Stability of landscape trees in engineered and conventional urban soil mixes

Urban trees are frequently exposed to unsuitable soil conditions that can hamper root system development, potentially affecting both tree health and stability. Engineered soil designs have been developed to increase soil volume for trees planted in confined spaces, and past research has shown that these designs improve growing conditions. However, tree stability in these engineered soils has received limited attention from researchers. In this study, we evaluated the stability of two tree species of contrasting soil quality tolerance (Prunus serrulata and Ulmus parvifolia) after 3 years growth in two skeletal soil mixes, in a suspended pavement design (uncompacted soil), and in a conventionally prepared soil pit. Tree stability was evaluated by measuring trunk resistance to a lateral deflecting force applied with a rope winch system under both ambient and near-saturated soil conditions. Although heavily irrigating the experimental soils had no effect on tree stability, species-specific responses to soil mixes were observed. P. serrulata grown in the gravel-based skeletal soil showed greater trunk deflection resistance than trees grown in the other soil treatments, yet the stability of U. parvifolia was unaffected by soil type. These species-specific responses were consistent with earlier observations of root development in which P. serrulata grew up to 60 times greater root length in gravel-based skeletal soil whereas U. parvifolia root growth was similar in all soil treatments. This research provides evidence that certain tree species planted in conventional tree pits may be more prone to uprooting due to poor root development and that root anchorage might be improved for these species by utilizing a skeletal soil mix.     

Modelling the effects of soil water potential on growth and quality of cut chrysanthemum (Chrysanthemum morifolium)

A complete dynamic model was developed to describe the effects of soil water potential (WP) on the growth and external quality of standard cut chrysanthemum (Chrysanthemum morifolium) in order to optimise water management of greenhouse crops. Experiments using chrysanthemum cv. ‘Jinba’ with different planting dates and levels of water treatment were conducted in a lean-to type greenhouse from 2006 to 2008. The dynamics of leaf area index (LAI), dry matter partitioning, and external quality traits (plant height, number of leaves per plant, flower-head diameter and peduncle length) were first determined as functions of accumulated photothermal index (PTI). Impacts of WP on leaf photosynthetic rate, LAI, dry matter partitioning, and the external quality traits were quantified via introducing the experimentally identified effects of WP on the parameters in the light response curve of leaf photosynthetic rate and the PTI-based functions. These quantitative relationships were incorporated into a generic crop growth model SUCROS. Using independent experimental data, the model was found to give good predictions for biomass production, dry weight of organs, and the external quality traits of the chrysanthemum cultivar grown under different levels of water supply. The coefficient of determination (r²) between the predicted and measured results was 0.91 for LAI, 0.88 for biomass production, and varied between 0.83 and 0.93 for organ dry weight and the external quality traits. Further evaluation is needed when applying this model to a wider range.     

Influence of substrate on strawberry plug plant production

Summary

The plug plant technique for the commercial propagation of strawberries is increasing in importance. Several factors, including the properties of the substrate, can affect plug plant quality. Tests on nine substrates containing different proportions of perlite [from 0 – 75%, (v/v)], and dark and light peat [both from 0 – 80% (v/v)], were performed using a simplex-lattice design in order to establish a model for strawberry plug plant production based not only on the single component composition of the substrate, but also on the influences of the chemical and physical properties of the substrate on plug plant quality. Notable differences in physical and chemical properties were found among the nine different substrates tested, as a consequence of the broad range of their component compositions. Substrate mixes containing medium-to-high proportions [from 60 – 70% (v/v)] of light peat and low proportions of dark peat and perlite are recommended, as these resulted in a low nutrient content, a high organic matter content, a low pH, and a low “coarseness” index, which led to high-grade plug plants with greater root and crown dry weights.     

Estimation of individual leaf area,fresh weight,and dry weight of hydroponically grown cucumbers (Cucumis sativus L.) using leaf length,width, and SPAD value

Non-destructive and mathematical approaches of modeling can be very convenient and useful for plant growth estimation. To predict individual leaf area, fresh weight, and dry weight of a cucumber (Cucumis sativus L.), models were developed using leaf length, leaf width, SPAD value, and different combinations of these variables. Eight regression equations, commonly used for developing growth models, were compared for accuracy and adaptability. The three nonlinear models developed were as follows: individual leaf area (LA) = −210.61 + 13.358W + 0.5356LW (R² = 0.980^***), fresh weight (FW) = −2.72 + 0.0135LW + 0.00022LWS (R² = 0.956^***), and dry weight (DW) = 0.25 − 0.00102LS + 0.000077LWS (R² = 0.956^***), where L is the leaf length, W the leaf width, S the SPAD value, and LWS = L × W × S. For validation of the model, estimated values for individual leaf area, fresh weight, and dry weight showed strong agreement with the measured values, respectively. Leaf dry weight, especially, was estimated with a higher degree of accuracy through the use of a SPAD value, as well as leaf length and width. Therefore, it is concluded that models presented herein may be useful for the estimation of the individual leaf area, fresh weight, and dry weight of a cucumber with a high degree of accuracy.     

