Tree trunks and branches as optimum mechanical supports of the crown: II. The branches

Using assumptions made in a previous paper, a theory of the shapes of primary branches is developed. Two cases are studied: a primary branch which has a portion denuded of secondary branches, and a primary branch with a continuous load of secondary branches. The first case leads to hyperelliptic integrals, the second—to polynomials of second degree.     

The atrioventricular branches of the human coronary arteries

Branches of the coronary arteries of normal human hearts, supplying both atria and ventricles, were found by fine dissection and have been named rami atrioventriculares. They comprise atrial branches from ventricular arteries and ventricular branches from atrial arteries. Their incidence was 74% in the 50 adult individuals studied. The subjects had committed suicide with a poison which did not damage the coronary arteries. The atrioventricular branches constitute communications across the coronary sulcus, thus establishing a continuity between the atrial and the ventricular arterial supply. Therefore, there is not invariably a sharp demarcation of blood supply between atria and ventricles, as has been commonly taught. Neither atrial nor ventricular branches consist exclusively of ascending and descending branches of the coronary arteries, as has been assumed. Atrioventricular branches can play a role in collateral circulation and may, in individuals who are born with them, provide an explanation for some of the variability in signs and symptoms incidental to heart attacks.     

Foliar boron applications increase the final number of branches and pods on branches of field-grown soybeans

Our previous work demonstrated that boron (B) supplied to soybeans (Glycine max [L.] Merrill cv `Williams 82') by a stem infusion technique increased the number of pods on branches and led to a significant yield increase. Therefore, research was continued to determine whether soil or foliar applications of B could be used to achieve the same results. Field experiments were completed with both soil and foliar applications of B. Only the foliar applications of B resulted in a significant increase in the number of pods/branch. When split foliar treatments were applied twice during flowering, the total application of 0.56 kilograms of B per hectare was the optimal treatment for increasing pods/branch. In a second field experiment in 1987, soybeans were treated weekly from flowering through podfill with six split foliar applications of aqueous H₃BO₃ solutions so that total applications were either 0, 1.1, or 2.24 kilograms of B per hectare. Foliar applications increased the number of branches/plant at the end of the season and significantly stimulated the formation of pods on branches, with 1.12 kilograms of B per hectare being the optimal treatment for these variables. This rate also tended to increase the number of seeds/plant and seed yield/plant. A duplicate experiment with minor modifications was conducted during the summer of 1988, and again the 1.12 kilograms of B per hectare application rate resulted in significant increases in number of branches at harvest as well as number of pods on branches. The 2.24 kilograms of B per hectare application rate also significantly increased these parameters. Foliar B applications induced increases in leaf B concentration far above the 60 micrograms per gram level that was previously accepted as the upper level of tolerance for soybeans. Since optimal branching and per plant yield parameters were achieved by plants with B leaf concentrations greater than 160 micrograms per gram, the accepted range of soybean tolerance for B must be reconsidered when B is foliarly applied.     

Anatomy of the mandibular branches of the facial nerve.

In operative dissections of mandibular branches of the facial nerve, we identified certain branches below the inferior border of the mandible in all cases. These usually supplied the depressor labii inferioris and mentalis muscles, though infrequently the branch to the depressor anguli oris was also below the mandible. At least 3 nerve branches were identified in all dissections. The clinical applications of this include the necessity to identify and protect these nerve branches during operations in the submandibular triangle, as well as when incising the platysma muscle or removing fat from over the body of the mandible in a face-lift procedure.     

Transient axonal side branches in the developing mammalian optic nerve

Optic axons were labelled with horseradish peroxidase to establish the presence of side branches and examine their distribution and morphology in the developing optic nerve of the quokka wallaby, Setonix brachyurus, the cat and rat at stages when axon numbers are at their peak. In each species, three quarters of the axons were essentially straight and lacked side branches. The remaining axons took significantly longer paths and bore side branches, mostly at points where axons undulated or changed direction. Side branches occurred at intervals of 28–43 µm, had lengths of 2–3 µm and were usually simple rather than branched. A minority (1%) of the axons crossed diagonally between fascicles and two thirds of these had more side branches (interval: 10–18 µm) on the interfascicular portion than were found on the forward-directed axons. A small number of axons (0.01%) doubled back to grow retrogradely towards the eye, these axons also bore relatively more side branches (interval: 8–22 µm), especially at points where the axons changed direction. Ultrastructural reconstruction showed that side branches resembled small axonal profiles and constituted 2% of the total axon number. It is suggested that side branches are involved in the fine-tuning of growth cone navigation. Most side branches are lost by adulthood, indicating their transient nature. The absence of retrogradely-directed axons from adults suggests that cells with such axons are removed by naturally occurring cell death.     

