Cross-sectional Area Of Stem Research Articles

Effects of water and salt stresses on plant growth and xylem hydraulic properties of tomato.

Xylem is the main tissue for water transport in plants, and the changes of hydraulic properties in which would affect plant water relations and fruit water accumulation. It remains unclear regarding the responses of xylem anatomy and hydraulic properties to water and salt stresses in tomato plants and their relationships with plant growth and fruit water content. We conducted a pot experiment in a greenhouse to investigate the responses of plant growth, fruit water content, and xylem hydraulic properties of a cherry tomato (Hong Baoshi) and a medium-fruited tomato (Beifan 501). There were three treatments, control with a soil water content (θ) of 75%-95% of field capacity (FC) and an initial electrical conductivity (EC) of 0.398 dS·m-1; water stress with θ of 75%-95% of FC (before flowering) and 45%-65% of FC (from flowering until maturity) and an EC of 0.398 dS·m-1; and salt stress with θ of 75%-95% of FC and an EC of 1.680 dS·m-1. Results showed that water and salt stresses decreased the cross-sectional stem area and xylem vessel diameter by 22.0%-40.7% and 10.0%-18.3%, respectively, and reduced the specific hydraulic conductivity of stem and the hydraulic conductivity of peduncle by 8.8%-41.1% and 12.9%-28.4%, respectively. Those changes inhibited plant growth and reduced aboveground fresh weight, fruit size, fresh weight and water content, with a more pronounced negative effect in the medium-fruited tomato. More-over, fruit water content was positively correlated with the specific hydraulic conductivity of stem and peduncle. In conclusion, water and salt stresses would inhibit plant growht, fruit fresh weight, and consequently tomato yield, due to their negative effects on xylem hydraulic properties of the tomato plant. Medium-fruited tomatoes are more susceptible to water and salt stresses than cherry tomatoes.

Integrating Real Tree Skeleton Reconstruction Based on Partial Computational Virtual Measurement (CVM) with Actual Forest Scenario Rendering: A Solid Step Forward for the Realization of the Digital Twins of Trees and Forests

Digital twins of forests (trees) are computational virtual recreations of forests (trees) in which the entity distributions and physical processes in real-world forests (trees) are duplicated. It is expected that conventional forest science and management can be undertaken in a digital twin of forests (trees) if the recreation of a real-world forest (tree) has accurate and comprehensive enough information. However, due to the various differences between the current tree model and the real tree, these envisioned digital twins of the forests (trees) stay a theoretical concept. In this study, we developed a processing strategy that partially integrated computational virtual measurement (CVM) process into the tree modeling workflow. Owing to the feature of CVM, partial tree skeleton reconstruction procedures were considered to have higher mechanical objectivity compared to conventional mathematical modeling methods. The reason was that we developed a novel method called virtual diameter tape (VDT), which could provide a certain percentage of modeling elements using CVM. Technically, VDT was able to virtually measure diameters and spatial distribution of cross-sectional area of trees, including the basal area, from point clouds. VDT simulated the physical scenario of diameter tapes, observing point clouds of trees. Diameter and the cross-sectional area of stem and branches were obtained by two consecutive physical measurement processes, one in the forest sample site and another in the virtual space. At the same time, VDT obtained better or a similar accuracy compared to the mathematical methods, i.e., Hough transform-based methods, using the same data sets. The root-mean-square deviation (RMSE) of retrieval of diameter at breast height (DBH) using VDT was 1.02 cm, while DBH obtained from three conventional methods varied from 1.29 cm to 1.73 cm. Based on VDT measurement results, tree skeleton reconstruction and actual forest scenario rendering of our sample plots were further implemented. Beyond the visual consistency, we believe that our work might be a small and solid step in the technological evolution from tree models to the digital twin of forests (trees).

Why Be a Shrub? A Basic Model and Hypotheses for the Adaptive Values of a Common Growth Form.

