Increase In Total Leaf Area Research Articles

Effect of bioaugmented Linz-Donawitz slag and biochar on physiological and yield attributes of wheat (Triticum aestivum)

Industrial wastes and agricultural by-products are increasingly used in crop production as supplements along with fertilizers. An experiment was conducted during the winter (rabi) seasons of 2021 and 2022 at the research farm of the ICAR-Indian Agricultural Research Institute, New Delhi to determine the individual and combined effects of bioaugmented Linz-Donawitz (LD) slag and biochar on physiological and yield attributes of wheat (Triticum aestivum L.) variety HD 2967. Bioaugmented products with cow-dung, LD slag and biochar in different combinations were prepared in laboratory scale and applied in crates. All the treatments were applied with 100%RDF except control. Growth parameters such as total leaf area, chlorophyll content, NDVI; and leaf photosynthetic attributes such as net photosynthetic rate, stomatal conductance and transpiration rate were affected by bio-augmentation. Our study reported an increase in total leaf area (18.2–21.3%), chlorophyll content (26.5–31.0%), net photosynthetic rate (93.2%), stomatal conductance (61.3%), transpiration rate (24.7%) in bioaugmented treatments with LD slag and biochar over 100%RDF. A yield increase of 25.6 and 27.1% was found in bioaugmented treatments with a combination of LD slag (2 t/ha) and biochar (1 t/ha) over 100%RDF during 2021 and 2022, respectively. No. of spikes, grains per spike and dry biomass weight were positively influenced by bioaugmentation. The bioaugmented treatments with a combination of LD slag and biochar gave significantly higher grain yield, followed by bioaugmented LD slag compared to bioaugmented biochar alone in the respective application rate of treatments.

Combined effects of elevated CO2 and warmer temperature on limitations to photosynthesis and carbon sequestration in yellow birch.

Elevated CO2 and warmer temperature occur simultaneously under the current climate change. However, their combined effects on the photosynthetic traits in boreal trees are not well understood. This study investigated the morphological and photosynthetic responses of yellow birch (Betula alleghaniensis Britt.) to a combined treatment of CO2 and temperature (ambient, ACT (400μmolmol-1 CO2 and current temperature) vs elevated, ECT (750μmolmol-1 CO2 and current +4 °C temperature)). It was found that ECT significantly reduced leaf-area based photosynthetic rate (An), maximum Rubisco carboxylation rate (Vcmax), photosynthetic electron transport rate (Jmax), leaf nitrogen concentration, respiration and mesophyll conductance. There were two interesting findings: first, the primary mechanism of photosynthetic limitation shifted from Ribulose-1,5-bisphosphate (RuBP) carboxylation (related to Vcmax) to RuBP regeneration (related to Jmax) in response to ECT, leading to decreased transition point (Ci-t and An-t) from RuBP carboxylation to regeneration; second, the increase in total leaf area in response to ECT more than compensated for the downregulation of leaf-area based photosynthesis, leading to greater biomass in ECT than in ACT. We proposed a new protocol for evaluating photosynthetic limitations by comparing the relative relationship between the transition point (Ci-t and An-t) and the photosynthetic rate at growth CO2 (Ci-g and An-g). Furthermore, we found that Jmax (RuBP regeneration) was the primary limitation to An under ECT.

Spatiotemporal Changes in Leaf Area and Carbon Sequestration of Terrestrial Vegetation in China over the Last Two Decades

Spatio-temporal change characteristic in leaf area index (LAI), gross primary productivity (GPP), total leaf area and total carbon sequestration of terrestrial vegetation at different geographic regions, provinces and land cover change types over China during 2000–2018 were clarified, respectively. The net increase in total leaf area and carbon sequestration over China from 2000 to 2018 is 1.7491 × 106 km2 and 1957.36 TgC, and Southwestern part contributes the most with a contribution of 25.3% for leaf area and 20.1% for carbon sequestration, respectively. The overall contribution of northern provinces to enhanced carbon sequestration capacity is greater than that of southern provinces, with a maximum for Inner Mongolia, even though southern provinces have a much higher leaf area increase. The annual increase rates of LAI and GPP in returning cropland to forest–grassland and artificial restoration of forest–grassland are higher than that of self-rehabilitation of rapid growth stage for planted young vegetation. However, due to self-rehabilitation of forest–grassland has the largest area percentage of 59%, it contributes the most to the increases of leaf area and carbon sequestration among different land cover change types, except for northeastern China, where improved farmland productivity is a dominant factor. It should be noted that the leaf area and carbon sequestration exhibit upward trends in urbanized areas over China. whereas slight increasing and even negative trends are also observed in southwestern, southern, and eastern China (e.g., Shanghai), where artificial surface construction occupied more cropland during urbanization processing. Compared with climatic factors, LAI is the dominant factor influencing GPP increases over China since 2000, and gradually weakened coupling relationship between LAI and GPP is observed from north to south. For climatic factors, GPP is dominantly affected by precipitation in northern parts and by solar radiation in southern parts.