Effect of relative humidity on growth and flowering of some greenhouse plants

Young plants of 10 different greenhouse species were grown from 24 to 100 days at 55–60, 70–75 or 90–95% relative humidity (RH) in growth rooms. The dry weight increased significantly by increasing RH from the lowest to the highest level in Begonia × hiemalis (47%), Saintpaulia ionantha (17–36%), Euphorbia pulcherrima (31%), Chrysanthemum × morifolium (31%), Nephrolepis exaltata (68%) and Lycopersicon esculentum (20%). The dry weight of Campanula isophylla, Rosa, Cucumis sativa and Lactuca sativa was not affected by RH, while Soleirolia soleirolii was negatively affected. The fresh weights of Cucumis and Lactuca, however, increased with RH in spite of there being no effects on the dry weights. Shoot length increased very considerably by raising the RH in most of the species. The number of leaves was increased by RH in some of the species while not in others. Number of flowers and flower buds significantly increased with RH in Saintpaulia, and time to flowering was reduced with RH in Saintpaulia, Begonia and Campanula.     

Responses of some different pepper (Capsicum annuum L.) genotypes to inoculation with two different arbuscular mycorrhizal fungi

Eight different pepper genotypes inoculated by two different arbuscular mycorrhizal fungi (AMF) [Glomus intraradices (Gi) and Gigaspora margarita (Gm)] in a growth chamber experiment under normal seedling growing conditions were evaluated for seedling traits, colonization and relative mycorrhizal dependency (RMD). In general, inoculated plants had greater dry weights compared to non-inoculated plants. Five cultivars responded positively to inoculation with AM fungi and three responded negatively. A great variation in mycorrhizal colonization dependency was observed among the pepper genotypes, with the N52 genotype showing the highest RMD and the Karaisali genotype the lowest. RMD and dry weights of pepper genotypes were inversely correlated.     

Drought responses of six ornamental herbaceous perennials

Although low water use landscaping is becoming common in arid regions, little is known about drought tolerance and drought responses of many ornamental plants, especially herbaceous perennials. Drought responses were assessed for six herbaceous ornamental landscape perennials in a 38 l pot-in-pot system in northern Utah over a 2-year period. The first year was an establishment period. During the second year, drought responses were evaluated for established Echinacea purpurea (L.) Moench, Gaillardia aristata Pursh, Lavandula angustifolia P. Mill., Leucanthemum × superbum (J.W. Ingram) Berg. ex Kent, ‘Alaska’, Penstemon barbatus Roth var. praecox nanus rondo, and Penstemon × mexicali Mitch. ‘Red Rocks’. Plants were irrigated at frequencies of 1 (control), 2, or 4 weeks between June and September, simulating well-watered conditions, moderate drought, or severe drought. Osmotic potential (Ψ_s), gas exchange, visual quality, leaf area, and dry weight were assessed. In a confined root zone, P. barbatus showed the greatest tolerance to all levels of drought, avoiding desiccation by increasing root:shoot ratio and decreasing stomatal conductance as water became limiting. L. angustifolia and P. × mexicali showed tolerance to moderate drought conditions, but died after exposure to the first episode of severe drought. Neither G. aristata nor L. superbum were able to regulate shoot water loss effectively. Instead, both species displayed drought avoidance mechanisms, dying back when water was limiting and showing new growth after they were watered. Compared to control plants, G. aristata shoot dry weight was reduced by 50% and 84%, and L. superbum shoot dry weight was reduced by 47% and 99% for the 2- and 4-week irrigation intervals, respectively. Root dry weights were affected similarly for both species. E. purpurea exhibited poor visual quality at all irrigation intervals, in particular wilting severely in both drought treatments, but regaining turgor when watered again. P. barbatus is recommended for ornamental landscapes that receive little or no supplemental irrigation, while E. purpurea is not recommended for low water landscapes because of low visual quality under even mild drought.     