Shrubs are multi-stemmed short woody plants, more widespread than trees, important in many ecosystems, neglected in ecology compared to herbs and trees, but currently in focus due to their global expansion. We present a novel model based on scaling relationships and four hypotheses to explain the adaptive significance of shrubs, including a review of the literature with a test of one hypothesis. Our model describes advantages for a small shrub compared to a small tree with the same above-ground woody volume, based on larger cross-sectional stem area, larger area of photosynthetic tissue in bark and stem, larger vascular cambium area, larger epidermis (bark) area, and larger area for sprouting, and faster production of twigs and canopy. These components form our Hypothesis 1 that predicts higher growth rate for a small shrub than a small tree. This prediction was supported by available relevant empirical studies (14 publications). Further, a shrub will produce seeds faster than a tree (Hypothesis 2), multiple stems in shrubs insure future survival and growth if one or more stems die (Hypothesis 3), and three structural traits of short shrub stems improve survival compared to tall tree stems (Hypothesis 4)—all hypotheses have some empirical support. Multi-stemmed trees may be distinguished from shrubs by more upright stems, reducing bending moment. Improved understanding of shrubs can clarify their recent expansion on savannas, grasslands, and alpine heaths. More experiments and other empirical studies, followed by more elaborate models, are needed to understand why the shrub growth form is successful in many habitats.

Is the WBE model appropriate for semi-arid shrubs subjected to clear cutting?

It is crucial to understand the adaptive mechanisms of woody plants facing periodic drought to assess their vulnerability to the increasing climate variability predicted in the Sahel. Guiera senegalensis J.F.Gmel is a semi-evergreen Combretaceae commonly found in Sahelian rangelands, fallows and crop fields because of its value as an agroforestry species. We compared canopy leafing, and allometric measurements of leaf area, stem area and stem length and their relationships with leaf water potential, stomatal conductance (gs) and soil-to-leaf hydraulic conductance (KS-L), in mature and current-year resprouts of G. senegalensis in Sahelian Niger. In mature shrubs, seasonal drought reduced the ratio of leaf area to cross-sectional stem area (AL : AS), mainly due to leaf shedding. The canopy of the current-year resprouts remained permanently leafed as the shrubs produced leaves and stems continuously, and their AL : AS ratio increased throughout the dry season. Their KS-L increased, whereas gs decreased. West, Brown and Enquist's (WBE) model can thus describe allometric trends in the seasonal life cycle of undisturbed mature shrubs, but not that of resprouts. Annual clear cutting drives allometric scaling relationships away from theoretical WBE predictions in the current-year resprouts, with scaling exponents 2.5 times greater than those of mature shrubs. High KS-L (twice that of mature shrubs) supports this intensive regeneration process. The adaptive strategy described here is probably common to many woody species that have to cope with both severe seasonal drought and regular disturbance over the long term.

Bud development and shoot morphology in relation to crown location.

Plant architecture is shaped by endogenous growth processes interacting with the local environment. The current study investigated crown development in young black alder trees, assessing the effects of local light conditions and branch height on individual bud mass and contents. In addition, we examined the characteristics of parent shoots [the cross-sectional area (CSA) of stem and total leaf area, shoot length, the number of nodes, the number and total mass of buds per shoot] and leaf-stem as well as bud-stem allometry, as several recent studies link bud development to hydraulic architecture. We sampled shoots from top branches and two lower-crown locations: one subjected to deep shade and the other resembling the upper branches in light availability. Sampling was carried out three times between mid-July and late October, spanning from the early stages of bud growth to dormancy. Individual bud mass and shoot characteristics varied in response to light conditions, whereas leaf-stem allometry depended on branch height, most likely compensating for the increasing length of hydraulic pathways. Despite the differences in individual bud mass, the number of preformed leaves varied little across the crown, indicating that the plasticity in shoot characteristics was mainly achieved by neoformation. The relationship between total bud mass and stem CSA scaled similarly across crown locations. However, scaling slopes gradually decreased throughout the sampling period, driven by bud rather than by stem growth. This suggests that the allometry of total bud mass and CSA of stem is regulated locally, instead of resulting from crown-level processes.

