Turgor loss point and vulnerability to xylem embolism predict species-specific risk of drought-induced decline of urban trees.

Increasing frequency and severity of drought events is posing risks to trees' health, including those planted in urban settlements. Drought-induced decline of urban trees negatively affects ecosystem services of urban green spaces and implies cost for maintenance and removal of plants. We aimed at identifying physiological traits that can explain and predict the species-specific vulnerability to climate change in urban habitats. We assessed the relationships between long-term risk of decline of different tree species in a medium-sized town and their key indicators of drought stress tolerance, i.e. turgor loss point (TLP) and vulnerability to xylem embolism (P50 ). Starting from 2012, the study area experienced several summer seasons with positive anomalies of temperature and negative anomalies of precipitation. This trend was coupled with increasing percentages of urban trees showing signs of crown die-back and mortality. The species-specific risk of decline was higher for species with less negative TLP and P50 values. The relationship between species-specific risk of climate change-induced decline of urban trees and key physiological indicators of drought tolerance confirms findings obtained in natural forests and highlights that TLP and P50 are useful indicators for species selection for tree plantation in towns, to mitigate negative impacts of climate change.

Hydraulic architecture of plants of Helianthus annuus L. cv. Margot: evidence for plant segmentation in herbs.

The hydraulic architecture of sunflower (Helianthus annuus L. cv. Margot) was studied in terms of the partitioning of the hydraulic conductance (Kleaf) of leaves inserted at progressively more apical nodes both in growing plants (GP) and in plants at full anthesis (mature plants, MP). Leaf conductance to water vapour (gL), leaf water potential (PsiL), leaf water potential at zero turgor (Psi tlp), and leaf osmotic potential at full turgor (pi0) were also measured. Sunflower plants showed gL and Kleaf values significantly increasing in the acropetal direction, while PsiL of basal leaves was significantly more negative than that of distal leaves; Psi tlp markedly decreased in the acropetal direction in MP so that leaves of MP retained increasingly more turgor the more apical they were. This hydraulic pattern, already present in very young plants (GP), strongly favours apical leaves. These data suggest that the progressive leaf dieback starting from the stem base, as observed when the inflorescence of sunflower reached maturity, might be due to time-dependent loss of hydraulic conductance. In fact, Kleaf loss was correlated with PsiL drop and stomatal closure. Leaf dehydration was aggravated by solute exportation from the basal towards the apical leaves, as revealed by the acropetal decrease of pi0. Kleaf was shown to be linearly and positively related to the prevailing ambient irradiance during plant growth, thus suggesting that leaf hydraulics is very sensitive to environmental conditions. It was concluded that the pronounced apical dominance of some sunflower cultivars is determined, among other factors, by plant hydraulic architecture.

Drought resistance of Ailanthus altissima: root hydraulics and water relations.

Drought resistance of Ailanthus altissima (Mill.) Swingle is a major factor underlying the impressively wide expansion of this species in Europe and North America. We studied the specific mechanism used by A. altissima to withstand drought by subjecting potted seedlings to four irrigation regimes. At the end of the 13-week treatment period, soil water potential was -0.05 MPa for well-watered control seedlings (W) and -0.4, -0.8 and -1.7 MPa for drought-stressed seedlings (S) in irrigation regimes S1, S2 and S3, respectively. Root and shoot biomass production did not differ significantly among the four groups. A progressively marked stomatal closure was observed in drought-stressed seedlings, leading to homeostasis of leaf water potential, which was maintained well above the turgor loss point. Root and shoot hydraulics were measured with a high-pressure flow meter. When scaled by leaf surface area, shoot hydraulic conductance did not differ among the treated seedlings, whereas root hydraulic conductance decreased by about 20% in S1 and S2 seedlings and by about 70% in S3 seedlings, with respect to the well-watered control value. Similar differences were observed when root hydraulic conductance was scaled by root surface area, suggesting that roots had become less permeable to water. Anatomical observations of root cross sections revealed that S3 seedlings had shrunken cortical cells and a multilayer endodermal-like tissue that probably impaired soil-to-root stele water transport. We conclude that A. altissima seedlings are able to withstand drought by employing a highly effective water-saving mechanism that involves reduced water loss by leaves and reduced root hydraulic conductance. This water-saving mechanism helps explain how A. altissima successfully competes with native vegetation.

