Measurement of sap flow dynamics through the tomato peduncle using a non-invasive sensor based on the heat field deformation method

Recent contradicting evidence on the contributions of xylem and phloem to tomato fruit growth highlights the need for a more thorough insight into the dynamics of sap flow through the tomato peduncle. In fact, knowledge on sap flow dynamics through small plant parts remains scarce, due to a lack of direct measurements. Most currently available sap flow sensors use needles, making them inappropriate for the direct measurement of sap flow through small plant parts such as a tomato peduncle. Therefore, a non-invasive sap flow sensor based on the heat field deformation (HFD) principle was tested on the peduncle of a tomato truss. This mini HFD sensor, consisting of a heater element and three thermocouples stitched on insulation tape, was wrapped around the peduncle and allowed continuous monitoring of changes in the heat field around the heater caused by sap flow. Actual influx into the tomato truss was calculated based on fruit growth data and estimates of fruit transpiration and was compared with the dynamics measured with the mini HFD sensor. Additionally, heat girdling of the peduncle was performed to block phloem influx to study the dynamics of xylem and phloem influx using the mini HFD sensor. First results of the mini HFD sensor were promising and the measured sap flow dynamics through the tomato peduncle agreed well with the calculated sap influx. Results of the girdling experiment suggested opposite patterns of xylem and phloem influx, with a decreased xylem influx during the daytime. Furthermore, the pattern of xylem influx revealed a close relation with the total water potential in the stem. As such, the mini HFD sensor provided direct measurements of sap flow dynamics through a tomato peduncle and, hence, has a large potential to finally resolve the controversy on water influx into developing fruits

Water and forests in the Mediterranean hot climate zone: a review based on a hydraulic interpretation of tree functioning

Aim of the study: Water scarcity is the main limitation to forest growth and tree survival in the Mediterranean hot climate zone. This paper reviews literature on the relations between water and forests in the region, and their implications on forest and water resources management. The analysis is based on a hydraulic interpretation of tree functioning. Area of the study: The review covers research carried out in the Mediterranean hot climate zone, put into perspective of wider/ global research on the subject. The scales of analysis range from the tree to catchment levels. Material and methods: For literature review we used Scopus, Web of Science and Google Scholar as bibliographic databases. Data from two Quercus suber sites in Portugal were used for illustrative purposes. Main results: We identify knowledge gaps and discuss options to better adapt forest management to climate change under a tree water use/availability perspective. Forest management is also discussed within the wider context of catchment water balance: water is a constraint for biomass production, but also for other human activities such as urban supply, industry and irrigated agriculture. Research highlights: Given the scarce and variable (in space and in time) water availability in the region, further research is needed on: mapping the spatial heterogeneity of water availability to trees; adjustment of tree density to local conditions; silvicultural practices that do not damage soil properties or roots; irrigation of forest plantations in some specific areas; tree breeding. Also, a closer cooperation between forest and water managers is neededinfo:eu-repo/semantics/publishedVersio

Root functioning, tree water use and hydraulic redistribution in Quercus suber trees: a modeling approach based on root sap flow

