scholarly journals Are extrafloral nectaries efficient against herbivores? Herbivory and plant defenses in contrasting tropical species

2020 ◽  
Vol 13 (4) ◽  
pp. 423-430 ◽  
Author(s):  
Cássio Cardoso Pereira ◽  
Maria Gabriela Boaventura ◽  
Gislene Carvalho de Castro ◽  
Tatiana Cornelissen

Abstract Aims Plants have limited resources for defenses and species that invest in biotic defenses might exhibit leaves that invest less in other types of defenses. We have investigated whether plants that have few mechanical defenses, but have extrafloral nectaries (EFNs) patrolled by ants, are less prone to herbivory, compared with plants without EFNs that have tougher leaves. Methods Data from the literature were extracted to examine the reported levels of herbivory in plants with or without EFNs. In a savanna vegetation in southern Brazil, field data were collected in leaves from six tropical species and herbivory and specific leaf area (SLA) levels were measured. We further evaluated differences in herbivory and SLA among species and between plants with or without EFNs. In order to test the relationship between herbivory and leaf toughness we regressed average herbivory and average SLA per plant. Important Findings Plants exhibited variable levels of leaf damage, but plants without ant defenses experienced the highest levels of leaf area loss to herbivory. Levels of mechanical defenses were also variable among the plant species. Plants without EFNs were tougher, exhibiting lower values of SLA. Although plants without EFNs had more sclerophyllous leaves, this mechanical defense was not sufficient to impair and/or reduce herbivore feeding, suggesting that the biotic defenses performed by patrolling ants might be more effective than investment in mechanical defenses associated with leaf palatability.

2021 ◽  
Author(s):  
Kristiina Visakorpi ◽  
Sofia Gripenberg ◽  
Yadvinder Malhi ◽  
Terhi Riutta

AbstractOur current understanding of the relationship between insect herbivory and ecosystem productivity is limited. Previous studies have typically quantified only leaf area loss, or have been conducted during outbreak years. These set-ups often ignore the physiological changes taking place in the remaining plant tissue after insect attack, or may not represent typical, non-outbreak herbivore densities. Here, we estimate the amount of carbon lost to insect herbivory in a temperate deciduous woodland both through leaf area loss and, notably, through changes in leaf gas exchange in non-consumed leaves under non-outbreak densities of insects. We calculate how net primary productivity changes with decreasing and increasing levels of herbivory, and estimate what proportion of the carbon involved in the leaf area loss is transferred further in the food web. We estimate that the net primary productivity of an oak stand under ambient levels of herbivory is 54 - 69% lower than that of a completely intact stand. The effect of herbivory quantified only as leaf area loss (0.1 Mg C ha−1 yr−1) is considerably smaller than when the effects of herbivory on leaf physiology are included (8.5 Mg C ha−1 yr−1). We propose that the effect of herbivory on primary productivity is non-linear and mainly determined by changes in leaf gas exchange. We call for replicated studies in other systems to validate the relationship between insect herbivory and ecosystem productivity described here.


2006 ◽  
Vol 66 (2b) ◽  
pp. 671-680 ◽  
Author(s):  
E. M. Varanda ◽  
M. P. Pais

Susceptibility of Didymopanax vinosum (Apiaceae) to insect herbivores was investigated in three sites of a cerrado mosaic - composed of campo cerrado (a grassland with scattered trees and shrubs), cerradão (a tall woodland) and cerrado sensu stricto (intermediate between the two) - situated in Cerrado Pé-de-Gigante, Santa Rita do Passa Quatro, SP, Brazil. We also examined the relationship of folivory with the composition and abundance of the insect herbivore fauna, and with several nutritional and defensive plant characteristics (water, nitrogen, cellulose, lignin, tannin leaf contents, and leaf toughness). We collected insects associated with D. vinosum every month, and we measured leaf damage every three months. In general, the annual folivory differed among sites. It reached the highest rates in site 1 and site 3: 7.33 and 8.5 percent, respectively. Only 1.32 percent of annual folivory was observed in site 2. These levels resulted from the higher abundance, in sites 1 and 3, of the thrips Liothrips didymopanacis (Phlaeothripidae), the most abundant herbivore sampled, responsible for more than 90 percent of the observed damage. However, no significant relationship was found between insect activity and the chemical and physical composition of the leaves. Our findings suggest that, at least in this species, other chemical compounds or variables related to plant apparency and resource availability to herbivores (e.g. plant architecture) might play a more decisive role in the spatial variation of folivory than the nutritional and defensive traits that were analyzed.