The effects of pre-harvest dehydration on the composition of once-over harvested sweet paprika

When paprika fruits (Capsicum annuum L.) were allowed to dry in the sun, on the plant itself, before harvest, there was a considerable increase in the dry matter content of the subsequently harvested fruit, along with a decrease in the total fresh yield. The dry matter yield did not vary during the drying period, but the colour intensity of the fruit increased continuously. Early cessation of irrigation accelerated the drying rate and intensified fruit colour, but lowered the total dry matter yield.Removal of seeds, placenta parts and stalk after harvest increased fruit colour intensity but lowered yields.Leaving fruit to dry in the sun before harvest resulted in a considerable saving in transport and storage volume, as well in the amount of energy required otherwise to dry the fruit in the dehydration plant. It also opens up possibilities of once-over mechanized harvesting of high quality fruit.     

Influence of temperature,soil moisture and CCC on the flowering of Euphorbia fulgens

In the short-day plant Euphorbia fulgens under short-day conditions the flower induction in the shoot apex is delayed more and more nodes are formed beneath the final cyathium, the higher the temperature up to 28°C. The delay of induction is greater with plants growing in a moist soil than in a dry soil. The difference between moist and dry soil is greater, the higher the temperature. There are slight temporal differences in the induction of the lateral shoots in the temperature range between 15°C and 25°C, but the number of nodes formed at the lower paracladia is greater at the higher temperature. The development of the cyathia is enhanced at high temperatures. At temperatures above 28°C induction is prevented. The temperature limit for induction is some degrees higher for plants in dry soil than for those in moist soil. Cycocel causes effects similar to those caused by water deficiency, although the newly formed internodes become shorter.     

Climatic conditions affect the texture and colour of Cavendish bananas (Grande Naine cultivar)

Relationships between natural production conditions (soil and climate) and physical fruit traits (texture and colour) were studied in Martinique to fuel discussions on creating a label for bananas from the French West Indies. Bananas produced at six sites, under very different conditions, during three different periods of the year, were harvested at the same temperature sum and ripened under identical conditions. The peel of green bananas harvested during the hot humid season was not as hard as that of bananas harvested during the cool dry season. In ripe bananas, an increasing correlation was noted between the rainfall level and fruit firmness (R = 0.88) and peel hardness (R = 0.80). This correlation could explain why bananas produced during the dry season were less firm and, conversely, those produced in highland areas, where rainfall is highest, were firmer. In ripe bananas, a decreasing correlation was also noted between the mean daily temperature and the fruit yellowness (R = 0.84). This interaction could be responsible for the yellower colour of mountain banana pulp and of bananas harvested during the coolest seasons. The green life of bananas harvested during the hot humid season was shorter than that of bananas harvested during the dry and intermediate seasons.     

Effect of intermittent as compared to continuous CO2 enrichment on growth and flowering of Chrysanthemum × morifolium Ramat. and Saintpaulia ionantha H. Wendl

Plants of three cultivars of Saintpaulia ionantha and Chrysanthemum × morifolium were grown until flowering at 335 (normal) or 900 μl l⁻¹ CO₂ (high). Continuous high CO₂ concentration increased the final dry weights from 76 to 123% in Saintpaulia and from 15 to 32% in Chrysanthemum compared to the normal concentration. Changing the CO₂ concentration from normal to high (intermittent) in intervals of 1 h resulted in dry weights intermediate to that of constant normal or constant high CO₂ concentrations in both species. Morning and evening enrichment gave the same effect as 1-h intermittent enrichment in Saintpaulia. High CO₂ concentration given every other day gave the same effect as 1 h intermittent CO₂ in Chrysanthemum. Increased dry weights were accompanied by more and larger leaves in Saintpaulia, and mainly by thicker and longer stem and more lateral breaks in Chrysanthemum.Time to flowering was significantly reduced by CO₂ enrichment in Saintpaulia, but was generally not affected in Chrysanthemum. Number of flowers and flowerbuds was increased by CO₂ application in both species. Constant high CO₂ concentration generally had effects superior to that of the intermittent treatments.     

Growth,root morphology and boron uptake by citrus rootstock seedlings differing in boron-deficiency responses

