Types Of Plant Organs Research Articles

Antimicrobial Activity of Excoecaria Agallocha Mangrove Extract in Inhibiting the Growth of Aeromonas Hydrophila by in-Vitro

One of the bacterial diseases that often attack freshwater fish is the red-sore disease, also known as aeromoniasis or Motile Aeromonas Septicemia (MAS). It is caused by bacteria from Aeromonas genus, such as Aeromonas hydrophila. A safe alternative treatment for pathogenic bacteria is the use of antibacterial compounds made from natural ingredients. The Excoecaria agallocha mangrove extract is one of potential alternatives that is useful as natural antimicrobials due to its various contents of antibacterial bioactive compounds. The objective of this study was to determine the antimicrobial activity of E. agallocha mangrove extract in inhibiting the growth of A. hydrophila. The research method was experimental with complete randomized design and factorial pattern of 3 factors (type of plant organ, bacterial strain, and concentration of extract), in 48 treatments and 3 replications. The solvents used consisted of methanol (polar) and n-hexane (non-polar). The plant organs used included leaves and stems. The bacterial strains consisted of GPl-04, GB-01, GL-01, GL-02, GJ-01, and GK-01 with concentrations of leaves and stems extracts of 0, 10, 20, and 30%. The parameter measured was the diameter of inhibition zone, which was done by using disc paper (Kirby Bauer method). Non-parametric Kruskall-Wallis Test and qualitative-descriptive data analysis were applied. The methanol extract of E. agallocha leaves in GJ-01 strain at 10 and 20% concentrations had antimicrobial activity with inhibition zone in 2.55 mm and 2.46 mm, respectively. The n-hexane extract of E. agallocha stem at 20 and 30% concentrations had antimicrobial activity with inhibition zones of 1.88 mm in GPl-04 strain and 1.58 mm in GB-01 strain, respectively. Extract of E. agallocha mangrove exhibited potential as a natural antibacterial to prevent aeromoniasis in fish.

TISSUE-SPECIFIC RESPONSES IN SOYBEAN PLANTS EXPOSED TO CADMIUM

Cadmium seriously affects plant growth, development, homeostasis and yield production. The effect of two doses of cadmium (10 and 100 mg.kg-1 Cd2+) on plants of sensitive soybean variety (Glycine max L. cv. Kyivska 98) were studied after short treatment in a pot experiment. Several parameters were determined in roots and leaves, including cell viability, the content of malondialdehyde and proline, and activity of defense proteins (catalases, guaiacol peroxidases, ascorbate peroxidases, superoxide dismutases, chitinases, β-1,3-glucanases). Changes caused by cadmium depended both on the concentration of cadmium, as well as on the type of plant organ and its developmental stage. Soybean tissues generally showed low levels of oxidative stress and reduced proline content likely due to activity or depletion by different mechanisms (respectively). The activity of catalases and guaiacol peroxidases was inhibited by cadmium concentrations only in younger leaves. The enzymatic activities of superoxide dismutases, chitinases and β-1,3-glucanases were highly variable depending on the cadmium concentration as well as the soybean organ analyzed. Our experiments revealed differences in defense strategies and regulatory mechanisms between plant organs as well as developmental stages of leaves in response to cadmium toxicity.

Soil pH influences the organic acid metabolism and exudation in cluster roots of Protea species from the Mediterranean-type fynbos ecosystem, Western Cape, South Africa

