Leaf Nitrogen Levels Research Articles

Fertilization Affects Leaf Consumption and Utilization by Porthesia scintillans Walker (Lepidoptera: Lymantridae)

Application of the nitrogen fertilizer urea to the host plant Ricinus communis L. at the rate of 75, 150, 300, and 400 g/m2 increased leaf nitrogen, water, and energy levels. Higher fertilization dosages were correlated with increased consumption and utilization of the leaf by the pest Porthesia scintillans Walker. A statistically significant linear relationship existed between the rates of feeding, assimilation, and tissue production of the pest and the fertilizer dosage and leaf nitrogen content. Increase in fertilizer dose of >150 g/m2 significantly increased the net production efficiency of the larva, whereas the efficiency of assimilation of the pest did not significantly vary with fertilizer dosage. Increased fertilizer application resulted in large adults with high fecundity and egg-production efficiency.

Growth, flowering and yield of lychee cultivars

The main period of vegetative flushing in high-yielding lychee trees ( Litchi chinensis Sonn. cultivars ‘Tai So’, ‘Haak Yip’ and ‘Wai Chee’) in seven orchards in subtropical Australia (latitude 27°S) occurred after harvest from late summer and ceased 4–6 weeks before panicle emergence in May–July. Trees did not flush during winter or spring unless flowering or fruit set failed. There was no evidence of concurrent vegetative and reproductive growth in the same shoot. There was an inverse correlation between the percentage of branches flowering and the percentageof branches flushing vegetatively in the 4–6 weeks preceding panicle emergence. Satisfactory yields were usually obtained when more than 90% of the terminal branches flowered. Flushing did not appear to be affected by temperature and rainfall or leaf nitrogen levels. The interaction of these factors demonstrates the difficultiss in separating the effects of different environental factors on vegetative growth in lychee.

Aspen Wood Chip and Stone Mulches for Landscape Plantings in Interior, Alaska

Abstract Five woody landscape plants were grown on five mulch treatments: 2.5 or 5 cm (1 or 2 in) crushed basaltic rock, 5 or 10 cm (2 or 4 in) of aspen wood chips and a non-mulched control, to determine the usefulness of these mulches in subarctic landscape plantings. Weed control was best, but growth and plant nutrition poorest on the wood chip mulches. White spruce, Siberian crabapple, Peking cotoneaster, and rugosa rose had low levels of leaf nitrogen on the wood chip plots, and all species except cotoneaster and lodgepole pine showed significant N deficiency symptoms after 2 years. With the exception of the roses, all species grew best on the stone mulch plots. Roses grew vigorously on the stone mulches and the unmulched soil, but were subject to winter dieback. After 3 years, their total biomass did not exceed the recumbent, spindly and nitrogen deficient roses that were growing on the wood chip mulches. Plant growth, nutrition, and weed control were best achieved on the 5 cm (2 in) stone mulch plots.

Changes in phenolic production in the hay-scented fern ( Dennstaedtia punctilobula) in relation to resource availability

Field studies of hay-scented fern ( Dennstaedtia punctilobula) were conducted to examine the relationships between environmental factors and levels of phenolics in leaves. Several predictions related to the carbon-nutrient balance hypothesis were examined. Light availability showed a significant positive correlation to total phenolics ( R 2 = 0.57; P<0.05 ). Although soil nitrogen was not significantly correlated with total phenolics, nitrogen in leaves was the most important factor in determining levels of phenolics. No single environmental factor significantly influenced levels of leaf nitrogen, indicating that a plant's integration of the combined availability of multiple resources determines the carbon-nitrogen balance in plant tissues, and consequently levels of chemical defense.

Relationship between wheat grain protein percentage and grain yield, plant growth, and nutrition at anthesis

Abstract Winter wheat (Triticum aestivum L.) var. Astral was grown in 1983–1984 in 12 experimental fields located in the Middle of the Duero Basin (Spain). The fields were fertilized at several rates of N, P, and K. Grain protein yield increased linearly with grain yield and with above‐ground plant dry weight at anthesis. Above ground dry weight of the crop accounted for 91.1% of the variance in grain protein yield among the different fields. The grain protein yield also increased linearly with leaf nitrogen level at anthesis. However, within each field, grain protein yield was generally more closely related with above‐ground dry weight at anthesis multiplied by the level of nitrogen in the two uppermost leaves (X3), than with any of these factors considered separately. The regressions over X3 were positive and varied among some of the fields. The intercept increased with grain yields and the slope with the concentration of magnesium. In addition, the ratio between grain protein yield and X3 increased wit...

