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  • 1
    ISSN: 1432-1939
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Seedlings of Betula pendula Roth. and Gmelina arborea L. were subjected to variation in temperature and irradiance. The influence of a mild water-stressing treatment on the photosynthetic performance and stomatal behaviour of these plants was assessed. For both species, the shape of the relationships between irradiance and photosynthesis and temperature and photosynthesis resembled those reported for other species. The effect of water stress was to reduce the rate of photosynthesis, particularly at high temperatures. This was largely a function of a reduction in mesophyll conductance under these conditions. The optimum temperature for stomatal opening was significantly lower than the optimum temperature for photosynthesis, which was in turn lowered by the water stress treatment. The stomata of birch seedlings showed maximum opening at an intermediate temperature while the stomata of Gmelina generally exhibited a closing movement when leaf temperatures increased from 15° C. Mesophyll conductances of both species increased with increasing temperature. The physiological basis for the variation in photosynthetic performance and stomatal behaviour and the ecological significance of this variation are discussed.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-1939
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Leaves of well-watered and mildly water-stressed seedlings of Betula pendula Roth. and Gmelina aroborea L. were subjected to a range of vapour pressure deficits (VPD) between 10 and 24 kPa. The stomatal conductance of birch seedlings decreased as VPD was increased and at least in mildly-stressed seedlings this response seemed to be closely linked to the water status of the air rather than to the bulk water status of the plant. Mild water stressing enhanced the degree of the stomatal humidity-response and resulted in a significant increase in the efficiency of water use at high VPD. Stomata of Gmelina were apparently insensitive to variation in VPD, but were more sensitive to a decrease in bulk leaf water status than were stomata of birch. Water use efficiency of Gmelina seedlings was comparatively high, even when VPD was high and the stomata were fully open.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Oecologia 51 (1981), S. 343-350 
    ISSN: 1432-1939
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary First year seedlings of English oak (Quercus Cobur) and silver birch (Betula pendula) were subjected to pressure-volume analysis to investigate the water potential components and cell wall properties of single leaves. It was hoped that this rapid-drying technique would differentiate between reductions in plant solute potential resulting from dehydration and the effects of solute accumulation. Comparison of results from these experiments with those of slow drying treatments (over a number of days) with plants growing in tubes of soil, indicated that some solute accumulation may have occurred in drying oak leaves. High leaf turgor and leaf conductance were maintained for a significant period of the drying cycle. Roots of well-watered oak plants extended deep into the soil profile, and possibly as a result of solute regulation and therefore turgor maintenance, root growth of unwatered plants was greater than that of their well-watered counterparts. This was particularly the case deep in the profile. As a result of deep root penetration, water deep in the soil core was used by oak plants to maintain plant turgor, and quite low soil water potentials were recorded in the lower soil segments. Root growth of well-watered birch seedlings was prolific but roots of both well-watered and unwatered plants were restricted to the upper part of the profile. Root growth of unwatered plants was reduced despite the existence of high soil water potentials deep in the profile. Shallow rooting birch seedlings were unable to use this water. Pressure-volume analysis indicated that significant reductions of water potential, which are required for water uptake from drying soil, would occur in oak with only a small reduction in plant water content compared to the situation in birch. This was a result of the low solute potential in oak leaves combined with a high modulus of elasticity of cell walls. Deep rooting of oak seedlings, combined with these characteristics, which will be particularly important when soil deep in the profile begins to dry, mean that this species may be comparatively successful when growing on dry sites.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Biology and fertility of soils 27 (1998), S. 9-14 
