Increased Leaf Dry Weight Research Articles

Effects of Micronutrients on the Growth and Phytochemical Composition of Basil (Ocimum basilicum L.) in the Field and Greenhouse (Hydroponics and Soil Culture).

The current research was conducted to compare the growth, yield, and phytochemical composition of basil (Ocimum basilicum) in the open field and the soil and hydroponic cultivation in a greenhouse. Furthermore, the effect of foliar spraying of micronutrients on this crop was also evaluated. In each of the cultivation systems, foliar spraying of one micronutrient, either iron sulfate (Fe), zinc sulfate (Zn), copper sulfate (Cu), manganese sulfate (Mn), or boric acid (B), at a concentration of 0.1% was applied in a randomized complete block design. Plants grown in the hydroponic system had higher yield and biomass. The concentration of the elements K, Ca, Mg, N, P, Mn, Fe, B, and Zn in the leaves of hydroponic plants was higher. Contrarily, plants cultivated in the field showed higher stem dry weight, essential oil content, phenolic and flavonoid content, and antioxidant activity. The level of methyl chavicol was higher in the hydroponic culture, but the level of 1,8-cineole was much lower in this cropping system. Foliar spraying of Cu, Mn, Zn, Fe, or B significantly increased leaf dry weight and anthocyanin content. In field conditions, the highest levels of phenolics, flavonoids, and antioxidant capacity were observed with Zn or Mn application. In the hydroponic system, foliar spraying of Zn or B led to the highest antioxidant capacity, and total phenolic and flavonoid contents. Overall, the basil plants cultivated in the field showed higher bioactive ingredients. However, the essential oil of plants cultivated in the hydroponic system had a higher economic value due to its higher percentage of methyl chavicol.

A novel plant growth regulator B2 mediates drought resistance by regulating reactive oxygen species, phytohormone signaling, phenylpropanoid biosynthesis, and starch metabolism pathways in Carex breviculmis

Drought is one of the most common environmental stressors that severely threatens plant growth, development, and productivity. B2 (2,4-dichloroformamide cyclopropane acid), a novel plant growth regulator, plays an essential role in drought adaptation, significantly enhancing the tolerance of Carex breviculmis seedlings. Its beneficial effects include improved ornamental value, sustained chlorophyll content, increased leaf dry weight, elevated relative water content, and enhanced root activity under drought conditions. B2 also directly scavenges hydrogen peroxide and superoxide anion contents while indirectly enhancing the activities of antioxidant enzymes (superoxide dismutase, peroxidase, catalase, and ascorbate peroxidase) to detoxify reactive oxygen species (ROS) oxidative damage. Transcriptome analysis demonstrated that B2 activates drought-responsive transcription factors (AP2/ERF-ERF, WRKY, and mTERF), leading to significant upregulation of genes associated with phenylpropanoid biosynthesis (HCT, POD, and COMT). Additionally, these transcription factors were found to suppress the degradation of starch. B2 regulates phytohormone signaling related-genes, leading to an increase in abscisic acid contents in drought-stressed plants. Collectively, these findings offer new insights into the intricate mechanisms underlying C. breviculmis' resistance to drought damage, highlighting the potential application of B2 for future turfgrass establishment and management with enhanced drought tolerance.

Multi-walled carbon nanotubes affect yield, antioxidant response, and rhizosphere microbial community of scented rice under combined cadmium-lead (Cd–Pb) stress

Rice production is threatened by heavy metal stress. The use of multi-walled carbon nanotubes (MWCNTs) in agriculture has been reported in previous studies. We aimed to quantify the impact of MWCNTs on the growth and physiological characteristics of scented rice under cadmium (Cd) and lead (Pb) stresses. Therefore, a pot experiment was conducted, two scented rice varieties Yuxiangyouzhan and Xiangyaxiangzhan were used as materials grown under different concentrations of MWCNTs (0, 100, and 300 mg kg−1 recorded as CK, CNPs100, and CNPs300, respectively). The yield, antioxidant response, and rhizosphere microbial community of scented rice were studied. The results showed that compared with the CK treatment, the CNPs100 and CNPs300 treatments increased leaf dry weight by 17.95%–56.22% at the heading stage, and the H2O2 content in leaves decreased significantly by 36.64%–42.27% at the maturity stage. Under CNPs100 treatment, the grain yield of two scented rice varieties increased significantly by 17.54% and 27.40%, respectively. The MWCNTs regulated the distribution of the Cd and Pb in different plant tissues. The content of Cd (0.11–0.20 mg kg−1) and Pb (0.01–0.04 mg kg−1) in grain were at a safety level (<0.2 mg kg−1). Moreover, MWCNTs increased soil microbial community abundance and altered community composition structure under Cd–Pb stress, which in turn improved agronomic traits and quality of scented rice. Overall, this study suggested that the application of MWCNTs regulates the growth, yield, physiological response, and soil microbial community, the genotypes response effect of scented rice to MWCNTs is needed further studied.

