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Neoplastic Pod in the Pea
Abstract
RECENTLY, Nuttall and Lyall7 reported that neoplastic pod in the pea, (the name they used to describe a pustular-like growth on the outside of the pod), was controlled by a dominant gene, which they designated Np. This note puts on record supplementary information about the character that we have obtained.
... Some genotypes of the Pisum species, when deprived of ultraviolet (UV) light in glasshouse conditions, form neoplasm on the pods. Neoplasm emerges as a response to the lack of UV light [14,15] on the surface of young pods with the growth of non-meristematic tissue. It is also stated that neoplasm is triggered by the pea weevil (Bruchus pisorum L.) [16,17]. ...
... It is also stated that neoplasm is triggered by the pea weevil (Bruchus pisorum L.) [16,17]. Neoplasm found in domesticated plants occurs as a result of mutation, and a smooth pod without neoplasm is governed by a recessive "np" gene, while neoplasm is controlled by a single dominant gene "Np" [14,15]. Pods with neoplasm are not preferred by consumers due to the unpleasant image of the pods. ...
... & Noe. when grown under glasshouse conditions [15]. However, the expression and inheritance of neoplasm have not been adequately studied in progeny obtained from inter-subspecific crosses between P. sativum subsp. ...
The Neoplasm trait in pea pods is reported to be due to the lack of ultraviolet (UV) light in glasshouse conditions or in response to pea weevil (Bruchus pisorum L.) damage. This pod deformation arises from the growth of non-meristematic tissue on pods of domesticated peas (Pisum sativum L. subsp. sativum). Neither expressivity, nor the effect of pea weevil on neoplasm in the tall wild pea (P. sativum L. subsp. elatius (M. Bieb.) Asch. & Graebn.), have been adequately studied. We aimed to study the expression and inheritance of neoplasm in the tall wild pea and crosses between domesticated and tall wild peas grown in the glasshouse (without pea weevils) and in the field (with pea weevils) under natural infestation conditions. Neoplasm was found in all pods in tall wild peas when grown in the glasshouse, while it was not detected on pods of field-grown plants despite heavy pea weevil damage. In inter-subspecific crosses between P. sativum subsp. sativum and P. sativum subsp. elatius, all F 1 plants had neoplastic pods, and the F 2 populations segregated in a good fit ratio of 3 (neoplasm): 1 (free from neoplasm) under glasshouse conditions, which suggests that neoplasm on pods of the tall wild pea was controlled by a single dominant gene. Expressivity of neoplasm in the progeny differed from parent to parent used in inter-subspecific crosses. There was no relationship between neoplasm and damage by pea weevil under heavy insect epidemics under field conditions. The neoplasm occurring under glasshouse conditions may be due to one or to a combination of environmental factors. Since wild peas are useful genetic resources for breeding programs aiming at fresh pea production that could be utilized under glasshouse conditions, negative selection could be considered in segregating populations.
... sativum L.) produce neoplasm on its pods when grown under greenhouse conditions. This phenomenon is a non-meristematic tissue growth on the surface of young pods in response to absence of UV light (Nuttall and Lyall, 1964;Dodds and Matthews, 1966). This trait can also be triggered by pea weevil (Bruchus pisorum L.) as a direct response to oviposition (Berdnikov et al., 1992;Doss et al., 2000). ...
... Despite the fact that the expression of this trait is controlled by the dominant (Np) allele, its penetrance is influenced by the genotype (homozygosity: Np/Np vs. heterozygosity: Np/np), and the level of UV light intensity or humidity (Nuttall and Lyall, 1964;Burgess and Fleming, 1973;Doss et al., 2000). This trait has also been reported in other Pisum species like P. elatius and P. humile under greenhouse conditions (Dodds and Matthews, 1966). ...
... Furthermore, when these genotypes were grown under field conditions, the percentage of Np pods dropped to only 7%. This result is consistent with previous findings that reported a negative influence of UV light on neoplasm formation (Nuttall and Lyall, 1964;Dodds and Matthews, 1966). Previous studies showed that the oviposition of female pea weevil on pods of Np genotypes triggers the expression of Np gene (Berdnikov et al., 1992;Hardie, 1992;Doss et al., 2000). ...