Relationship between wheat grain protein yield and grain yield, plant growth, and nutrition at anthesis

Abstract Winter wheat (Triticum aestivum L.) var. Astral was grown in 1983–1984 in 12 experimental fields located in the Middle of the Duero Basin (Spain). The fields were fertilized at several rates of N, P, and K. Grain protein yield increased linearly with grain yield and with above‐ground plant dry weight at anthesis. Above ground dry weight of the crop accounted for 91.1% of the variance in grain protein yield among the different fields. The grain protein yield also increased linearly with leaf nitrogen level at anthesis. However, within each field, grain protein yield was generally more closely related with above‐ground dry weight at anthesis multiplied by the level of nitrogen in the two uppermost leaves (X3), than with any of these factors considered separately. The regressions over X3 were positive and varied among some of the fields. The intercept increased with grain yields and the slope with the concentration of magnesium. In addition, the ratio between grain protein yield and X3 increased with the leaf magnesium level. This suggests that grain might favour the assimilation of exogenous nitrogen during its development and/or the translocation of nitrogen from the vegetative parts of the plant to the grain. Moreover, magnesium might increase the efficiency of protein accumulation in grain. Among fields, the relationship of grain protein yield with leaf magnesium level depended on the level of nitrogen.

Leaf nitrogen and its effects on the rate of herbivory on selected eucalypts in the jarrah forest

This study measured the relationship between the rate of leaf consumption by insect herbivores and the level of leaf nitrogen in selected species of eucalypts. Sampling was carried out on a monthly basis from Eucalyptus accedens, Eucalyptus resinifera and Eucalyptus marginata in areas rehabilitated following bauxite mining and from E. marginata in a forest regenerated after clearfelling. The rate of herbivory was examined on leaves aged 1–3 years. The mean monthly rate of herbivory of all species varied from 0.9 to 1.9% of the total leaf area and was positively correlated ( P < 0.05) with the level of leaf nitrogen in E. marginata. The previous month's level of nitrogen was also positively correlated to the rate of herbivory in the current month in all species. The level of leaf nitrogen was negatively correlated to the current and previous month's level of herbivore abundance and the current month's rate of herbivory in E. resinifera. These correlations suggest two possibilities. Firstly, that in some eucalyptus the level of leaf nitrogen may be lowered when the level of predation on leaves is high. Secondly, the herbivorous insects may preferentially feed on eucalypt leaves having a high amount of nitrogen.

Effect of nitrogen fertilizers on leaf and soil nitrogen levels in highbush blueberries

Abstract Leaf N and soil nitrate and ammonium levels were monitored in 1986 and 1987 following N fertilization of 8–9 year old highbush blueberries. Urea was applied at 76 kg N/ha in a single application at bud break or in two applications (split) at bud break and petal fall. Controlled release fertilizers (CRF), of two different residual effects (Osmocote 3 mo., Osmocote 8 mo.) were applied at 38 kg N/ha or 76 kg N/ha at bud break. Compared to controls, N applications increased soil ammonium and nitrate levels early in the season and leaf N levels throughout the season. Urea provided a greater increase in leaf N and soil ammonium levels than CRF. Split urea applications increase leaf levels slightly over single urea treatments. Fertilizers increased soil ammonium and nitrate levels below the root zone, indicating that some leaching losses occurred.