Xylem cavitation in the leaf of Prunus laurocerasus and its impact on leaf hydraulics.

This paper reports how water stress correlates with changes in hydraulic conductivity of stems, leaf midrib, and whole leaves of Prunus laurocerasus. Water stress caused cavitation-induced dysfunction in vessels of P. laurocerasus. Cavitation was detected acoustically by counts of ultrasonic acoustic emissions and by the loss of hydraulic conductivity measured by a vacuum chamber method. Stems and midribs were approximately equally vulnerable to cavitations. Although midribs suffered a 70% loss of hydraulic conductance at leaf water potentials of -1.5 MPa, there was less than a 10% loss of hydraulic conductance in whole leaves. Cutting and sealing the midrib 20 mm from the leaf base caused only a 30% loss of conduction of the whole leaf. A high-pressure flow meter was used to measure conductance of whole leaves and as the leaf was progressively cut back from tip to base. These data were fitted to a model of hydraulic conductance of leaves that explained the above results, i.e. redundancy in hydraulic pathways whereby water can flow around embolized regions in the leaf, makes whole leaves relatively insensitive to significant changes in conductance of the midrib. The onset of cavitation events in P. laurocerasus leaves correlated with the onset of stomatal closure as found recently in studies of other species in our laboratory.

Refilling of embolized vessels in young stems of laurel. Do We need a new paradigm?

Recovery of hydraulic conductivity after the induction of embolisms was studied in woody stems of laurel (Laurus nobilis). Previous experiments confirming the recovery of hydraulic conductivity when xylem pressure potential was less than -1 MPa were repeated, and new experiments were done to investigate the changes in solute composition in xylem vessels during refilling. Xylem sap collected by perfusion of excised stem segments showed elevated levels of several ions during refilling. Stem segments were frozen in liquid N2 to view refilling vessels using cryoscanning electron microscopy. Vessels could be found in all three states of presumed refilling: (a) mostly water with a little air, (b) mostly air with a little water, or (c) water droplets extruding from vessel pits adjacent to living cells. Radiographic probe microanalysis of refilling vessels revealed nondetectable levels of dissolved solutes. Results are discussed in terms of proposed mechanisms of refilling in vessels while surrounding vessels were at a xylem pressure potential of less than -1 MPa. We have concluded that none of the existing paradigms explains the results.

[Frey's syndrome: physiopathology and medical therapy]. / Sindrome di Frey: fisiopatologia e terapia medica.

Frey syndrome (gustatory sweating, auricolotemporal syndrome) is a complication of parotidectomy, probably caused by misdirection of regenerating fibers in the auricolotemporal nerve. The authors review the pathophysiology and describe the treatment used in this entity.

[Femoro-popliteal bypass with reversed saphenous vein. Experience in a General Surgery Department]. / Bypass femoro-poplitei in safena invertita. Esperienza di una divisione di chirugia generale.

Femoro popliteal bypass with reversed saphenous vein are "the gold standard" for revascularization of lower extremities with femoro popliteal occlusion. This form of therapy is usually performed in a Vascular Surgery Department. We report the experience of a General Surgery Department, with patency of 90% at two years.

[The conservative treatment of infected vascular prostheses in surgery to revascularize the lower limbs]. / Trattamento conservativo delle protesi vascolari infette nella chirurgia di rivascolarizzazione degli arti inferiori.

Infected vascular grafts are associated with very high rates of limb loss and mortality. "Classic" treatment has invariably included graft excision. Recent reports have suggested that a more conservative approach may be indicated in selected cases, leaving the graft in place and using an aggressive local treatment associated with appropriate intravenous antibiotics. The authors report their experience with two patients with infected prosthetic vascular grafts in the groin. They both had purulent drainage from the groin wound, with the graft exposed close to the femoral anastomosis. They were both treated successfully without graft removal, and both graft maintained patency, with a follow-up of 22 and 19 months.

[Intraportal air secondary to gastric dilatation. A clinical case]. / Aria intraportale secondaria a dilatazione gastrica. Un caso clinico.

The authors report a case of hepatic portal venous gas (HPVG) secondary to massive gastric dilatation in a diabetic patient following blunt trauma. Both flat plate of the abdomen and ultrasound of the liver were necessary to reach the correct diagnosis. They review the pertinent literature and stress the importance of an accurate nosologic assessment of this uncommon entity in order to avoid undue mishaps.