Neoplasm formation, a non-meristematic tissue growth on young field pea (Pisum sativum L.) pods is triggered in the absence of UV light and/or in response to oviposition by pea weevil (Bruchus pisorum L.). This trait is expressed in some genotypes (Np genotypes) of P. sativum and has the capacity to obstruct pea weevil larval entry into developing seeds. In the present study, 26% of the tested accessions depicted the trait when grown under greenhouse conditions. However, UV light inhibits full expression of this trait and subsequently it is inconspicuous at the field level. In order to investigate UV light impact on the expression of neoplasm, particular Np genotypes were subjected to UV lamp light exposure in the greenhouse and sunlight at the field level. Under these different growing conditions, the highest mean percentage of neoplastic pods was in the control chamber in the greenhouse (36%) whereas in single and double UV lamp chambers, the percentage dropped to 10% and 15%, respectively. Furthermore, when the same Np genotypes were grown in the field, the percentage of neoplastic pods dropped significantly (7%). In order to enhance neoplastic expression at the field level, intercropping of Np genotypes with sorghum was investigated. As result, the percentage of neoplastic pods was threefold in intercropped Np genotypes as compared to those without intercropping. Therefore, intercropping neoplastic genotypes with other crops such as sorghum and maize can facilitate neoplasm formation, which in turn can minimize the success rate of pea weevil larvae entry into developing seeds. Greenhouse artificial infestation experiments showed that pea weevil damage in neoplastic genotypes is lower in comparison to wild type genotypes. Therefore, promoting neoplastic formation under field conditions via intercropping can serve as part of an integrated pea weevil management strategy especially for small scale farming systems.
... The bruchins are the first natural products found with the capacity to stimulate neoplasm development when applied to pods of peas. This distinctive form of induced resistance is conditioned by the dominant allele, neoplastic pod (Np), present in the host-plant genotype (Dodds and Matthews 1966). At present, the receptors have not been identified for these oviposition-associated elicitors. ...
Being sessile organisms, plants have evolved a vast range of resistance mechanism to offset biotic stress caused by insect herbivores. The coevolution of plants and insect herbivores has not only generated advanced defense strategies in plants but also led to development of feeding strategies and counter-adaptive mechanisms in insects. Several plant species can differentiate insect attack from mechanical damage by the perception of a suite of chemical signals or herbivore-associated elicitors (HAEs), also known as herbivore-associated molecular patterns (HAMPs), produced by the insect. HAMPs could arise from insect oral secretions (OS), saliva, digestive waste products, and ovipositional fluids. Apart from elicitors, OS from some insect herbivores also contain effectors that suppress plant antiherbivore defenses. HAEs are dissimilar in their origin and structure, ranging from FACs (fatty acid-amino acid conjugates) such as volicitin, chemically related oxylipins, sulfur-containing fatty acids (caeliferins), peptides (systemins and inceptins) to high-molecular-weight enzymes (glucose oxidase and glucosidase). The perception of HAEs leads to the commencement of specific physiological processes in plants in order to defend themselves from insect attack. These responses can vary from changes in plant’s metabolic activity and gene expression pattern to changes in their overall growth and development. Some HAEs are also known to counteract the defense response of plants. However, relatively less is known about the molecular components used by plants to perceive and recognize HAEs and the downstream signaling pathways leading to the initiation of plant response. In this chapter, we will focus on the recent developments made in the field of insect HAEs and their role in modulating plant defenses which will provide novel insights into our understanding of the interaction between plant and insects.
... Possibly the neoplastic outgrowth represents uncontrolled proliferation and differentiation of cells directly from the parenchymal cell layer. It has been discussed before whether the proliferation comes from hypodermis or epidermis (Nuttall and Lyall, 1964;Dodds and Matthews, 1966;Snoad and Matthews, 1969). The latter has also described the hair-like filaments at the later stages of neoplasm formation as seen in light microscope. ...