PRODUCTIVITY OF ELEPHANT GRASS (Pennisetum purpureum) PLANTED WITH LEGUMINOSE AT VARIOUS DOSAGES OF BIOORGANIC FERTILIZER

&#x0D; &#x0D; &#x0D; The purpose of this study was to determine the productivity of elephant grass (Pennisetum purpureum) planted with leguminosae at various doses of bioorganic fertilizers. This study used a completely randomized design with two factorial patterns. The first factor was the type of leguminosae (T= without leguminosae; R= Arachi pintoi; L= Alysicarpus vaginalis; and the second factor was the dose of bioorganic fertilizer (D0= 0 kg Nha-1; D1= 100 kg Nha-1; D2= 200 kg Nha-1; and D3= 300 kg Nha-1) There were 12 treatment combinations, each treatment was repeated 5 times so that it consisted of 60 experimental units. The observed variables included growth, yield and growth characteristics variable. The results showed that there was no interaction between leguminous species and fertilizer dosage, both leguminous species only increased leaf area per pot, bioorganic fertilizer D1 and D2 doses tended to increase, while D3 dose increased leaf dry weight, total forage dry weight, and leaf area per pot of elep- hant grass (Pennisetum purpureum). It was concluded that the type of leguminous did not affect the productivity of elephant grass, the dose of bioorganic fertilizer increased crop yields, the highest yields at a dose of 300 kg Nha-1 bioorganic fertilizer.&#x0D; &#x0D; &#x0D;

The Effect of Stopping Irrigation, Potassium and low Consumption Elements on Growth Indicators of Fodder Corn

In order to investigate the effect of irrigation, potassium and low-use elements on the growth indicators of fodder corn 704, a study in 2022 in the form of split-split plots in the form of a basic randomized complete block design in three replications at the city of urmia was implemented. Irrigation treatment as the main factor in two levels (full irrigation and interruption of irrigation), potassium consumption as a secondary factor in two levels (no consumption and consumption of 200 kg/ha of potassium) and low-consumption elements as a secondary factor in three levels. (non-use, soil use and foliar spraying were low-use elements). Plant height, fresh fodder yield, stem and leaf dry weight, biological yield, flag leaf area, ear length and diameter, proline and leaf relative water content were studied. According to the results, the main effects of irrigation interruption were significant in reducing plant height, flag leaf area, ear length, fresh fodder yield, stem and leaf dry weight, and increasing proline. Potassium consumption had a significant effect in increasing plant height, biological yield, ear length and diameter, proline, and also reducing stem dry weight. The three-way interaction effect of irrigation interruption, potassium consumption and soil consumption of low consumption elements significantly increased leaf dry weight by 20% and proline by 0.34%. But in the condition of stopping irrigation and using potassium, the non-use of low-use elements increased the relative water content of the cell by 8% compared to the foliar application of low-use elements. Therefore, in the conditions of drought stress, the use of potassium together with low-use elements has improved the mentioned traits, under such conditions, the use of these elements is recommended for the cultivation of fodder corn in the region.

Changes in biochemical and morphological characters of garden cress (Lepidium sativum L.) as affected by foliar application with casein amino acid and salicylic acid under greenhouse conditions