Increased leaf area compensated photosynthetic downregulation in response to elevated CO2 and warming in white birch

Predicting photosynthetic acclimation to elevated CO2 and warming is difficult because they have opposite effects. We investigated physiological and morphological responses in white birch ( Betula papyrifera Marshall) to a combination of CO2 and temperature (ACT — 400 µmol·mol–1 CO2, current temperature; ECT — 750 µmol·mol–1 CO2, current + 4 °C temperature). ECT reduced photosynthesis, maximum Rubisco carboxylation ( Vcmax), maximum electron transport rate ( Jmax), photorespiration, daytime respiration, leaf N, and stomatal and mesophyll conductance, but increased biomass, height, total leaf area, electron partitioning to carboxylation and oxygenation ratio, and CO2 compensation point. The photosynthetic acclimation is consistent with the optimal carbon gain theory (carbon gain drives the coordination of carboxylation, electron transport, and respiration). While the photosynthetic acclimation was similar to acclimation to elevated CO2, ECT reduced Jmax/ Vcmax, which is consistent with the response to warming but opposite to the response to elevated CO2, suggesting that thermal acclimation may be the primary mechanism of photosynthetic acclimation to ECT and ECT probably altered N allocation between machinery for carboxylation and that for ribulose-1,5-bisphosphate regeneration. The increase in total leaf area by ECT more than offset the negative effect of photosynthetic downregulation on carbon sequestration, resulting in faster growth and greater biomass under ECT.

EFFECT OF MEZORHIZOBIUM CICERY STRAIN AND CHLORMEQUAT CHLORIDE ON MORPHOGENESIS AND PRODUCTIVITY OF CHICKPEA PLANTS

The effect of strain Mezorhyzobium cicery MS 285 and that of the strain combined with preparation of the quaternary ammonium class retardant -chlormequat chloride on the culture of Triumph chickpea were studied in the field experiment. The positive effect of the strain Mezorhyzobium cicery in complex with synthetic growth inhibitor chlormequat chloride (used in the budding phase of the culture) on the morphometric parameters and crop capacity of Cicer arietinum was established. It was found that both the strain and the retardant against inoculation background of Mezorhyzobium cicery led to a change in the habitus of experimental plants. There was also observed increase of total leaf area in the conditioned plants on account of the additional leaf shooting that enabled more essential donor sphere formation. This enhanced better crop capacity of the plants and positively influenced the yield. At the end of vegetation there was ndicated an increase of nitrogen and potassium contents in the seeds under the effect of both the strain of Mezorhyzobium cicery and the integrated use of the preparations. There was a simultaneous decrease in the amount of sugars in the variants with growth regulators ( the strain of Mezorhyzobium cicery MC 285 ; the strain of Mezorhyzobium cicery MC 285 + chlormequat chloride). The most productive option proved to be in the variant with integrated application of the strain and retardant.

Effects of light spectrum on morpho-physiological traits of grafted tomato seedlings.

It is already known that there are many factors responsible for the successful grafting process in plants, including light intensity. However, the influence of the spectrum of light-emitting diodes (LEDs) on this process has almost never been tested. During the pre-grafting process tomato seedlings grew for 30 days under 100 μmol m-2 s-1 of mixed LEDs (red 70%+ blue 30%). During the post-grafting period, seedlings grew for 20 days under the same light intensity but the lightening source was either red LED, mixed LEDs (red 70% + blue 30%), blue LED or white fluorescent lamps. This was done to determine which light source(s) could better improve seedling quality and increase grafting success. Our results showed that application of red and blue light mixture (R7:B3) caused significant increase in total leaf area, dry weight (total, shoot and root), total chlorophyll/carotenoid ratio, soluble protein and sugar content. Moreover, this light treatment maintained better photosynthetic performance i.e. more effective quantum yield of PSII photochemistry Y(II), better photochemical quenching (qP), and higher electron transport rate (ETR). This can be partially explained by the observed upregulation of gene expression levels of PsaA and PsbA and the parallel protein expression levels. This in turn could lead to better functioning of the photosynthetic apparatus of tomato seedlings and then to faster production of photoassimilate ready to be translocated to various tissues and organs, including those most in need, i.e., involved in the formation of the graft union.