    ISSN: 1432-0789
    Keywords: Key words Cassava ; Alley-cropping ; Glomus clarum ; Leaf area index ; Hedgerow trees
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The effect of inoculation with Glomus clarum, a vesicular-arbuscular mycorrhiza fungus, and alley-cropping on the growth of the cassava cultivar, TMS 30572, was investigated under field conditions in a low nutrient tropical soil. Cassava was grown either interplanted between two hedgerow tree species (alley-cropped) or sole-cropped. Sub-plots were either inoculated with G. clarum or were not inoculated. No effort was made to destroy the indigenous mycorrhizal fungi. Three months after planting, no significant influence of G. clarum inoculation was observed on the growth of roots, shoots or leaf area index (LAI). However, with time, inoculation and system of cropping enhanced these growth parameters. Nine months after planting, the total biomass of alley-cropped cassava was significantly higher than that of inoculated and non-inoculated sole-cropped cassava. Inoculation had led to an increase in the fresh tuber yield of both the alley- and sole-cropped cassava 12 months after planting. The LAI of both alley- and sole-cropped cassava inoculated with G. clarum increased.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1432-0789
    Keywords: Alley-cropped cassava ; Manihot esculenta Crantz ; Hedgerow tree legumes ; Nutrient extraction ; Vesicular-arbuscular mycorrhizal inoculation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Leaf and root (tuber) nutrient uptake patterns of cassava (Manihot esculenta Crantz) alley-cropped with gliricidia (Gliricidia sepium), leucaena (Leucaena leucocephala), and senna [(Senna (syn. Cassia) siamea] as influenced by vesicular-arbuscular mycorrhizal (VAM) inoculation in a degraded Alfisol were investigated in consecutive years. The cassava plants were mulched with fresh prunings of each hedgerow tree species at 2-month intervals in the second and third years of alley cropping. While VAM inoculation significantly influenced the root uptake of nutrients, the leaf uptake was not affected except for the uptake of P. In most cases, there was no difference in the nutrient concentration between inoculated and uninoculated plants, either in the leaf or in the root, indicating that the productivity of cassava was regulated by the amount of nutrients the roots could absorb. In spite of similar total soil N in all inoculated and uninoculated alley-cropped cassava plots and similar exchange-able soil K contents in inoculated and uninoculated alley-cropped cassava plots with leucaena and senna, greater uptake of N, P, and K and greater concentrations of K were observed in roots of inoculated alley-cropped cassava with gliricidia and leucaena than with senna. These results indicated that greater mineralization and availability of nutrients to cassava roots from prunings of nodulating gliricidia and leucaena than from non-nodulating senna may be important, particularly with efficient VAM inoculation, in these alley-cropping systems. Also, for similar nutrients in the inoculated and uninoculated cassava soils alley-cropped with each hedgerow species, VAM inoculation significantly enhanced cassava root dry weights, indicating that an effective VAM fungus can be an agent of greater nutrient uptake in a competitive environment.
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 1432-1939
    Keywords: Forest decline ; Spruce ; Nutrients ; Xylem sap
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The nutrient relations (nitrogen, magnesium, calcium, potassium, and manganese) of the xylem sap of spruce trees, Picea abies (L.) Karst., growing at a healthy and a declining site in Northern Bavaria, were followed on a diurnal and seasonal basis between April and October 1985. There were significant differences between the two sites in the xylem sap concentrations of all elements investigated except nitrogen. Nutrient concentrations remained constant diurnally despite changes in transpiration and xylem water potential. However, during periods between precipitation events, concentrations of elements in xylem sap decreased with decreasing xylem water potential. Apparent differences in needle chlorosis of spruce trees at the two sites were associated with consistent differences in nutrient contents of their xylem sap and needles.