The pea weevil, Bruchus pisorum L. is a major insect pest of field pea, Pisum sativum L. worldwide and current control practices mainly depend on the use of chemical insecticides that can cause adverse effects on environment and human health. Insecticides are also unaffordable by many small-scale farmers in developing countries, which highlights the need for investigating plant resistance traits and to develop alternative pest management strategies. The aim of this study was to determine oviposition preference of pea weevil among P. sativum genotypes with different level of resistance (Adet, 32410-1 and 235899-1) and the non-host leguminous plants wild pea (Pisum fulvum Sibth. et Sm.) and grass pea (Lathyrus sativus L.), in no-choice and dual-choice tests. Pod thickness and micromorphological traits of the pods were also examined. In the no-choice tests significantly more eggs were laid on the susceptible genotype Adet than on the other genotypes. Very few eggs were laid on P. fulvum and L. sativus. In the dual-choice experiments Adet was preferred by the females for oviposition. Furthermore, combinations of Adet with either 235899-1 or non-host plants significantly reduced the total number of eggs laid by the weevil in the dual-choice tests. Female pea weevils were also found to discriminate between host and non-host plants during oviposition. The neoplasm (Np) formation on 235899-1 pods was negatively correlated with oviposition by pea weevil. Pod wall thickness and trichomes might have influenced oviposition preference of the weevils. These results on oviposition behavior the weevils can be used in developing alternative pest management strategies such as trap cropping using highly attractive genotype and intercropping with the non-host plants.
... Callusforming tissue was observed on the pod surfaces of several of the F 2 plants at the site of pea weevil egg inoculation. Pod neoplasty (Np) and its relationship with pea weevil resistance, mediated by bruchins, has been documented in cultivated pea (Doss et al. 2000) and in P. fulvum (Dodds and Matthews 1966). Np expression might be responsible for some of the observed pod wall effects. ...
Interspecific populations derived from crossing cultivated field pea, Pisum sativum, with the wild pea relative, Pisum fulvum, were scored for pod and seed injury caused by the pea weevil, Bruchus pisorum. Pod resistance was quantitatively inherited in the F 2 population, with evidence of transgressive segregation. Heritability of pod resistance between F 2 and F 3 generations was very low, suggesting that this trait would be difficult to transfer in a breeding program. Seed resistance was determined for the F 2 population by testing F 3 seed tissues of individual F 2 plants and pooling data from seed reaction for each F 2 plant (inferred F 2 genotype). Segregation for seed resistance in the F 2 population of the cross Pennant/ATC113 showed a trigenic mode of inheritance, with additive effects and dominant epistasis towards susceptibility. Seed resistance was conserved over consecutive generations (F 2 to F 5) and successfully transferred to a new population by backcross introgression. Seed resistance in the backcross introgressed population segregated in a 63 : 1 ratio, supporting the three-gene inheritance model. It is proposed that complete resistance to pea weevil is controlled by three major recessive alleles assigned pwr 1 , pwr 2 , and pwr 3 , and complete susceptibility by three major dominant alleles assigned PWR 1 , PWR 2 , and PWR 3 . It is recommended that large populations (>300 F 2 plants) would be required to effectively transfer these recessive alleles to current field pea cultivars through hybridisation and repeated backcrossing.
... Although Dodds and Matthews (1966) could not rationalize a selective value for Np, this question was answered when Berdnikov, et al (1992) observed that Np provided resistance to pea weevil (Bruchus pisorum L.). They reported that callus developed under weevil eggs laid on Np/pods. ...