Far-red radiation promotes growth of seedlings by increasing leaf expansion and whole-plant net assimilation

By definition, photosynthetically active radiation (PAR) includes wavelengths between 400 and 700nm and thus, far-red radiation (FR, 700–800nm) is excluded when the photosynthetic photon flux density (PPFD) is measured and reported. However, FR radiation [and the ratio of red (R; 600–700nm) to FR] regulates phytochrome-mediated morphological and developmental plant responses to promote radiation capture and survival under shade. We postulated that the inclusion of FR in a radiation spectrum would have little effect on photosynthesis but would increase radiation capture and plant growth, while accelerating the subsequent flowering of shade-avoiding species. Geranium (Pelargonium×hortorum), petunia (Petunia×hybrida), snapdragon (Antirrhinum majus), and impatiens (Impatiens walleriana) were grown at 20°C under an 18-h photoperiod provided by sole-source lighting from light-emitting diodes that included 32μmolm−2s−1 of blue and the following intensities of R and FR radiation: R128 (128μmolm−2s−1 of R), R128+FR16, R128+FR32, R128+FR64, R96+FR32, and R64+FR64. Plant height in all species studied and total leaf area of geranium and snapdragon linearly decreased as the R:FR (or the estimated phytochrome photoequilibrium) of each treatment increased. In geranium and snapdragon, the increase in total leaf area (by 7%) with the addition of FR to the same PPFD subsequently increased shoot dry weight (DW) (by 28–50%) while the increase in total leaf area (by 30–40%) with the partial substitution of R with FR partly compensated for the reduction in PPFD (by 40%), producing a similar shoot DW. Whole-plant net assimilation of geranium, snapdragon, and impatiens increased with additional FR radiation, showing a linear relationship with the calculated yield photon flux density of each radiation treatment. In addition, inclusion of FR during seedling growth promoted flowering in the long-day plant snapdragon. We conclude that FR radiation increases plant growth indirectly through leaf expansion and directly through whole-plant net assimilation and in at least some species, promotes subsequent flowering.

UNTERSUCHUNGEN ÜBER DIE GESCHWINDIGKEIT DES WASSERAUFSTIEGES IM SPROFI UND DEN BLATTFLÁCHENZUWACHS VON COFFEA ARABICA L. UND CITRUS AURANTIUM SINENSIS ENGLER IN VERSCHIEDENEN KLIMAZONEN KOLUMBIENS

The total increase of leaf area and the rate of water movement in the stems of Coffea arabica L. and Citrus aurantium sinensis Engler were deter- *) Gekürzte Fassung einer am 18. 12. 1969 von der Naturwissenschaftlichen Fakultat der Universitát Giessen als Dissertation angenommenen Abhandlung. mined in various climatic regions of Columbia. During the rain season the maximum rate of water transport decreased with increasing height above sea level. This effect was observed to be more evident in Citrus than in Coffea. At the end of the dry season however, the maximum rate of water movement was measured in 1250 m (Citrus) and 1850 m (Coffea) above sea level. In case of sunshine the maximum values were higher than in case of clouded sky. The most considerable increase of total leaf area was reached at Coffea in 1850 m and at Citrus in 1250 m respectively. With reference to the water economy the cultivation of Citrus could be forced in sea levels about 1250 m with simultaneous displacement of Coffea cultivation to colder climatic regions. Diurnal variations showed, that if the intensity of radiation increased suddenly, the rate of water movement in the stems of Citrus trees accordingly increased. With Coffea trees different results were obtained. During the morning the rate of water transport in trees always increased. At noon the values either remained high or varied in irregular intervals. Moreover, in the hot climatic regions diurnal variations sometimes showed two maximums of rate of water flow in the stems of Coffea arabica. Above all, the type of observed diurnal variations depended on the sea level distance of the measuring point, the season, the intensity of radiation and the species of plant.

Necrotrophic effector epistasis in the Pyrenophora tritici-repentis-wheat interaction.