In nutrient-poor ecosystems, certain plant families have evolved specific adaptations for phosphate acquisition, namely cluster roots or proteoid roots. Cluster rooted species have a unique suite of adaptations that enable them to survive in nutrient poor ecosystems, such as the Fynbos biome of South Africa. The Fynbos biome has heterogeneous soils which caused radiation of varying soil pH within small localised areas. Previous studies on cluster rooted species ignored the possibility that cluster root functioning may differ at varying soil pH levels and soil types. Therefore, two native Fynbos protea species, Protea cynaroides (L.) L. and Protea obtusifolia H.Buek ex Meisn. were compared to assess the impact of different soil pH levels on organic acid metabolism and exudation in cluster rooted species. Our results show that cluster roots of the acidic-soil grown P. cynaroides is more effective and more efficient than that of the alkaline-soil grown P. obtusifolia. Our findings indicated that the mechanisms for P acquisition vary greatly, depending on substrate and plant organ type. This suggested that the metabolism of each species is adapted to specific soil pH and that these species have evolutionary adapted their P acquisition mechanisms for these extreme soils. The limited nutrient availability and variation in soil pH South African soils has led to various localised adaptations for cluster rooted species.

Fungal Communities in the Native New Zealand Medicinal Plant Pseudowintera colorata (Horopito) Are Determined by Plant Organ Type and Host Maturity with Key Members Promoting Plant Growth.

The plant Pseudowintera colorata is well known for its antimicrobial and medicinal properties and is endemic to New Zealand. Using PCR-Denaturing gradient gel electrophoresis (DGGE), we investigated the factors influencing the composition of endophytic fungal communities in P. colorata from ten distinct sites across New Zealand. Our results showed that plant organs of P. colorata influenced the diversity and richness of endophytic fungi (PERMANOVA, p < 0.05). In addition, plant maturity and its interactions revealed that endophytic fungal communities formed discrete clusters in leaves, stems, and roots of mature and immature P. colorata plants (PERMANOVA; p = 0.002, p = 0.001 and p = 0.039, respectively). For identifying isolates with biocontrol potential, dual culture tests were set up against four different phytopathogenic fungi. Isolates with high activity (zone of inhibition > 10 mm) were sequenced and identified as Trichoderma harzianum, Pezicula neosporulosa, Fusarium tricinctum, Metarhizium sp., and Chaetomium sp. Applying selected endophytic fungi (n = 7) as soil drenchers significantly increased the growth of P. colorata seedlings and produced more internodes. Seedling shoots treated with Trichoderma sp. PRY2BA21 were 2.2 × longer (8.36 cm) than the untreated controls (3.72 cm). Our results elucidate the main plant factors influencing fungal community composition and demonstrate a role for endophytic fungi in P. colorata growth and further demonstrate that medicinal plants are a rich source of endophytes with potential as biocontrol agents.

Arsenic-induced oxidative stress in Brassica oleracea: Multivariate and literature data analyses of physiological parameters, applied levels and plant organ type

Plant redox homeostasis governs the uptake, toxicity and tolerance mechanism of toxic trace elements and thereby elucidates the remediation potential of a plant. Moreover, plant toxicity/tolerance mechanisms control the trace element compartmentation in edible and non-edible plant organs as well as the associated health hazards. Therefore, it is imperative to unravel the cellular mechanism involved in trace element toxicity and tolerance. The present study investigated the toxicity and tolerance/detoxification mechanisms of four levels of arsenic (As(III): 0, 5, 25 and 125µM) in Brassica oleracea under hydroponic cultivation. Increasing As levels significantly decreased the pigment contents (up to 68%) of B. oleracea. Plants under As stress showed an increase in H2O2 contents (up to 32%) in roots while a decrease (up to 72%) in leaves because As is mostly retained in plant roots, while less is translocated toward the shoot, as evident from the literature. Arsenic treatments caused lipid peroxidation both in the root and leaf cells. Against As-induced oxidative stress, B. oleracea plants mediated an increase in the activities of peroxidase and catalase. Contradictory, the ascorbate peroxidase and superoxide dismutase activities slightly decreased in the As-stressed plants. In conclusion and as evident from the literature data analysis, As exposure (especially high level, 125µM) caused pigment toxicity and oxidative burst in B. oleracea. The ability of B. oleracea to tolerate As-induced toxicity greatly varied with applied treatment levels (As-125 being more toxic than lower levels), plant organ type (more toxicity in leaves than roots) and physiological response parameter (pigment contents more sensitive than other response variables). Moreover, the multivariate statistical analysis appeared to be a useful method to estimate plant response under stress and trace significant trends in the data set.