Hedgehog signaling patterns the tracheal branches

The elaborate branching pattern of the Drosophila tracheal system originates from ten tracheal placodes on both sides of the embryo, each consisting of about 80 cells. Simultaneous cell migration from each tracheal pit in six different directions gives rise to the stereotyped branching pattern. Each branch contains a fixed number of cells. Previous work has shown that in the dorsoventral axis, localized activation of the Dpp, Wnt and EGF receptor (DER) pathways, subdivides the tracheal pit into distinct domains. We present the role of the Hedgehog (Hh) signaling system in patterning the tracheal branches. Hh is expressed in segmental stripes abutting the anterior border of the tracheal placodes. Induction of patched expression, which results from activation by Hh, demonstrates that cells in the anterior half of the tracheal pit are activated. In hh-mutant embryos migration of all tracheal branches is absent or stalled. These defects arise from a direct effect of Hh on tracheal cells, rather than by indirect effects on patterning of the ectoderm. Tracheal cell migration could be rescued by expressing Hh only in the tracheal cells, without rescuing the ectodermal defects. Signaling by several pathways, including the Hh pathway, thus serves to subdivide the uniform population of tracheal cells into distinct cell types that will subsequently be recruited into the different branches.     

Atrioventricular and ventriculoatrial branches of the coronary arteries in human hearts

Atrioventricular (AV) and ventriculoatrial (VA) branches of the coronary arteries are vessels which supply simultaneously atrial and ventricular walls by means of recurrent rami. The terminology indicates the name of the main vessel followed by the name of the recurrent vessel both combined in an adjective. These branches establish a vascular 'suture' across the coronary sulcus in front (superficially to) or behind (deeply to) the trunks of the right coronary artery and of the left coronary artery (circumflex artery). The AV and VA branches, found in 95% of 40 human hearts, should be considered a normal characteristic of the coronary circulation and an important anatomical factor for the clinical interpretation of pathological cardiac phenomena.     

Suppression of branches in Eucalyptus trees

The effect of neem oil, which acts as a suckericide in tobacco, on branch suppression in Eucalyptus tereticornis was assessed to help maximize stem biomass. Lateral branches of selected trees were pruned, and neem oil solutions at concentrations of either 80%, 40%, 20%, 10%, or 0% (untreated control) were applied to leaf axils of the pruned branches. Regeneration of branches was suppressed, and the magnitude of suppression was proportional to the concentration of neem oil. Compared to the control, the percentage reduction in branching at 80% neem oil was 41.6%. When regenerated branches were repruned and neem oil applied at either 100%, 80%, or 0% (control), the regenerating ability of these branches was severely repressed by 78% at 100% neem oil relative to the control. Apical shoots were also topped and treated at either 100% or 0% (control) neem oil to identify the principal suppressive component in neem oil. The principal component azadirachtin was tested at 375, 750, 1500, 3125, 6250, 12?500, 25?000, 50?000, and 100?000 ppm and 0 ppm as the control. Reduction in the coppicing shoot was as high as 85%. Azadirachtin was responsible for the suppression. By pruning the lateral branches with neem oil, wasteful consumption of photosynthates can be precluded and the stem biomass maximized.     

Individual differences in the ophthalmic artery and its branches in man

Structural peculiarities and topography of the ophthalmic artery and its branches have been studied in 105 mature persons. Owing to the topogapho-anatomical peculiarities, three parts of the ophthalmic artery have been detected; their form, size and interconnections with the surrounding formations are determined by the form of the skull and that of the orbit. The topography, structure and places where the ophthalmic artery branches get off are variable and have correlative connections with the orbital form.     

截干及修枝整形对有效枝条萌发能力及其对紫胶虫产紫胶的影响

为了研究紫胶虫的寄主植物久树抚育对紫胶产量的影响,通过对云南元江和红河干热河谷区中的久树分别进行截干和修枝整形处理,调查有效枝条的萌发能力和紫胶产量。结果表明,截干高度及截干处的平均直径对有效枝条的总长度和数量无显著影响,但截干位置的分支数量与有效枝条的总长度和数量显著正相关。保留12支左右枝条的中度模式的修枝整形较轻度和重度模式中有效枝条的长度、直径和表面积更加有利于紫胶生产;截干的高度和截干处平均直径对紫胶产量无显著影响,但截干位置的分支数量、萌发的有效枝条总长、数量和着胶枝长与紫胶产量显著正相关,中度模式的修枝整形亩产和单数紫胶产量最高。截干和修枝整形能够影响紫胶的产量,对寄主植物合理的抚育有助于提高紫胶产量。     