Pyrenophora tritici-repentis, the causal agent of tan spot disease of wheat, mediates disease by the production of host-selective toxins (HST). The known toxins are recognized in an ‘inverse’ gene-for-gene manner, where each is perceived by the product of a unique locus in the host and recognition leads to disease susceptibility. Given the importance of HSTs in disease development, we would predict that the loss of any of these major pathogenicity factors would result in reduced virulence and disease development. However, after either deletion of the gene encoding the HST ToxA or, reciprocally, heterologous expression of ToxA in a race that does not normally produce the toxin followed by inoculation of ToxA-sensitive and insensitive wheat cultivars, we demonstrate that ToxA symptom development can be epistatic to other HST-induced symptoms. ToxA epistasis on certain ToxA-sensitive wheat cultivars leads to genotype-specific increases in total leaf area affected by disease. These data indicate a complex interplay between host responses to HSTs in some genotypes and underscore the challenge of identifying additional HSTs whose activity may be masked by other toxins. Also, through mycelial staining, we acquire preliminary evidence that ToxA may provide additional benefits to fungal growth in planta in the absence of its cognate recognition partner in the host.

Influence of light intensity on the rate of photosynthesis and dry matter accumulation in Oriental hybrid lily ‘Siberia’ at different developmental stages

SummaryWe investigated the effects of light intensity on various photosynthetic characteristics on a whole-plant (WP) basis, focussing on three developmental stages from leafing (when young leaves unfolded) to flowering in the Oriental hybrid lily ‘Siberia’. On a WP basis, the net photosynthetic rate (Pr) was low at the leafing stage, but increased rapidly at the visible flower bud and flowering stages. However, on a leaf area (LA) basis, plants at the leafing stage exhibited a high Pr, peaking at the visible flower bud stage and diminishing slightly at the flowering stage.The rapid increase in total LA due to plant growth and development had a strong influence on Pr on a WP basis. ‘Siberia’ plants were grown under various reduced levels of natural light (0%, 40%, or 60%), achieved by shading, to evaluate the contribution of photosynthetic assimilates at various developmental stages and to compare the consistency of these results with the photosynthetic characteristics of the plants. The final dry matter (DM) content on a WP basis was determined by the light intensity applied after the visible flower bud stage, but not before. These experiments indicated that, during the growth of ‘Siberia’ lily, photosynthesis determined DM accumulation after the visible flower bud stage. Low or high light intensities before or after this stage promoted stem elongation and leaf thickening, respectively. Therefore, shading during the early developmental stages and high sunlight during the later developmental stages were beneficial for the quality of Oriental hybrid lily cut flowers.

Recurrent selection for wider seedling leaves increases early biomass and leaf area in wheat (Triticum aestivum L.).

The breeding of wheat with greater early vigour has potential to increase water- and nutrient-use efficiency, as well as to improve weed competitiveness to raise crop yields profitably. Given that wheat is inherently conservative in its early growth, a sustained breeding effort was initiated to increase genetically seedling leaf area in developing novel high vigour germplasm. A recurrent selection programme was initiated by intercrossing a genetically diverse set of 28 vigorous wheat lines identified globally. These were intercrossed at random and S1:2 progeny with the largest leaf 1 and 2 widths were intermated to develop new populations for assessment of early growth. This procedure was repeated for up to 60 segregating families per cycle across six cycles over 15 years. Thirty random S1:2 progeny were retained from each cycle and seed-increased together to produce seed for early vigour assessment in multiple sowings. The most vigorous wheat seedlings were identified in later cycles, with some lines producing more than double the leaf area and biomass of elite commercial wheat varieties. Phenotypic selection for greater leaf width was associated with a realized significant (P<0.01) linear increase per seedling of 0.41 mm per cycle (+7.1%) for mean leaf width, and correlated linear increases in total leaf area and biomass of 4.48 cm(2) per cycle (+10.3%) and 10.8 mg per cycle (+5.3%), respectively. Genetic gains in widths of leaves 2 (+8.4%) and 3 (+11.5%) were significantly (P<0.01) greater than for leaf 1 (+5.3%). Selection for greater leaf width was associated with linear increases in coleoptile tiller leaf area, small curvilinear increases in leaf 1 length, and reductions in numbers of leaves and mainstem tillers. Genetic variances were large and heritabilities high for leaf width and total leaf area in each cycle, but reduced linearly in size with selection across cycles. Coupling diverse germplasm with a simple, inexpensive, and repeatable selection process has confirmed the value of recurrent selection in developing uniquely vigorous wheat germplasm for use as parents in commercial breeding.