Foliar feeding of plants can effectively supplement soil fertilization. The effects of foliar application of different levels of casein (CSN: 0, 50, 100 and 150 mg. L−1) and salicylic acid (SA: 0, 75, 150, and 300 µM) were investigated on some vegetative and reproductive growth as well as pigments, phenolic compounds and total antioxidants content indices of garden cress (Lepidium sativum L.) at greenhouse condition. It was observed that CSN applied to at 50 mg. L−1 resulted in the highest stem and root fresh weights, stem dry weight, and diameter of the main stem. Also, the highest chlorophyll b content was obtained in plants treated with 50 and 100 mg. L−1 CSN. In addition, the application of 100 mg. L−1 CSN resulted in the highest leaf nitrogen and phosphorous content, while the lowest values were recorded in the control. The results show that SA application exerted a significant effect on the plant height, leaf fresh and dry weights, stem fresh and dry weights, and the number of florets. The highest plant height and leaf fresh weight were obtained in plants treated with 150 and 300 µM SA. Furthermore, levels of 75, 150, and 300 µM SA application significantly increased leaf dry weight, and chlorophyll b. As well, applications of 150 µM SA led to higher stem fresh and dry weights than the control. Moreover, the number of florets in the levels of 0 and 150 µM SA were higher than in other treatments. Overall, the results suggested that spays of CSN and SA, which showed better growth characters, could be more appropriate for application in garden cress spraying programs.

Dual effects of biochar and hyperaccumulator Solanum nigrum L. on the remediation of Cd-contaminated soil.

Biochar was widely developed for the soil amendment and remediation of heavy metal contaminated soil. The Cd hyperaccumulator, Solanum nigrum L., has been paid much more attention with the wide application of phytoremediation. The effects of biochar on the growth and accumulation capacity of Solanum nigrum L. in Cd contaminated soil have not been explored so far. The objectives of this study were to explore the dual effects of biochar addition on available Cd in the soil and hyperaccumulation of Cd in Solanum nigrum L. under different Cd contaminated levels. The correlations of soil physicochemical and biochemical properties and Cd absorption of Solanum nigrum L. were analyzed after a 60-day pot experiment under three biochar doses (0%, 1% and 5%) and four Cd concentrations (0, 25, 50 and 100 mg kg−1). The availability of Cd obtained by DTPA extraction significantly decreased after biochar application (P = 0.003, P = 0.0001, P = 0.0001 under 1% biochar addition for 25, 50, and 100 mg kg−1 Cd concentrations, P = 0.0001, P = 0.0001, P = 0.0001 under 5% biochar addition for 25, 50, and 100 mg kg−1 Cd concentrations, n ≥ 3). The 1% biochar dose significantly increased leaf dry weight (P = 0.039, P = 0.002 for the Cd concentrations of 50 and 100 mg kg−1, n ≥ 3) compared with the control in higher Cd concentrations (50 and 100 100 mg kg−1). In the presence of biochar, the bioconcentration factor (BCF) increased under the Cd concentrations of 50 and 100 mg kg−1. The translocation factors (TF) decreased with the biochar doses under the Cd concentration of 100 mg kg−1. The dose of 5% biochar significantly increased the urease activity by 41.18% compared to the 1% biochar addition in the Cd contaminated soil of 50 mg kg−1 concentration. The activities of acid phosphatase were inhibited by 1% biochar dose in all the Cd contaminated soils. The dry weight of the root of Solanum nigrum L. was significantly negatively correlated with acid phosphatase activity and BCF, respectively, indicating acid phosphatase in the rhizosphere soil of Solanum nigrum L. were repressed by Cd toxicity despite of biochar amendment. Biochar had no negative effect on Cd accumulation ability of Solanum nigrum L. Two-way ANOVA analysis showed that both biochar and Cd significantly affected the height of Solanum nigrum L. and the dry weight of leaf and stem. This study implied that biochar addition does not limit the absorption of hyperaccumulator Solanum nigrum L. in the remediation of Cd-contaminated soil. This study implied that the simultaneous application of biochar and hyperccumulator Solanum nigrum L. is promising during the remediation of Cd-contaminated soil.

Leaf Fresh Weight Versus Dry Weight: Which is Better for Describing the Scaling Relationship between Leaf Biomass and Leaf Area for Broad-Leaved Plants?

