Rhythmic growth and carbon allocation in Quercus robur. Sucrose metabolizing enzymes in leaves

Abstract

The high sucrose phosphate synthase (SPS) capacity and the low soluble acid invertase activity of mature leaves of the first flush of leaves remained stable during second flush development. Conversely, fluctuations of sucrose synthase (SS) activity were in parallel with the sucrose requirement of the second flush. Sucrose synthase activity (synthesis direction) in first flush leaves could increase in ‘response’ to sink demand constituted by the second flush growth. Only the ptotosynthates provided by flush mature leaves were translocated for a current flush, while the starch content of these leaves remained stable. After their emergence, second flush leaves showed an increase in SPS and SS (Synthetic direction) activities. The high sucrose synthesis in second flush leaves was used for leaf expansion. When young leaves were 30% fully expanded (stage II20), SPS activity showed little change whereas SS activity declined rapidly toward and after full leaf expansion. The starch accumulation in the young leaves occured simultaneously with their expansion. Developing leaves showed a high level of acid invertase activity until maximum leaf expansion (stage II1). In first and second flush leaves, changes in acid invertase activity correlated positively with changes in reducing sugar concentrations. Alkaline invertase and sucrose synthase (cleavage direction) activities showed similar changes with low values when compared with those of acid invertase activity, especially in second flush leaves. The present results suggest that soluble acid invertase was the primary enzyme responsible for sucrose catabolism in the expanding common oak leaf.

Effect of NaCl salinity on growth and mineral partitioning in Quercus robur L., a rhythmically growing species

“…Carbohydrate reserves of the first flush stems and accorns are necessary to insure the second flush expansion (Alaoui-Sossé et al 1994). At the end of this growth period, they have to be restored in stem compartments from photoassimilate supply (Alaoui-Sossé et al 1994).…”

“…At the end of this growth period, they have to be restored in stem compartments from photoassimilate supply (Alaoui-Sossé et al 1994).…”

“…Furthermore, these plants present a rhythmic growth -one flush produced every 3-4 weeks -which could influence their ability to survive in salted areas. The rhythmic growth is tightly linked to mobilization and restoration of stem carbohydrate reserves (Alaoui-Sossé et al 1994). The response of these storage reserves to salt stress and the ability they could give the tree to cope with that NaCl stress is worthy of examination.…”

“…The response of these storage reserves to salt stress and the ability they could give the tree to cope with that NaCl stress is worthy of examination. In addition, it was interesting to determine whether the storage-utilization process described by Alaoui-Sossé et al (1994) was disturbed. The aim of this paper is to investigate the strategy brought into operation by common oak seedlings to cope with salt stress.…”

Photosynthesis studies on European evergreen and deciduous oaks grown under Central European climate conditions. I: a case study of leaf development and seasonal variation of photosynthetic capacity in Quercus robur (L.), Q. ilex (L.) and their semideciduous hybrid, Q. × turneri (Willd.)

“…in June) are relatively high as compared to herbal plants growing under warm conditions; they rather resemble values found in chilled plants with sink limitation of growth (Brüggemann et al 1992b). In a study on sucrose metabolism in growing Q. robur saplings, Alaoui-Sossé et al (1996) reported that first flush (source) leaves revealed sucrose concentrations of 50-60 mg g -1 dry matter during the development of the second flush (sink) leaves, which can be converted to approximately 50-60 lmol hexose units g -1 fw, the units used in our analysis.…”