Stage Of Physiological Development Research Articles

Influence of the Nut's Internal Oxygen Partial Pressure on the Induction of Pigmentation in the Kernels of Pecan1

Abstract The O2 and CO2 concentration between the shuck and shell and within the nut of individual pecans (Carya illinoensis (Wang.) K. Koch cv. Stuart) was monitored over a 4 week period from predehiscence to post-dehiscence. Internal O2 levels increased after dehiscence from initial concentrations of 16-17% to near that of the external environment after 3 weeks. Internal CO2 concentration, conversely, decreased substantially after dehiscence. Treatment of nuts over the same physiological stages of development with 2.5, 5.0, 10.0, 21.0 and 100% O2 had little effect on the induction and development of the kernel's normal pigmentation. Both high and low O2 levels did, however, produce some discoloration after 21 days of treatment. Changes in the internal nut O2 partial pressure are apparently not a significant factor in the induction and development of the normal complement of pecan kernel pigments during fruit maturation.

Varietal Response of Burley Tobacco to Stage of Physiological Development when Topped1

AbstractLittle is known about the effects of stage of physiological development at which the plants are topped on early vs. late flowering cultivars of burley tobacco (Nicotiana tabacum L.). Four cultivars with a range of 18 days in flowering were topped at different stages of development to determine the optimum topping date for specific cultivats, whether discrimination would exist if all cultivars were topped simultaneously, and whether or not it would be feasible to use an extremely late‐flowering cultivar commercially.Topping ‘MS Burley 37 × LS’ or ‘Burley 37’ earlier than full bloom, ‘Burley 49’ later than 50% bloom, or ‘Burley 64’ later than button stage did not increase yield significantly. Percent total N and percent total alkaloids in leaf from plots of the respective cultivars topped at these stages were within normally accepted ranges. Thus, all entries in a variety trial may be topped at the same time without creating undue bias of the estimates obtained. Maximum performance of Burley 64 was obtained when it was topped in the button stage. This indicates that a late flowering cultivar may be grown commercially if it is topped at an earlier stage of development but about the same date as early flowering cultivars.

A rapid micro-starch quantitation method for potato callus and its application with potato tubers

The procedure described was developed as a micro-starch method for potato callus tissue (0.1-0.2% starch on a fresh weight basis) and then evaluated with macro-starch samples of potato tubers harvested during three physiological stages of development. This method consisted of the following steps: (a) a mild alkaline-sonic extraction of starch from lyophilized 80% aqueous ethanol-washed samples, (b) starch hydrolysis of the neutralized, filtered extracts by 1 N HC1, and (c) the determination of liberated glucose by the specific glucose oxidase system. Results with this procedure were as sensitive and accurate (SD ± 0.86%) as with other starch-specific methods with more extensive starch isolation and purification steps.

Methods of quality assessment of seed potatoes

The yielding capacity of the potato depends largely on the quality of the seed. The quality is determined by a number of factors such as absence of pathogens (viruses, fungi, bacteria, nematodes), physiological stage of development, place of origin, authenticity and purity of variety. In addition size-grading and the prevalence of defects, such as malformed or damaged tubers, may affect yielding capacity. Not all the factors mentioned are of equal importance. Since freedom from pathogens counts very much in quality assessment of seed, methods and difficulties in determination of the presence of pathogens will be discussed extensively; whereas size-grading and defects in tubers, caused by handling, effect of cold or frost, green tubers, and necrotic spots caused by spraying herbicides will be excluded from discussion. Neither will the ways of sampling be discussed. One should keep in mind, however, that sample size is determined by the criteria which the seed material must fulfil. For instance, if one diseased tuber is found in a sample of 6600 or 600 tubers there is a 95 probability that the batch of potatoes will not contain more than 0.1 ~ or 1 diseased tubers, respectively. It is clear that samples of a few hundred tubers/ha are too small to give reliable information on the real level of infection. In practice, however, checking of large samples of potato tubers is very difficult. A survey is given of methods of disease assessment in the field during growing season and after lifting. Only the most important diseases are treated. Some remarks are made on the effect of physiological stage of development and of place of origin of seed on yield. Methods to check authenticity are mentioned briefly. Finally, it is pointed out which methods should be developed and improved (see Conclusions). For requirements of the officially recognized grades (basic and certified)of seed in the European Economic Community, see Jacobsen (1973). Before discussing methods of assessment of diseases caused by pathogens it must be pointed out that such assessment has to reckon with: I. The danger of transmission of the disease by the seed tubers to the next crop. 2. The influence of the pathogens on the keeping quality of the seed tubers. The greater the danger of transmission or (and) the influence on keeping quality, the more important the assessment. The danger of transmission is great if the disease is only or mainly tuber-borne as with most virus and several bacterial and fungal diseases. This danger may still be of importance if