Boron (B) is an essential microelement for higher plants and has important physiological functions in plant growth and development. Citrus plants are frequently exposed to B-deficiency, but knowledge regarding the effects of B-deficiency on rootstock growth, root morphology and genotypic variations in citrus is limited. To evaluate the variations in plant-growth parameters in response to B-deficiency, five citrus rootstocks seedlings that grown in modified 1/2-strength Hoagland's solution that contained 0.25 μM H₃BO₃ (moderate B-level, Control) or 0 μM H₃BO₃ (B-deficiency, −B) were investigated before and 90 days after treatment. There are significant genotypic variations in plant-growth parameters (dry mass, leaf area and seedling height), root-morphological traits and B-concentrations. B-deficiency inhibited plant dry mass and leaf area expansion of Fragrant citrus, Sour orange and Trifoliate orange seedlings significantly (P < 0.05), whereas no effect was found on the total dry mass of Carrizo citrange and Red tangerine seedlings. Further, B-deficiency reduced the root number, root length and root surface area in Fragrant citrus and Trifoliate orange significantly (P < 0.05); however, no significant effect was detected on these root morphological traits of Carrizo citrange and Red tangerine (P > 0.05). In addition, B-deficiency reduced the B-concentration in the leaves of all the five genotypes and the B-concentration in the roots of Fragrant citrus and Sour orange, none effect was observed on the B-concentration in stems of all studied genotypes and roots. However, there were significant relationships between the root-morphological traits and B-uptake efficiency. These results showed that Carrizo citrange and Red tangerine are B-efficient, Trifoliate orange is the moderate B-efficient genotypic rootstocks, whereas Fragrant citrus and Sour orange are B-inefficient genotypic rootstocks. In addition, Trifoliate orange was the moderate B-efficient rootstocks of five genotypes. The root-to-shoot dry mass ratio (R/S) and longer root numbers were higher in the Carrizo citrange and Red tangerine than that of Trifoliate orange, Fragrant citrus and Sour orange genotypes. That is to say, maintaining higher R/S and numerous longer lateral roots is very important in improving the B-efficiency and thus contribute much to the resistance of seedlings to B-deficiency in the Carrizo citrange and Red tangerine genotypes.     

Nitrogen and calcium nutrition of Petunia × hybrida ‘Coral Sea’

The effects of N and Ca nutrition on plant growth and shoot elemental content of Petunia × hybrida Hort. Vilm. - Andr. ‘Coral Sea’ were evaluated. Nitrogen and Ca were applied separately or in combination in three experiments: (1) N at 0, 100, 200 or 400 mg l^?1; (2) Ca at 0, 75, 150 or 300 mg l^?1; (3) N at 0 or 100 mg l^?1 and Ca at 0 or 150 mg l^?1 combined factorially. Shoot and root dry weights, branch length and flower number were highest when plants received 100 mg l^?1 N. Plants treated with 150 mg l^?1 Ca had the highest shoot and root dry weights. Branch length was maximal at 300 mg l^?1 Ca.Nitrogen and Ca interacted to increase shoot dry weights, branch number and length, leaf area and flower number. Increasing N concentrations increased N and decreased P, Mn and Zn shoot contents. Calcium content of shoots increased while N, P and Mg decreased in response to increasing applications of Ca to petunia plants. Minimal N and Ca tissue concentrations for optimal P. × hybrida growth were 3.3 and 0.67%, respectively.     

The effect of defoliation on bulb production of tulip cultivar ‘Apeldoorn’

The distribution of dry matter between the different bulblets of tulip is not markedly influenced by either changes in leaf area or the position of the leaf. On the contrary, total bulb yield is strongly affected.A reduction factor, S_c, for incomplete soil coverage, when the leaf area index (LAI) is less than 4, normally used for evaluation of planting density effects, can also be used for the effects of defoliation on dry matter increase. This LAI-dependent factor shows a distinctly asymptotic pathway closely resembling

$\text{S}{}_{\mathrm{c}}\text{=}\text{P}{}_{\mathrm{act}}\text{P}{}_{\mathrm{pot}}\text{=1?e}{}^{\mathrm{?k1LAI}}$

where k ～ 0.6 and in which P_act is the actual measured dry weight increase and $\text{P}\text{?}{}_{\mathrm{<mtext>pot</mtext>}}$ the potential net dry weight increase for a closed canopy.     

Growth and quality of Brazilian accessions of Capsicum chinense fruits

Total fresh and dry weight of Capsicum chinense fruit accessions were inversely correlated with accumulation of dry matter, and fruits with a higher percentage of dry matter accumulated proportionally more total soluble solids. Based on regression analysis, a 1% increase in fruit dry weight was associated with a 0.28% improvement in total soluble content, up to a maximum total soluble solid content of 10.25%. Regardless of shape, larger fruits had thicker pericarps, and were therefore more suitable for open air fresh markets. Smaller fruits had thinner pericarps and higher concentrations of total soluble solids and were more appropriate for dehydration and paprika production. Dry fruits with color intensities greater than 200 ASTA units, as required for paprika production, were found in 18.4% of the analyzed accessions. A large number of accessions, close to 27%, had total capsaicinoid concentrations less than or equal to 1.9 mg g⁻¹ dry weight, and can be considered as sweet or light pungent fruits. A small percentage of accessions (2.5%) were classified as extremely hot fruits.     