Combining taper and basic wood density equations for estimating stem biomass of the Populus x canadensis I - 488 variety

Stem biomass estimates are useful for various purposes. For example, the amount of commercially usable timber, carbon stock and energy fuel potential are directly related to biomass quantity. This paper describes the development of a biomass flexible equation for poplar (Populus x canadensis I - 488) combining stem profile and basic wood density models, which were fitted and validated with a sample of 60 trees of this variety of poplar. The biomass equation, which is obtained from the double integral of the product between the basic wood density and cross-sectional stem area, was analyzed in four scenarios given by combining average and individual tree models for both stem profile and basic wood density. The most accurate results in both stem profile and basic wood density modeling, as in the stem biomass estimates, were obtained with individual tree models.

Effect of Plant Density on Microstructure of Stalk Vascular Bundle of Summer Maize ( Zea mays L.) and Its Characteristics of Sap Flow

Improving plant density is an important measure to get high yield of summer maize. Two varieties of summer maize with different density tolerances, Zhengdan 958 and Nongda 108, were used to study the effect of plant density on structure of vascular bundles of the third internode and its characteristics of sap flow under three plant densities. The results showed that the cross sectional area of stem and the amount and area of big, small vascular bundles in stalks decreased significantly with the increase of plant density, which resulted in the total number and area of vascular bundle decreased. Nongda 108 was more sensitive to plant density than Zhengdan 958. The sap flow rate and amount of sap during 8:00–17:00 decreased significantly with the increase of plant density, while the transport efficiency of stalk vascular bundle increased. There was a positive correlation between area of big vascular bundles and amount of sap flow during 8:00–17:00. The structure and function of stalk vascular bundles in Zhengdan 958 were superior to these in Nongda 108, it might be one of the reason that Zhengdan 958 with better density tolerance could get high yield.

Quantitative Genetics of Traits Indicative of Biomass Production and Heterosis in 34 Full-sib F1 Salix eriocephala Families

This project examined the heritability of traits that affect biomass production of Salix eriocephala, a shrub willow native to North America and an essential species in the breeding of bioenergy crop varieties. Using an incomplete factorial design, seven females and eight males were crossed to produce 34 full-sib F1 families. Five to 12 entries per family were planted in four-plant plots in a randomized complete block design on two sites. Melampsora rust incidence was scored in the fall of the first growing season (prior to coppice). Height of the tallest stem, cross-sectional stem area per stool, and number of stems per stool were recorded in the winter after the first growing season post-coppice. Plants were harvested 3 years post-coppice and biomass yield was determined. A large percentage of the total variance was additive for all of the traits studied and heritability estimates were low to moderate, suggesting that phenotypic expression of these traits is predictable and can be improved through breeding. Based on yield 3 years after coppice, 29 of the 34 families displayed midparent heterosis, ranging from 1–115%, for the composite trait—biomass yield, strongly indicating that offspring often perform better than their parents in this population. This study will assist in selecting parents which may produce superior progeny in the breeding program.