Leaf dry mass per unit area (LMA) is considered to represent the photosynthetic capacity, which actually implies a hypothesis that foliar water mass (leaf fresh weight minus leaf dry weight) is proportional to leaf dry weight during leaf growth. However, relevant studies demonstrated that foliar water mass disproportionately increases with increasing leaf dry weight. Although scaling relationships of leaf dry weight vs. leaf area for many plants were investigated, few studies compared the scaling relationship based on leaf dry weight with that based on leaf fresh weight. In this study, we used the data of three families (Lauraceae, Oleaceae, and Poaceae, subfamily Bambusoideae) with five broad-leaved species for each family to examine whether using different measures for leaf biomass (i.e., dry weight and fresh weight) can result in different fitted results for the scaling relationship between leaf biomass and area. Reduced major axis regression was used to fit the log-transformed data of leaf biomass and area, and the bootstrap percentile method was used to test the significance of the difference between the estimate of the scaling exponent of leaf dry weight vs. area and that of leaf fresh weight vs. area. We found that there were five species across three families (Phoebe sheareri (Hemsl.) Gamble, Forsythia viridissima Lindl., Osmanthus fragrans Lour., Chimonobambusa sichuanensis (T.P. Yi) T.H. Wen, and Hibanobambusa tranquillans f. shiroshima H. Okamura) whose estimates of the scaling exponent of leaf dry weight to area and that of leaf fresh weight to area were not significantly different, whereas, for the remaining ten species, both estimates were significantly different. For the species in the same family whose leaf shape is narrow (i.e., a low ratio of leaf width to length) the estimates of two scaling exponents are prone to having a significant difference. There is also an allometric relationship between leaf dry weight and fresh weight, which means that foliar water mass disproportionately increases with increased leaf dry weight. In addition, the goodness of fit for the scaling relationship of leaf fresh weight vs. area is better than that for leaf dry weight vs. area, which suggests that leaf fresh mass might be more able to reflect the physiological functions of leaves associated with photosynthesis and respiration than leaf dry mass. The above conclusions are based on 15 broad-leaved species, although we believe that those conclusions may be potentially extended to other plants with broad and flat leaves.

Chitosan as Soil Amendment Affects Lettuce Growth, Photochemical Efficiency, and Gas Exchange

Chitosan has become of interest as a crop biostimulant suitable for use in sustainable agriculture since it is biocompatible, biodegradable, environmentally friendly, and readily available in large quantity. Short-term (35 d after transplanting) effects of chitosan, applied as a soil amendment at 0%, 0.05%, 0.10%, 0.15%, 0.20%, or 0.30% (w/w), on lettuce (Lactuca sativa) growth, chlorophyll fluorescence, and gas exchange were evaluated in a growth chamber study. Chitosan at 0.05%, 0.10%, and 0.15% increased leaf area from 674 to 856, 847, and 856 cm2, and leaf fresh weight from 28.6 to 39.4, 39.1, and 39.8 g, respectively. Only chitosan at 0.05% and 0.10% increased leaf dry weight from 3.42 to 4.37 and 4.35 g, respectively, while chitosan at 0.30% decreased leaf number, area, fresh and dry weight. Chitosan at 0.10%, 0.15%, 0.20%, and 0.30% increased leaf chlorophyll index from 29.8 to 34.4, 35.4, 37.5, and 41.4, respectively. Chitosan at 0.20% and 0.30% increased leaf maximum photochemical efficiency and photochemical yield, and chitosan at 0.10%, 0.15% 0.20%, and 0.30% increased leaf electron transport rate. Leaf photosynthesis rate and stomatal conductance (gS) increased from 9.3 to 12.7, 14.0, and 16.6 μmol·m−2·s−1 carbon dioxide, and from 0.134 to 0.183, 0.196, and 0.231 mol·m−2·s−1, under chitosan at 0.15%, 0.20%, and 0.30%, respectively. The results indicated that chitosan, at appropriate application rates, enhanced lettuce growth, and might have potential to be used for sustainable production of lettuce.

Carbohydrate and Nutritional Responses to Stem Girdling and Drought Stress with Respect to Understanding Symptoms of Huanglongbing in Citrus