Patterns of growth, reproduction, defense, and herbivory in the dioecious shrub Baccharis halimifolia (Compositae)

Patterns of growth, reproduction, defense (leaf resin) and herbivory were compared between the sexes of the dioecious shrub Baccharis halimifolia (Compositae). Male plants possessed longer shoots and more tender leaves, grew faster, and flowered and senesced earlier than female plants. Levels of leaf nitrogen, water content, and acetone-soluble resin (shown to deter feeding by polyphagous insect herbivores) did not differ between male and female plants. When offered a choice between leaves from male and female plants, adults of two leaf beetles (Chrysomelidae), the monophagous Trirhabda bacharidis and the polyphagous Paria thoracica, both preferred to feed on male leaves. Similarly, the daily fecundity of older females of T. bacharidis was higher when they were fed leaves from male compared to female plants. However, adult survivorship and total fecundity of T. baccharidis did not differ between male and female leaf treatments. We attribute the feeding preference for and slight increase in fecundity on male plants to the tenderness of male leaves. Larvae of the fly Tephritis subpura (Tephritidae) fed exclusively in the sterile receptacle of male flower heads (85% infested), but the phenology was such that pollen production was not adversely affected. Larvae of two other flies Dasineura sp. and Contarinia sp. (Cecidomyiidae) occupied >95% of only female flower heads where they fed among and on the developing seeds. We conclude that foliage-feeding herbivores are unlikely candidates to explain the female-biased sex ratio (59% female) of B. halimifolia plants in the field, and that their preference for male plants is a result of plant characteristics (e.g. rapid growth) that have been selected by some other factor. However, our data on selective floral herbivory in B. halimifolia are in accord with the argument that dioecy reduces the inadvertent loss of flower parts of one sex when herbivores feed on flower parts of the opposite sex.

On the Role of Photosynthetic Responses in Constraining the Habitat Distribution of Rainforest Plants

Two rainforest species that differ in the range of light environments encountered by an individual provide a model system for illustrating implications of diurnal variation and spatial heterogeneity of the light environment within single canopies. The two species are similar in the acclimation of leaf-level photosynthetic characteristics to the leaf's past light environment, but are distinguished by the limited ability of the high-light species to decrease dark respiration in response to growth under shade. Over 24 h, total carbon gain from a leaf increases with increasing light, but may increase or decrease with increasing nitrogen. Intermediate nitrogen levels and photosynthetic capacities yield maximum daily carbon gain in only a narrow range of light environments. The ratio of daily photosynthesis to leaf nitrogen is a complex function of nitrogen, photosynthetic characteristics, and light availability in a microsite. Nitrogen levels in real leaves may be close to the optima, but leaf nitrogen levels are clumped relative to the optima. Daily carbon gain from a canopy of fixed total nitrogen tends to increase as the leaf area of the canopy decreases, a trend caused by two factors. First, photosynthetic capacity is a nearly linear function of leaf nitrogen up to the highest nitrogen levels observed in nature. Second, only leaves with nitrogen levels above a substantial threshold are competent to generate positive rates of net photosynthesis. Differences between the species in canopy architecture and leaf duration have counteracting effects on long-term nitrogen-use efficiency.

Crop development and leaf nitrogen in lychee in subtropical Queensland

Heaviest flowering of 6-9-year-old lychee trees (Litchi chinensis cv. Tai So) over 3 seasons in subtropical Queensland (lat. 27�S.) was associated with a growth check in the terminal shoots prior to panicle emergence (May-June). Leaf nitrogen was the main factor controlling the level of flushing before panicle emergence. Flushing was active (on &gt;40% of terminal branches) when leaf nitrogen concentration exceeded 1.85% N in April. These results suggest that flowering of lychee in subtropical environments where heavy rain precedes panicle emergence in autumn can be promoted by restricting leaf nitrogen levels prior to panicle emergence below 1.75-1.85% N to reduce vegetative flushing. Studies on the seasonal pattern of leaf nitrogen showed that the period during flowering to just after fruit set was the most stable for sampling for leaf nitrogen.

Changes in Leaf Quality Following Clipping and Regrowth of Urtica dioica, and Consequences for a Specialist Insect Herbivore, Aglais urticae

The hypothesis that interruption of normal plant phenology may provide opportunities for insect herbivores to escape the nutritional constraints imposed by their foodplant is tested using Urtica dioica and its specialist herbivore Aglais urticae. The changes in water content, total organic nitrogen, soluble protein nitrogen, insoluble organic nitrogen and fibre were measured in U. dioica leaves at one site for two years both before and after summer cutting. Leaf water content and nitrogen levels were high during the spring followed by a decline during flowering. Subsequent increases were noted in plants regrowing after being cut. Mature uncut plants did not show increases in water and total organic nitrogen. Growth rates of larvae feeding on regrowth plants were higher than those on mature plants and pupal weights were greater. Higher efficiencies of conversion of ingested and digested food appear to be the major contributors to this. The consequences of interrupted plant phenology for the life cycles of insects are discussed.