Growth Response of Crapemyrtle to Coppicing and Production Light Level

Abstract The effects of production light level on coppicing and coppice timing were evaluated as means of accelerating the development of tree-form crapemyrtles. By the end of the growing season, ‘Fantasy’ and ‘Tuscarora’ coppiced in March and grown under 80% shade were 23 and 18% taller, respectively, than coppiced plants in full sun, but similar in height to plants under 50% shade. Coppiced Dynamite™ under 80% shade and coppiced ‘Carolina Beauty’ under 50% shade were 11 and 26% taller than coppiced plants in full sun, respectively, by the end of the growing season. Height of ‘Fantasy’ and ‘Tuscarora’, but not ‘Natchez’, at the end of the growing season decreased as coppicing was delayed from January to June. ‘Natchez’ coppiced in March were taller than plants coppiced in January or February and 68% taller than plants coppiced in June by the end of the growing season. Cross-sectional stem area of coppiced Dynamite™ and ‘Fantasy’ grown in full sun was greater than that of plants under 50 or 80% shade. Stem area of coppiced ‘Tuscarora’ under 50% shade was greater than that under 80% shade, but similar to that of coppiced plants in full sun. Stem area of coppiced ‘Carolina Beauty’ was greatest when grown in full sun, followed by growth under 50% shade, and least in plants grown under 80% shade. Stem area of ‘Fantasy’, ‘Natchez’, and ‘Tuscarora’ at the end of the growing season decreased linearly as coppicing was delayed from January to June. Visually, coppiced plants had straighter shoots, more uniform shoot diameters, and less branching off the main trunks than non-coppiced plants.

A comparative histological study between normal and fasciated shoots of Prunus avium generated in vitro

A combination of Murashige and Skoog’s medium and N6−benzyladenine (BA) at various concentrations (0, 0.1, 0.25, 0.5, 0.75, 1.0, 1.25 and 1.5 mg l−1) was supplied to shoot tips from root cuttings of a 50-year-old wild-cherry tree (Prunus avium). The concentration of BA in the growing medium was a determining factor with respect to the number of proliferated shoots per explant in vitro.Normal and fasciated shoots were generated when BA was present at 0.5, 0.75, 1.0 and 1.25 mg l−1 in the medium and the mean numbers of normal shoots per explant were 3.63, 5.37, 8.93 and 7.30 respectively, and those of the fasciated shoots per explant were 0.03, 0.1, 0.47 and 0.4 respectively. Anatomical analysis by confocal microscopy of sections of paraffin-embedded specimens revealed that the cell structure and organization of the cortex and vascular cylinder in the fasciated shoots was similar to that in normal shoots. However, the cross-sectional area of stem of the fasciations was apparently greater than that of the normal shoots. In particular, the volume of vascular tissues, of pith and of some individual parenchyma cells in the cortex and pith was apparently greater in fasciated shoots than in normal shoots. Increases in cytokinesis and morphogenetic activity, such as the development of callus-like regions and the formation of adventitious shoots, were observed in the cortex and pith throughout the fasciations. The fasciated shoots had numerous buds and initiating new shoots at their apices while normal shoots had a single dominant axial bud.

Allometry for estimating aboveground tree biomass in tropical and subtropical eucalypt woodlands: towards general predictive equations

A fundamental tool in carbon accounting is tree-based allometry, whereby easily measured variables can be used to estimate aboveground biomass (AGB). To explore the potential of general allometry we combined raw datasets from 14 different woodland species, mainly eucalypts, from 11 sites across the Northern Territory, Queensland and New South Wales. Access to the raw data allowed two predictor variables, tree diameter (at 1.3-m height; D) and tree height (H), to be used singly or in various combinations to produce eight candidate models. Following natural log (ln) transformation, the data, consisting of 220 individual trees, were re-analysed in two steps: first as 20 species–site-specific AGB equations and, second, as a single general AGB equation. For each of the eight models, a comparison of the species–site-specific with the general equations was made with the Akaike information criterion (AIC). Further model evaluation was undertaken by a leave-one-out cross-validation technique. For each of the model forms, the species–site-specific equations performed better than the general equation. However, the best performing general equation, ln(AGB) = –2.0596 + 2.1561 ln(D) + 0.1362 (ln(H))2, was only marginally inferior to the species–site-specific equations. For the best general equation, back-transformed predicted v. observed values (on a linear scale) were highly concordant, with a slope of 0.99. The only major deviation from this relationship was due to seven large, hollow trees (more than 35% loss of cross-sectional stem area at 1.3 m) at a single species–site combination. Our best-performing general model exhibited remarkable stability across species and sites, when compared with the species–site equations. We conclude that there is encouraging evidence that general predictive equations can be developed across sites and species for Australia’s woodlands. This simplifies the conversion of long-term inventory measurements into AGB estimates and allows more resources to be focused on the extension of such inventories.