The most important worldwide problem in citrus production is the bacterial disease Huanglongbing (HLB; citrus greening) caused by a phloem-limited bacterium Candidatus Liberibacter asiaticus. The earliest visible symptoms of HLB on leaves are vein yellowing and an asymmetrical chlorosis referred to as “blotchy mottle,” thought to be the result of starch accumulation. We tested the hypothesis that such visible symptoms are not unique to HLB by stem girdling 2-year-old seedlings of two citrus rootstocks with and without drought stress in the greenhouse. After 31 days, girdling had little effect on shoot growth but girdling increased the relative growth rate of shoots in drought-stressed trees. Starch content in woody roots of non-girdled trees was three to 19 times higher than in girdled trees. In non-girdled trees, drought stress induced some starch accumulation in roots, but there were no effects of drought stress on root starch or sucrose in girdled trees. Girdling induced a 4-fold greater starch content in leaves on well-watered trees but leaf sucrose content was unaffected. Girdling reduced leaf transpiration in well-watered trees but net assimilation of CO2 was unaffected by girdling or leaf starch accumulation. Leaves on girdled trees clearly had visible blotchy mottle symptoms but no symptoms developed on non-girdled trees. The increase in leaf starch, up to 50% dry weight (DW), resulted in an increase in leaf DW per leaf area (LA) and an artificial reduction of many leaf nutrients on a DW basis. Most of these differences disappeared when expressed on a LA basis. Leaf boron (B), however, was inversely related to leaf starch when both were expressed on a LA basis. In the absence of HLB, girdling increased leaf starch, decreased root starch, and duplicated the asymmetric blotchy mottled visual leaf symptoms that have been associated with HLB-infected trees. This supports our contention that such symptoms generally attributed to HLB are not uniquely related to HLB infection, but rather are directly related to starch accumulation and secondarily to nutrient deficiencies in leaves.

Response of Eight Maple Cultivars (Acer spp.) to Soil Compaction and Effects of Two Rates of Pre-plant Nitrogen on Tree Establishment and Aboveground Growth

This study assessed soil compaction effects on aboveground growth of maple cultivars, and compared two nitrogen rates applied pre-planting for their influence on establishment and growth of trees planted into compacted soils. Eight commonly used maple cultivars of Acer rubrum and Acer × freemanii were evaluated. During container production, plants received either 25 or 100 mg·L-1 nitrogen through fertigation twice per day. Trees were planted into non-compacted field plots with a mean bulk density of 1.40 g·cm-3, or into compacted plots with a mean bulk density of 1.60 g·cm-3. In 2002, researchers randomly selected half of the compacted plots and applied an additional soil treatment. At the completion of this treatment, mean bulk density was 1.55 g·cm-3. Trees growing in higher density soils had significantly smaller aboveground biomass measures (P &lt; 0.05), than those growing in non-compacted plots. There was a significant difference between cultivars (P &lt; 0.0001); for example, ‘Celzam’ and ‘Fairview Flame’ had greater aboveground biomass values than other cultivars when grown in compacted soils, but compaction still affected growth. The 100 mg·L-1 nitrogen rate increased leaf dry weight and area, but did not impact height and caliper growth or stem dry weight.

تأثیر باکتریهای تثبیت کننده آزادزی و همزیست نیتروژن بر ویژگیهای بذری و گیاهچه های بذرهای سویا تولید شده در شرایط آبیاری محدود

در این پژوهش تأثیر باکتری‌های تثبیت کننده آزادزی و همزیست نیتروژن بر ویژگی‌های گیاهچه و بذر‌های سویای تولید شده در شرایط آبیاری محدود، در آزمایشگاه و مزرعه در سال 1385 ارزیابی گردید. در آزمایشگاه)، موسسه تحقیقات ثبت و گواهی بذر و نهال کرج آزمایش به صورت فاکتوریل در قالب طرح کاملا تصادفی با چهار تکرار و در مزرعه آموزشی پژوهشی دانشگاه آزاد اسلامی واحد ورامین به صورت اسپلیت فاکتوریل در قالب طرح بلوک کامل تصادفی با سه تکرار اجرا گردید. تیمارها شامل بذرهای تولید شده در شرایط آبیاری محدود (آبیاری گیاهان مادری پس از مقادیر 50 (آبیاری مطلوب)، 100 (تنش متوسط)، 150 (تنش شدید) میلی متر تبخیر از تشت تبخیر کلاس A)، رقم (منوکین، ویلیامز و لاین اس.آر.اف× تی3) و تلقیح بذر (تلقیح با برادی‌ریزوبیوم‌ژاپونیکوم، تلقیح با برادی‌ریزوبیوم‌ژاپونیکوم توأم با ازتوباکتر‌کروکوکوم، عدم تلقیح) بود. نتایج نشان دادند که تنش خشکی باعث کاهش سرعت و عدم یکنواختی جوانه‌زنی و ظهور گیاهچه گردید. باکتری تأثیری بر ظهور گیاهچه نداشت ولی پس از رویش وزن خشک برگ و ساقه، سطح برگ و شاخص بنیه گیاهچه را نسبت به عدم تلقیح افزایش داد. در سطوح مختلف آبیاری، تیمارهای تلقیح با باکتری از ارتفاع، وزن خشک برگ، ساقه، گیاهچه و بنیه بیشتری نسبت به عدم تلقیح برخوردار بودند. تلقیح بذرهای حاصل از شرایط تنش شدید با برادی ریزوبیوم ژاپونیکوم وزن خشک ریشه‌چه را نسبت عدم تلقیح افزایش داد. بنابراین کاربرد باکتری باعث افزایش بنیه گیاهچه بذرهای حاصل از شرایط آبیاری محدود گردید.