Detection and annotation of plant organs from digitised herbarium scans using deep learning.

As herbarium specimens are increasingly becoming digitised and accessible in online repositories, advanced computer vision techniques are being used to extract information from them. The presence of certain plant organs on herbarium sheets is useful information in various scientific contexts and automatic recognition of these organs will help mobilise such information. In our study, we use deep learning to detect plant organs on digitised herbarium specimens with Faster R-CNN. For our experiment, we manually annotated hundreds of herbarium scans with thousands of bounding boxes for six types of plant organs and used them for training and evaluating the plant organ detection model. The model worked particularly well on leaves and stems, while flowers were also present in large numbers in the sheets, but were not equally well recognised.

A multivariate analysis of comparative effects of heavy metals on cellular biomarkers of phytoremediation using Brassica oleracea

The biochemical/physiological variations in plant responses to heavy metals stress govern plant’s ability to phytoremediate/tolerate metals. So, the comparative effects of different types of heavy metals on various plant responses can better elucidate the mechanisms of metal toxicity and detoxification. This study compared the physiological modifications, photosynthetic performance and detoxification potential of Brassica oleracea under different levels of chromium (Cr), nickel (Ni) and selenium (Se). All the heavy metals induced a severe phytotoxicity to B. oleracea in terms of chlorophyll contents, Ni being the most toxic (76% decrease). Brassica oleracea showed high lipid oxidation: 87% and 273%, respectively in leaves and roots. Furthermore, all the metals increased the activities of catalase and peroxidase, while decreased superoxide dismutase and ascorbate peroxidase. Interestingly, heavy metals decreased hydrogen peroxide contents perhaps due to their possible transformation to another form of reactive oxygen species such as hydroxyl radical. Among the three metals, Ni was more phytotoxic than Cr and Se. Moreover, the phytoremediation/tolerance potential of B. oleracea to Ni, Cr and Se stress varied with the type of metal, their applied levels, response variables and plant organ type (root/shoot). The multivariate analysis separated different plant response variables and heavy metal treatments into different groups based on their correlations.

Characterization and comprehensive analysis of the ecological interaction networks of bacterial communities in Paullinia cupana var. sorbilis by 16S rRNA gene metabarcoding.

Endophytes improve the host performance in areas of high plant endemicity. Paullinia cupana is an Amazonia plant species of economic and social importance due to the high caffeine concentration in its seeds. An interesting strategy to identify endophytic microorganisms with potential biotechnological application is to understand the factors that influence the endophytic community to rationalize the host management programs. We used the next-generation sequencing for bacterial 16S rRNA gene to examine how the P. cupana organ, genotype, and geographic location influenced its endophytic bacterial community. We obtained 1520 operational taxonomic units (OTUs) distributed in 19 phyla, 32 classes, 79 orders, 114 families and 174 genera. The P. cupana roots and leaves were specifically colonized by the bacterial genera Acidothermus and Porphyromonas, respectively, with high relative frequency. The plant organ type influenced the endophytic community's richness, diversity, OTUs composition, relative abundance of phyla and genera, and genera interaction network. However, the host plant genotype and geographic location influenced the composition and interaction among genera in the network analysis. Prevotella is a super-generalist genus in the interaction network of endophytic bacteria of P. cupana. This study revealed endophytic bacterial groups of importance to P. cupana and stressed that the host plant organ modulates the structure and interactions within this community. Our results indicated that the microbial community adapted to colonize P. cupana by adjusting to its composition and interaction network. The isolation of abundant and super-generalist bacterial genera shall help to examine their functionality to the composition and fitness of the endophytic community of P. cupana.