Higher leaf area and post-silking P uptake conferred by introgressed DNA segments in the backcross maize line 224

Many quantitative trait loci (QTLs) associated with phosphorus (P) acquisition and use efficiency in maize have been identified. To get a better understanding of the genetic control of P acquisition and grain yield in maize, a two-year field experiment with a line 224 from a backcross population, its donor parent 478 and recurrent parent 312 was conducted at three P levels. The results demonstrated an increased total leaf area and whole plant dry weight (DW), P uptake and grain yield in 224, compared with its recurrent parent 312, especially under extremely low P condition. The increase in total leaf area was explained by the increased length of immediately neighboring leaves around the ear. Similar with its donor parent 478, 224 took up more post-silking P than 312 at all P levels in both years, revealing previously unidentified functions of introgressed DNA segments from 478. On the other hand, irrespective of the increased P uptake, total root length and root vertical distribution in 0–40cm soil profile of 224 was not increased compared with 312, although some QTLs related to root traits in line 224 had been proved to be derived from 478, an inbred line with larger root system. The results provide positive evidence for developing P-efficient crops with improved ability to acquire P and to increase grain yield under suboptimal P conditions through genetic approaches.

Impact of Prebloom and Fruit Set Basal Leaf Removal on the Flavonol and Anthocyanin Composition of Tempranillo Grapes

The influence of timing and method of basal defoliation on the profile and content of anthocyanins and flavonols in Tempranillo grapes was investigated. Basal leaf removal was manually and mechanically performed at two phenological stages, prebloom and fruit set. Phenolic composition was determined in grape extracts by HPLC-UV-Vis and 13 anthocyanin and flavonol compounds were identified and quantified. Regardless of the timing and method of defoliation, basal leaf removal led to more ripened fruit in terms of higher soluble solids and reduced acidity and favored the accumulation of flavonols and anthocyanins, which was related to the increase in total leaf area per yield observed in defoliated vines. For anthocyanins, there was a significant relationship between their concentrations and the larger relative skin mass observed in berries of defoliated vines. In general, the enhancement in flavonols and anthocyanins observed in berries from basal-defoliated vines tended to be greater when defoliation was conducted mechanically; yet overall, no evident differences between prebloom and fruit-set defoliation were found.

Relações entre transpiração máxima, evapotranspiração de referência e área foliar em quatro variedades de mangueira

Nas condições edafoclimáticas de Cruz da Almas - BA, na Embrapa Mandioca e Fruticultura Tropical, foi realizado um estudo no qual se relacionou a transpiração máxima (Litros m-2 folha/dia -1) de quatro variedades de mangueira (Tommy Atkins, Palmer, Haden e Van Dyke, com áreas foliares totais de 14; 8; 33 e 12 m², respectivamente) com a evapotranspiração de referência (ETo). A transpiração das plantas (L dia-1) foi estimada por meio de sensores que realizam o balanço de calor no caule (modelos SAG13; SGB9; SGB16; SGB19 e SGB25, Dynamax Inc.) dispostos nos sentidos norte (N), sul (S), leste (E), oeste (W) e centro (C) de cada planta. A transpiração por unidade de área foliar (Lm-2 folha dia-1) variou em média de 1,58 ao longo do período estudado, e linearmente com o aumento da área foliar total da planta, independentemente da variedade estudada. A transpiração (Litros m-2 folha/dia -1) variou de 0,36 a 3,00, dependendo da demanda atmosférica. A transpiração máxima (T) das quatro variedades de mangueira (Litros m-2 folha/dia -1) relacionouse linearmente com a ETo (T = 0,44. ETo; r² = 0,78), sendo um excelente subsídio para o manejo de irrigação por gotejamento nesta cultura.

