xylem taper

The widening of xylem vessels from tip to base of trees is an adaptation to minimize the hydraulic resistance of a long pathway. Given that parallel veins of monocot leaves do not branch hierarchically, vessels should also widen basipetally but, in addition to minimizing resistance, should also account for water volume lost to transpiration since they supply water to the lamina along their lengths, that is 'leakiness'. We measured photosynthesis, stomatal conductance, and vessel diameter at five locations along each leaf of five perennial grass species...

Parsnip ( Pastinaca sativa L.) is an edible root that has long been used in cooking and preparing baby food and livestock. The present study was performed to evaluate the phenotypic diversity of 69 accessions of this species to select superiors in terms of root quality in Paykan village, Isfahan province, Iran, in the year 2022. There were significant differences among the accessions investigated (ANOVA, p  < .01). Coefficient of variation (CV) was more than 20.00% in the majority of measured characters (64 out of 66 characters), indicating high diversity among the accessions...

Vessel traits are key in understanding trees' hydraulic efficiency, and related characteristics like growth performance and drought tolerance. While most plant hydraulic studies have focused on aboveground organs, our understanding of root hydraulic functioning and trait coordination across organs remains limited. Furthermore, studies from seasonally dry (sub-)tropical ecosystems and mountain forests are virtually lacking and uncertainties remain regarding potentially different hydraulic strategies of plants differing in leaf habit...

Paeoniae radix Rubra is a traditional Chinese herbal medicine, which has the effect of clearing heat and cooling blood, activating blood and removing stasis. It has become popular in the Chinese market in recent years due to its extremely high medicinal value and showy flower color. In May 2021, typical symptoms of root rot were observed in a field (35°7'12″ N, 103°58'48″ E) in Dingxi, Gansu province, China. Approximately 10% of the plants in the field had typical root rot symptoms, and the root of each affected plant is at least 5% severe...

Lianas combine large leaf areas with slender stems, features that require an efficient vascular system. The only extant member of the Austrobaileyaceae is an endemic twining liana of the tropical Australian forests with well-known xylem hydraulics, but the vascular phloem continuum aboveground remains understudied. Microscopy analysis across leaf vein orders and stems of Austrobaileya scandens revealed a low foliar xylem:phloem ratio, with isodiametric vascular elements along the midrib, but tapered across vein orders...

The soilborne ascomycete fungus Verticillium dahliae causes destructive vascular wilt disease in hundreds of dicotyledonous plant species. However, our understanding of the early invasion from the epidermis to the vasculature and the prompt proliferation and colonization in the xylem tissues remains poor. To elaborate the detailed infection strategy of V. dahliae in host plants, we traced the whole infection process of V. dahliae by live-cell imaging combined with high-resolution scanning electron microscopy...

Mango (Mangifera indica L., Anacardiaceae), the fifth most consumed fruit worldwide, is one of the most important fruit crops in tropical regions, but its vascular anatomy is quite unexplored. Previous studies examined the xylem structure in the stems of mango, but the anatomy of the phloem has remained elusive, leaving the long-distance transport of photoassimilates understudied. We combined fluorescence and electron microscopy to evaluate the structure of the phloem tissue in the tapering branches of mango trees, and used this information to describe the hydraulic conductivity of its sieve tube elements following current models of fluid transport in trees...

Archidendron clypearia (Jack) Benth. (common name: Monkey-pod) is a perennial arbor tree belonging to the family Fabaceae. It is used to produce a traditional medicine to treat a variety of heat toxicity symptoms in China. The distribution of A. clypearia mainly include Guangdong, Fujian, and Zhejiang provinces in China as well as other countries in Southeast Asia. In 2018, about 30 Monkey-pod trees were observed showing typical dieback symptoms in a commercial plantation (114°36'09.401″E, 22°58'38.553″N) of Huizhou, Guangdong Province, China...

Trees grow by vertically extending their stems, so accurate stem hydraulic models are fundamental to understanding the hydraulic challenges faced by tall trees. Using a literature survey, we showed that many tree species exhibit continuous vertical variation in hydraulic traits. To examine the effects of this variation on hydraulic function, we developed a spatially explicit, analytical water transport model for stems. Our model allows Huber ratio, stem-saturated conductivity, pressure at 50% loss of conductivity, leaf area, and transpiration rate to vary continuously along the hydraulic path...

In this work, we analyse morpho-physiological modifications presented during the allomorphic growth of the aroid vine Rhodospatha oblongata Poepp throughout its ascent into the forest canopy. We test the hypothesis that morphological modifications in the root, shoot and leaf are followed by a gradual improvement of the xylem vascular system in order to increase water acquisition and transport as body size increases. The characterisation of these structural modifications was based on 30-35 specimens divided into six size classes...