Saprotrophic survival of Magnaporthe oryzae in infested wheat residues

Wheat blast caused by Magnaporthe oryzae is a relatively new disease that has caused considerable losses in wheat fields of several South American countries, including Brazil. The 2016 report of wheat blast occurrence in Bangladesh raised concern in South Asia where wheat represents a significant crop. The sources of primary inoculum and survival from season to season of the fungus remain largely unknown. The effect of wheat residues on the onset of blast epidemics and the potential for survival of M. oryzae in the residues were studied under subtropical climatic conditions, in the South of Brazil. The objective of this study was to monitor the saprotrophic development of M. oryzae on wheat debris and explore the relative importance of crop residues as a source of inoculum. The wheat cultivars BRS 229 and Anahuac 75, moderately and highly susceptible to the disease, respectively, were inoculated with a spore suspension of 10−5 conidia mL−1 using an aggressive (Py 12.1.209) and a less aggressive (Py 12.1.132) isolate. At maturity, a portion of leaves, stems and spikes were detached from plants, and a group of ten lesions were randomly selected and marked on each type of plant organ. The air-dried plant organs were placed separately inside bags and exposed outside. The experiment was conducted over three different time intervals. Each 14 days, samples were taken from the field and tested for sporulation. The survival of the blast fungus decreased rapidly on the rachis when compared to stems and leaves. Sporulation of the fungus was observed on the wheat residues for up to five months. Based on the results of this study, the possibility that the causal agent of wheat blast survives under Brazilian conditions from one crop to another in wheat residues is very low. The management of crop residues is not a key point to control the development of wheat blast. A strong emphasis should be placed on the presence of other hosts.

P 113 - Antioxidant activity of Crataegus Monogyna L flowers

Crataegus species are known by their biological effects for many years. Crataegus monogyna Jacq. flowers have been ethnomedically used in different parts of Turkey for their many biological effects such as against tachycardia and sedative, antihypertensive, antispasmodic and diuretic. In addition to the widespread use of Crataegus species, many pharmacopoeias and monografts are registered, and a large number of in vitro, in vivo and clinical studies have been carried out with respect to bioactivity and mechanism of action. In vitro, leaves and fruits of Crataegusspecies have also been shown to exhibit antioxidant. However, these properties are influenced by the type of plant organ, the harvest season, the species and the geographical origin. In this contex, different extracts of ripe flowers of Crataegus monogyna (CM) collected from natural habitats on the limit of Konya/Seydisehir-Turkey at September 2015 were evaluated for their antioxidant capacity. Rutin contents was determined as 2.68 μg/ml in ethanolic extract of Crataegus monogyna Jacq., % ABTS· radical scavenging activity of the extract is 78.80±4.09 and 1.080±0.08 μg trolox/mg extract in CUPRAC method. In conclusion, the results of this study indicate that flowers of Crataegus monogyna provide considerable antioxidant protection and can be suitable raw material for the medicine, food and cosmetic industries.

Phenotypic and genetic characterization of Pseudomonas syringae strains associated with the recent citrus bacterial blast and bacterial black pit epidemics in Tunisia

In the spring of 2012, symptoms of a disease resembling citrus blast and citrus black pit were observed in some orchards in Tunisia. The epidemic spread rapidly in the following years. Twenty‐four commercial citrus orchards from four Tunisian regions showing characteristic symptoms of bacterial diseases were surveyed during a 3‐year study. Eighty‐eight Pseudomonas‐like bacterial isolates were successfully obtained from the northeast and west of Tunisia. No isolates were recovered from the central region. Overall, 46 isolates were identified as Pseudomonas syringae pv. syringae and most of them showed similar phenotypic and genetic profiles. The virulence of three selected isolates differed from one plant cultivar to another as well as from the type of plant organ used for the inoculation. In a bioassay test, all isolates produced syringomycin, which was confirmed by molecular detection based on the syrB and syrD genes. Only EC122 possessed syrD but not syrB. DNA fingerprints, based on repetitive sequence‐based polymerase chain reaction (rep‐PCR) and PCR melting profile (PCR MP), were used to determine the potential genetic diversity among strains. Clustering of PCR MP fingerprinting data matched with rep‐PCR fingerprinting data. The generated distribution tree showed that Tunisian isolates were closely related to the citrus reference strain LMG5496. In contrast, EC112, isolated from citrus, and the almond isolate EC122 were distantly related to the type strain LMG1247T isolated from lilac. Such studies have not been reported until now for P. syringae from citrus.

