Plant Ontogeny Research Articles

Limitations on photosynthesis under environment-simulating culturein vitro

Limitations on photosynthesis, characterized by leaf CO2 exchange, chlorophyll fluorescence, and thylakoid structure, were studied under environmental conditions simulating culturein vitro. These were simulated by growingPhaseolus vulgaris plants in nutrient solution under high relative humidity of air (>90%), and CO2 concentrations (ca) that decreased with the development of photosynthetic activities during plant ontogeny (1200 to 300 mg m−3). The ontogeny of such model plants was more rapid, primary leaves reached photosynthetic maturity 2 to 3 d earlier and their life span was 7 to 14 d shorter than in control plants. Their photosynthetic activityin situ was limited, after reaching “photosynthetic maturity”, similarly to plants grownin vitro. When measured under optimal conditions, however, 50 to 70% higher net photosynthetic rates (PN) were found in leaves of different ages as compared with plants grown under ca of 700 mg m−3 and a lower air humidity (30–35%). This increase in PN was associated with a high conductance for CO2 transfer by adaxial and abaxial epidermes. In model plants, the dark respiration rate (RD) was almost twice that in the control, while the photorespiration rates were similar to controls; CO2 compensation concentration was about 50% of that in controls. The ratios PN/RD were similar in control and in model plants. Chlorophylla+b content in leaves of the model plants was lower than that in the control plants. Grana extent increased with plant age in the model plants while it decreased in the control ones. In both the stromal and granal membranes of the chloroplasts in model plants, a marked accumulation of carotenoids occurred independent of age. The ratio of variable to maximal fluorescence, Fv/Fm, did not differ in the model and the control plants. In the control plants, photochemical quenching (qP) slightly increased with plant age and was not affected by CO2 concentration present during measurement. In the model plants, qP increased with elevated CO2 concentration in young plants and decreased in saturating CO2 concentrations in older plants. Nonphotochemical quenching (qNP) was lower in the model plants and increased under CO2 saturating conditions. Vitality index, Rfd, was markedly lower in the model plants than in the control ones and a decline was found in saturating CO2 concentration.

Transcription of the Zea mays homeobox (ZmHox) genes is activated early in embryogenesis and restricted to meristems of the maize plant

AbstractFour Zea mays homeobox (ZmHox) genes have been analyzed in their spatial expression pattern during development of the maize plant. The ZmHox1a or b and ZmHox2a or b gene pairs encode putative plant transcriptin factors; the mRNA transcripts belong to the rare class of mRNA molecules. Expression of the ZmHox1 and 2 genes is activated very early in embryonic development and restricted to the embryo proper in the proembryo stage. After establishment of the root/shoot axis, transcripts are prevalent in the embryonic root and shoot apical meristems but later are also found in provascular tissues and young leaf primordia. In the vegetative plant body the transcription of the ZmHox genes marks several types of meristems of the shoot and root system, the descending proliferating regions and provascular strands. Expression persists in the developing reproductive organs, but results obtained in the male flower indicate that transcription of ZmHox genes here may become confined to specific cell types. The data obtained during this study show that these four ZmHox genes are expressed very specifically in cells where developmental decisions contribute to the ontogeny of the maize plant. The overall expression pattern suggests that the ZmHox class of maize homeobox genes will be involved in transcriptional control during maize development from the embryonic to the reproductive phase. © 1995 Wiley‐Liss, Inc.

THE ROLES OF HETEROCHRONY AND HETEROBLASTY IN THE DIVERSIFICATION OF LEAF SHAPES IN BEGONIA DREGEI (BEGONIACEAE)

The relationship between shape variation in the transitional series of leaves and in adult leaves was examined in seedlings of seven morphs of Begonia dregei using several quantitative methods of shape analysis. There is variation in the shape of adult leaves among individuals as well as in juvenile leaves within individuals in B. dregei. As an individual grows, there is a gradual transition in leaf shape from the symmetrical, oval, smooth‐margined leaves through a series of more than ten transitional leaves to a stable adult leaf shape. There appear to be two basic patterns to the acquisition of adult traits. Traits that differ among morphs are acquired gradually throughout the entire transitional series while those that are similar among morphs are acquired by about leaf 5 and remain stable through the later juvenile leaves. There is no identity of leaf shape between the earlier leaves of some morphs and the later leaves of others. Evolutionary diversification in adult leaf morphology in this species is not related to simple changes in ontogeny of the whole plant.

