To determine the effects of lifting time and storage on water-stress resistance of nursery-grown white spruce (Picea glauca (Moench) Voss) seedlings, we compared gas exchange, water relations and mortality of 3-year-old seedlings lifted in October 1991 and stored at -2 degrees C for 3 months with seedlings lifted in January 1992. The seedlings were placed in nutrient solution and subjected to -1.1 or -2.7 MPa water stress induced by polyethylene glycol 3350 for 9 days. Water stress, but not lifting time, had a significant effect on seedling net assimilation, symplastic volume and turgor loss point. In a second experiment, seedlings lifted in October 1991 were stored at -2 degrees C for 7 months and compared with seedlings lifted in May 1992. The seedlings were planted in pots, and their gas exchange and water relation parameters measured in response to gradual water stress. The results suggest that prolonged cold storage retards photosynthetic recovery of seedlings after planting. Higher rates of net assimilation in seedlings lifted in May were not directly related to their water status. Nonstomatal limitations were the primary factor influencing photosynthetic rate. We conclude that the inferior ability of cold-stored seedlings to tolerate water stress was due to poor osmotic adjustment and a lag in recovery of photosynthesis.

We designed a simple, portable, battery-operated, temperature-controlled cuvette to measure respiration of small samples of plant tissue in the field. The cuvette is built around a peltier cell and is controlled with a data logger. The cuvette maintained sample temperature within 0.5 degrees C over a temperature range of 5 to 45 degrees C and operated for 6-8 h from a 12 V 105 ampere-hour "deep-cycle" battery. Based on measurements with this cuvette, we found that, at 15 degrees C, CO2 efflux from dark respiration of white pine (Pinus strobus L.) foliage was 40% greater during the day than at night.

Three controlled water supply treatments were applied to l-year-old peach trees grown in root observation boxes. The treatments were: I0, growth medium maintained at 50% field capacity; I1, water supplied when daily net tree stem diameter change was negative or zero for l day; I3 as for I0 except that water was applied after net daily stem diameter change was negative or zero for 3 consecutive days. Trees in treatment I0 had the greatest mean daily first-order shoot growth rates, and trees in treatment I3 had the lowest shoot growth rates. Because leaf production rate (apparent plastochron) of first-order shoots was unaffected by treatment, differences in shoot length were due to differences in internode extension and not to the number of internodes. Trees in treatment I0 had a greater number of second-order shoot axes than trees in treatment I1 or I3. Furthermore, an increase in the rate of growth of the first-order shoot axis was associated with an increased tendency for branching (i.e., the development of sylleptic second-order shoots). Increased leaf length was also associated with more frequent watering. Trees in treatment I0 had the greatest root lengths and dry weights, and this was attributed to a greater number of first- and second-order (lateral) root axes compared with trees in the I1 and I3 treatments. The extension rate and apical diameter of first-order roots were reduced by the I3 treatment. The density of second-order roots along primary root axes was not affected by any of the treatments.

We tested the hypothesis that the leaf area/sapwood area ratio in Scots pine (Pinus sylvestris L.) is influenced by site differences in water vapor pressure deficit of the air (D). Two stands of the same provenance were selected, one in western Scotland and one in eastern England, so that effects resulting from age, genetic variability, density and fertility were minimized. Compared with the Scots pine trees at the cooler and wetter site in Scotland, the trees at the warmer and drier site in England produced less leaf area per unit of conducting sapwood area both at a stem height of 1.3 m and at the base of the live crown, whereas stem permeability was similar at both sites. Also, trees at the drier site had less leaf area per unit branch cross-sectional area at the branch base than trees at the wetter site. For each site, the average values for leaf area, sapwood area and permeability were used, together with values of transpiration rates at different D, to calculate average stem water potential gradients. Changes in the leaf area/sapwood area ratio acted to maintain a similar water potential gradient in the stems of trees at both sites despite climatic differences between the sites.

