Quantitative estimation of phenolic compounds in plant tissues remains uncertain, mainly because those substances are unstable and easily degradable. In this research we have developed and tested a new method for extracting phenolic compounds from sugar maple (Acersaccharum Marsh.) leaves. The research involved three steps: (i) various procedures currently used for extraction of phenolic compounds were tested with five pure phenolic acids; (ii) the extraction solvent, the procedure for dissolving the phenolic compounds, the temperature, and the duration of the treatment were tested on maple leaves; (iii) two methods that were found equally efficient for litter maple leaves were tested on maple leaves collected in June, on barley leaves, and on four pure phenolic acids. Based on those tests, the dissolution of phenolic compounds in 50% aqueous ethanol (v/v) at 40 °C for 3 h appeared to be the most reliable and the least destructive method. We also recommend the use of Polyclar AT, a resin that retains phenolics in solution, to assess the amount of reductive nonphenolic substances present in the plant material analyzed.
The root systems of two sugar maple groves, one on acidic parent material, the other on calcareous parent material, were studied in Quebec. The microrelief of both sites consisted of bumps and holes. Bumps represented 65% of the area. On acidic parent material, the roots > 1 cm in diameter were more than 5 m long. On calcareous parent material, they rarely exceeded 4 m in length. These larger roots branched out into many smaller roots in all directions in the bumps, and in the upper soil horizons of the holes. In the acidic site, the rootlet mass was smaller (about 16 t•ha−1) than that observed in calcareous site (about 19 t•ha−1). In both sites, rootlet mass was higher in the bumps (14–17 t•ha−1) than in holes (2–4 t•ha−1). In bumps, 80 and 69% of these rootlets grew in the B horizons in acidic and calcareous sites, respectively. In the holes, rootlets were concentrated (> 65%) in the F and Ah horizons. In the acidic site, rootlets < 0,5 mm in diameter were longer, more entangled, and more densely packed (7–11 mg•cm−3) in the F and Ah horizons than in the B horizons (1–2 mg•cm−3); F and Ah horizons of the bumps also produced the highest density of rootlets < 0,3 mm in diameter (about 50 and 20 mg•cm−3, respectively). In the other horizons of this site, as well as in all horizons of the calcareous site, the rootlets were short and developed in tufts. In the calcareous site, rootlets < 0,3 mm in diameter were less abundant in the Ah horizons of bumps (about 10 mg•cm−3). This site contained more rootlets 1–2 mm in diameter than the acidic site.
. 2002. A comparison of soil fertility and leaf nutrient status of sugar maples (Acer saccharum) in relation to microrelief in two maple forests in Québec. Can. J. Soil Sci. 82: 23-31. This study was conducted to provide a better understanding of the relationship between foliar nutrient status, maple dieback and soil quality. Fieldwork was conducted in four maple stands, two of which were located in the Appalachians at Tingwick and two in the Laurentians at Duchesnay. All stands were characterised by a mound and depression microrelief. In one of the Tingwick maple stands (T 1 ) the predominant soil type was found on mounds, and was well to moderately well-drained (Leeds and Woodbridge series). At the other site (T 2 ), the predominant soil type was in depressions, and imperfectly to poorly drained (Sainte-Marie and Brompton series). At the first Duchesnay site (D 1 ) the predominant soil type was found on mounds and was well to rapidly drained (Ste Agathe series). At the second Duchesnay site (D 2 ), the predominant soil type was also found on mounds, but was well to moderately well-drained (Sergent series). On all sites, the soils were acidic and nutrient poor. The lowest pH values and nutrient concentrations (in the H-Ah horizons) were found in maple stands with well-drained soils (T 1 and D 1 ) (P < 0.05). On these sites, maple dieback was less than 10%. It was on the poorly to imperfectly drained soils at Tingwick (T 2 ), as well as on the moderately drained soils at Duchesnay (D 2 ), that we observed the lowest biological activity. Although these soils were the most nutrient rich, we observed foliar nutrient deficiencies, and maple dieback in excess of 25%. Our results suggest that maple dieback is the result of a poor physiological adaptation of sugar maple to poor drainage conditions in the areas studied. Dans l'autre érablière (D 2 ), les sols dominants se retrouvent également sur les bosses mais le drainage est de bien à modérément bien drainé (séries de Sergent). Les sols sont pour l'ensemble acides et pauvres en éléments nutritifs. Le pH et les teneurs en éléments nutritifs (horizons H-Ah) les plus faibles se retrouvent dans les érablières dominées par les sols bien à très bien drainés (T 2 et D 1 ) (P < 0,05). Dans ces milieux, les érables présentaient un dépérissement moyen inférieur à 10 % et n'indiquaient aucune carence foliaire. C'est dans le milieu dominé par des sols mal à imparfaitement drainés de Tingwick (T 2 ) et modérément bien drainés de Duchesnay (D 2 ), que l'on a observé la plus faible activité biologique. Bien que ces sols étaient les plus riches en éléments nutritifs, on a observé des carences foliaires et un dépérissement supérieur à 25 %. Les résultats obtenus indiquent que le dépérissement est la conséquence d'une adaptation physiologique des érables à sucre aux mauvaises conditions de drainage du milieu.
We conducted a study on the influence of microrelief on the content of phenolic compounds and mineral elements in leaves of sugar maple (Acersaccharum Marsh.) at various stages of decline. The stand of origin was located in the Appalachian Highlands of Quebec, on acidic material with a microrelief constituted of hollows and bumps, the height of the latter varying between 30 and 60 cm. Well aerated podzols developed on bumps, while gleysols developed in hollows. Trees generally grew on bumps and their roots could extend as far as 5 m away from the tree. Microrelief and soils were described within a 5-m radius around every sugar maple under study. Pedological sites were classified into three categories according to their microrelief (percent surface area covered by bumps): (i) less than 30% of surface (dominance of poorly drained soils), (ii) between 30 and 50% of surface (dominance of imperfectly drained soils), and (iii) more than 50% of surface (dominance of well drained soils). A principal component analysis on site distribution and a chemical analysis of soils showed an increase in total N and in K, Ca, and Mg availability with an increase in soil humidity. The principal component analysis and chemical analysis of leaves indicated that the content of phenolic compounds was highest, and those of N and K lowest, in moistest soils. The decline was also greatest on those sites. There was a strong correlation between synthesis of phenolic compounds and foliar N contents, and between decline intensity and foliar N content. The high humidity of some soils of the study sites reduces the availability of N, causing a stress to sugar maples. This phenomenon would result in an increased synthesis of phenolic compounds and a decline in less resistant trees. Phenolic compounds could then be utilized as a physiological indicator of stress. Those results explain why healthy trees can grow next to declining trees.
The effect of two application modes of nitrogen fertilization on leaf nitrate reductase activity, Ieaf nitrate content and grain and straw protein content was studied in three oat cultivars: Lamar, Cascade and Cabot. The enzymatic activity shows the same biological rhythm for the three cultivars, no matter when the nitrogen was applied; the activity was high at the coleoptile stage, reached a maximum at tillering and then decreased until heading. However, Lamar presented a higher maximum activity at tiliering when nitrogen fertilizer was applied at sowing. Ammonium nitrate applied twice during growth resulted for all cultivars in a longer period of higher activity and at the same time a decrease of its amplitude. In leaves, the nitrate availability at the site of reduction was different according to t"ertilization mode: maximum nitrate content Can. J. Plant
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