Emergence and seedling growth of pepper as influenced by soil compaction,nutrient status and moisture regime

Studies on the influence of seed-bed condition on the emergence and development of pepper seedlings (Capsicum frutescens L.) revealed that seed-bed compaction delayed and reduced seedling emergence. High nutrient and organic matter content accentuated the severity of soil compaction, regardless of whether the soil moisture was low or high. Influence of compaction was less on “dry” poor soil. Best seedling emergence was obtained from “moist” crumbly “rich” soil. However, “moist” crumbly “poor” soil, moist compacted poor soil, “dry” crumbly rich soil and “dry” crumbly poor soil also gave very high seedling emergence. The dry compacted rich soil gave the poorest cumulative emergence figures. High soil moisture regime and high nutrient content reduced the severity of soil compaction on seedling root and shoot development. Soil compaction also caused abnormal hypocotyl morphology in seedlings that germinated but failed to emerge.     

Effect of irrigation on near-infrared (NIR) based prediction of mango maturity

This study investigated the effect of irrigation on the ability of near-infrared (NIR) measurements to predict maturity stage of mango. Fruits from irrigated and non-irrigated trees were sampled on six dates during the final three weeks of development and subjected to NIR and conventional laboratory analyses. Spectral assessment showed differentiation between irrigated and non-irrigated fruits on earlier dates, which was not evident later on. NIR measurements of irrigated samples correlated well to dry matter, this was not the case for non-irrigated samples (r = 0.80 compared to 0.57, respectively), while the reverse was true for acidity with r increasing from 0.55 to 0.85 between irrigated and non-irrigated. Second derivative spectra of all samples best correlated with acid content (r = 0.73). Although dry matter was previously proposed as the most suitable parameter for NIR calibration, this study suggests acidity might be an appropriate harvesting index when considering irrigation effects. Interestingly, NIR technology has been found to adequately predict acidity in other fruits, but results of this study require additional investigation.     

Influence of soil temperature on the early growth of three muskmelon cultivars

Three cultivars of muskmelon (Cucumis melo L. ‘Honey Dew’, ‘TAM-Dew’ and ‘TAM-Uvalde’) were seeded and grown under four different soil-temperature regimes. Internode length, leaf area and total shoot dry weight increased with the addition of supplemental soil heating in all cultivars. ‘TAM-Uvalde’ was more responsive to changes in soil temperatures than the other cultivars. Stem growth as measured by dry weight was favored over leaf growth in all cultivars subjected to warmer soil temperatures. Female flowering and fruit set of only one cultivar, ‘TAM-Uvalde’, were accelerated by elevating the soil temperature.     

Relationship of endomycorrhizal association of unsterilized soils with available soil phosphorus,plant growth,phosphorus uptake and oil synthesis in peppermint

The effect of inoculation of peppermint (Mentha piperita L.) with Glomus fasciculatus (Thaxter sensu Gerdemann) Gerdemann and Trappe in unsterilized soils and differential phosphorus (P) availability was studied. Inoculation produced better root infection, consistent with significantly higher total root length, shoot dry weight, P uptake, organic and inorganic P fractions in leaf tissues, and oil yield as compared to uninoculated control, both at deficient and high levels of native soil P.     

Evaluating variability of root size system and its constitutive traits in hot pepper (Capsicum annum L.) under water stress

The importance of root size system has long been recognized as crucial to cope with drought conditions. This investigation was conducted to: (i) evaluate the variability in root size system of hot pepper at maturity; (ii) estimate the effect of root size system on yield under drought conditions; and (iii) effect of water stress on xylem vessel development and total xylem cross-sectional area in roots of hot pepper cultivars. Twelve diverse hot pepper cultivars were grown in wooden boxes with two different water treatments, normal and in 50% water application as water deficit condition. Mean primary root length (PRL) showed a significant positive correlation with final fruit yield at normal as well as stressed condition. Total dry mass of fruit was reduced by 34.7% in drought treatments (DI) compared to full watered treatment (FI). At harvest, water-stressed plants had 21% lower root dry weight mass but higher root:shoot ratio other than FI. PRL, lateral root density, total xylem area per root cross-section showed a significant positive relationship with fruit yield. Also, lateral root density was higher in cultivars with higher xylem density, particularly in tolerant cultivars. Lateral root density (r = 0.847, P < 0.001) and total xylem cross-sectional area in root (r = 0.926, P < 0.001) were tightly related with total biomass production. The importance of root traits contributing to withstand drought in hot pepper is discussed.