In Pisum, the Np gene conditions two mitotic responses - to bruchid weevil oviposition on the pod and to reduced UV light. Oviposition by the weevil results in tumorous or neoplastic growth under the egg. Biochemically active compounds, called bruchins, were isolated from two bruchid insects (Doss et al, 2000). Femtomolar concentrations of bruchin result in programmed cell death (PCD) and neoplasm formation on the pod at the application site. PCD is evident at the application site within four hours and a large (several mg) neoplasm in five to seven days. Low UV light results in growth of neoplasm, termed spontaneous neoplasm (SN), over the entire surface of the pod and, as with bruchin application, appears to begins with PCD followed by mitosis. Genotypes containing np/np do not develop SN and respond only weakly to bruchin. Both responses conditioned by Np initiate at the stomatal complex and are first detected by increased auto-fluorescence. In both cases, this is accompanied by increased peroxide/peroxidase activity first at the stomata, then radiating outward across the epidermal surface and into the mesophyll cells. Nuclei in the epidermis stained strongly for peroxide/peroxidase within 3 h of bruchin application. Nuclei in the mesophyll stained for peroxide/peroxidase by 24 h. Rose Bengal, which generates singlet oxygen, stimulated site-specific neoplasm formation on greenhouse grown pods. Lanthanum, an inhibitor of Ca2+ influx, inhibited both ROS production and bruchin action. ZnCl2 inhibited ROS production and bruchin response less effectively than LaCl3. Epidermal cell death demonstrated hallmarks of apoptosis. TUNEL demonstrated the presence of oligonucleosomal fragmentation, which is associated with PCD. Pods treated with bruchin demonstrated progressive TUNEL staining. The first areas to test positive for endogenous nuclease activity were the subsidiary cells of the stomatal complex. Transmission electron microscopy (TEM) found nuclear blebbing, chromatin condensation, mitochondrial swelling, changes in cytosol density and increased vacuolization. This work demonstrates that the bruchin and SN responses conditioned by the Np gene originate from similar cellular events: increased auto-fluorescence, increased peroxide/peroxidase, and PCD. Printout. Thesis (M.S.)--Oregon State University, 2007. Includes bibliographical references (leaves 60-64).
... The calli formed on np/np pods are much smaller than those seen on Np/Np pods and much of their mass results from cell enlargement rather than cell division; however, the minimum dose required to elicit a response on pods of either genotype appears to be about the same . Interestingly, the Np gene was described 30 years ago, long before its role in insect resistance was noted, because its presence causes pods grown under greenhouse conditions to develop patches of callus (neoplasms) on their surface (Dodds and Matthews, 1966;Snoad and Matthews, 1969). Such neoplasms do not form under natural sunlight, as their formation is stimulated by the attenuation of ultraviolet wavelengths (UV) by greenhouse coverings (Snoad and Matthews, 1969), nor do they form spontaneously in the greenhouse in peas homozygous for the recessive allele (np). ...
Bruchins, mono and bis (3-hydroxypropanoate) esters of long chain α,ω-diols, are a recently discovered class of insect elicitors
that stimulate cell division and neoplasm formation when applied to pods of peas and certain other legumes. Differential display
analysis resulted in the identification of an mRNA whose level was increased by the application of Bruchin B to pea pods.
The corresponding amplification product was cloned and sequenced and a full length cDNA sequence was obtained. This cDNA and
the gene from which it was derived were assigned the name CYP93C18 based upon sequence similarities to the cytochrome P450 mono-oxygenase CYP93C subfamily, which contains isoflavone synthase
genes from legumes. RNA gel blots and quantitative RT-PCR demonstrated that expression of CYP93C18 increased within 8 h of bruchin treatment to a maximum of 100–200-fold of the level in untreated pods, and then declined.
The up-regulation of CYP93C18 was followed by an increase in the level of the isoflavone phytoalexin, pisatin. Pisatin was detectable in the bruchin-treated
pods after 16 h and reached a maximum between 32 h and 64 h. This, the first report of induction of phytoalexin biosynthesis
by an insect elicitor, suggests that Bruchin B not only stimulates neoplasm formation, but also activates other plant defence
responses.
... Intumescences or abnormal, non-pathogenic, blister-like protuberant growths that develop on oedematous plant tissues, predominantly occur on leaves (Wolf and Lloyd 1912 ), although they may also arise on stems (Atkinson 1893), roots (Hahn et al. 1920), flowers and fruits (Wolf and Lloyd 1912). First described by Sorauer in 1886 (La Rue 1933c), intumescences have since been referred to as excrescences (Hahn et al. 1920, La Rue 1933c), neoplasms (Dodds and Matthews 1966, Nilsen and Lersten 1977), galls (Warrington 1980), enations (Mitchell and Vojtik 1967, Kirkham and Keeney 1974, Warrington 1980), genetic tumours (Jones and Burgess 1977, Morrow and Tibbitts 1988), leaf lesions (Petitte and Ormrod 1986) and oedemata (Digat and Albouy 1976). Deferring to history, we refer to these structures as intumescences. ...