Effects of elevated CO 2 on growth and morphological characteristics of ornamental bromeliads

Three ornamental bromeliads, i.e. Aechmea ‘Maya’ (CAM), Aechmea fasciata ‘Primera’ (CAM) and Guzmania ‘Hilda’ (C 3) were grown under greenhouse conditions at ambient (380 ppm) and elevated (750 ppm) CO 2. The effects of long-term exposure (34 weeks) to elevated CO 2 on growth and morphological traits constituting the ornamental value were assessed. Aechmea ‘Maya’ and A. fasciata ‘Primera’ showed a different growth response to elevated CO 2 exposure. Aechmea ‘Maya’ showed for both CO 2 concentrations an equal biomass enhancement throughout the experimental period. In accordance leaf micromorphology remained unaffected. For A. fasciata ‘Primera’ CO 2 fertilisation led to a decreased biomass production (25% less fresh and dry weight) due to a reduced total leaf area (41%) and lower leaf thickness (9%). These responses of both Aechmea hybrids are quite uncommon for CAM plants. Doubling the atmospheric CO 2 concentration stimulated growth for Guzmania ‘Hilda’ shown by an increase in total leaf area (34%) and leaf thickness (11%). However, the surplus in biomass production (57% more fresh weight and 69% more dry weight) was gained only in the first 22 weeks of the experiment as afterwards acclimation occurred. For all three bromeliads elevated CO 2 exposure led to adverse effects on the ornamental value. Leaves from high CO 2 grown plants displayed a visual paler green colour than leaves from control plants due to halving of the total chlorophyll content. Furthermore, allometric relations changed between leaf length and leaf width causing a more compact plant shape. This ultimately resulted in the loss of the typical plant shape for ornamental bromeliads with long and slender leaves. Overall the results in the current study show that long-term exposure to elevated CO 2 does not always lead to enhanced biomass production. Moreover it can lead to adverse effects on the ornamental value. Thus, it is apparent that caution is needed with the application of CO 2 fertilisation in commercial ornamental cultures. The CO 2 plant response can seriously differ among individual species in one family and even in one genus. Therefore it is important to realise that the study of only one representative for a certain plant family or a genus is not adequate to make the proper interpretations concerning general CO 2 responses!

Evidence for “diminishing returns” from the scaling of stem diameter and specific leaf area

Research indicates that increases in total leaf area (A(T)) may fail to keep pace with increases in total leaf mass (M(L)) across plants differing in size (e.g., as measured by stem diameter, D). This "diminishing returns" hypothesis predicts that the scaling exponent for A(T) vs. M(L) will be less than one and that the exponent for specific leaf mass (i.e., A(T) / M(L)) vs. D will be negative. These predictions were examined using data from 46 plants ranging between 0.125 cm ≤ D ≤ 0.485 m across 25 woody dicot species. Standardized major axis slopes were used to quantify scaling exponents and random effects models were used to quantify species and size effects on the numerical values of exponents. The exponents for A(T) vs. M(L) and A(T) / M(L) vs. D differed among species and different species groupings. In general, the exponent for A(T) vs. M(L) was less than one and the exponent for A(T) / M(L) vs. D was negative, as predicted. However, random effects models indicated that species effects overshadowed size effects, although size effects were statistically significant. The diminishing returns hypothesis therefore receives statistical support, i.e., although the numerical values of exponents are "species-dependent," they are less than unity, as predicted by theory.

Plant Canopy Affects Sprinkler Irrigation Application Efficiency of Container-grown Ornamentals

Marketable size plants of sweet viburnum (Viburnum odoratissimum Ker-Gawl.), waxleaf ligustrum (Ligustrum japonicum Thunb.), and azalea (Rhododendron spp. L. `Southern Charm') grown in 11.4-L containers were irrigated with overhead impact sprinklers at container spacings ranging from 0 to 51 cm apart. Water reaching the substrate surface was quantified and the percentage of that applied calculated as percent capture (% capture). Percent capture is defined as the percentage of water falling above the plant within a projected vertical cylinder of a container that reaches the substrate surface. For all species, % capture increased linearly with the decline in adjacent canopy interaction, which results from canopies extending beyond the diameter of a container. Increases in total leaf area or leaf area outside the cylinder of a container, in conjunction with increasing distance between containers, were significantly (P &lt; 0.05) correlated with increases in % capture for ligustrum and viburnum. Increases in % capture partially compensated for decreases in percentage of production area occupied by viburnum containers as distances between containers increased, but not for the other two species. Under commercial conditions, optimal irrigation efficiency would be achieved when plants are grown at the minimum spacing required for commercial quality. This spacing should not extend beyond the point where canopies become isolated.