Diurnal and Seasonal Trends in Nitrate Reductase Activity in Field Grown Sorghum Plants1

AbstractNitrate reductase activity in plants has been suggested as a sensitive indicator of water stress. We studied nitrate reductase activities in sorghum (Sorghum bicolor L. Moench cv. ‘Pioneer #846’) using in vivo assay and compared activities by leaf position on culms and various positions on leaves — through diurnal and seasonal trends (from stalk elongation to maturity, 1971). We related leaf water potential (measured with pressure bomb) and atmospheric demand for water (solar radiation measured with a pyranometer) with nitrate reductase activity. Nitrate reductase activity was highest in the upper, fully‐expanded leaves — in the flag leaf at the 5.5 stage of physiological development. We also compared relative amounts of hydrocyanic acid in sorghum, which other workers have observed in relation to physiological age, with seasonal nitrate reductase activities. Diurnal water stress (shown as leaf water potential in relation to high solar radiation) lowered nitrate reductase activity. Nitrate reductase activity decreases as plant age and water stress increases and likely decreases as hydrocyanic acid increases.

Effects of Different Initial Cutting Treatments on the Production and Quality of Climax Timothy and Reed Canarygrass1

AbstractTotal yield, aftermath, and total digestible nutrients (TDN) production of perennial grasses when harvested at various physiological stages of development were investigated. The initial harvest of Climax timothy (Phleum pratense L.) and reed canarygrass (Phalaris arundinacea L.) was removed at eight physiological stages of development corresponding to plant heights of 20, 30, 41, 46, 51, 61, 71, and 81 cm.Removal of the initial harvest of timothy when the apical meristem was at a transition stage (plants 30 cm tall) resulted in highest total seasonal yield, aftermath, and TDN/ha. Reed canarygrass, however, produced lowest total seasonal yield and TDN when the initial harvest was removed early, at the first two stages of development. This species was less influenced by initial plant cutting height. Total seasonal aftermath of reed canarygrass varied by only 1,973 kg/ha regardless of when the initial crop was removed. These data indicate a differential response of timothy and reed canarygrass to specific cutting management practices.

Symbiotic Nitrogen Fixation in Soybeans. II. Interrelationship Between Carbon and Nitrogen Assimilation1

Reciprocal intervarietal grafts were made in all root: shoot combinations using seedlings of eight soybean (Glycine max (L.) Merr.) genotypes, grown in sandfilled pots in the greenhouse. After grafting, the plants were inoculated with Rhizobium japonicum (USDA strain #138) and watered with a low‐nitrogen nutrient solution. Two replicate plants of each root:shoot combination were sampled at each of four times, 28, 38, 50, and 58 days after grafting, for photosynthetic rate of leaves; leaf area, shoot and root dry weight; and number, fresh weight, and acetylene reduction activity of nodules.Significant shoot genotype, sampling date, and shoot genotype ✕ sampling date effects occurred for all traits measured. Root genotype effects, independent of the shoot genotype, occurred for all root traits measured, except nodule fresh weight. No overall root effects occurred for any of the shoot traits. Shoot genotype effects were small at the first two sample dates relative to root genotype effects, but were large at the last two sampling dates due to differences in stage of physiological development. Shoot genotype effects on total nodule activity (TNA) per plant were strongly and positively associated with shoot effects on nodule fresh weight, but showed no association with shoot effects on specific nodule activity (SNA). Shoot genotype effects on nodule fresh weight per plant were, in turn, strongly and positively associated with shoot effects on photosynthesis per plant and shoot dry weight. Root genotype effects on TNA per plant were due to inherent differences in SNA.

