Effects of Cutting Back on the Carbohydrate and Lipid Reserves in the Tree of Heaven (Ailanthus glandulosa Desf, Simaroubaceae)

1991

S. 1-13

4 Abb., 5 Tab.

Unselbständiges Werk

200041294

Annales des Sciences Forestieres 1991 ; 48,Nr. 1, S. 1-13

Seedlings of Ailanthus glandulosa show a remarkably early development of stump shoots and suckers. The removal of aerial parts induced the development of shoots of different origins (fig. 3). They may originiate from pre-existing buds in the hypocotyl, adventitious buds on a cut section, or axillary buds of cataphylls present at the base of the new shoots. These cataphyllary shoots separated from seedlings very easily. After 2 or 3 cuts, seedlings also produced adventitious buds on roots and some started to develop suckers (tables I, II). The 8-month-old seedlings raised under controlled greenhouse conditions were cut back 1, 2 or 3 times (fig. 1). Dry weights and nutrient reserves of cut and intact seedlings were determined at 30-d intervals from the first cut. The root system of the seedlings increased in dry weight throughout the successive cuts and the dry weight increase was higher in the lateral roots than in the taproot. At 90 d, the largest increase in the total dry weight was observed in seedlings after 3 cuts. Growth of the collar which then became a stump only occurred in seedlings after 3 cuts (table III). Contrary to some observations concerning deciduous trees, repetitive cutting back had a positive effect on the carbohydrate accumulation in the subterranean system. This result was related to the photosynthetic efficiency and the colonization of this species. The distribution and the quality of the carbohydrate and lipid reserves were also modified by repetitive cuts. At 90 d, the carbohydrates were distributed in similar quantities between the aerial and subterranean parts of intact seedlings (table IV). After 2 or 3 successive cuts, the greater proportion of the starch reserve was then located in the root system. In this case, the lateral roots represented the principal site of starch accumulation whereas the taproot played this role in intact seedlings. The stump mainly accumulated soluble sugars (table IV). In intact seedlings, the level of lipids was higher in the root system than in stems (table V). Cutting back induced a significant decrease to total lipids which occurred in shoots developed after 3 cuts at 30 and 90 d. At the same time, the stump also represented the site of lipid accumulation for cut seedlings (table V). In other areas, cutting back caused an increase in the desaturation of the total fatty acids of the lateral roots, expressed as an increase in linoleic and linolenic acids (table V, fig. 4). In contrast, the most important fatty acids in the taproot were palmitic and stearic acids (fig. 4).