Subtending Tissue Research Articles

The Influence of Water Deficit Stress on the Grapevine Trunk Disease Pathogens Eutypa lata and Diplodia seriata.

The increasing prevalence of the grapevine trunk diseases Eutypa and Botryosphaeria dieback has been attributed, in part, to abiotic stresses imposed on vineyards as production intensifies worldwide. The aim of this study was to evaluate the influence of water deficit irrigation practices on the infection of pruning wounds by Eutypa lata and Diplodia seriata and the subsequent rate of colonization. Two vineyard trials were conducted over two consecutive seasons in South Australia, one in the Riverland with 'Cabernet Sauvignon' with four irrigation treatments (100, 50, 25, and 12.5% of the standard irrigation program) and another in the Barossa Valley with 'Shiraz' on six rootstocks and own roots, either irrigated or not irrigated. According to leaf water potential assessments, vines with reduced irrigation were generally in water deficit and therefore subjected to stress. On the whole, incidence of wound infection and distance of colonization were similar between irrigation treatments for both pathogens, except in the Riverland, where E. lata colonized canes to a greater extent in well-watered vines than those in water deficit. Only vines on rootstock 'Ramsey' in the Barossa Valley had greater extent of colonization by E. lata in the nonirrigated vines. There was no correlation between internal staining and colonization, with both pathogens recovered to nearly 20 cm ahead of the staining. Water deficit did not increase the susceptibility of grapevine pruning wounds to infection or colonization of the subtending tissue by E. lata and D. seriata. In fact, there was evidence of lower susceptibility to colonization by E. lata in vines subjected to severe water deficit.

Myocardial, Perivascular, and Epicardial Fat

Myocardial fat content refers to the storage of triglyceride droplets within cardiomyocytes. In addition, the heart and arteries are surrounded by layers of adipose tissue, exerting vasocrine and paracrine control of the subtending tissues. The rapid development of the field of noninvasive imaging has made it possible to quantify ectopic fat masses and contents with an increasing degree of accuracy. Myocardial triglyceride stores are increased in obesity, impaired glucose tolerance, and type 2 diabetes. The role of intramyocardial triglyceride accumulation in the pathogenesis of left ventricular (LV) dysfunction remains unclear. Increased triglyceride content is associated with states of fatty acid overload to the heart, saturating the oxidative capacity. It may initially serve as a fatty acid sink to circumscribe the formation of toxic lipid species and subsequently foster cardiac damage. Epicardial and perivascular fat depots may exert a protective modulation of vascular function and energy partition in a healthy situation, but their expansion turns them into an adverse lipotoxic, prothrombotic, and proinflammatory organ. They are augmented in patients with metabolic disorders and coronary artery disease (CAD). However, the progressive association between the quantity of fat and disease severity in terms of extent of plaque calcification or noncalcified areas, markers of plaque vulnerability, and number of vessels involved is less confirmed. Functional or hybrid imaging may contribute to a better definition of disease severity and unveil the direct myocardial and vascular targets of adipose tissue action.

Fatty Heart, Cardiac Damage, and Inflammation

Type 2 diabetes and obesity are associated with systemic inflammation, generalized enlargement of fat depots, and uncontrolled release of fatty acids (FA) into the circulation. These features support the occurrence of cardiac adiposity, which is characterized by an increase in intramyocardial triglyceride content and an enlargement of the volume of fat surrounding the heart and vessels. Both events may initially serve as protective mechanisms to portion energy, but their excessive expansion can lead to myocardial damage and heart disease. FA overload promotes FA oxidation and the accumulation of triglycerides and metabolic intermediates, which can impair calcium signaling, β-oxidation, and glucose utilization. This leads to damaged mitochondrial function and increased production of reactive oxygen species, pro-apoptotic, and inflammatory molecules, and finally to myocardial inflammation and dysfunction. Triglyceride accumulation is associated with left ventricular hypertrophy and dysfunction. The enlargement of epicardial fat in patients with metabolic disorders, and coronary artery disease, is associated with the release of proinflammatory and proatherogenic cytokines to the subtending tissues. In this review, we examine the evidence supporting a causal relationship linking FA overload and cardiac dysfunction. Also, we disentangle the separate roles of FA oxidation and triglyceride accumulation in causing cardiac damage. Finally, we focus on the mechanisms of inflammation development in the fatty heart, before summarizing the available evidence in humans. Current literature confirms the dual (protective and detrimental) role of cardiac fat, and suggests prospective studies to establish the pathogenetic (when and how) and possible prognostic value of this potential biomarker in humans.

Polyamines and their biosynthetic enzymes during somatic embryo development in red spruce (Picea rubens Sarg.)

The major objective of this study was to determine if the observed changes in polyamines and their biosynthetic enzymes during somatic embryo development were specifically related to either the stage of the embryo development or to the duration of time spent on the maturation medium. Somatic embryos of red spruce (Picea rubens) at different developmental stages, grown in the embryo development and maturation media for various lengths of time, were separated from the associated subtending tissue (embryogenic and the suspensor cell masses) and analyzed for their polyamine content as well as for polyamine biosynthetic enzyme activities. Polyamine content was also analyzed in embryos representing different stages of development that were collected from the same culture plate at the same time and the subtending tissue surrounding them. Putrescine was the predominant polyamine in the pro-embryogenic tissue, while spermidine was predominant during embryo development. Significant changes in spermidine/putrescine and spermine/putrescine ratios were observed at all stages of embryo development as compared to the pro-embryogenic cell mass. Changes in the ratios of various polyamines were clearly correlated with the developmental stage of the embryo rather than the period of growth in the maturation medium. Whereas the activities of both ornithine decarboxylase and arginine decarboxylase increased by week 3 or 4 and stayed high during the subsequent 6 wk of growth, the activity of S-adenosylmethionine decarboxylase steadily declined during embryo development.