Intumescences or abnormal, non-pathogenic, blister-like protuberant growths, form on Eucalyptus globulus Labill. and, to a much lesser extent, Eucalyptus nitens (Deane and Maiden) Maiden leaves when plants are grown in a high relative humidity environment. We examined the histology of intumescences and their effects on leaf photosynthetic processes. Intumescences were induced by placing E. globulus and E. nitens seedlings in a relative humidity of 80% in a greenhouse for 5 days. Symptomatic and asymptomatic leaves of plants with intumescence development were compared with leaves of control plants. Light-saturated carbon dioxide (CO(2)) assimilation (A(max)) and responses of CO(2) assimilation (A) to varying intercellular CO(2) partial pressure (C(i)) were measured. Symptomatic and asymptomatic leaf samples were fixed and sectioned and cellular structure was examined. Intumescences greatly reduced the photosynthetic capacity of E. globulus leaves and were associated with reduced electron transport rate and ribulose bisphosphate (RuBP) regeneration capacity. Tissue necrotization and cellular collapse of the palisade mesophyll and deposition of phenolic compounds in the affected areas, probably reduced light penetration to photosynthesizing cells as well as reducing the amount of photosynthesizing tissue. Photosynthetic capacity of E. nitens was unaffected. The intumescences resembled simple lenticels, both morphologically and developmentally. To our knowledge, this is the first time that lenticel-like structures developed in response to environmental conditions have been described on leaves.
... As a consequence, this hinders larval entry into the pod tissue and presents the larvae to enemies and promotes desiccation (Doss et al., 2000). Interestingly, formation of neoplasms strongly depends on the presence of the dominant wild-type allele, Neoplastic pod (Np), in the host plant genotype (Dodds and Matthews, 1966). Moreover, application of bruchins initiated the induction of CYP93C18, a putative isoflavone synthase gene, and the formation of the isoflavonoid phytoalexin pisatin (Cooper et al., 2005). ...
During their long, approximately 350 million-year pe- riod of coexistence, plants, insects, and other arthropods evolved a variety of different interactions (Gatehouse, 2002). Some interactions can be beneficial for the plant, as in the case of insect-mediated pollination or seed dispersion, and others are deleterious, as in the case of attack by herbivorous insects (Fig. 1). To successfully combat aggressors, plants must be equipped with a sophisticated sensory system to perceive signals fast and efficiently from their environment and thereby de- tect potential enemies and subsequently translate and integrate such signals into appropriate biochemical and physiological responses. Thus, upon attack, a number of reactions are detectable in plant cells, including changes in ion flux and protein phosphorylation, formation of reactive oxygen species and oxylipins, as well as initia- tion of various defense reactions in the host plant (Kessler and Baldwin, 2002; Maffei et al., 2007b). Intriguing questions arising from these observations are how plants recognize the particular herbivores, what kinds of signals are involved, how such signals are perceived, and how they are converted into downstream signaling pathways involved in plant defense activation. Signal perception in the plant cell may rely on the presence of specific receptors for chemical signals or on general recognition processes based on localized tissue injuries. In principle, the feeding process combines two sites of the same coin: mechanical wounding of the infested tis- sue and introduction of oral secretions that are delivered from the feeding organism into the wounded tissue (i.e. the attacked plant is challenged by both a mechanical as well as a chemical stimulus). This Update introduces herbivore-derived metabolites, which represent seri- ous candidates for signaling compounds; we will also discuss advances in herbivore recognition, namely, the perception of insect-derived signals by specific binding proteins. The properties of these binding proteins sug- gest their involvement in signal perception.