Analysis of the relationship between blue-light photon flux density and the photosynthetic properties of spinach (Spinacia oleracea L.) leaves with regard to the acclimation of photosynthesis to growth irradiance

Blue light has been suggested to participate in the acclimation of photosynthesis to growth irradiance. We analyzed the effects of blue light intensity on the photosynthetic properties of leaves with regard to acclimation to irradiance. Spinach (Spinacia oleracea L.) plants were grown under mixtures of blue and red light with blue-light photon flux densities (PFDs) of 0, 30, 100 and 150 µmol m−2 s−1 at a total photosynthetic PFD of 300 µmol m−2 s−1. The light-saturated rate of photosynthesis under white light, leaf N content per unit leaf area, leaf dry weight per unit leaf area and the ratio of cytochrome (Cyt) f content to light-harvesting chlorophyll-binding protein of photosystem II (LHCII) content were evaluated. The photosynthetic rate tended to increase with increasing blue-light PFD up to 100 µmol m−2 s−1, and this was associated with an increase in leaf N content per unit leaf area. However, the increase in leaf N content per unit leaf area did not necessarily result from an increase in leaf dry weight per unit leaf area. The Cyt f to LHCII content ratio increased linearly with increasing blue-light PFD up to 100 µmol m−2 s−1, indicating that plants grown under higher blue-light PFD up to this value resembled plants grown under higher irradiance in terms of N partitioning between electron-transport components and light-harvesting components. This result suggests that the level of blue light is involved only in the acclimation to relatively low growth irradiances at the chloroplast level.

Growth and nutrient concentration of two native forage legumes inoculated with Rhizobium and Mycorrhiza in Missouri, USA

The Center for Agroforestry at the University of Missouri has tested numerous native legumes for potential use in agroforestry and selected Illinois bundleflower (Desmanthus illinoensis (Michaux) MacMillan ex Robinson and Fern.) and panicled tick clover (Desmodium paniculatum (L.) DC.) for further testing. Our objective was to document the effect of arbuscular mycorrhizae (AM) (Glomus spp.) and Rhizobium on growth and nutrient concentration of these legumes. Seeds were planted in a greenhouse and inoculated with one of two species of AM and/or one of two strains of Rhizobium. Plants were harvested after 80 d and data taken on leaf and stem dry weight, root fresh weight, stem height, nodulation, AM colonization, and N, P, K, Ca, and Mg concentration. Inoculation with Rhizobium did not affect plant growth in Illinois bundleflower, but colonization by Glomus intraradices increased all plant growth variables except stem height. Nutrient concentration was unaffected by the presence of either endophyte. In contrast, inoculation of panicled tick clover with Rhizobium str. 41Z10 increased leaf dry weight (32%) compared to the control and root fresh weight (41%) compared to str. 32Z3, and colonization by G. intraradices increased leaf dry weight (35%) and stem height (26%). Both species of AM increased P and K concentration (41% and 55%, respectively) in panicled tick clover. Our results suggest that the growth of these legumes can be improved by the use of proper AM species and/or Rhizobium strains. However, additional research to identify the best Rhizobium and AM inoculates for these plant species is important in developing strategies for their use in agroforestry.