Experimental Evaluation of the Performance of Local Shape Descriptors for the Classification of 3D Data in Precision Farming

Object classification in high-density 3D point clouds with applications in precision farming is a very challenging area due to high intra-class variances and high degrees of occlusions and overlaps due to self-similarities and densely packed plant organs, especially in ripe growing stages. Due to these application specific challenges, this contribution gives an experimental evaluation of the performance of local shape descriptors (namely Point-Feature Histogram (PFH), Fast-Point-Feature Histogram (FPFH), Signature of Histograms of Orientations (SHOT), Rotational Projection Statistics (RoPS) and Spin Images) in the classification of 3D points into different types of plant organs. We achieve very good results on four representative scans of a leave, a grape bunch, a grape branch and a flower of between 94 and 99% accuracy in the case of supervised classification with an SVM and between 88 and 96% accuracy using a k-means clustering approach. Additionally, different distance measures and the influence of the number of cluster centres are examined.

Study on the chemical composition and antioxidant activity of extracts from shoot culture and regenerated plants of Scutellaria altissima L.

The flavonoid (baicalin, wogonoside, luteolin, luteolin-7-glucoside) and verbascoside contents of Scutellaria altissima in both shoot cultures, and the shoots and roots of micropropagated plants grown in the greenhouse for 12 weeks or in the field for 2 years were determined. The level of secondary metabolites was found to be strongly affected by the age and type of plant organ. A comparative analysis of S. altissima plants propagated in vitro and from seeds revealed no differences in the level of secondary metabolites when plants of the same age were studied. The antioxidant potential of methanolic extracts from shoot cultures, and the shoots and roots of S. altissima plants propagated in vitro, were evaluated using ABTS radical scavenging, FRAP metal reduction power and the lipid peroxidation test, in relation to the content of baicalin, wogonoside, verbascoside, total phenolic and total flavonoid compounds. Extracts from the roots of field-grown regenerated plants at the flowering stage were found to possess the strongest antioxidant activity. Correlation analysis revealed that the antioxidant activity of extracts correlated most closely with their total phenolic content estimated by the Folin-Ciocalteu method.

Starch mobilization in leaves.

Starch mobilization is well understood in cereal endosperms, but both the pathway and the regulation of the process are poorly characterized in other types of plant organs. Arabidopsis leaves offer the opportunity for rapid progress in this area, because of the genomic resources available in this species and the ease with which starch synthesis and degradation can be monitored and manipulated. Progress in understanding three aspects of starch degradation is described: the role of disproportionating enzyme, the importance of phosphorolytic degradation, and new evidence about the involvement of a starch-phosphorylating enzyme in the degradative process. Major areas requiring further research are outlined.

Phenology of Growth and Resource Deployment in Alexgeorgea nitens (Nees) Johnson and Briggs (Restionaceae), a Clonal Species From South-Western Western Australia