The Roles of Heterochrony and Heteroblasty in the Diversification of Leaf Shapes in Begonia dregei (Begoniaceae)

The relationship between shape variation in the transitional series of leaves and in adult leaves was examined in seedlings of seven morphs of Begonia dregei using several quantitative methods of shape analysis. There is variation in the shape of adult leaves among individuals as well as in juvenile leaves within individuals in B. dregei. As an individual grows, there is a gradual transition in leaf shape from the symmetrical, oval, smooth-margined leaves through a series of more than ten transitional leaves to a stable adult leaf shape. There appear to be two basic patterns to the acquisition of adult traits. Traits that differ among morphs are acquired gradually throughout the entire transitional series while those that are similar among morphs are acquired by about leaf 5 and remain stable through the later juvenile leaves. There is no identity of leaf shape between the earlier leaves of some morphs and the later leaves of others. Evolutionary diversification in adult leaf morphology in this species is not related to simple changes in ontogeny of the whole plant.

COMPARATIVE ONTOGENY OF A WILD CUCURBIT AND ITS DERIVED CULTIVAR.

Most previous studies of evolutionary modification of form in plants have focused primarily on individual organs or flowers. Few have investigated the role of evolutionary changes in timing or position at the level of whole plant ontogeny. This study compares ontogenies of the primary shoots of two subspecies of Cucurbita argyrosperma, one a cultivar and the other its wild progenitor. Differences in flowering times between these subspecies suggested that the cultivar may have evolved from the wild subspecies via heterochronic processes leading to paedomorphosis. Analyses showed that both subspecies are similar in vegetative architecture and rates of leaf production. Earlier flowering in the cultivar, both in terms of position and absolute time, appears to have arisen through progenesis. Initial observations of leaf blade morphology led to the hypothesis that paedomorphosis and gigantism also may have been involved in the evolution of leaf blade shape in the cultivar: all leaves of the cultivar are larger and visually similar in shape to early leaves of the wild subspecies. However, quantitative analysis revealed that leaves of the cultivar are neither geometrically, nor solely allometrically larger versions of early leaves of the progenitor. Leaf shape in the cultivar exhibits novel features as well as effects of allometry shared with the progenitor, hence a simple hypothesis of paedomorphic evolution of leaf shape is not supported.

Significance of Leaf Phosphorus Remobilization in Yield Production in Soybean

The remobilization of mineral nutrients from vegetative to reproductive structures may influence plant productivity by affecting the timing and/or rate of leaf senescence. Experiments were conducted to ascertain the importance of P remobilizatlon, particularly from leaves, in seed production of soybean (Glycine max [L.] Merr. cv. McCall). For two separate greenhouse experiments, plants were grown in pots of soil that contained three levels of P fertility (PI, P2, and P3) that provided deficient, optimum, and supraoptimum P nutrition, respectively. Plants were sampled four times from growth stages R5 to RS. For both experiments, P nutrition did not influence plant ontogeny. Plant P accumulation, biomass, and yield were depressed by the P1 treatment. For the P2 and P3 treatments, however, biomass and yield production were similar, even though plant P accumulation was twoto threefold greater for the P3 treatment. Yield decreases for the P1 treatment resulted from a proportional adjustment in the number of seeds and pods per plant. Yield components were similar for the P2 and P3 treatments. Leaf P concentration was similar for the P1 and P2 treatments, even though biomass production and yield were markedly different. There was no net remobilization of P from leaf tissue for the P3 treatment during reproductive growth in either experiment. Additionally, for Exp. 1 there was no net leaf P remobilization from the P1 and P2 treatments. These results indicate that seed development in soybean may occur independently of net P remobilization from the leaves. For all P treatments, N remobilization from leaves was extensive, even though leaf N concentration was increased significantly by the P1 treatment. Thus, N remobilization from leaves was not altered by the internal P or N status of the plants.

Ontogeny, cell differentiation, and structure of vascular plants.

Ontogeny, cell differentiation, and structure of vascular plants.

Growth responses of rice in ammonium-based nutrient solution with variable calcium supply

It is commonly known that calcium promotes NO3 - uptake in many crop species. However, calcium enhancement of NH4 + uptake by plants has received little attention. This study aimed to evaluate the effect of Ca supplements on NH4 + uptake and plant growth in solution cultured rice. Supplemental Ca applied at vegetative and reproductive phases of plant ontogeny tended to stimulate NH4 + absorption, and accordingly resulted in a better straw and grain yield. However, excessively supplied Ca (400 ppm) was detrimental to plant growth. