WO2007023204A1

WO2007023204A1 - Device for measuring the hydraulic conductivity of xylem

Info

Publication number: WO2007023204A1
Application number: PCT/ES2006/070128
Authority: WO
Inventors: Pablo Jorge Duran Levrero; Vanessa Chamorro; José Enrique FERNANDEZ LUQUE
Original assignee: Consejo Superior De Investigaciones Científicas
Priority date: 2005-08-25
Filing date: 2006-08-10
Publication date: 2007-03-01
Also published as: ES1061747U; ES1061747Y

Abstract

The invention relates to a device for measuring hydraulic conductivity, which is suitable for samples of branches ranging from a few millimetres in diameter to several centimetres and which can precisely measure low conductivities in up to five samples simultaneously. The inventive device is cheap, sturdy and easy to maintain since it is not made from sophisticated elements. The invention consists in using precision pipettes in order to measure volumes passed through samples. The pressure and, consequently, the flow of the perfusion solution can be adjusted by varying the height of the container. In addition, valves enable the solution to pass through the samples and the system to be emptied for cleaning. The invention also comprises a device which enables the perfusion to be stopped instantaneously, without the measurement being affected by undesired variations in the pressure. The inventive device further comprises a high-pressure perfusion system which can be used to eliminate embolism from the samples and, in this way, to measure the maximum hydraulic conductivity.

Description

TITLE

Xylem hydraulic conductivity meter

SECTOR OF THE TECHNIQUE Agriculture. Plant Physiology

STATE OF THE TECHNIQUE

Since simulation models began to be used in Biology, the interest in studying the transport of the sap in the xylem (axial flow) of plants under different conditions has been increasing.

Several authors have carried out hydraulic conductivity measurements in different organs of the plant of numerous species, to clarify the functional significance of the resistances involved (Beckman CH, Keller JL. 1977. Vessels do end! Phytopatology 67, 954-956); Laurus nobilis (Salleo S, Nardini A, Pitt F, Lo GuIIo MA. 2000. Xylem cavitation and hydraulic control of stomatal conductance in Laurel (Laurus nobilis L.). Plant, CeII and Environment 23, 71-79; Salleo S, Lo GuIIo MA, DePaoli D, Zippo M. 1996. Xylem recovery from cavitation-induced embolism in young plants of Laurus nobilis: A possible mechanism. New Phytologist 132, 47-56); Olea europaea (Salleo S, Lo GuIIo MA. 1983. Water transport pathways in nodes and intemodes of 1-year-old twigs of Olea Europaea L. Giomale Botánico Italiano 117, 63-74); Acer saccharum (S pe rry JS, Donnelly JR, Tyree MT. 1988. Seasonal occurrence of xylem embolism in Sugar maple (Acer saccharum). American Journal of Botany 75, 1212-1218; Tyree MT, Yang SD. 1992. Hydraulic conductivity recovery versus water pressure in xylem of Acer saccharum. Plant Physiology 100, 669-676); Vitis vinifera Salleo S, Rosso R, Lo GuIIo MA. 1982. Hydraulic architecture of Vitis vinifera L. and Populus deltoides Bartr. 1 -year-old twigs: I - Hydraulic conductivity (LSC) and water potential gradients. Giomale Botánico Italiano 116, 15-27; Populus deltoides (Larson PR, lsebrands JG. 1978. Functional significance of nodal constricted zone in Populus deltoides. Canadian Journal of Botany-Revue Canadienne de Botanique 56, 801-804; Salleo S, Rosso R, Lo GuIIo MA. 1982. Hydraulic architecture of Vitis vinifera L. and Populus deltoides Bartr. 1 -year-old twigs: I - Hydraulic conductivity (LSC) and water potential gradients. Giomale Botánico Italiano 116, 15-27; Tyree MT, Alexander J, Machado JL. 1992. Loss of hydraulic conductivity due to water-stress in intact juveniles of Quercus rubra and Populus deltoides. Tree Physiology 10, 411-415) ;, Thuja occidentalis (Tyree MT, Graham MED, Cooper KE, Spleens LJ. 1983. The hydraulic architecture of Thuja occidentalis. Canadian Journal of Botany-Revue Canadienne de Botanique 61, 2105-2111), etc.