Seasonal patterns are described for growth and partitioning of dry matter and selected nutrients between different age classes and types of plant organs of ramets of non-reproductive, presumed female clones of Alexgeorgea nitens in native sandplain habitat at Eneabba, south-western Western Australia. New rhizome extension and associated production of new culms and nodal roots are initiated following onset of rain in autumn. Rate of growth of these parts remains slow through winter, peaks in spring and early summer and then becomes much reduced in the hot, dry summer. The bulk (87%) of the season's dry matter increment of new ramet parts is estimated to be derived from current photosynthesis, the remaining 13% by mobilisation of dry matter from older parts of the ramet, especially from 1- and 2-yearold culms. Growth of new organs is severely reduced by removal or shading of culms at the beginning of the season. Older culms and rhizomes carry substantial starch reserves, but mobilisation of this reserve accounts for 2% at most of the dry matter gain of new organs of intact ramets, 19% of that of shaded and 65% of detopped ramets. A substantial fraction of the starch pool of a rhizome segment normally remains until its senescence, possibly as a long-term energy reserve, utilisable after destruction of above-ground parts by fire or grazing. Concentrations of N, P, K, Ca and Mg in organ dry matter of A. nitens are generally very low in comparison with species other than those Cyperaceae or Restionaceae from similar habitats. There is no evidence of preferential storage in below-ground parts, and efficiencies of emptying of nutrient reserves from senescing ramet parts are not high. Mobilisation from older source organs of ramets of intact, unstressed clones is estimated to provide 14% of the new organ's seasonal gain of P, 16% of Mg, 21% of Ca, 22% of N and 58% of K. Annual factorial increases of a ramet in the studied nutrient elements range from 1.3 (for K) to 2.4 (for P), indicating flexibility in exploiting sources of different nutrients as their respective availabilities change from season to season.

Developments in the chemistry and biochemistry of pectic and hemicellulosic polymers.

Improved methods of isolation and analysis of cell walls from a range of plant tissues have shed new light on the structure of the constituent polymers, and have also helped to clarify some of the conflicting opinions on their mode of occurrence and association within the walls. The chemistry (and biochemistry) of pectic and hemicellulosic polymers in different types of plant organs is outlined, with particular emphasis on parenchymatous and immature tissues. The following aspects are discussed: the mode of occurrence of arabinans, galactans and arabinogalactans, and the possible association of some of them with proteins; the structural features of the esterified rhamnogalacturonans and associated neutral sugar residues in the pectic substances of middle lamellae and primary cell walls; the occurrence of acidic xylans, acidic arabinoxylans, and acidic arabinoxylans in association with other polymers in the cell walls of cambial, suspension-cultured and parenchymatous tissues of dicotyledons; evidence for the occurrence of small but significant amounts of xyloglucans in association with other polymers, and the occurrence of a range of xyloglucans in parenchymatous tissues; evidence for the occurrence of phenolic ester and phenolic cross-linkages between the cell wall polymers of parenchymatous tissues of both dicotyledons and monocotyledons, particularly the association of hydroxycinnamic acids with some pectic substances; the occurrence of proteoglycans and proteoglycan-polyphenol complexes and their relationship to the traditional hemicelluloses; and some aspects of the non-cellulosic polymers of non-endospermic and endospermic seeds.

Foliar and twig macronutrients (N, P, K, Ca and Mg) in selected species ofEucalyptus used in rehabilitation: sources of variation

The macronutrient variation within four 6 year oldEucalyptus saligna and four 5 year oldE. wandoo growing on rehabilitated bauxite pits was determined. Significant differences in mean nutrient concentrations were generally recorded between good soil condition sites and poor soil sites, between tree individuals, branch height, and plant organ type; but mean nutrient values were not different among canopy aspects. Fully expanded leaves of the current year provided the most uniform nutrient levels among the plant organs and showed major differences between sites with good soil nutrient conditions and those with poor conditions. Differences in foliar and branch levels of N, P, K, Ca and Mg, the variation between sites, canopy heights and plant organ types, and the use of foliar nutrient levels to indicate deficiencies are discussed.