Variation in morphology, anatomy and chemistry of stems of Miscanthus genotypes differing in mechanical properties

The aim of this experiment was to measure the chemical composition and morphological and mechanical properties, and to determine the contribution of different tissue components and chemical constituents to the modulus of elasticity of Miscanthus. Randomly selected stems of Miscanthus ‘Giganteus’, 10 numbered clones and 6 named cultivars of M. sinensis were harvested in February 1999. Determination of morphological characteristics included counting the number of internodes, measurement of the length of stems and internodes, and size of outer and inner diameter. Culm wall thickness, cross sectional stem area and moment of inertia were calculated, and modulus of elasticity was measured using a three point method. Chemical analysis included determination of the concentration of dry matter, cellulose, lignin, and ashes. Studies of anatomy encompassed determination of number of vascular bundles, area of parenchyma vascular bundles, and outer heavily lignified ring (outer ring). Substantial variations and significant differences between genotypes were found for all morphological and anatomical characteristics and for concentrations of chemical constituents except dry matter. A stepwise regression analysis was carried out on the relationship between modulus of elasticity as the dependent variable, and the morphological characteristics, anatomical characteristics, and the concentration of chemical constituents as independent variables. Modulus of elasticity depended significantly of the area parenchyma vascular bundles and outer heavily lignified tissue (outer ring) and of the concentration of lignin and cellulose. Based on the measured characteristics it was hypothesized that the cultivar ‘Purpurescens’ may have the highest lodging resistance followed by ‘Braunschweigh’ and ‘Giganteus’.

Analysis of form and function in North American columnar cacti (tribe Pachycereeae)

Simple and multivariate linear models were used to demonstrate the influence of mechanical design and climate on stem morphology and branching architecture in 25 species of North American columnar cacti. The effect of phyletic inertia was tested by the method of independent contrasts. Stem girth was found to increase significantly slower with increased height within taxa (cross-sectional stem area ;ps [plant height] 0.603), than across taxon (cross-sectional stem area ;ps [plant height] 1.451). Juveniles are shown to be mechanically overbuilt and subsequently grow into more slender adult forms determined in part by structural limitations and the optimization of other stem functions. We make a structural analogy of relatively rigid columnar cacti to concrete columns and compare plants and models with similar growth forms lacking woody skeletons (barrel cacti). Taxa with woody support achieved a surface-to-volume ratio six times greater than taxa without woody support. Across taxon, cooler winter temperatures were associated with larger stem girths, and greater annual precipitation was associated with less frequent branching. The relationship between total plant surface and volume approaches isometry within taxa, but across taxon average individuals are scaled replicates. We hypothesize that architecture and average plant height are adjusted, in an evolutionary sense, to maintain geometric similitude between surface and volume along a climatic gradient.

Seasonal development of leaf area in a young, widely spaced Pinus radiata D. Don stand.