The hydraulic conductivity (K _h , gs ^"1 m MPa ¹ J reflects the efficiency of the xylem water conduction (Salleo S, Rosso R, Lo GuIIo MA. 1982. Hydraulic architecture of Vitis vinifera L. and Populus deltoides Bartr. 1 -year- old twigs: I - Hydraulic conductivity (LSC) and water potential gradients, Giomale Botánico Italiano 116, 15-27), and is defined as the flow conducted through the vessels, divided by the pressure gradient. pressure is the difference in pressure between the ends of the segment of conductive tissue, divided by the length of the segment.

conductivity is expressed as: K. = —l where Q is the expressed flow

AP in g / s, / is the length in m of the xylem in the sample and ΔP is the pressure difference in MPa. Other authors (Salleo.S., MA Lo GuIIo and F. Oliveri. 1985. Hydraulic Parameters Measured in 1 -Year-Old Twigs of some Mediterranean Species with Diffuse-Porous Wood: Changes in Hydraulic Conductivity and Their Posible Functional Significance. Journal of Experimental Botany, VoI. 36, N ⁰ 162, pp 1-11, January 1985) measured the volume of flow passing through the internodes of Vitis vinifera, Populus deltoides and Olea europaea using a system consisting of an inlet pipette and another outlet, full of perfusion solution. The flow volume was calculated by measuring the volume displaced in both pipettes. Sperry et al. (Sperry JS, Donnelly JR, Tyree MT. 1988. Seasonal occurrence of xylem embolism in Sugar maple (Acer saccharum). American Journal of Botany 75, 1212-1218) designed a system to measure conductivity in segment segments, using a gravity-induced flow. The perfusion solution was stored in a tank pressurizing compressed air from where the sample was injected or using an elevated container (gravity flow). The solution that perfused the bouquet was taken to a container located on an electronic scale. The weight variation was recorded in a computer connected to the balance. This device only allowed measuring the conductivity of a single stem segment in each measurement. There are equipment on the market that includes micro flowmeters capable of measuring small flows, with several models operating in certain ranges of flows (HFPM and HCFM-XP from Dynamax Inc., Iberfluid Instruments, Bronkhorst High-Tech, etc.). However, they are not always suitable in cases of extremely low conductivities, such as those found in olive branches and other species with small diameter conductive vessels. Given the variability in the conductivity of the different organs of the different species under study, the equipment capable of covering such a wide range of flows has a high cost. Said cost is multiplied if the simultaneous measurement of several samples is required.

The equipment presented in this application allows the simultaneous measurement of multiple samples of plant conducting tissue. It adapts to the variability present in nature, especially in cases of very low conductivity values. Due to its design and the elements that compose it, it would have a lower cost than the available equipment, which together with the simultaneity of measurement results in a low cost per analyzed sample.

EXPLANATION OF THE INVENTION

The object of the present invention is a xylematic hydraulic conductivity meter that allows the simultaneous measurement of several samples and consists of the following elements: a) pressurization device that supplies water at a pressure between 0.01 and 0.15 bar b) conduit for the transport of water from the pressurization device to the samples of plant conductive tissue, a mechanism that includes allow to regulate the infusion of water through the samples. c) between 2 and 20 devices containing samples of plant conductive tissue, particularly roots, stems and petioles, said devices being located in a container that keeps them under water d) graduated elements measuring the volume of water pre-set through each sample of individually conductive plant tissue. A water column with a height between 0.1 and 1.5 m with a high tank can be used as a pressurization device. As a mechanism that allows regulating the perfusion of water through the samples, a system of at least two valves that control the inlet and relief can be used, or a three-way solenoid. The conduits are manufactured in any transparent material that allows the observation of the flow through them, particularly polyethylene or glass and the devices containing the samples are of any material that has sufficient elasticity to correctly adjust and prevent leaks, particularly silicone or latex .

The meter can additionally include a high pressure device, particularly a pump, which allows the pressure to be raised up to 2 bars to eliminate the embolism present in natural conditions in the xylem vessels of plants. In this case, the assembly must have at least two maneuver valves to regulate the entry of water from the water column or from the high pressure device or alternatively a three-way solenoid for the same purpose.

BRIEF DESCRIPTION OF THE FIGURES

Figure 1: General scheme of the xylem conductivity meter Figure 2: Prototype configuration of the xylem conductivity meter Figure 3: Detail of pipettes and zeroing syringes