Water-Yield Relations for Nonforage Crops

This paper examines the relationship between soil moisture stress, evapotranspiration, and marketable yield of crops–where the yield is a reproductive organ or associated product. It is shown that under conditions of constant stress, yield is reduced as a linear function of stress. However, where stress is applied at different stages in the development of the crop, no simple relationship exists. To predict yield from the water available or from evapotranspiration, the severity of stress and the physiological stage of development must be defined. A disproportionate reduction in yield is induced by water stress during the phases of reproduction. This time corresponds to the period of peak evapotranspiration. Therefore, if irrigation engineers cannot plan their systems for times of peak demand, cost-benefit analyses should reflect probable yield reductions.

Assimilation of 14 CO 2 by Catkins of Carya illinoensis and Apparent Translocation to the Pollen

Carbon-14 dioxide and autoradiography were employed to determine if the catkins (staminate inflorescence) of Carya illinoensis Koch ‘Stuart’ are a sink for photosynthates produced by the current season's leaves; to observe 14CO2 assimilation by the catkin at different stages of physiological development; and to determine if photosynthates produced by the catkins are utilized in pollen production. For a brief period in their development, the catkins were a sink for photosynthates produced by the leaves of the current season. The catkins assimilated 14CO2 from time of emergence from the bud until senescence, and photosynthates produced by the catkins were incorporated into the pollen.

ASSIMILATION OF 14CO2 BY CATKINS OF CARYA ILLINOENSIS AND APPARENT TRANSLOCATION TO THE POLLEN

Carbon‐14 dioxide and autoradiography were employed to determine if the catkins (staminate inflorescence) of Carya illinoensis Koch ‘Stuart’ are a sink for photosynthates produced by the current season's leaves; to observe 14CO2 assimilation by the catkin at different stages of physiological development; and to determine if photosynthates produced by the catkins are utilized in pollen production. For a brief period in their development, the catkins were a sink for photosynthates produced by the leaves of the current season. The catkins assimilated 14CO2 from time of emergence from the bud until senescence, and photosynthates produced by the catkins were incorporated into the pollen.

Unification of foetal and neonatal immunology.

By applying age equivalence to available information it is possible to show that the onset of immunocompetence occurs at the same stage of physiological development in all mammals and birds.

Deoxyribonucleic acid content and proliferative activity of rabbit mammary gland epithelial cells

The DNA contents of individual nuclei of rabbit mammary gland epithelial cells at various physiological stages of development were measured with a microspectrophotometer. The results showed the Feulgen nucleal reaction to be a reliable method for quantitative work and reproducible when carried out under standardized and rigidly controlled conditions. The DNA contents of nuclei of the epithelial cells are not equal. Significant differences in DNA content per nucleus were present among individual animals, among glands of the same animal, and among areas within the glands. The proliferative activity of the cells was studied by the administration of tritiated thymidine to the rabbits 1 h before they were sacrificed. Radioautography of the mammary gland tissue was carried out to detect incorporation of thymidine into nuclei that synthesize DNA. It was found that a considerable proliferative activity takes place in the adult virgin rabbit. The largest proliferative activity occurs during the first half of pregnancy. Proliferative activity exists during the second half of pregnancy, but at the slower rate. The activity increases markedly one day prior to parturition, though it is somewhat lower than that during the first part of pregnancy. The high rate of proliferative activity continues during the day of parturition. A sharp drop occurs on the first day of lactation and remains low during lactation. There appeared to be a relationship between the DNA content per nucleus and the secretory activity of the cell. The content was high at times of high secretory activity and low at times of secretory quiescence. An inverse relationship between the proliferative activity and the quantity of DNA per nucleus also existed. The presence of non-genetic DNA in excess to the genetic diploid quantity is suggested. This additional DNA is postulated to be responsible for the increased DNA content per nucleus and may play a role in the secretion process.