Mediterranean evergreen oaks have to survive a long summer drought. Roots may play a relevant role under these conditions. We studied their structure and function in a mature Quercus suber L. tree in central Portugal. The root system was mapped till the lowest water table level (4.5 m depth). Xylem anatomy was analyzed in a vertical profile belowground. Sap flow was continuously monitored for 1.5 yrs in the stem and roots of this intensively studied tree (heat field deformation method) and in the stem of four trees (Granier method), in relation to environmental variables and predawn leaf water potential. The sources of water uptake were assessed by stable isotope analyses in summer. Results showed a dimorphic root system with a network of superficial roots linked to sinker roots, and a taproot diverting into tangles of deep fine roots submerged for long periods, with parenchyma aerenchyma. Transpiration was not restricted in summer due to root access to groundwater. The isotopic d18O signature of twig xylem water was similar to that of groundwater in the dry season. Two functional types of superficial roots were identified: shallow connected and deep connected roots. A modeling approach was built considering that each superficial root was linked to a sinker, with part of the root deep connected (between the stem and the sinker) and part shallow connected (between the sinker and topsoil). This conceptual framework simulated tree stem sap flow from root sap flow with a high efficiency (R2 = 0.85) in four plot trees. On an annual basis, soil water and groundwater contributions were 69.5% and 30.5% of stem flow, respectively. Annual hydraulic lift and hydraulic descent were 0.9% and 37.0% of stem flow, respectively. The trees maximize the exploitation of the environmental resources by using the topsoil water during most of the year, and groundwater together with hydraulic lift (nutrient supply) in the dry summer. This study shows that a dimorphic root system, with roots reaching groundwater, is an efficient strategy of Q. suber trees to cope with seasonal drought. Knowledge of the functional behavior of Q. suber trees under shallow water table conditions may contribute to the definition of better adapted management practices and to anticipate their responses to climate chang

Seasonal variation of water uptake of a Quercus suber tree in Central Portugal

Hydraulic redistribution (HR) is the phenomenon where plant roots transfer water between soil horizons of different water potential. When dry soil is a stronger sink for water loss from the plant than transpiration, water absorbed by roots in wetter soil horizons is transferred toward, and exuded into dry soil via flow reversals through the roots. Reverse flow is a good marker of HR and can serve as a useful tool to study it over the long-term. Seasonal variation of water uptake of a Quercus suber tree was studied from late winter through autumn 2003 at Rio Frio near Lisbon, Portugal. Sap flow was measured in five small shallow roots (diameter of 3–4 cm), 1 to 2 m from the tree trunk and in four azimuths and at different xylem depths at the trunk base, using the heat field deformation method (HFD). The pattern of sap flow differed among lateral roots as soil dried with constant positive flow in three roots and reverse flow in two other roots during the night when transpiration ceased. Rain modified the pattern of flow in these two roots by eliminating reverse flow and substantially increasing water uptake for transpiration during the day. The increase in water uptake in three other roots following rain was not so substantial. In addition, the flux in individual roots was correlated to different degrees with the flux at different radial depths and azimuthal directions in trunk xylem. The flow in outer trunk xylem seemed to be mostly consistent with water movement from surface soil horizons, whereas deep roots seemed to supply water to the whole cross-section of sapwood. When water flow substantially decreased in shallow lateral roots and the outer stem xylem during drought, water flow in the inner sapwood was maintained, presumably due to its direct connection to deep roots. Results also suggest the importance of the sap flow sensor placement, in relation to sinker roots, as to whether lateral roots might be found to exhibit reverse flow during drought. This study is consistent with the dimorphic rooting habit of Quercus suber trees in which deep roots access groundwater to supply superficial roots and the whole tree, when shallow soil layers were dry

YB-1 promotes microtubule assembly in vitro through interaction with tubulin and microtubules

<p>Abstract</p> <p>Background</p> <p>YB-1 is a major regulator of gene expression in eukaryotic cells. In addition to its role in transcription, YB-1 plays a key role in translation and stabilization of mRNAs.</p> <p>Results</p> <p>We show here that YB-1 interacts with tubulin and microtubules and stimulates microtubule assembly <it>in vitro</it>. High resolution imaging via electron and atomic force microscopy revealed that microtubules assembled in the presence of YB-1 exhibited a normal single wall ultrastructure and indicated that YB-1 most probably coats the outer microtubule wall. Furthermore, we found that YB-1 also promotes the assembly of MAPs-tubulin and subtilisin-treated tubulin. Finally, we demonstrated that tubulin interferes with RNA:YB-1 complexes.</p> <p>Conclusion</p> <p>These results suggest that YB-1 may regulate microtubule assembly <it>in vivo </it>and that its interaction with tubulin may contribute to the control of mRNA translation.</p