Pistachio Rootstocks Influence Scion Growth and Ion Relations under Salinity and Boron Stress

Performance of `Kerman' pistachio (Pistacia vera L.) trees on three rootstocks (P. atlantica Desf., P. integerrima Stewart and `UCB-1', a P. atlantica × P. integerrima hybrid) was evaluated with 2-year-old trees grown in sand-tank lysimeters under combined SO42- and Cl- salinity and boron (B) stress for 6 months. Four salinity treatments were imposed by irrigating the plants with water at electrical conductivity (ECiw) of 3.5, 8.7,12, or 16 dS·m-1 each containing B at 10 mg·L-1. Growth of `Kerman' was evaluated based on increase in total leaf area, increase in trunk diameter, and total above-ground biomass production. All growth parameters decreased as salinity increased, but were not significant until ECiw exceeded 12 dS·m-1. However, growth of `Kerman' on P. atlantica and `UCB-1' was considerably better than on P. integerrima at 16 dS·m-1. The onset and severity of foliar injury differed among scions and treatments and was attributed primarily to B toxicity, rather than the effects of salinity. Concentrations of B in injured leaf tissue ranged from 1000 to 2500 mg·kg-1. Leaf injury decreased with increasing salinity, although leaf B was not significantly reduced suggesting an internal synergistic interaction between B and other mineral nutrients. However for P. vera on P. integerrima, the highest level of salinity produced the greatest injury, possibly as a combination of B plus Cl- and/or Na+ toxicity. Leaf transpiration, stomatal conductance, and chlorophyll concentration of P. vera, determined by steady-state porometry, were also reduced to a greater degree by combined salinity and B when budded on P. integerrima than on the other two rootstocks.

Effects of N management on growth, N 2 fixation and yield of soybean

Soybean (Glycine max) is one of the most importantfood and cash crops in China. Although soybean has the capacity to obtain alarge proportion of its N from N2 fixation, it is commonfarmer's practice to apply an N top dressing to maximize grain yield. Afield experiment was conducted to study the effects of N application as urea atvarious stages during the vegetative and reproductive phases on crop biomass,N2 fixation and yield of two soybean genotypes, Luyuebao and Jufeng.Starter N at 25 kg ha−1 resulted in minimumbiomass and pod yield while starter N at 75 kgha−1 had no significant effect and N top dressing, ateither the R1 or R5 stage, resulted in increased biomass and pod yield. Maximumbiomass and pod yield were obtained when a top dressing of 50 kgha−1 was applied at the flowering stage. The effects oftop dressing on the capacity to fix N2 were complex. The proportionof plant N derived from N2 fixation (Pfix) was highest when onlystarter N at 25 kg ha−1 was applied. Any topdressing reduced nodulation and Pfix, but increased biomass, so that totalN2 fixed increased for top dressing at the flowering or pod fillingstage. Common farmer's practice of applying 75 kg Nha−1 at the V4 stage, resulted in a significantreduction in N2 fixation. To evaluate the application of Nfertilization at various stages ofdevelopment on growth, nodulation and N2 fixation in more detail, anexperiment in nutrient solution with or without 20 mMNO3− was conducted with genotype Tidar. The N-freetreatment gave the lowest biomass and total N accumulation, as in the fieldexperiment. A continuous nitrate supply resulted in the highest biomass,associated with an increase in total leaf area per plant, maximum individualleaf area, branch and node number per plant, shoot/root ratio and leaf arearatio, compared to the N-free treatment. R1 was the most responsive stage fornitrate supply as well as for interruption of the nitrate supply. Since theresults from the field experiment were in agreement with thosefrom the experiment in nutrient solution in a greenhouse, the latter can beusedto predict crop performance in the field.

Hydraulic architecture and water relations of Spartium junceum branches affected by a mycoplasm disease

ABSTRACTPlant water relations, xylem anatomy and the hydraulic architecture of 1‐year‐old twigs of Spartium junceum, both healthy and affected by a phytoplasm disease, were studied. The disease causes twigs to be either shortened (witches broom disease, WBD) or flat (fasciate disease, FD). WBD twigs show a sevenfold increase in total leaf area, smaller and shorter xylem conduits, a higher stomatal conductance (gl) and a decline of minimum leaf water potentials (Ψl) below the turgor loss point. FD twigs had nearly twice the leaf area of the healthy controls as well as high gl values and Ψl values below the turgor loss point. Moreover, significant differences between healthy and affected twigs in stem stomatal conductance (gs) and in the total stem area were recorded. Affected twigs die back under drought stress, which is explained by a pronounced loss of hydraulic conductivity of the infected stems (40 and 60%) in FD and WBD as well as by the unfavourable ratio of weighted conduit radius (Σr4) to total surface area (At), so that the efficiency of the stem in supplying the whole transpiring area with water is strongly reduced.