This chapter discusses the physiological aspects of tumor formation in interspecies hybrids. An interspecific incompatibility in some crosses of Bryophyllum and of Gossypium leads to tumorous growth of hybrid shoots. Neoplasia can affect practically all plant organs besides the roots and shoots. Genetic studies on these plants have shown that tumor expression is controlled in inheritance by a single dominant gene (Frs) from L. chilense, which is often deficient in transmission. Tissue culture studies have shown that genetically tumorous and nontumorous segregants of tomato can be distinguished by their growth patterns in various culture media supplemented with nutrients and phytohormones. Tumor formation in these hybrids usually occurs at a mature stage in plant development but can be accelerated or repressed by chemical treatment. The physiological and biochemical processes underlying tumorigenesis are reflected in the persistent activation of normally repressed biosynthetic systems. The enhanced activity of growth factors, enzymes, and cell metabolites in tumorous plants and tissues provides evidence for an increased biosynthetic capacity in neoplastic cells.
Experimental evidence has shown that all forms of peas previously described as species have a diploid chromosome number of 14, that no sterility barriers exist, and that gene exchange is complete. The genus Pisum is therefore best regarded as monospecific in accordance with Lamprecht’s (1966) view. He classified the different forms as ecotypes included under Pisum arvense Linné, the wild-growing form of the two described by Linné. The ecotypes abyssinicum Braun; arvense (Linné) Lamprecht (including elatius Steven, jomardi Schrank, and transcaucasicum Stankov); fulvum Sibthorp and Smith; and humile Boissier (including syriacum/Berger/Lehmann) occur as wild-growing populations. All man-made genetic variations were collected together under the name sativum, the domesticated race. This system of classification is practical and workable, though perhaps not taxonomically orthodox. Pisum formosum Steven, which is a tuber-forming perennial, was separated to form the genus Alophotropsis (Boissier) Lamprecht.
Plant cells cultured in vitro normally need an exogenous supply of plant hormones, namely an auxin and/or a cytokinin, for continued growth. Sometimes the cells lose this requirement during subculturing and become able to grow on hormone-free medium or on medium that lacks one or other of the hormones. This phenomenon is called as auxin habituation. The chapter presents the phemomena of habituation and genetic tumors as systems that allow the interconversion of two different states (normal and tumorous) without any apparent genetic modification. With respect to reversion from a tumorous to a normal state, there are a few reports in the case of crown gall and hairy root induced by Agrobacterium infection. In these cases, evidence for methylation and subsequent inactivation of genes in the T-DNA have been presented. Similar modifications of genes may occur in genetic tumors, but the modification reactions must be much more rapidly reversible than methylation. In the case of habituation, reversibility to a normal, hormone-requiring state is reduced during subcultures. This is the case in decreases of organforming capacity and also in increases in the variability of regenerated plants.
Field pea (Pisum sativum L. subsp. sativum) is an important agricultural crop worldwide, as a main source of protein in human diet and as animal fodder. In Ethiopia, it is the second most important legume crop next to faba bean (Vicia faba L.). However, the production is threatened by pea weevil (Bruchus pisorum L.), which is a rapidly spreading insect pest throughout the country. During June–October 2011, a total of 602 pea accessions from Ethiopia were screened for pea weevil resistance at three field sites in Ethiopia. From this trial, accessions with relatively low mean percent seed damage (PSD) were selected and evaluated during June-October 2012 in replicated trials. Some genotypes from the selected accessions were also studied under greenhouse conditions for up to three generations. Both in the field and greenhouse trials, a significant level of variation in PSD were observed among accessions/genotypes. However, a few of them showed relatively consistent results across sites and years. The gene bank accessions 32454 and 235002 had consistently <40 % PSD. These accessions had 17 and 33 % PSD, respectively, at a site where the highest and overall mean PSD were 92 and 75 %, respectively. Also, promising genotypes with consistently low levels of seed damage were identified in accessions 226037 and 32410. The incorporation of such promising accessions/genotypes into pea breeding programs may lead to the development of field pea varieties with enhanced resistance against pea weevil and consequently contribute to sustainable field pea production in Ethiopia and beyond.