Integration of water transport pathways in a maple tree: responses of sap flow to branch severing

• It has been known for a long time that sectored and integrated patterns of vascular systems exist in different species and even within the same tree, depending on its age and history. However, very few publications consider the topology of the vascular pathways between roots and branches. • Some results on this important aspect of the vascular system are presented in this paper. They have been obtained with adult maple trees by directly studying the water movement in the stem and root xylem with the heat field deformation (HFD) method for sap flow measurements. • Multi-point HFD sensors were installed at different heights of a Norway maple tree (Acer platanoides L.) along its stem axis. Single-point HFD sensors were installed in three small lateral roots of another sample maple. Experimental treatments (branch severing) triggered changes in sap movement in the stem and root sapwood. • The sample trees belong to the group with an integrated transport system (“integrated pipes”), sharing stem space on both sides of the tree to supply two large parts of the crown with water from each root sector. Nevertheless, conducting pathways had their autonomy for axial transport and the pipe model theory describes the vascular system of the studied trees well. Thus, the integration of axial transport in the stem xylem should presumably occur through the cross-grained network of axial vessels

Sapwood as the scaling parameter- defining according to xylem water content or radial pattern of sap flow?

Sapwood cross-sectional area is a simple biometric parameter widely used for scaling up the transpiration data between trees and forest stands. However, it is not always clear how the sapwood can be estimated and considered, which may cause scaling errors. We examined the sapwood depth according to xylem water content and more precisely according to radial patterns of sap flow rate in five coniferous and four broad-leaved species of different diameter, age and site conditions. Sapwood estimated by the two methods was almost equal in some species (e.g. Cupressus arizonica), but differed significantly in other species (e.g. Olea europaea, Pinus pinea). Radial pattern of sap flow rate is a more reliable indicator of sapwood then xylem water content for sap flow scaling purposes. Percentage of sapwood along radius changed with tree diameter and age. Sapwood also changes substantially under severe drought (e.g. in spruce, Picea abies, up to 1:3 in the course of several months). Sapwood should be used for upscaling sap flow data from measuring points to the whole trees and from trees to stands only for the period when it was actually measured, or the radial profile of sap flow should be measured continuously to avoid possible scaling errors. (© Inra/Elsevier, Paris)Le bois d'aubier : paramètre de changement d'échelle défini en relation avec le contenu en eau du xylème ou avec le type radial de flux de sève ? La surface de la section de bois d'aubier est un paramètre biométrique largement utilisé pour effectuer des changements d'échelle concernant la transpiration des arbres et des peuplements forestiers. Cependant, la façon dont le bois d'aubier est évalué peut être la cause d'erreurs dans les changements d'échelle. L'épaisseur du bois d'aubier est ici examinée en relation avec la teneur en eau du xylème et plus précisément en relation avec le type radial de densité de flux de sève (cinq conifères et quatre feuillus) de diamètre, âge et situation différents. Le bois d'aubier estimé à l'aide de deux méthodes était presque identique chez quelques espèces (Cupressus arizonica) mais diffère significativement chez d'autres espèces (Olea europaea, Pinus pinea). Le type radial de densité de flux de sève est un meilleur indicateur de bois d'aubier que la teneur en eau du xylème pour un objectif de changement d'échelle du bois de sève. Le pourcentage de bois d'aubier sur un rayon varie avec le diamètre et l'âge de l'arbre. Le bois d'aubier change aussi substantiellement avec la sécheresse (Picea abies, dans une proportion de 1 à 3 en l'espace de quelques mois). Le bois d'aubier devrait être utilisé pour le changement d'échelle des flux de sève en mesurant à l'échelle de l'arbre entier et à l'échelle des peuplements, seulement pour la période pendant laquelle il a été de fait mesuré, ou bien le profil radial de densité de flux devrait être mesuré en continue pour éviter des possibles erreurs de changement d'échelle. (© Inra/Elsevier, Paris