Size dependence of leaf area and the mass of component organs during a course of self‐thinning in a hinoki (Chamaecyparis obtusa) seedling population

The allometric equation, y = gxh, was applied monthly to the relationships between two different dimensions of tree seedlings of hinoki cypress (Chamaecyparis obtusa) during a course of self‐thinning from April 1990 to March 1991 to detect differences in biomass allocation among individuals. As the h‐value in the allometry of crown length and seedling height was greater than unity for all seasons, crown ratio became greater as seedling height increased. Leaf weight ratio increased with increasing seedling size because the h‐value in the allometry of leaf dry weight and whole seedling dry weight was greater than unity in every month. Therefore, smaller seedlings are disadvantageous to photosynthetic production by leaves. In contrast, the leaf area ratio was constant irrespective of seedling size because the h‐value in the allometry of leaf area and whole seedling dry weight was nearly equal to unity in most seasons. In addition, because the h‐value in the allometry of leaf area and leaf dry weight was less than unity in all seasons, specific leaf area decreased with an increase in leaf dry weight, indicating that smaller seedlings adapt to low light environments by possessing shade leaves. Root weight ratio decreased with increasing seedling size because the h‐value in the allometry of root dry weight and whole seedling dry weight was less than unity in most seasons.

Increased growth of young citrus trees under reduced radiation load in a semi-arid climate.

This study investigated the effects of radiation heat-load reduction by shading on the growth and development of citrus trees in a warm subtropical region. The experiment was conducted from mid-June until late October when daily maximal air temperature averaged 29.3 degrees C. Two-year-old de-fruited Murcott tangor (Citrus reticulata BlancoxCitrus sinensis (L.) Osb.) trees were grown under 30% or 60% shade tunnels, or 60% flat shade (providing midday shade only), using highly reflective aluminized nets. Non-shaded trees were used as the control. Shading reduced direct more than diffuse radiation. Daily radiation was reduced by 35% for the 30% Tunnel and 60% Flat treatments, and by 55% for the 60% Tunnel. Two days of intensive measurement showed that shading increased average sunlit leaf conductance by 44% and photosynthesis by 29%. Shading did not significantly influence root and stem dry weight growth, but it increased the increment in leaf dry weight during the three month period by an average of 28% relative to the control, while final tree height in the 30% Tunnel treatment exceeded the control by 35%. Shoot to root and shoot mass ratios increased and root mass ratio decreased due to shading because of the increase in leaf dry weight. Shading increased starch concentration in leaves while the shadiest treatment, 60% Tunnel, decreased starch concentration in the roots. Carbon isotope ratio (delta(13)C) of exposed leaves that developed under shading was significantly reduced by 1.9 per thousand in the 60% Tunnel, indicating that shading increased CO(2) concentrations at the chloroplasts (C(c)), as would be expected from increased conductance. Substomatal CO(2) concentrations, C(i), computed from leaf net CO(2) assimilation rate and conductance values, also indicate that shading increases internal CO(2) concentrations. Based on tree dry mass, tree height, and total carbohydrates fractions, the 30% Tunnel and the 60% Flat were the optimal shade treatments.

Synthetic autotetraploid plants of Phlox drummondii exhibit significantly higher photosynthetic rate at C11 generation than teh diploid progenitor

Multiplication of genome has significant roles in the adaptation and evolution of plants and is accompanied by various physiological changes. Synthetic autotetraploids and its diploid progenitor in Phlox drummondii (Polemoniaceae) have given us a unique opportunity to effectively study the effect of gene dosage on biochemical and physiological activities of the plants. The entire genome was doubled by colchicine and now the synthetic autotetraploids are running into 11th generation (C11). They are not only morphologically healthier than their diploid progenitor but are also photosynthetically more efficient on leaf area basis. Moreover, using different generations of tetraploid plants, we are able to study whether the better growth and physiological performance is the result of only genome duplication or the product of genome dosage combined with gradual environmental adaptation over the years. The increase in leaf dry weight is 55% and 80% in C0 and C11 generations, respectively. The increase in chlorophyll content is about 18% in C0 generation while it is 110% in C11 generation over the diploid progenitors. The light saturation point of tetraploids of both the generations is much higher. The stomatal conductance is only little higher at C0 generation while it has increased 2.75 times in C11 generation. Net photosynthetic assimilation is increased by about 43% in C0 generation (12 µmol CO2 m-2s-1) and more than doubled in C11 generation (17 µmol CO2 m-2s-1). We intend to present the anatomical details, quantification of enzymes, DNA and chlorophyll per cell and, assess the response of photosynthesis to CO2 concentration on per cell and per unit DNA basis and discuss its theoretical and practical implications.