Motor unit territories supplied by primary branches of the phrenic nerve

Recent studies have demonstrated that, under certain circumstances, the diaphragm does not contract as a homogeneous unit. These observations suggest that motor units may not be randomly distributed throughout the muscle but confined to localized subvolumes. In the present study, electromyographic (EMG) and glycogen depletion methods were combined to investigate the organization of motor units supplied by the primary branches of the phrenic nerve in the cat. Four primary branches are generally present, one branch to the crus and three branches to the sternocostal region. The gross motor-unit territory of each of the four phrenic primary branches was determined by stimulating each nerve separately, while recording from nine EMG electrodes distributed over the hemidiaphragm. Stimulation of the crural branch evoked activity in the ipsilateral crus, whereas stimulation of each of the remaining branches evoked activity in discrete but overlapping areas of the sternocostal diaphragm. A more precise analysis of the distribution and borders of the motor territories was obtained by mapping regions depleted of muscle glycogen due to stimulation of each primary branch for 90 min. Glycogen depletion results closely matched the EMG findings of a localized distribution of motor units served by single primary branches. Stimulation of the crural branch typically caused depletion of the ipsilateral crus, whereas the sternocostal branches each served a striplike compartment. In the majority of cases, the borders of the sternocostal compartments were relatively abrupt and consisted of a 1- to 2-mm transition zone of depleted and nondepleted fibers. These studies demonstrate that motor unit territories of the primary branches of the phrenic nerve are highly delineated. This compartmentalization provides the central nervous system with the potential for a more precise regional motor control of costal and crural diaphragm than previously suspected.     

The occurrence of non-ring producing branches in Abies lasiocarpa

Lack of annual growth ring production at the base of branches in the lower portion of the crown is a commonly observed phenomenon. In this study, branches with missing rings were found on 47 of 49 Abies lasiocarpa trees sampled. The number of missing rings on the lowest live branch in the crown averaged 12, and ranged as high as 28. The lower one-third of the live crown tended to consist of branches without rings; these branches contained an average of 30% of the total crown leaf area. The ratio of foliage weight to total branch weight, in combination with position of the branch in the canopy, was an effective discriminator of non-ring producing branches. This suggests that both structural and environmental factors influence the cessation of ring production. The potential ecological implications of branches that fail to produce rings are discussed.     

Spatial arrangement of branches in relation to slope and neighbourhood competition

To gain a better understanding of the effects of spatial structure on patterns of neighbourhood competition among hardwood trees, the three-dimensional extension of primary branches was surveyed for ten community-grown Castanea crenata (Fagaceae) trees with respect to the positioning of neighbouring branches and the slope of the forest floor. There were significantly more branches extending towards the lower side of the slope than towards the upper side, but structural properties such as branch length and vertical angle were not affected by slope. When horizontal extension of a branch towards its neighbour was compared for a C. crenata branch and a neighbouring heterospecific, the former was significantly narrower than the latter when the inter-branch distance (horizontal distance between the base positions of two neighbouring branches) was short (< approx. 5 m). Castanea crenata branches tended to extend in a direction avoiding neighbouring branches of heterospecifics when the inter-branch distance was short. Furthermore, for an inter-branch distance <3 m, the horizontal extension of a C. crenata branch was less when it was neighbouring a heterospecific branch than when neighbouring a conspecific branch. These results suggest that horizontal extension of C. crenata branches is more prone to spatial invasion by nearby neighbouring branches of heterospecifics, and that the invasion can be lessened when C. crenata trees are spatially aggregated. The reason why such an arrangement occurs is discussed in relation to the later leaf-flush of C. crenata compared with that of other species in the forest.     

Anomalous course and branches of human coronary arteries

132 hearts obtained from cadavers were dissected in order to study anomalies in the course and branches of human coronary arteries. Only in 1 heart was a deviation of the circumflex branch of the left coronary artery taking a course inferior to the coronary sulcus observed. The right coronary artery travelled the entire length of the coronary sulcus on the back of the heart and gave both a posterior ventricular and a collateral branch. Circumflex branches of the right and left coronary arteries did not anastomose.     

Drivers of apoplastic freezing in gymnosperm and angiosperm branches

It is not well understood what determines the degree of supercooling of apoplastic sap in trees, although it determines the number and duration of annual freeze–thaw cycles in a given environment. We studied the linkage between apoplastic ice nucleation temperature, tree water status, and conduit size. We used branches of 10 gymnosperms and 16 angiosperms collected from an arboretum in Helsinki (Finland) in winter and spring. Branches with lower relative water content froze at lower temperatures, and branch water content was lower in winter than in spring. A bench drying experiment with Picea abies confirmed that decreasing branch water potential decreases apoplastic ice nucleation temperature. The studied angiosperms froze on average 2.0 and 1.8°C closer to zero Celsius than the studied gymnosperms during winter and spring, respectively. This was caused by higher relative water content in angiosperms; when branches were saturated with water, apoplastic ice nucleation temperature of gymnosperms increased to slightly higher temperature than that of angiosperms. Apoplastic ice nucleation temperature in sampled branches was positively correlated with xylem conduit diameter as shown before, but saturating the branches removed the correlation. Decrease in ice nucleation temperature decreased the duration of freezing, which could have an effect on winter embolism formation via the time available for gas escape during ice propagation. The apoplastic ice nucleation temperature varied not only between branches but also within a branch between consecutive freeze–thaw cycles demonstrating the stochastic nature of ice nucleation.     