It is generally assumed that the largest vessels are occurring in the roots and that vessel diameters and the related hydraulic conductance in the xylem are decreasing acropetally from roots to leaves. With this study in five tree species of a perhumid tropical rainforest in Sulawesi (Indonesia), we searched for patterns in hydraulic architecture and axial conductivity along the flow path from small-diameter roots through strong roots and the trunk to distal sun-canopy twigs. Wood density differed by not more than 10% across the different flow path positions in a species, and branch and stem wood density were closely related in three of the five species...

Variation in angiosperm vessel diameter is of major functional significance. In the light of recent models predicting optimal vessel taper given resistance imposed by conductive path length, we tested the prediction that plant size should predict vessel diameter, with dryland plants having narrower vessels for their stem sizes. We assembled a comparative dataset including vessel and stem diameter measurements from 237 species from over 40 angiosperm orders across a wide range of habits and habitats. Stem diameter predicted vessel diameter across self-supporting plants (slope 0...

In plants, water flows from roots to leaves through a complex network of xylem conduits. The xylem architecture is characterized by the conduit enlargement towards the stem base and the multiplication of conduits near the apices of lateral branches. The xylem architecture of a small ash tree was analysed by measuring the vessel hydraulic diameter (Dh) and number (N) at different heights along the stem and branches. Along the stem, Dh and N increased from the apex to the point of crown insertion. Below, Dh and N decreased and remained constant, respectively...

The adaptational characteristics due to long-term adaptation in the natural habitats of common reed (Phragmites communis Trin.) contrasted considerably among three different ecotypes: dune reed (DR), Gobi salt reed (GSR) and swamp reed (SR). The micromorphologies of leaf adaxial surfaces showed tapered setae and a non-smooth surface in DR, compound papillose structures with wax and hairs in GSR, but only papillose structures for the smooth surface of SR. Anatomical analysis showed that DR and GSR had higher bundle-sheath cell areas and a lower xylem/phloem ratio than SR...

A recent paper by Meinzer et al. (Oecologia, 2010, 164:287-296) has reviewed the topic of conflicts between hydraulic efficiency and safety in vascular plants. The authors raised the question that reliable interpretations of results on the mechanisms behind this trade-off requires an integrated approach that considers the variations in hydraulic traits throughout the entire plant and between different individuals, species and environments. Nonetheless, the literature review was only partial. Here, we discuss that an important feature of the whole tree xylem architecture, conduit tapering, is one of traits that must be considered when planning analyses of hydraulic properties of plants and interpreting the results...

Plant vascular networks are central to botanical form, function, and diversity. Here, we develop a theory for plant network scaling that is based on optimal space filling by the vascular system along with trade-offs between hydraulic safety and efficiency. Including these evolutionary drivers leads to predictions for sap flow, the taper of the radii of xylem conduits from trunk to terminal twig, and how the frequency of xylem conduits varies with conduit radius. To test our predictions, we use comprehensive empirical measurements of maple, oak, and pine trees and complementary literature data that we obtained for a wide range of tree species...

We studied the effect of tree architecture on xylem anatomy in three Betula pendula Roth., three Picea abies (L.) H. Karst. and three Pinus sylvestris (L.) trees (mean age 35 years). First, the analysis of conduit anatomy in different tree parts showed that conduits tapered and their frequency increased from roots (≥ 2 mm) to stem, from stem to branches and further to leaf petioles in B. pendula. Conduit anatomy in lateral and main roots, as well as lateral and main branches, significantly differed from each other in all the studied species...

Determining the pH values of microscopic plant samples may help to explain complex processes in plants, so it is an area of interest to botanists. Fiber-optic probes with small dimensions can be used for this purpose. This paper deals with the fiber-optic detection of the pH values of droplets of plant xylem exudate based on ratiometric fluorescence intensity measurements with an internal reference. For this purpose, novel V-taper sensing probes with a minimum diameter of around 8 μm were prepared that enable the delivery of fluorescence signal from the detection site on the taper tip to the detector...

*Recent research suggests that increasing conduit tapering progressively reduces hydraulic constraints caused by tree height. Here, we tested this hypothesis using the tallest hardwood species, Eucalyptus regnans. *Vertical profiles of conduit dimensions and vessel density were measured for three mature trees of height 47, 51 and 63 m. *Mean hydraulic diameter (Dh) increased rapidly from the tree apex to the point of crown insertion, with the greatest degree of tapering yet reported (b > 0.33). Conduit tapering was such that most of the total resistance was found close to the apex (82-93% within the first 1 m of stem) and the path length effect was reduced by a factor of 2000...

Leaf venation architecture is tremendously diverse across plant species. Understanding the hydraulic functions of given venation traits can clarify the organization of the vascular system and its adaptation to environment. Using a spatially explicit model (the program K_leaf), we subjected realistic simulated leaves to modifications and calculated the impacts on xylem and leaf hydraulic conductance (K(x) and K(leaf), respectively), important traits in determining photosynthesis and growth. We tested the sensitivity of leaves to altered vein order conductivities (1) in the absence or (2) presence of hierarchical vein architecture, (3) to major vein tapering, and (4) to modification of vein densities (length/leaf area)...