Differences between Indica and Japonica rice varieties in CO2 exchange rates in response to leaf nitrogen and temperature

Four Indica and five Japonica varieties of rice (Oryza sativa L.) were examined to elucidate their differences in photosynthetic activity and dark respiratory rate as influenced by leaf nitrogen levels and temperatures. The photosynthetic rates of single leaf showed correlations with total nitrogen and soluble protein contents in the leaves. Respiratory rate was also positively correlated with the leaf nitrogen content. When compared at the same level of leaf nitrogen or soluble protein content, the four Indica varieties and one of Japonica varieties, Tainung 67, which have some Indica genes derived from one of its parents, showed higher photosynthetic rates than the remaining four Japonica varieties. At the same photosynthetic rate, the Indica varieties showed lower respiratory rate than Japonica varieties. When the leaf temperature rose from 20°C to 30°C, the photosynthetic rate increased by 18 to 41%, whereas the respiratory rate increased by 100 to 150%. These increasing rates in response to temperature were higher in the Japonica than in the Indica varieties. In this respect, Tainung 67 showed the same behavior as of the other four Japonica varieties.

Standard leaf nutrient levels for bearing macadamia trees in south east Queensland

The mean monthly nutrient composition of macadamia leaves was assessed over three seasons on 10 trees each of two cultivars at three orchards in south east Queensland. Leaf nitrogen (N), phosphorus (P), sulphur (S) and boron (B) levels were lower and potassium (K), copper (Cu), iron (Fe), zinc (Zn) and manganese (Mn) were higher than the Hawaiian standards. Tentative standard leaf levels of 1.4–1.5% for N, 0.6–0.7% for K, 0.18% for S and 40–70 mg kg −1 for B are suggested as being more suitable for macadamias under Australian conditions. The other Hawaiian standards are accepted. Additional work is needed to further refine the standard levels, with emphasis on the effect of leaf nutrient composition on yield and quality of kernels. In Australia, leaves should be sampled in spring, preferably at the commencement of the spring flush and after anthesis. At this time, 6–7-month-old leaves which dominate the canopy and which have a relatively stable nutrient composition from the previous summer flush should be sampled from dormant terminals. Small but statistically significant differences were obtained in leaf nutrient levels between cultivars ‘Keauhou’ (246) and ‘Kakea’ (508). Differences are unlikely to be of physiological importance, except perhaps for N and K which were higher in (508), and Ca which was higher in (246).

Mistletoes: a hypothesis concerning morphological and chemical avoidance of herbivory.

Leaves from many misletoe species in Australia strongly resemble those of their hosts. This cryptic mimicry has been hypothesized to be a means of reducing the likelihood of mistletoe herbivory by vertebrates. Leaf Kjeldahl nitrogen contents (a measure of reduced nitrogen and thus amines, amino acids and protein levels) of mistletoes and their hosts were measured on 48 mimetic and nonmimetic host-parasite pairs to evaluate hypotheses concerning the significance of crysis versus noncrypsis. The hypothesis that mistletoes mimicking host leaves should have higher leaf nitrogen levels than their hosts is supported; they may be gaining a selective advantage through crypsis (reduced herbivory). The second hypothesis that mistletoes which do not mimic their hosts should have lower leaf nitrogen levels than their hosts is also supported; they may be gaining a selective advantage through noncrypsis (reduced herbivory resulting from visual advertisement of their reduced nutritional status).

Effects of foliar-applied nitrogen during winter on growth, nitrogen content and production of passionfruit

The effects of foliar-applied nitrogen (11.5 g N l −1) during winter on growth, nitrogen content and production of passionfruit ( Passiflora edulis f. edulis × P. edulis f. flavicarpa cultivar E-23 grafted onto P. edulis f. flavicarpa) was investigated in subtropical Queensland, Australia. Vegetative growth and flowering were severely restricted during winter in the untreated vines, despite the maintenance of leaf nitrogen levels within the range presently believed to be optimum for Queensland conditions after nitrogen was applied to the soil in autumn. Foliar urea applications during winter (monthly or twice monthly) increased leaf nitrogen levels but reduced growth and subsequent fruitlet number. Reductions in vegetative growth during winter in passionfruit appear to be due to a direct effect of cool soil and/or air temperatures, unrelated to nitrogen uptake, translocation and leaf nitrogen level.