Figure 4: Detail of solenoid and system power

Figure 5: Pressure device for disbursement treatment

DETAILED DESCRIPTION OF THE INVENTION

The object of the present invention is a device that allows measuring the hydraulic conductivity of the conductive vessels of the plants. The xylem hydraulic conductivity is the conductive capacity of the vessels that lead the sap from the root to the leaves, through trunks and branches. To obtain the conductivity of an organ of a plant, an aqueous solution is passed through a sample of stem (or root) of known length, by applying a water column of known height and the pre-set volume is measured in a certain period of time. In general, the repetition of the measurement is required to arrive at conclusions regarding the hydraulic characteristics of the material, which is why it is very useful to process the largest number of samples simultaneously. This reduces labor and costs per processed sample. The equipment currently available in the market does not allow simultaneous measurement of samples and they are also high cost equipment. The equipment presented in this application allows the measurement of several simultaneous samples and for the components and materials necessary for its construction would cost much less than the existing equipment in the market. The meter consists of a series of tubes that conduct water (or aqueous solution) simultaneously to several samples of plant stems (or roots). Water is injected into the samples at preset pressures using a column of water of known height. The preset flow for each sample is collected by tubes and the volume is obtained using graduated elements. The perfusion time Io that allows to obtain the flow rate (volume per unit of time) is measured. The flow of water to the samples is controlled by a series of valves that allows opening and closing, as well as the suppression of the water pressure in the samples, in order to stop the infusion instantaneously. It has a cuvette where the samples to be measured are placed and that allows the manipulation of the samples under water to prevent the entry of air into the vessels of the conductive tissue, which would cause the occlusion of the vessels by embolism. The equipment is complemented by a device that allows high pressure water infusion to eliminate possible embolisms present in the conductive vessels. By measuring the pre-set flow rate, the height of the water column and the length of the samples it is possible to obtain the hydraulic conductivity (Kh) of the samples, before and after the disbursement treatment, thus obtaining the degree of embolism present in the sample. The adaptation of samples of different conductivity and diameter is achieved, using tubes of different diameter and volume measuring elements according to the magnitude of the expected flows.

Figure 1 shows a general scheme of the xylem conductivity meter.

The apparatus consists of a water column (1) that supplies water at a known pressure (h). This is conducted to samples of plant conductive tissue (6) by tubes (5). When the inlet valve (2) is opened, keeping the pressure relief valve (3) closed, water circulates through the system, perfusing the samples. Once the predetermined time to perform the measurement has elapsed, the inlet valve (2) is closed simultaneously and the relief valve (3) is opened in order to completely stop the infusion of water through the samples. The volume of water infused in each sample is measured with the graduated volume measuring elements (7). The samples are placed and handled under water in a bucket arranged for this purpose (8). The maneuvering valves (9) allow to choose between working using the water column or with pressurized water from the corresponding device. This would connect to the site (10) indicated in the scheme. In order to keep the value of the water column unchanged during the measurement, a tank with sufficient volume is added so that its water level does not vary throughout the measurement, due to the effect of the water flow towards the samples.

The xylem conductivity meter is complemented with elements that allow a high pressure disbursement treatment. The high pressure device could be a pump or other element capable of raising the water pressure to 1.5 to 2 bars, enough to eliminate the embolism present in natural conditions in the xylem vessels of plants. Said pressurized water is stored in a tank that is connected to the conductivity meter at point (10) of Figure 1. The pressure device has a pressure gauge to measure the pressure reached and the required maneuver valves to adjust the same to the desired value. The equipment allows, by measuring the pre-set flow rate, the height of the water column and the length of the samples to obtain the hydraulic conductivity (Kh) of the samples. If this measurement is performed before and after the disbursement treatment, the degree of embolism present in the sample is obtained.

EMBODIMENT OF THE INVENTION

Figure 2 shows the configuration of a prototype of the xylem conductivity meter.

The apparatus consists of a water column that supplies water at a known pressure measured by the piezometer (2). The high tank (1) fulfills the function of keeping the value of the water column unchanged during the measurement, since it has a sufficient capacity so that its water level does not vary significantly throughout the measurement (due to the effect of the water outlet to the samples).

Water enters the system through the inlet tube (18), passes through the solenoid (3) and continues through the sample feed tube (16). This is distributed and conducted to samples of plant conductive tissue (6) through multiple connections (4) and tubes (5). The samples are placed and handled under water in a bucket arranged for this purpose (8). The valves of maneuver (9) allow to choose between working using the water column or with pressurized water from the boiler. This is connected at the site (10) indicated in the scheme. The water flow of the system is controlled by means of a solenoid (3) that is operated by the electrical control panel (15) that contains a switch and a 220v-24v AC transformer. When the solenoid is activated, the passage of water between the tubes 18 and 16 is opened and the water passes from the raised tank to the samples of plant tissue (eg, segments of stems or roots).