2001 ◽  
Vol 17 (2) ◽  
pp. 285-302 ◽  
Author(s):  
BRUCE E. HOWLETT ◽  
DIANE W. DAVIDSON

Leaf defences, leaf nutritional quality and leaf expansion rates may vary with resource availabilities to plants. Such variation could affect rates of leaf loss to herbivores, particularly along the steep resource gradients in disturbed forests. Intraspecific and interspecific variation in leaf damage and leaf expansion rates were measured on dipterocarp seedlings planted into secondary forests 1, 5 and 15 y after logging, and in adjacent primary forest of Sabah, Malaysia. Herbivory rates or amounts of leaf damage were compared across habitats and species for expanding, recently expanded, and mature leaves of Shorea leprosula and Dryobalanops lanceolata (Dipterocarpaceae). In all four habitats, leaves of the faster growing S. leprosula sustained higher rates and amounts of leaf-area loss than did the tougher leaves of slower growing D. lanceolata. Expanding leaves accumulated more leaf-area loss per week than did mature leaves. In all habitats and in both species, more than 25% of expanding leaves disappeared entirely. Rates of leaf-area loss per week differed among habitats for expanding leaves but not for mature leaves. In a relatively open, 1-y-old logged forest, faster leaf expansion reduced the time leaves spent in the most vulnerable stage; however, in S. leprosula a greater rate of leaf area loss countered the shorter expansion time. Thus, leaves accumulated similar total damages across habitats, and herbivory did not produce differences among habitats in seedling growth or mortality. High levels of resources may increase both leaf palatability and leaf expansion rates, with counteracting effects on herbivory.


2019 ◽  
Vol 118 (8) ◽  
pp. 347-355
Author(s):  
Hye- RimPark ◽  
Yen-Yoo You

Unlike non-profit organizations, social enterprises must be sustainable through profit-making activities in order to pursue social purposes.However, the most important of the poor limited resources is also human resources, and for the efficient use of human resources, empowerment should be given to members. This study proves whether job engagement mediates the effect on sustainability when psychological empowerment is given to employees in social enterprises.


2004 ◽  
Vol 34 (12) ◽  
pp. 2501-2507 ◽  
Author(s):  
Takahide A Ishida ◽  
Kouhei Hattori ◽  
Masahito T Kimura

We examined responses of phytophagous insects to hybrids between Quercus crispula Blume and Quercus dentata Thunberg in a natural population in northern Japan. The abundance of leafminers and leaf area loss by chewing insects in hybrids were intermediate between those in the parental species (additive mode), close to those of either of the parental species (dominance mode), or similar to those of both parental species (no difference). Hybrids were neither more susceptible nor resistant to the insect herbivores we monitored. In Phyllonorycter (Gracillariidae) species, which are specialized to either of the parental oak species, the mortality of sap-feeding early instar larvae did not differ between hybrids and the parental species. The abundance of four leafminer taxa was correlated with environmental conditions (i.e., distance from the coastal edge of the forest or the timing of budbreak) as well as genetic factors.


2005 ◽  
Vol 94 (2) ◽  
pp. 244-255 ◽  
Author(s):  
Quan Wang ◽  
Samuel Adiku ◽  
John Tenhunen ◽  
André Granier

2021 ◽  
Author(s):  
Jiří Mihola

The monograph develops the theory of production functions and their systematic typology. It looks at the relationship between inputs and outputs as a universal relationship that is used not only in economics but also in other disciplines. In addition to the static production function, special attention is paid to the dynamization of individual quantities and the issue of expressing the effect of changes in these quantities on the change in production. It is explained why in the aggregate production function expressed through aggregate factor input and aggregate factor productivity it is necessary to use a multiplicative relationship, why the multiplicative link is also suitable in terms of total input factor and why the share of weights in labor and capital should be the same. The use of the production function is demonstrated on the development of the economies of the USA, China and India and on the ten largest economies of the world in terms of absolute GDP, on cryptocurrencies and on the so-called farming role.In addition to a comprehensive overview of production functions, the monograph also enriches new ideas that arose during long-term computational and analytical activities of economic and business. Particularly innovative is the generalization of the production function to any system with variable inputs and outputs. The production function can thus be recognized in many identities. The original intention of the research was to examine the intensity of economic development, but it turned out that it is closely related to production functions. The impetus for this research comes from Prof. Ing. František Brabec, DrSc. a genius mathematician, designer, economist and manager, former general director of Škoda in Pilsen and later rector of ČVÚT.The presented typology of production functions is not limited to one area of economics, but goes beyond it. The monograph respects the definition of the static production function as the maximum amount of production that can be produced with a given number of production factors. On this function, which can be effectively displayed using polynomial functions of different orders,significant points can be systematically defined, ie the inflection point, the point of maximum efficiency, the point of maximum profit and the point of maximum production. The purpose is to optimize the number of inserted production factors. The text is preferred the point with the greatest effectiveness. If this quantity does not correspond, for example, to demand, it is possible to choose another technology, which will be reflected in a shift in the static production function. At the same time, the important points of these functions describe the trajectory, which has the nature of a dynamic production function. For a dynamic production function, the crucial question is how the change in individual factors contributes to the overall change in output. If the production function is expressed through inputs and their efficiency, dynamic parameters of extensibility and intensity can be defined, which exactly express the effect of changes in inputs and the effect of changes in efficiency on changes in outputs for all possible situations. Special attention is paid to the aggregate production function. It explains why it should be expressed as the product of the aggregate input factor (TIF) and aggregate factor productivity (TFP), or why the term TIF should be expressed as a weighted product of labor and capital, in which the value of labor and capital weights could be and identical. The monograph here surpasses the traditional additive view of the multi-factor production function by proposing a multiplicative link, which also allows the derivation of growth accounting, but with a new interpretation of weights and (1-), which do not need to be calculated for each subject and each year.The time production function is used to forecast the GDP development of the US, China and India economies until 2030 and 2050, respectively. It is also predicted an increase in the absolute GDP of Indonesia, a stable position of Russia and the loss of the elite position of Japan and Germany.The monograph also deals with the hitherto unresolved question of whether, even in economics, it is also necessary in certain circumstances to take into account a phenomenon called quantization in physics. It turns out that quantization is a common thing in economics, which is documented on specific forms of production functions that respect quantization in economics.The monograph also deals with the relationship between the efficiency of an individual given the use of a certain point on a specific static production function and common efficiency, ie all actors together. These examples assume limited resources. The sum of the outputs of all actors depends on how the actors share these limited resources. It can be expected that there will be at least one method of distribution that will bring the highest sum of outputs (products, crops) of all actors. This result, however, also depends on the shape of the production functions. This is investigated using EDM, i.e.elementary distribution models. EDM for polynomial production functions of the 2nd to 5th order are not yet published in summary. Of the new findings, they are the most interesting. When using two polynomial production functions, the EDM boundary becomes linear if the inflection point is used for both production functions. If we are above the inflection point, the EDM is properly concave. It turned out that the "bending" of the production function in the region of the inflection point can be modeled using a quantity of the order of the respective polynomial. The higher the order of the polynomial, the higher the deflection can be achieved. This proved to be a very important finding in modeling specific production functions. This effect cannot be achieved by combining other parameters.