Measurements of needle elongation and needle death were made at two-week intervals during a year on 250 branch units spread throughout the crowns of six trees (three high-pruned, three low-pruned) in a widely spaced, 6- to 7-year-old Pinus radiata D. Don plantation in New Zealand. The trees were well supplied with nutrients and water. During the year, mean tree height increased by 1.2 m and the cross-sectional area of stem below the green crown (used to predict leaf area) for the average tree increased from 8.7 x 10(3) to 13.9 x 10(3) mm(2). The increase in stem cross-sectional area occurred throughout the year except for two months in early winter (May and June). Elongation of Age 0 needles began in Spring (October), continued through summer, and the mean date for 95% completion of elongation was in autumn (early May), approximately 200 days after elongation began. Mean maximum needle length in the canopy decreased with increasing branch order and was 136 and 94 mm for Order 1 and Order 3 units, respectively. Needle elongation was related to thermal time, using growing degree days with a base temperature of 6 degrees C. The mean maximum rate of needle elongation in the canopy was 0.11 m ( degrees C day)(-1) and this occurred in early summer (mid-December), 47 days after elogation started. Maximum needle length and the rate of elongation increased, and the time taken to reach 95% elongation decreased with increasing height in the canopy. A smaller autumn flush of needles started in summer (January) and the needles elongated linearly at a mean rate of 0.07 mm ( degrees C day)(-1) until the end of the growing season when temperatures fell below the base value. At the end of the year, the mean length of needles from the autumn flush was 66 mm. The density of needles did not change with height in the canopy and there were no significant changes seasonally. The mean density values for Age 1 and Age 0 needles were 336 and 286 kg m(-3), respectively. Dry weight per unit length did not change seasonally for Age 1 needles, but the mean values for Order 1 and Order 2 needles were 0.32 and 0.23 mg mm(-1), respectively. Dry weight per unit length for Age 0 needles increased during the growing season (October to February). This was particularly apparent for Order 1 needles where the mean value increased from 0.12 to 0.25 mg mm(-1). Death of Age 1 needles started in midsummer (mean date was January 24) which coincided with the time of maximum elongation of Age 0 needles, but there were differences in timing among individual trees. The mean rate of death was 1.7% day(-1) and the mean duration was 59 days. Leaf area index for the stand increased from 3.2 to 5.3 (all-surfaces basis) during the year. At the end, 92% of the leaf area had grown during the year and 60% of it was on Order 2 branch units. The models for needle elongation and needle death were used to scale up to seasonal changes in canopy leaf area index. Leaf area index peaked with increasing Age 0 leaf area to 6.1 in summer (January), fell to 4.7 in March as Age 1 needles died, then increased slightly again. The seasonal dynamics are consistent with the hypothesis of Cannell (1989) that the timing of maximum leaf area index within a year is optimal for maximizing biomass production.

Waterlogging responses of Sporobolus virginicus (L.) Kunth.

Flooding responses in Sporobolus virginicus (L.) Kunth., a perennial C4 grass, propagated from plants collected on the fringes of a mangrove swamp, were examined in a glasshouse study over 42 days. Flooding significantly reduced soil redox potential, induced adventitious root development, shifted resource allocation from below- to above-ground components without affecting total biomass accumulation and significantly decreased below-ground/above-ground biomass ratios. Although soil waterlogging significantly increased alcohol dehydrogenase activity (ADH) after 30 h, significant increase in central air space by 45-50% of the cross-sectional stem area eliminated root hypoxia, and ADH activity decreased to levels equivalent to drained controls after 42 days. In addition, flooded plants exhibited significantly higher carbon dioxide assimilation rates but similar relative growth rates (RGR) to drained controls. The results indicate that S. virginicus responds to water-logging by a combination of metabolic, morphological and anatomical mechanisms, which may account for its widespread distribution in coastal lagoons, estuaries and marshes.

Water relations of ‘Wijcik McIntosh’ apple trees

SummaryAspects of water flow in columnar apple trees were analysed in relation to variation with height of leaf conductance to water vapour, tree morphology and vascular anatomy. Water potential gradients in transpiring trees were in the range of 0.02-0.09 MPa m1. Although the cross-sectional area of stem per unit leaf area supplied increased towards the tip of the tree, there was no evidence for a corresponding decline in water potential gradient, implying a decreased stem conductivity with height. Measurements of stem conductivity confirmed this, and the mean diameter of xylem vessels was also found to decrease with height. Mean leaf size, leaf area per unit length of stem, and specific leaf area were all smallest at the tops of the trees. Although leaf conductance tended to increase with height, it was most closely related to irradiance, not to leaf water status. The results indicate that columnar apple trees provide a useful model system for studying the limitations to water flow within fruit trees, ...