PHOTOSYNTHETIC RESPONSES TO LIGHT IN AN UNDERSTORY HERB, ASTER ACUMINATUS

Previous studies of the understory herb, Aster acuminatus, have shown that variation among natural patches in ramet growth, reproduction and population dynamics reflects environmentally induced responses to differences in patch light regimes. This set of experiments was undertaken to determine if photosynthetic responses to variation in light could provide a physiological explanation for the observed differences among patches. Ramets were raised in pots under different light regimes in either the field or growth chambers and then were taken to the lab for analyses of photosynthetic light responses. Ramets acclimated to the light conditions they experienced. Low‐light plants had lower maximum photosynthetic rates, light saturation points and light compensation points compared to high‐light plants. These differences were more pronounced for growth chamber‐grown plants than for those from the field. Differences between ramets grown in deep shade and partial sun in the field were greatest early in the season and then became less as photosynthetic rates for all plants declined. Photosynthetic rates were strongly correlated with leaf nitrogen level, and there was no evidence that nitrogen was any more limiting for one treatment compared to others. These results demonstrate a physiological basis for patch differences in growth, reproduction and dynamics.

Photosynthetic Responses to Light in an Understory Herb, Aster acuminatus

Previous studies of the understory herb, Aster acuminatus, have shown that variation among natural patches in ramet growth, reproduction and population dynamics reflects environmentally induced responses to differences in patch light regimes. This set of experiments was undertaken to determine if photosynthetic responses to variation in light could provide a physiological explanation for the observed differences among patches. Ramets were raised in pots under different light regimes in either the field or growth chambers and then were taken to the lab for analyses of photosynthetic light responses. Ramets acclimated to the light conditions they experienced. Low-light plants had lower maximum photosynthetic rates, light saturation points and light compensation points compared to high-light plants. These differences were more pronounced for growth chamber-grown plants than for those from the field. Differences between ramets grown in deep shade and partial sun in the field were greatest early in the season and then became less as photosynthetic rates for all plants declined. Photosynthetic rates were strongly correlated with leaf nitrogen level, and there was no evidence that nitrogen was any more limiting for one treatment compared to others. These results demonstrate a physiological basis for patch differences in growth, reproduction and dynamics.

Growth pattern and carbon allocation to volatile leaf terpenes under nitrogen-limiting conditions in Heterotheca subaxillaris (Asteraceae).

Rosettes of Heterotheca subaxillaris were grown at four levels of nitrate. Individual leaf volatile mono- and sesquiterpene content, leaf nitrogen content, and root and shoot dry weight were measured on individual leaves every two weeks for 18 weeks. Rosettes with the highest nitrate availability had 2.2-fold greater leaf nitrogen levels compared to plants with the lowest availability. As nitrate availability became increasingly limited, carbon allocation to both volatile leaf terpenes and root growht increased. Leaf mono- and sesquiterpene content was greatest in the young leaves of individuals growing at the lowest nitrate availability conditions. Higher levels of carbon-based herbivore-deterring chemicals in nitrate-limited plants may increase net productivity through retention of nitrogen that would otherwise be lost to herbivory.

Effect of 2,4-DB on Soybeans (Glycine max)

Field and greenhouse studies conducted in North Carolina in 1981 and 1982 evaluated the effect of the dimethylamine salt of 2,4-DB [4-(2,4-dichlorophenoxy) butyric acid] on soybeans. In the field, 2,4-DB at and above 0.07 kg ae/ha reduced soybean shoot mass, leaf nitrogen levels, and nodule activity. Soybean seed yields were reduced by 2,4-DB at and above 0.07 kg/ha. In greenhouse studies, total nodule activity was reduced by 0.07 and 0.14 kg/ha of 2,4-DB. Soybeans treated with 2,4-DB at initiation of flowering (R1 stage) or when pods were 1.9 cm long (R4 stage) yielded progeny with visible injury symptoms. Seedling emergence was also reduced in progeny of soybeans.