Search results for " xylem"
showing 10 items of 10 documents
Water relations of two Sicilian grapevine cultivars in response to potassium availability and drought stress
2020
Abstract We investigated the response of two Sicilian grapevine cultivars, Catarratto and Nero d'Avola, to potassium deficiency and drought stress. Two-year-old plants grafted on 1103 Paulsen were grown in agriperlite, with or without potassium in the fertigation solution for six weeks, and subjected to moderate drought stress by suspending irrigation for one week. Potassium content of leaves, roots and xylem sap were measured with an ion-selective electrode. Changes in stomatal conductance, stem and leaf water potential and hydraulic conductance were compared between genotypes and treatments. Potassium deficiency led to significant decreases in leaf potassium content in both cultivars and …
Direct exposure to solar radiation causes radial growth eccentricity at the beginning of the growing season in Robinia pseudoacacia
2020
Abstract Our study investigated the effect of stem temperature increase on xylem formation in Robinia pseudoacacia tree-trunks, caused by direct exposure to solar radiation. It is important to determine factors which may improve the concentricity of deposited wood tissue and intensify xylogenesis because a strong irregularity of wood tissue deposited in the radial direction in mature trees of R. pseudoacacia reduces the commercial value of the wood. Samples of vascular cambium along with adjacent tissues were collected from the southern (illuminated) and northern (shaded) side of tree-trunks growing in the inner and peripheral (thus exposed to direct sunlight) zones of the research plot. Sa…
Experimental conditions for respiration and growth studies of F0 and F1 larval and juvenile European seabass Dicentrarchus labrax
2022
Water parameters in the 2 years before spawning of F0 (08.02.2016-06.03.2018) and during larval and juvenile phase of F1: Larval period until 17.05.2018 (48 dph, 900 dd) and 01.06.2018 (63 dph, ~900 dd) for warm and cold life condition respectively, for the juveniles until 28.09.2018 (180 dph, ~4000 dd) and 12.02.2019 (319 dph, ~5100 dd) for warm and cold conditioned fish respectively. Means ± s.e. over all replicate tanks per condition. Temperature (Temp.), pH (free scale), salinity, oxygen and total alkalinity (TA) were measured weekly in F1 and monthly in F0; sea water (SW) measurements were conducted in 2017 and 2018. Water parameters during larval and early juvenile phase of F0: Larval…
Leaf and stem anatomy in eight Hypericum species (Clusiaceae).
2013
Abstract - Foliar micromorphology, epicuticular wax morphology and anatomical features of leaves and stem, particularly secondary xylem, were examined with light microscopy, general and histochemical staining and scanning electron microscopy in eight Hypericum species. Outer tegument tissue and type of secondary xylem are determining characteristics. Secondary xylem is ring-porous in H. perforatum, H. perfoliatum, H. tetrapterum, H. triquetrifolium, H. androsaemum and H. hircinum. In H. aegypticum and H. pubescens xylem is diffuse-porous, which is considered to be a more primitive type. These characteristics may be considered an additional criterion for species identification.
Does short-term potassium fertilization improve recovery from drought stress in laurel?
2014
Xylem hydraulic conductance varies in response to changes in sap solute content, and in particular of potassium (K(+)) ion concentration. This phenomenon, known as the 'ionic effect', is enhanced in embolized stems, where it can compensate for cavitation-induced loss of hydraulic conductance. Previous studies have shown that in well-watered laurel plants (Laurus nobilis L.), potassium concentration of the xylem sap and plant hydraulic conductance increased 24 h after fertilization with KCl. The aim of this work was to test whether water-stressed laurel plants, grown under low potassium availability, could recover earlier from stress when irrigated with a KCl solution instead of potassium-fr…
Cortical Bundles in the Persistent, Photosynthetic Stems of Cacti
1992
We examined 62 species in 45 genera of the cactus subfamily Cactoideae; all had collateral cortical bundles that permeated the broad, water-storing inner cortex and extended to the base of the outer, photosynthetic palisade cortex. Mean distance between cortical bundles was 0.75 mm, similar to the mean spacing (0.74 mm) of veins in leaves of Pereskia, a genus of relict leaf-bearing cacti. In 16 species, both young and extremely old stem cortex was available for study: in all of these, older bundles had larger amounts of phloem than did younger bundles, indicating that phloem had been produced for many years. In ten species, older bundles also had more xylem than younger bundles. In two gene…
Evolution of growth form in epiphytic Dissochaeteae (Melastomataceae)
2001
Abstract We trace the evolution of root climbing and scrambling in Dissochaeteae and Sonerileae, two closely related groups that comprise the majority of Old World climbing Melastomataceae. The morphological and anatomical adaptations of the different climbers are interpreted in the context of a phylogeny based on chloroplast (cp) DNA sequences of the ndhF gene, generated for 31 representatives of Dissochaeteae and Sonerileae/Oxysporeae plus nine outgroups. For 20 of these taxa, the ndhF sequences were combined with cpDNA rpl16 intron sequences to obtain higher statistical support. Parsimony, minimum evolution, and maximum likelihood approaches yield congruent topologies that imply that scr…
Effects of reduced irradiance on hydraulic architecture and water relations of two olive clones with different growth potentials
2009
Abstract The hydraulic architecture and water relations of two olive genotypes, ‘Leccino Dwarf’ (LD) and ‘Leccino Minerva’ (LM) growing at two irradiance levels i.e. full sunlight irradiance (HI) and 50% sunlight irradiance (LI) were studied. The two clones showed similar plant hydraulic conductances (Kplant) and similar conductance of roots and leaves (Kroot and Kleaf) when growing at equal irradiance levels. However, both Kplant and Kroot were significantly lower in LI plants than in HI ones. On the contrary, Kleaf was unaffected by the light regime. One-year-old twigs of LI plants produced longer xylem conduits but lower average diameter of conduits and less conduits per unit xylem cross…
Effect of potassium fertilization on the hydraulic conductance of laurel plants
2009
The effect of potassium fertilization on hydraulic conductance was tested in 2-year-old potted laurel seedlings, grown in a greenhouse at the Botanical Garden of Palermo. Plants were divided into a control group (+K) and a potassium starved group (-K). A set of randomly chosen -K plants received irrigation with 25 mM KCl (KCl plants) 24 hours before measurements, to test the short term effect of potassium fertilization. Measurements were carried out in July and October 2008. Whole-plant hydraulic conductance was measured by the evaporative flux method; root and shoot hydraulic conductance were measured by the vacuum chamber. Potassium availability or season did not significantly affect leaf…
Short-term effects of potassium fertilization on the hydraulic conductance of Laurus nobilis L.
2011
This study reports experimental evidence on the effect of short term potassium fertilization on potassium uptake, tissue concentration and hydraulic conductance of pot-grown laurel plants. Potassium uptake and loading into the xylem of laurel seedlings increased within 24 h from fertilization. Potassium was not accumulated in roots and leaves, but the [K+] of xylem sap was 80% higher in fertilized plants (+K) than in potassium starved plants (-K), likely as a result of recirculation between xylem and phloem. This increase in xylem sap [K+] resulted in a 45% increase in transpiration rate, a 30% increase in plant hydraulic conductance (Kplant) and a 120% increase in leaf specific conductivit…