1977 ◽  
Vol 25 (4) ◽  
pp. 238-242
Author(s):  
A.S.R. Pereira

For studies on the relationship between photosynthetic capacity and yield components in sunflower a method for estimating leaf area was required. To this end use of the leaf area coefficient (LAC), i.e. the quotient area/(length X max. width), was evaluated. It was found that LAC may be a function of leaf position and plant density, depending on the cv. concerned. For the Russian cv. Armavirec, LAC was independent of leaf position and plant density. For the Rumanian hybrid HS 18, LAC was dependent on leaf position but not plant density. For the French hybrid INRA 4701, LAC depended on both leaf position and plant density, but even in this case, it was concluded that LAC can be a useful aid in leaf area estimation. (Abstract retrieved from CAB Abstracts by CABI’s permission)


OENO One ◽  
1987 ◽  
Vol 21 (2) ◽  
pp. 81
Author(s):  
M. Nikov

<p style="text-align: justify;">L'étude est menée avec le cépage Merlot conduit en forme haute et à une distance de 3,40 x 1,20 m. Les vignes supportent des charges individuelles de 26, 32, 38 ... jusqu'à 62 bourgeons par cep. La relation entre le nombre d'yeux et le rendement par souche se caractérise par une courbe parabolique avec un maximum autour de 50 bourgeons par cep. L'augmentation de charge au-delà de l'optimum exerce une influence inhibitrice sur la croissance des rameaux individuels depuis la première année. Le rapport entre la surface foliaire et la production représente un facteur essentiel pour la qualité du raisin.</p><p style="text-align: justify;">+++</p><p style="text-align: justify;">The study involves Merlot variety trained with an high trunk and a 3,40 x 1,20 m spacing. The vines support individual pruning levels of 26, 32, 38 ... up to 62 buds/vine. The relationship between bud number and yield per vine is characterized by a parabolic curve with a maximum around 50 buds/vine. The increase in pruning level beyond the optimum induces an inhibitory effect on single shoot growth since the first year. The leaf area : yield ratio represents a primary factor of grape quality.</p>


2018 ◽  
Vol 23 (4) ◽  
pp. 426-447 ◽  
Author(s):  
Megan Wainwright

Technologies for medicinal oxygen delivery at home are increasingly part of the global health technology landscape in the face of rising rates of chronic lung and heart diseases. From the mere notion of harvesting and privatizing oxygen from the atmosphere to its status as both dangerous and therapeutic, and finally to its capacity to both extend and limit life, oxygen as therapy materializes its status as an ambivalent object in global health. This analysis of ethnographic material from Uruguay and South Africa on the experience of home oxygen therapy is guided by philosopher Don Ihde’s postphenomenology – a pragmatic philosophical approach for analysing the relationships between humans and technologies. Participants related to their oxygen devices as limiting-enablers, as markers of illness and measures of recovery, and as precious and limited resources. Oxygen was materialized in many forms, each with their own characteristics shaping the ‘amplification/reduction’ character of the relationship as well as the degree to which the devices became ‘transparent’ to their users. Ihde’s four types of human–technology relations – embodiment, hermeneutic, alterity and background relations – are at play in the multistability of oxygen. Importantly, the lack of technological ‘transparency’, in Ihde’s sense of the term, reflects not only the materiality of oxygen but inequality too. While postphenomenology adds a productive material and technological flavour to phenomenology, the author argues that a critical postphenomenology is needed to engage with the political-economy of human–oxygen technology relations.


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