[Crural hernia after inguinal hernia repair. A technical note]. / Ernia crurale dopo plastica per ernia inguinale. Note di tecnica.

A case of femoral hernia following repair of an inguinal hernia with the Shouldice method is presented. The authors discuss the pathogenesis, suggest the use of ultrasound for a precise preoperative diagnosis, and propose the "plug" technique of Lichtenstein as the method of choice for the repair. This method offers a minimally invasive approach, without disturbing the previous inguinal repair and it is very simple to perform.

[Infected pseudoaneurysms of the upper limb. A case re-evaluation]. / Pseudoaneurismi infetti dell'arto superiore. Rivalutazione di un caso.

The authors report a case of infected pseudoaneurysm of the brachial artery in a drug addict, treated with aneurysm excision and brachio-brachial bypass with inverted saphenous vein. They review the literature on the subject and management options.

[The Knight-Griffen technique in colorectal surgery]. / La tecnica di Knight-Griffen nella chirurgia colorettale.

The use of stapling devices has changed the practice of colorectal surgery. The authors report their experience with the "double stapling" technique introduced by Knight and Griffen in 1980 for the performance of low colorectal anastomosis. They treated 42 patients, with a mean age of 63.2 years. In 34 surgery was performed for rectal adenocarcinoma, while 8 patients were being reoperated on for closure of a colostomy after Hartmann's operation. In one patient a diverting colostomy was fashioned because of poor bowel cleansing, secondary to a stenosing rectal carcinoma. Mortality was nil. There were no clinical anastomotic leaks. There were 2 cases of late postoperative anastomotic stenosis that responded to endoscopic pneumatic dilatation.

[Local anesthesia in anal surgery. Technical note and immediate results]. / L'anestesia locale nella chirurgia anale. Note di tecnica e risultati immediati.

The authors report their experience with the use of local anesthesia in anal surgery (hemorrhoids, anal fissures and fistulas). They describe their technique in detail, stressing the importance of thorough knowledge of the neuroanatomy of the anal canal and of a stepwise blockage of all sensory and motor fibers to the area. They report their results on 300 anal procedures performed under local anesthesia, with good patient acceptance.

[Subacute Budd-Chiari syndrome treated with rTPA. Considerations on a case]. / Sindrome di Budd-Chiari subacuta trattata con rTPA. Considerazioni a proposito di un caso.

The authors report on a case of hepatic vein thrombosis or Budd-Chiari syndrome (BCS) successfully treated with recombinant Tissue Plasminogen Activator (rTPA). They briefly outline the etiology and symptomatology of this disease as well as the various surgical procedures used for treatment. Medical therapy has been so far poorly effective in treatment BCS, but recently various reports seem to indicate that rTPA may have a role. The authors suggest that rTPA may be used as the only therapy in selected cases, or in treating patients that are not candidates for surgical intervention, or as a temporizing measure to improve symptoms in patients awaiting surgery.

[Rectal foreign bodies. Principles of therapy]. / Corpi estranei endorettali. Principi di terapia.

The authors report their experience with the treatment of endorectal foreign bodies (EFB). They review the literature on the subject and examine the various therapeutic options. Considering the possible complications of leaving an EFG in place for prolonged period of times in the hope of spontaneous delivery, they suggest that immediate removal is always indicated. They describe various technical modalities for endoscopic removal, that can avoid laparotomy in the majority of cases.

[Caroli's disease associated with cholangiocarcinoma. A case of our own observation]. / Malattia di Caroli associata a colangiocarcinoma. Un caso di nostra osservazione.

The authors report a case of Caroli's disease associated with cholangiocarcinoma. The patient presented with pain and jaundice and ultrasonography disclosed multiple common bile duct stones, cystic dilatation of the extrahepatic biliary tree and a mass in the right lobe of the liver. At operation, after a frozen section demonstrated cholangiocarcinoma, a common bile duct exploration, right hepatic lobectomy and hepato-jejunostomy were performed. They review the literature on the subject and stress the fact that hepatic tumors are associated with Caroli's disease in 7% of cases. Therefore, in these patients, when a stenosis of the biliary tree is found, multiple diagnostic manoeuvres are indicated in order to exclude the presence of malignancy.