0.2 ml pipettes with 0.002 ml graduations have been used as measuring elements of the perfused volume in each sample. The pipettes are mounted on a horizontal support and can easily be changed by others, which can vary according to the volume that is expected to be measured depending on the plant material to be used.

Although the present prototype was implemented to measure 5 samples simultaneously (see figure 3), it is possible to measure a larger number of samples, adding the corresponding pipettes and pipettes. The diameters of the tubes where the samples are connected will depend on their diameter.

Transparent polyethylene tubes have been used for conduits, while the tubes that connect the plant samples are made of silicone, a material that has sufficient elasticity to adjust correctly and prevent leaks.

Before starting the measurement, the entire pipe system must be completely filled with water to prevent the entry of air into the conductive vessels of the plant sample.

Likewise, the volume measuring pipettes (7) must be reset, which is achieved by manually operating the three-way valves (11) and the syringes (14).

After the predetermined time to perform the measurement has elapsed, the solenoid activated by the switch of the control panel is closed. This action It interrupts the connection between the tubes 16 and 18 and simultaneously connects the tube 16 with the relief tube 17, which returns the excess water to the cuvette (8) in order to completely stop the perfusion of water through the samples. The volume of water infused in each sample is measured by graduated pipettes (7).

In the implementation of this prototype the valves (2) and (3) have been replaced by a three-way solenoid (see figure 4) electrically operated (24v, 4w), of the type used in the hydraulic control of irrigation valves . It is connected to an electrical panel with a bipolar switch and a 220v-24v AC transformer. This ensures the simultaneity of the water supply cutting and pressure relief operations. Said solenoid can be operated manually by a switch or automatically by a timer. In this prototype the solenoid is manually operated. The two operating valves (9) can be replaced by a single manual or electrically operated three-way valve (solenoid), also automating this function.

The xylem conductivity meter is complemented with elements that allow a high pressure disbursement treatment. In this prototype the following pressure device has been used, detailed in figure 5:

The compressed air tube (1) provides the required pressure to the boiler (2). It consists of an air chamber (3) and a chamber that is filled with water (5) separated by an elastic membrane (4). The pressurized water is connected by means of the tube (6) to the water inlet of the xylem hydraulic conductivity meter (10 in Figure 1). For the alternation of the operation with high pressure or by means of the water column, stop keys for the maneuvers are inserted (9 in Figure 1). The water pressure supplied by the boiler is regulated by an air stopcock and a pressure gauge. The equipment allows, by measuring the perfused flow, the height of the water column and the length of the samples to obtain the hydraulic conductivity (Kh) of the samples. If this measurement is performed before and after the disbursement treatment, the degree of embolism present in the sample is obtained.

Claims

1.- Xylematic hydraulic conductivity meter characterized in that it allows the simultaneous measurement of several samples and consists of the following elements: a) pressurization device that supplies water at a pressure between 0.01 and 0.15 bar b) conduction for transport of water from the pressurization device to the samples of plant conductive tissue, a mechanism that regulates the perfusion of water through the samples being included in said conduction. c) between 2 and 20 devices containing samples of plant conductive tissue, particularly roots, stems and petioles, said devices being located in a container that keeps them under water d) graduated elements measuring the volume of water infused through each sample of individually conductive plant tissue.

2. Xylematic hydraulic conductivity meter according to claim 1, characterized in that the pressurization device consists of a column of water between 0.1 and 1.5 m high with a high tank.

3. Xylematic hydraulic conductivity meter according to claims 1 and 2, characterized in that the mechanism that allows to regulate the perfusion of water through the samples is a system of at least two valves that control the inlet and relief.

4. Xylematic hydraulic conductivity meter according to claims 1 and 2, characterized in that the mechanism that regulates the perfusion of water through the samples is a three-way solenoid.

5. Xylematic hydraulic conductivity meter according to claims 1-4, characterized in that the water column and the pipes are of any transparent material that allows the observation of the flow through them, particularly polyethylene or glass, and because the devices The samples contained are of any material that has sufficient elasticity to properly adjust and prevent leaks, particularly silicone or latex.

6. Xylematic hydraulic conductivity meter according to claims 1-5, characterized in that it additionally includes a high pressure device, particularly a pump, which allows the pressure to be raised up to 2 bars to eliminate the embolism present in natural conditions in the xylem vessels of the plants.

7. Xylematic hydraulic conductivity meter according to claim 6, characterized in that it includes at least two maneuvering valves to regulate the entry of water from the water column or from the high pressure device.

8. Xylematic hydraulic conductivity meter according to claim 6, characterized in that it includes a three-way solenoid to regulate the entry of water from the water column or from the high pressure device.