The activities of ribulose-1,5-bisphosphate carboxylase-oxygenase, Rubisco (E.C. 4.1.1.39) and phosphoenolpyruvate carboxylase, PEPc (E.C. 4.1.1.31), and concentrations of protein and chlorophyll were measured in extracts from cotyledons and first leaves of Qualea grandiflora Mart. (Vochysiaceae) seedlings after transfer from high-light (20 days at 320 micromoles m-2 s-1, PAR) to low-light (35 days at 120 micromoles m-2 s-1, PAR) conditions. When Tween 20 and glycerol were added to the extraction medium, Rubisco activities obtained for Qualea grandiflora were comparable to published values for several coniferous species and the broad-leaved species, Prunus avium L. Stella, grown in a similar light environment. Rubisco activity in cotyledons of Q. grandiflora grown in high light for 20 days and then transferred to low light for a further 35 days was similar to the activity in cotyledons of plants grown continuously in high light. However, the first leaf above the cotyledons showed a greater response to the change in irradiance; in high light, Rubisco activity of the first leaf was 1.8 times higher on a fresh weight basis and 2.7 times higher on an area basis than that of leaves transferred from high to low light. Fresh weight and chlorophyll concentration expressed on a unit leaf area basis were also higher in the high-light treatment. These responses to irradiance are indicative of a species adapted to growth in an unshaded habitat. The PEPc activity in leaves was 15% of Rubisco activity, which is typical of species with a C3 photosynthetic pathway. The relatively slow growth rate of Q. grandiflora observed in these experiments could not be attributed to a low carboxylation capacity per unit leaf area.

Beech leaves were sampled during two consecutive years from three sites characterized by forest decline. Both monomeric and oligomeric flavanols from green and yellowing leaves were determined quantitatively by reversed-phase, high-performance liquid chromatography (HPLC) combined with a chemical reaction detection technique (CRD). Yellowing leaves generally contained more than twice the quantity of flavanols than normal green leaves. The monomeric flavanols, epicatechin and (+)-catechin, comprised up to 80% of the total flavanol fraction. Histochemical staining with p-dimethylaminocinnamaldehyde was used to determine local deposition of flavanols, including insoluble oligomeric flavanols, in leaf tissues. The yellowing leaves stained intensely, whereas the green leaves stained lightly. Flavanol staining was strongest in the spongy parenchyma followed by the palisade cells. The upper epidermis stained more intensely than the lower epidermis. A 4-day treatment of small leaf pieces (5 X 5 mm) with 0.04 mM paraquat resulted in browning of the leaf pieces. The browning reaction was prevented when the paraquat treatment was carried out in the presence of 0.16 mM (+)-catechin, indicating an antioxidative property for this flavanol.

During different phases of the annual growth cycle, xylem sap was collected from trunk segments of adult beech (Fagus sylvatica L.) trees by the water displacement technique. Irrespective of the height of the trunk, both sulfate and reduced sulfur compounds were detected in the xylem sap throughout the year. Sulfate was the predominant sulfur compound in all samples analyzed. Its concentration in the xylem sap varied between 10 and 350 micromoles l(-1), with highest concentrations in April, shortly before bud break. In contrast to other tree species, cysteine and not glutathione was the predominant thiol transported in the xylem sap of beech trees. The cysteine concentration ranged between 0.1 and 1 micromole l(-1). As observed for sulfate, maximum cysteine concentrations were found in April. Apparently, both sulfate and cysteine transport contribute to the sulfur supply of the developing leaves. Seasonal changes in the axial distribution of cysteine and sulfate differed, indicating differences in the source-sink relations of these sulfur compounds. High, but uniform, xylem sap sulfate concentrations in April may originate from balanced sulfate uptake by the roots, whereas high cysteine concentrations in April, increasing with increasing height of the trunk, may originate in part from protein breakdown in the trunk. Reversal of the axial distribution of xylem sap cysteine in late summer-early fall to higher concentrations in the lower part of the trunk than in the upper part of the trunk suggests that the upper part of the trunk becomes a sink for cysteine as a result of the synthesis of storage proteins at this time of the year.