Involvement of endogenous gibberellins in the regulation of increased tomato shoot growth in solarized soil

Environmental factors often affect plant growth bymodifying the levels of endogenous gibberellins (GAs).In this study, the involvement of GAs in theregulation of enhanced shoot growth in tomato (Lycopersicon esculentum Mill.) plants grown in soiltreated by solarization (a soil disinfestation method)was investigated. Seedlings at the cotyledonary stagewere transplanted into either solarized or untreatedcontrol soil. Plants in both soils grew free of anydisease symptoms. As soon as four days after planting,seedlings in solarized soil had a higher dry weightcompared to the control. Throughout most of theexperimental period of 18 days, leaf weight ratio washigher in the solarized vs. the control soil. Treatingshoot tips of control plants with 0.1 mg.L-1GA3 resulted in enhanced leaf and stem growth,thus reaching values similar to those of plants grownin solarized soil. The opposite effect was obtained bytreating plants grown in solarized soil with1 mg.L-1 uniconazole, a GA biosynthesisinhibitor. Quantitative GC-MS analyses revealed thatGA1 content in one and two-weeks old transplantsgrown in various solarized soils was up to 1.8 fold,and that GA3 content in two-weeks old plants wasup to five fold the values in the control. Theseincreases were linearly correlated with the increasein leaf dry weight. It was concluded that theincreased quantities of GA1, and eventuallyGA3, play a role in the increased growth oftomato shoots in solarized soil as early as seven daysafter transplanting.

Nitrogen Metabolism in Tobacco Plants (Nicotiana tabacum L.): Role of Boron as a Possible Regulatory Factor

Tobacco plants (Nicotiana tabacum cv. Sevilla) were grown under controlled conditions and submitted to regular fertilization with macro- and micronutrients. The aim of the experiment was to determine the response of NO3- assimilation to four different boron (B) doses (B1: ; B2: 5 μM; B3: ; and B4: ). The content of foliar B and NO3-, the activity of the enzymes related to the process of NO3- reduction (NR, NiR, GS, GOGAT, and PEPC), and the end products of this process (amino acids and proteins) were analyzed. Our results indicate a positive effect of the B on its concentration in leaves and on NO3- assimilation, possibly by an activation of the enzymatic proteins involved in this process. Boron addition significantly reduced the foliar NO3- concentration. Finally, B affected plant growth, since an increase in leaf dry weight and in the content of proteins and amino acids was shown.

Response of nitrogen metabolism in beans (Phaseolus vulgaris L.) after exposure to ozone and nitrogen dioxide, alone and in sequence

Bush bean (Phaseolus vulgaris L.) plants were exposed to low levels of ozone (O3 ) and/or nitrogen dioxide (NO2 ) in open-top chambers during the growing seasons of 1988 and 1989. Treatments consisted of charcoal-filtered (CF) air, and CF air enriched with either O3 (50-60 nll -1 ), NO2 (30-40 nll-1 ) or both gases. A daily sequential exposure, O2 followed by NO2 , was used in each year in the combined treatment: O2 was added for 8 h d-1 from 08.00 h until 16.00 h, and NO2 for 16 h d-1 from 16.00 h until 08.00 h. Growth variables and key enzymes of N assimilation in leaves were investigated during vegetative growth and at anthesis. Pollutant effects varied between years. No significant effects were found in 1988. In 1989 NO2 , alone or in sequential exposure with O3+ , increased leaf dry weight and total biomass until anthesis. Moreover, there was a parallel increase in the extractable activity of both nitrate and nitrite reductase in the NO2 treatments during vegetative growth, while glutamine synthetase and glutamate dehydrogenase were only increased by sequential exposure to O3 + NO2 . In contrast, during anthesis the activities of nitrite reductase and glutamine synthetase were lowest in leaves sequentially exposed to O3 + NO2 . Ozone alone had very little effect on N metabolism but suppressed growth during anthesis. At pod maturity, the lowest leaf dry weight and leaf area occurred in plants exposed to the sequential combination of O3 + NO2 , but yield (pod weight) was not significantly affected by any of the pollutant treatments. It is concluded that chronic exposure especially to the sequence O3 -NO2 reduced the capacity of the plants for N assimilation. The observed shift in nitrogen metabolism during the plants' development may have contributed to the adverse effects of the sequential treatment O3 + NO2 on growth variables at the end of the exposure period.