Distribution of Soluble Proteins and Enzymes During Early Development of Pisum Sativum

Changes in soluble protein and in peroxidase, esterase, and amylase enzymes during development of the pea plant (P. sativum) have been investigated using a horizontal method of acrylamide gel electrophoresis. Both qualitative and quantitative variation between organs at different stages of physiological development are recorded.

Retardation of Flower Opening in Oenothera lamarckiana caused by Blue and Green Light

IF a plant of Oenothera lamarckiana Ser. is placed in a dark room 1 h before the flowers would have opened outdoors, all the flower buds open within 1 h because they have reached the physiological stage of development which permits them to bloom on the same evening. On the other hand, if the plant is exposed to continuous illumination with white light of sufficient energy there is no flowering as long as the plant is exposed to the light. These phenomena show that light retards the opening of the fully developed flower bud of this plant, and that the opening of the flower of O. lamarckiana has a response to light and dark which is different from the response shown by O. berteriana and several other species of Oenothera1–3. In addition, it was shown that the light sensitive region is located in the flower bud.

THE EFFECT OF RELATING APPLICATIONS OF NITROGEN TO THE STAGE OF DEVELOPMENT OF COCKSFOOT (DACTYLIS GLOMERATA L.) GROWN FOR PRODUCTION OF SEED

An experiment is described in which nitrogen was applied in relation to the physiological stage of development in cocksfoot grown for seed. All applications of N increased the yield of seed, but applying all the N during the phase of autumnal tillering was less effective than applying it at stages of development in spring (beginning of vernal growth, initiation of inflorescences, complete differentiation of inflorescences), or in autumn and spring, because of a decrease in the number of tillers which survived to flower in the following year. Differences due to the stage of development at which N was applied in spring were small. Primary effects of N were to increase the number of tillers and ears per plant, and to accelerate the rate of development of inflorescences; in addition, N advanced the date of initiation of inflorescences without similarly advancing the date of complete differentiation of inflorescences. It is concluded that a long period between the initiation and complete differentiation of the inflorescence is conducive to high yields of seed.

The influence of pre-weaning nutrition on subsequent growth and development of bacon pigs

SUMMARYThe growth and carcass data were determined for pigs reared on two creep rations to different weights, and subsequently fattened with and without an antibiotic.Pigs weaned at a ‘standard’ weight of 43·8 lb. at 56 days of age grew more quickly over the range 120 to 210 lb. live-weight than pigs weighing 51·0 lb. at weaning. Both groups were fed according to a fixed scale related to live-weight. Heavy weaners growing slowly in the later stages had slightly thicker backfat measurements, indicating that they were at a more advanced stage of physiological development than the light weaners.The presence of antibiotic in the fattening ration caused no significant difference in growth rate or carcass measurements, but there were significant interactions between weaning weight and presence or absence of antibiotic in the fattening ration for length of carcass, and between sex and presence or absence of antibiotic for the traits of age at 70 lb. live-weight, carcass length and depth of mid-backfat.Weaning weight and rate of gain from 70 to 120 lb. live-weight were significantly and positively related to carcass length.It is concluded that further studies of the growth curve of the pig are required to determine the scope and importance of compensatory growth, and the interaction of growth rates in the different phases of the pig's life and their relationships to carcass traits.