    Type of Medium: Electronic Resource
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  • 7
    ISSN: 1432-1939
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Stomatal conductance of unstrossed, soil drought, and previously drought (predrought) Gmelina arborea seedlings increased in the morning and decreased before or immediately after midday. In the unstressed and predrought seedlings, leaf water potential decreased with increases in transpiration. In soil drought seedlings, there was some evidence of decreased hydraulic conductivity from soil to the plant, as indicated by the shape in the slope of the water potential/transpiration relationship. Root growth of drought plants was greater than in their unstressed counterparts at the lowest soil segment of a pot. The partial recovery of predrought seedlings was attributed to this subtantial root growth in the lowest soil segment. In the second experiment, Gmelina arborea seedlings were partially waterlogged, by flooding the polyethylene bag to half its length, for a period of 23 days. Waterlogging induced stomatal closure and reduction in leaf water potential but there was some evidence of tolerance to waterlogging towards the end of treatment. Root growth, shoot and root dry weights were slightly reduced below those of controls. After 9 days of waterlogging, adventitious roots began to form which correlated with depletion of soluble sugars in the shoot but with an increase in the roots. It is suggested that the tolerance of Gmelina plants to either soil drought or waterlogging may partly be due to partitioning of the soluble sugars from shoot to roots for production of roots and formation of adventitious roots respectively which are likely to enhance the flow of water from the soils to the plant. Therefore the plant response is very similar under conditions of increased deficits and surplus of soil water.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Oecologia 66 (1985), S. 554-557 
    ISSN: 1432-1939
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Greenhouse-grown cowpeas, Vigna unguiculata (L.) Walp., were subjected either to well-watered or to progressive soil drought conditions between 10–40 days after emergence. Stomatal closure was found to correlate with the progressive drying of soil while leaf water potentials were not very different from the well-watered plants. Reduction in leaf turgor resulted in a reduced rate of leaf extension but increased that of root. Stomatal conductance and transpiration rates of soil-drought plants were similar to well-watered plants in the morning, but were greatly reduced in the afternoon till evening. It is suggested that the maintenance of transpiration rates per unit leaf area of soil-drought cowpeas in the morning is due to the reduction in the leaf area per plant and possibly the hydration of the plants in the night through enhanced root growth.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    Oecologia 32 (1978), S. 323-332 
    ISSN: 1432-1939
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Young seedlings of English Oak, Quercus robur L., and Silver Birch, Betula verrucosa Ehrl., were subjected to a number of consecutive periods during which water was withheld. During one 14-day period leaf-and soil-water potentials and leaf- and root-solute potentials of two groups of plants were sampled at noon of each day. One group of plants was watered every day while water was withheld from the other group. Solute accumulation in roots and leaves of oak seedlings subjected to water stress resulted in maintenance of turgor and high leaf conductance as the soil dried. In birch seedlings turgor was only maintained by stomatal closure at high soil water potential. Fourteen consecutive water stress cycles greatly reduced the growth of birch seedlings but had little effect on oak seedlings other than to alter root morphology. Water stress treatment resulted in the production of long thin roots in this plant. Stomatal behaviour in oak and birch seedlings during the 14-week stress period was consistent with observed changes in leaf water and solute potentials. Daily solute accumulation in oak leaves was presumably responsible for the maintenance of plant growth as water potentials fell.
    Type of Medium: Electronic Resource
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  • 10
    ISSN: 1432-0789
    Keywords: Acacia trees ; Drought tolerance ; Sterile and non-sterile soils ; Plant dry weights ; VAM fungi
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Faidherbia albida (syn. Acacia albida) (Del.) A. Chev. and Acacia nilotica (L.) Willd. were grown for 18 weeks in sterile and non-sterile soils inoculated with Glomus clarum (Nicolson and Schenck). During this period, drought stress was imposed for the last 10 (F. albida) or 12 weeks (A. nilotica) at 2-week intervals. A greater number of leaves abscissed in drought-stressed mycorrhizal plants of A. nilotica than drought-stressed non-mycorrhizal and unstressed plants. In F. albida, the number of abscissed leaves was few and similar for all treatments. At the end of the drought stress, inoculation with vesicular-arbuscular mycorrhizal (VAM) fungi in sterile soil increased the plant biomass of the two tree species compared to the control plants. In non-sterile soil, the mycorrhizal growth response of introduced G. clarum equalled the effect of indigenous VAM fungi. There were significant interactions between the mycorrhizal and drought stress treatments and between the mycorrhizal and soil treatments for plant biomass and P uptake in F. albida. The absence of these interactions except for that between the mycorrhizal and soil treatments in A. nilotica indicates that the increased plant biomass and nutrient uptake cannot be attributed directly to a mycorrhizal contribution to drought tolerance. F. albida tolerated the drought stress by producing long tap roots and similar weights of dry matter in shoots and roots. Whereas A. nilotica tolerated the drought stress by developing larger root systems able to explore a greater volume of soil, in addition to leaf abscission, for a favourable internal water status. The introduction of G. clarum increased nodulation by A. nilotica under unstressed conditions, but at the expense of a reduced P uptake in sterile soil.
    Type of Medium: Electronic Resource
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