TheNp mutant of pea (Pisum sativum L.) is characterized by two physiological responses: growth of callus under pea weevil (Bruchus pisorum L., Coleoptera: Bruchidae) oviposition on pods, and formation of neoplastic callus on pods of indoor-grown plants. Although these two responses are conditioned byNp, they are anatomically and physiologically distinguishable, based on sites of origin, distribution pattern, and sensitivity to plant hormones. Further characterization of the response to extracts of pea weevil showed that response of excised pods, measured by callus formation, was log-linear, and treatment with as little as 10−4 weevil equivalents produced a detectable response. Mated and unmated females contained similar amounts of callus-inducing compound(s), and immature females contained significantly less of the compound(s). Female vetch bruchids (Bruchus brachialis F., Coleoptera: Bruchidae), a related species, contained callus-inducing compound(s), but usually less than pea weevils on a per weevil basis. Males of both species contained less than 10% of the activity of the mature females. Extracts of female black vine weevils, a nonbruchid species, did not stimulate callus formation. Based on partitioning and TLC analysis, the biologically active constitutent(s) was stable and nonpolar. Thus, theNp allele probably conditions sensitivity to a nonpolar component of pea weevil oviposition as a mechanism of resistance to the weevil.
Summary The development of the neoplasm of the pea pod has been examined by electron microscopy. The subsidiary cells of the stomata are the site of neoplastic development, and the earliest signs of tumour growth are the accumulation of lipid material in these cells and a decrease in the degree of their vacuolation. Mitosis in these cells gives rise to a population of neoplastic cells similar in structure to normal parenchyma. The only structural abnormality which persists in mature neoplastic tissue is the degeneration of the plastids. The chloroplasts of the original subsidiary cells undergo a continuous series of degenerative changes involving loss of photosynthetic function. The mode of development of the neoplasm and the ultrastructural changes associated with it are discussed in relation to other plant tumours.
Pea weevil (Bruchus pisorum L.) oviposition on pods of specific genetic lines of pea (Pisum sativum L.) stimulates cell division at the sites of egg attachment. As a result, tumor-like growths of undifferentiated cells (neoplasms) develop beneath the egg. These neoplasms impede larval entry into the pod. This unique form of induced resistance is conditioned by the Np allele and mediated by a recently discovered class of natural products that we have identified from both cowpea weevil (Callosobruchus maculatus F.) and pea weevil. These compounds, which we refer to as "bruchins," are long-chain alpha,omega-diols, esterified at one or both oxygens with 3-hydroxypropanoic acid. Bruchins are potent plant regulators, with application of as little as 1 fmol (0.5 pg) causing neoplastic growth on pods of all of the pea lines tested. The bruchins are, to our knowledge, the first natural products discovered with the ability to induce neoplasm formation when applied to intact plants.
The regulation of nonpathogenic tumorous growths on tomato plants by red and far-red radiation was studied using leaf discs floated on water and irradiated from beneath. It was found that red light (600-700 nanometers) was required for the induction of tumors on tomato (Lycopersicon hirsutum Humb. & Bonpl. Plant Introduction LA 1625), while both blue (400-500 nanometers) and green (500-600 nanometers) light had little effect on tumor development. Detailed studies with red light demonstrated that tumor development increased with increasing photon flux and duration, though duration was the more significant factor. It was observed that tumor development could be prevented by the addition of far-red irradiance to red irradiance or by providing far-red irradiance immediately following red irradiance. The effectiveness of red and far-red irradiance in the regulation of tumor development indicates phytochrome involvement in this response. These findings should provide additional insight into the multiplicity of physiological factors regulating the development of nonpathogenic tumorous growths in plants.
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to the problem of the origin of cultivated peas. Essay II.
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radiant flux and radiant flux density in irradiation of plants
with artificial light. Jour. Hort. Sci. 28:177-184. 1953.
2. GOVOROV, L. I. The peas of Abyssinia. A contribution
to the problem of the origin of cultivated peas. Essay II.
Bot. Genet. Sdek. 24:399-431. 1930.
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