Graft-transmissible Induction of Elongation and Flowering in Scions of Sugar-beet red for Resistance to Bolting

THE main difference between this and other grafting experiments described in the literature appears to lie in the physiological ages of the scion and stock. In Russian work on vegetative hybridization, scions at the 4–6-leaves stage are held to be most susceptible to the influence of stocks of the same age. Here, however, it may be that the scion has not yet reached the stage of physiological development at which it would require the normal sequence of external factors to become vernalized and ready to flower in the appropriate conditions. The possible acceleration of breeding programmes involving bolting-resistant varieties must await the results of further experiments.

Light-Induced Inhibition of Potato Tuber Sprouting

In freshly harvested Alaska-grown potato tubers there is a"rest period" during which time no sprout growth can be visibly detected. This is followed by a physiological stage of development when sprout growth will occur in the dark but is suppressed by light. Following this is a stage of gradual resumption of growth of light-suppressed sprouts and a lessening of the inhibitory responses in tubers planted at successive lengthening periods of time after harvest.

A COMPARISON BETWEEN TWO METHODS OF MEASURING SEASONAL GROWTH OF TWO STRAINS OF DACTYLIS GLOMERATA WHEN GROWN AS SPACED PLANTS AND IN SWARDS

A trial is described which was designed to test the hypothesis that measurements taken of the leaf‐plus‐shoot length of spaced plants may give a good indication of dry‐matter yield of strains of Dactylis glomerata, as determined by cutting and weighing the produce of sward plots.Two contrasting strains of Dactylis glomerata were used: the British S.143, and the German von Kamekes. The strains were established during 1955 both as spaced plants (10 plants per plot) and as pure swards, with six replications of each. The two methods of establishment formed the main treatments, occupying whole plots, and each plot was divided into four sub‐plots each of which carried one of the combinations of the two strains with the following two management treatments: Treatment 1, cut at monthly intervals from 27 April to 23 August; Treatment 2, cut on 12 April and subsequently at the mean date of emergence of the inflorescence for each strain, followed by cutting at monthly intervals until the end of August.Spaced plants were measured before cutting by thrusting a measuring rod into the crown of the plant and measuring the leaf‐plus‐shoot length of one of the longer shoots. Produce cut from sward plots was weighed and sampled for dry‐matter content.Results from the swards showed that von Kamekes produced more dry matter in early spring, but that subsequently the advantage passed to S.143.Significant positive correlations were obtained in early spring between the sward yields and leaf‐plus‐shoot measurements from spaced plants. Subsequently there was no agreement between the two methods, and some significant negative correlations were obtained.The data are discussed in relation to the physiological stages of development of the strains, which suggests that: In the spring period the main factor contributing to yield was shoot elongation, with the majority of the tillers in the reproductive phase. In summer the main factor was new tiller formation, with the majority of tillers in the vegetative phase. In the early autumn neither factor was dominant and both contributed to yield. Attention is drawn to the danger of comparing yields from spaced plants with yields from swards where the management may influence the results obtained, and to the difficulty of assessing hay yields by means of height measurements of spaced plants.

THE ABSORPTION, TRANSLOCATION AND BREAKDOWN OF SCHRADAN APPLIED TO LEAVES, USING 32P‐LABELLED MATERIAL

When 32P‐labelled schradan was sprayed on the leaves of apple stocks and seedlings, broad and runner beans, Coleus and chrysanthemums, some was absorbed, some evaporated and the rest remained for a considerable time on the leaf surface as a residue removable by aqueous leaching. Absorbed material is defined as that present on or in the plant and not removable by aqueous leaching at the time of harvest.Evaporation losses even from glass slides were lower than theoretical expectation, from leaves they were much less.It is possible that some breakdown of the schradan occurs within the cuticular layer. Comparisons of the absorption rates of upper and lower surfaces of leaves support the theory that absorption proceeds through the cuticle in preference to vapour phase entry through the stomata.Temperature and illumination have important effects on absorption.Young leaves have been shown to be generally more absorptive than the older leaves. Comparisons have also been made of the absorption by different species. Such data must be accepted with caution as, although physical conditions were the same for all the species within an experiment, the physiological stage of development of the different plant species will not be strictly comparable.