Mutual support and selection between branches of damaged plants

Snow (1931) showed that the fate of a branch of a plant that had suffered local herbivory could be determined by correlative effects of other branches. This neglected work was continued in the current study, herbivory being simulated by the removal of leaves of different ages from pea plants with two branches. A damaged branch was suppressed when an undamaged alternative branch was present; otherwise the damage never prevented continued development. The removal of mature leaves had a smaller effect than the removal of immature, expanding leaves. When leaves were removed from both branches it was the branches that suffered less damage to their immature leaves that continued shoot development. Branches from which all photosynthetic leaves were repeatedly removed developed only when they retained their immature leaves and remained dominant, inhibiting the development — but not the photosynthesis — of the other branch on the same plant. Accounting for these results requires mechanisms that compare the different branches of the plant and select for development the ones that have the greatest potential for future, rather than present, photosynthesis. It is concluded that a compartmentalized or sectorial distribution of essential substrates can be modified by correlative relations that are probably mediated by hormones.     

The central branches of the anterior and median cerebral artery

1. In our examined subjects, the A. recurrens anterior was found to be more frequently doubled than as has been reported. 2. The number of central rami arising from the A. cerebri media varies between 3 and 13. 10% of these already divide extracerebrally so that the number of small asts actually present lies between 4 and 20. The count presented by Lazorthes appears to be based on the former method and by Jain on the latter. The ramifications arise from the main artery as well as from its insular branches. Arterial trunks are likewise often present that give off a large portion of the asts. When operating aneurysms of the A. cerebri media, these facts are of importance to the neurosurgeon who must sprare these vessels whenever possible. Should more of these branches or one of these arterial trunks be bound with a clip, serious neurological deficits will occur.     

Finding the optimal lengths for three branches at a junction

This paper presents an exact analytical solution to the problem of locating the junction point between three branches so that the sum of the total costs of the branches is minimized. When the cost per unit length of each branch is known the angles between each pair of branches can be deduced following reasoning first introduced to biology by Murray. Assuming the outer ends of each branch are fixed, the location of the junction and the length of each branch are then deduced using plane geometry and trigonometry. The model has applications in determining the optimal cost of a branch or branches at a junction. Comparing the optimal to the actual cost of a junction is a new way to compare cost models for goodness of fit to actual junction geometry. It is an unambiguous measure and is superior to comparing observed and optimal angles between each daughter and the parent branch. We present data for 199 junctions in the pulmonary arteries of two human lungs. For the branches at each junction we calculated the best fitting value of x from the relationship that flow ∞ (radius)^x. We found that the value of x determined whether a junction was best fitted by a surface, volume, drag or power minimization model. While economy of explanation casts doubt that four models operate simultaneously, we found that optimality may still operate, since the angle to the major daughter is less than the angle to the minor daughter. Perhaps optimality combined with a space filling branching pattern governs the branching geometry of the pulmonary artery.     

Cell wall branches, penicillin resistance and the secrets of the MurM protein

Production of low-affinity forms of penicillin-binding proteins (PBPs), although essential, is not sufficient to protect pneumococci against the inhibitory action of penicillin. Resistance also requires the newly identified protein MurM which, together with MurN, is involved with the synthesis of short peptide branches in the pneumococcal cell wall. Cells in which murM was inactivated produced cell walls without branches and also completely lost penicillin resistance. To understand these surprising observations a 3D-model of MurM was constructed, which helped to put into structural context several of the biochemical and genetic observations made about this protein.     

留营养枝对棉株同化物生产,运转,分配及产量的影响

运用＾１４Ｃ示踪技术研究了留营养支棉株＾１４Ｃ同化物生产运转分配规律。结果表明：留营养枝与否对全株＾１４Ｃ总同化量基本没有影响,但留营养２枝棉株果枝叶的相对光合强度（以放射性比强度表示）降低;主茎叶、果枝叶的＾１４Ｃ同化量显著降低;营养２叶具有较高的光合作用强度和向外输送＾１４Ｃ同化物的转运速率,在＾１４Ｃ同化物生产运转分配中占有很重要的地位。留营养枝棉株＾１４Ｃ同化物的转运速率,在＾１４Ｃ同化