The specific respiration rate at 20 degrees C (R20) of peach leaves and stems, declined rapidly from a high value in the early spring (22.5 nmol CO2 gdw(-1)s-1) to relatively constant rates by July (3.1 nmol CO2 gdw(-1) s(-1). Leaf declined more rapidly than current-year stem R20, but leaf and current-year stem R20S were similar by July. The R20 current-year stems in July was approximately 2.5 times greater than that of one-year-old stems (1.3 nmol CO2 gdw(-1)(s-1), and about 30 times greater than that of the trunk R20S (0.1 nmol CO2 gdw(-1)s(-1)). The Q10S of leaves and stems were approximately 2 for a temperature increase between 20 and 30. The Q10S above 30 were 2.03 for leaves but only 1.61 for stems. Leaves and current-year stems accounted for 2 and 17% of the aboveground vegetative biomass in April and August, respectively, but accounted for 59-80% of total daily (24 h) respiration. Although trunk biomass accounted for 91 and 77% of aboveground vegetative biomass, in April and August, respectively, trunk respiration accounted for only 8-15% of daily aboveground respiration. Before harvest, during a period when fruit growth was source-limited, daily fruit respiration exceeded respiration by all aboveground vegetative organs.

Annual cycles of change in bud morphology, bud burst ability, abscisic acid (ABA) concentration, and starch and water content were studied in mid-crown terminal buds of short shoots and underground basal buds of Betula pubescens Ehrh. In particular, we investigated the roles of ABA and bud water content in the regulation of bud growth. Basal buds differed morphologically from terminal buds of short shoots in that their leaf initials did not develop into embryonic foliage leaves and their total size did not increase significantly during summer. Bud burst ability, measured by forcing detached short shoots and stumps under controlled conditions, was maintained in the basal buds throughout the year, whereas the terminal buds of short shoots remained dormant until October, thereafter their bud burst ability increased gradually and reached a maximum in March-April. The ABA concentration of the basal buds was relatively constant throughout the sampling period (1-3 microgram gDW-1) whereas that of the terminal buds of short shoots, which was much higher (5-10 microgram gDW-1), showed a distinct seasonal cycle with a maximum from August to November. Bud ABA concentration decreased during the first 10 days of forcing. especially in basal buds. In both bud types, the amount of starch increased toward the autumn, declined in November, and was negligible in the terminal buds of short shoots between January and March, but in April, the amount was high again in both bud types. Water content varied characteristically in both bud types, although more distinctly in the terminal buds of short shoots, with an increase in spring before bud burst and a decrease during the summer until September The significant morphological and physiological differences between the mid-crown terminal buds of short shoots and the underground basal buds may partly explain the characteristic growth habit of the basal buds and their development into coppice shoots after cutting the tree.

Six-year-old cloned Betula pubescens Ehrh. trees, grown outdoors at 65 degrees 01 minute N, were cut on six dates during the growing season to study coppice shoot development in relation to root-produced cytokinin-like compounds. Bleeding sap was collected over timed intervals for two days after cutting, and endogenous cytokinin-like compounds were measured by ELISA assay in HPLC-purified fractions of xylem sap. Initiation and development of coppice shoots on the clonally propagated plants were comparable to those in seedlings. Coppice shoot initiation was affected by the time of cutting, diminishing significantly after June. Of the cytokinin-like compounds detected in the xylem sap, zeatin riboside-like (ZR) compounds were present in the highest concentrations, and the concentrations of dihydrozeatin riboside-like (DHZR) and isopentenyladenoside-like (IPA) compounds were approximately one third and one eighth of the ZR concentrations, respectively. The concentration of cytokinin-like compounds was positively correlated with xylem sap flow rate. The export of cytokinin-like compounds, especially DHZR- and ZR-types, was positively correlated with the initiation and elongation rate of coppice shoots, the number of lateral branches, and the radial growth of the more slowly growing coppice shoots. The export of cytokinin-like compounds collected immediately after cutting may represent the basal value for each tree. This value is probably affected by the size and activity of the root system and may be a relevant estimate for predicting the success of coppicing.