Hormones and Endodormancy Induction in Woody Plants

Summary The scope of this review is limited to hormonal involvement in the induction of woody bud endodormancy and does not address dormancy maintenance or release. Knowledge of hormonal regulation of processes has become increasingly more complex, particularly with recent findings of auxin- and ethylene-triggered abscisic acid induction revealing many more responses mediated by ABA than originally considered. The intent of this review is to provide an account of the current state of knowledge of hormones in bud dormancy research within an historical context with a focus on promising avenues of research. While hormones are undoubtedly involved at some point during dormancy induction, meaningful progress in unraveling the mechanism of endo-dormancy-induction is difficult through this hormone-centered approach. The path to dormancy acquisition is a continuum. In many plants, this path begins far earlier than the traditionally-examined autumn period. Aside from more useful hormonal localization studies within the bud and utilization of mutants, continued gross analysis of hormone presence/absence during dormancy induction may not be fruitful. Examining the regulation of the early molecular switch within key cells of the apical meristem or subtending tissues may provide greater insight into dormancy induction. Turgor pressure-dependent cellular differentiation within the apical meristem and the extrinsic and intrinsic factors regulating turgor may be central to that molecular switch. Simpler model systems may need to be utilized to test these hypotheses. Only then can the potential role of hormones in endodormancy induction be more clearly articulated.

Anatomical Features Facilitating Supercooling of the Flower within the Dormant Peach Flower Bud

Excision of the flower from the peach [Prunus persica (L.) Batsch.] flower bud raised the 50% injury temperature of flowers (cooled at 1C/hour) from -18 and -20C to -10 and -13C on two test dates, 26 Feb. 1988 and 5 Dec. 1990, respectively. Ice inoculation of the excised flowers at -3C further raised the 50% injury temperature to -7 and -8C for the two dates, respectively. These observations suggest that supercooling is a true mechanism for avoiding freezing injury. Low temperature scanning electron microscopy of freeze fractured cells verified that the flower froze intracellularly, whereas the subtending tissue froze extracellularly. Ice inoculation of the flower and the flower bud axis from which the scales were removed demonstrated that a barrier to ice propagation (effective to -11C) from the flower bud axis to the flower was present. This barrier may involve the provascular strands and a cell zone at the flower base (BZ) that were devoid of intercellular spaces. These tissues also had smaller cells, smaller vacuoles, greater ratio of cell wall thickness to cell size than tissue just below the BZ, which may result in greater cell rigidity and restriction of extracellular freezing. The cells outside the provascular strands at the base of the flower were also lacking in intercellular space, were smaller in size, and had a higher ratio of cell wall thickness to cell size compared to cells near the base of the scales. In the intact flower buds in which the flowers supercool below -11C, the presence of the first and second scales was important to full expression of supercooling because their removal raised the supercooling point, whereas the removal of lower scales did not. Sequestration of ice by the first two subtending scales during the early stages of freezing may be important to the creation of a dry region at the flower base that prevents ice propagation into the flower at temperatures below -11C.

Callus Cultures from Zygotic Embryos of Costus speciosus and Their Morphogenetic Responses

Soft, nodular and hard types of calli were initiated on mature zygotic embryo explants of two tetraploid clones of Costus speciosus, of which, only the hard calli were amenable to morphogenetic responses. The two clones differed in their growth regulator requirements both for the initiation of calli and for shoot regeneration. De novo formation of both shoot bud meristems and somatic embryoids were observed. Latter were encased partially or fUlly by coleoptilar sheath. Embryoids could be isolated as discrete units. On maturity, a stock like appendage developed from the base and finally embryoids got detached from the subtending tissue. Both shoot-bud meristems and somatic embryoids developed into complete plantlets, the former upon sequential transfer of calli on Schenk and Hildebrandt’s (SH) basal medium containing lower levels of growth hormones, while the latter only on basal medium. These culture regenerants were subsequently transferred to the field. The morphogenetic behaviour of these two tetraploid clones reflects their marked genotypic difference inspite of their same ploidy status.

Movement of Boron Out of Tree Fruit Leaves

Foliar B sprays (500 mg·liter-1) had increased the B content of apple (Malus domestics Borkh), pear (Pyrus communis L.), plum (Prunus domestics L.), and cherry (Prunus cerasus L.) leaves 90%) to 185% 3 days after treatment. Boron levels in treated apple, pear, and plum leaves decreased to levels similar to nontreated leaves by 9 days after application, whereas cherry leaves required 33 days to approach levels in nontreated leaves. Movement of applied B was also studied by treating cherry leaves with B solutions enriched in the stable isotope, 10B. Isotope analysis indicated that applied B moved out of leaves and into subtending tissues. The highest concentrations of applied B were found in buds, followed by bark and wood.

Movement of Foliar Applied Boron out of Leaves and Accumulation in Flower Buds and Flower Parts of ‘Italian’ Prune

Abstract To study the distribution of foliar applied B in ‘Italian’ prune (Prunus domestica L.) trees, 500 ppm B solutions were applied in July, September, and October. Boron applied in September or October moved readily out of senescing leaves and apparently into adjacent flower buds and subtending tissues. Boron applied in mid summer (29 July) moved out of nonsenescing leaves at a similar rate. Flower buds accumulated B slowly in the fall and winter, but rapidly during bud swelling. In flowers, the largest increases in B concentrations due to foliar sprays were in anthers (248%) and styles (162%).