and gibberellins (Junttila et al 1988) interact in regulating dormancy, bud burst and shoot growth. The rapid mobilization of resources and simultaneous development of many shoots from each stool leads to fast build up of large leaf area, rapid growth increment and early canopy closure; an effective strategy for biomass accumulation (Sennerby‐Forsse and Zsuffa 1995).…”

Genetics, Genomics and Crop Modelling: Integrative Approaches to the Improvement of Biomass Willows

“…Similarly, in S. pentandra GAs influence shoot elongation and cessation of apical growth can be prevented by exogenous GAs (Davies et al 1985). In elongating shoots of S. dasyclados and S. viminalis GA 1 , GA 4 , GA 8 , GA 9 , GA 19 , GA 20 and GA 29 were all detected but levels of GA 19 and GA 20 were particularly high in both species in the vegetative shoot (Junttila et al 1988).…”