Amino Acid Sequences of Cytochrome C and Plastocyanins in Phylogenetic Studies of Higher Plants

Boulter, Donald (Dept. of Botany, University of Durham, Durham, England) 1974. Amino Acid Sequences of Cytochrome c and Plastocyanins in Phylogenetic Studies of Higher Plants. Syst. Zool. 22:549-553.-The yields of cytochrome c from different types of plant organs is given and the use of cytochrome c sequence data for phylogenetic studies is briefly discussed. Sequences of cytochrome c of nineteen angiosperm species and a gymnosperm have been used to construct a molecular tree. This tree is discussed in relationship to existing phylogenetic schemes. The preliminary results of investigations on plastocyanin are mentioned. During the last two decades, chemical data on plants have accumulated at an ever increasing rate. Much of this data is now being collected in a way which is useful to systematists and is being critically evaluated by them. Macromolecular data on plants are still sparse however, and consequently there has not been very much debate as to their relevance for systematics. The present paper briefly presents the methods used by the Durham group and their latest results; these are discussed in relationship to the major phylogenetic schemes. Species and gene phylogenies are constructed by using homologous proteins, i.e., those specified by genes with a common ancestor. However, in assembling a set of protein sequences to be compared, it is necessary first of all to establish that they are a homologous set; similarities between sequences may also arise during evolution, either because of convergence of unrelated proteins, due to similar residues in the sequences having a common function, or because of chance. For the plant cytochromes discussed in the present paper, homology has been established, (1) by the use of the semi-rigorous methods devised by Fitch and his co-workers (Fitch and Margoliash, 1967a; Fitch and Markowitz, 1970), and (2) by constructing a model of plant cytochromes c using the a-carbon x-ray diffraction data of horse heart and bonito ferricytochrome c obtained by Dickerson et al. (1971), in conjunction with the sequences of fourteen plant cytochromes. This model indicates that the three-dimensional structure of plant cytochromes c is essentially the same as that of animal cytochromes c. Since about thirty residues are essential for function, the only reason the other seventy or so residues should occupy the same three-dimensional space in the different plant and animal molecules, is by virtue of their common ancestry. The proof of this suggestion must await the accurate determination of the three-dimensional structure of plant cytochrome c by x-ray diffraction methods. Klein and Cronquist (1967) have classified c-type cytochromes into three groups: firstly, those with low redox potentials, which function in anaerobic energy-yielding reactions as reductases; secondly, those with higher redox potentials which function in photo-reductive processes, such as photosynthesis; and thirdly, those which function in aerobic energy-yielding reactions. These types can usually be distinguished one from another by their a-absorption spectra, molecular weights and redox potentials, although in the procaryotes (blue-green algae and bacteria) the relationship of different c-type cytochromes is not always clear, and probably will not be so until more sequences have been determined. Cytochromes from two different groups cannot be used to construct species phylogenies, thus, the cytochrome sequences dis-

Analytic studies in plant respiration. I.—The respiration of a population of senescent ripening apples

Of all protoplasmic functions, the one which is, by tradition, most closely linked with our conception of vitality is the function for which the name of respiration has been accepted. It might, therefore, well be expected that every variation of the intensity of the metabolic activity of a cell would be correlated with some change in the respiration of that cell. Before we can decide whether respiration really holds this position as an index of the integrated activities of the cell, we need to accumulate respiration date for different types of plant organs throughout their life-history of development, maturity and senescence. These date must then be examined critically with the hope of establishing the nature of the major and minor determinants of the variations of intensity of respiration. No such collection of data has yet been published. The present paper aims at making a contribution to this collection and other contributions should follow. A good deal of work has already been carried out in the Cambridge Botany School upon respiration of evergreen leaves, which continue to exist in a state of maturity for very long periods of time. In striking contrast with this type of organ is the type of the ripening fruit. The natural biology of the two is so different that it is obviously of importance to establish whether the same fundamental principles are manifest in both. In the ripening fleshy fruit, senescence is the dominant stage of ontogeny. The fruit of the apple, which possesses such striking keeping properties, is most suitable for investigation, since it runs through its ripening senescence at a slow rate.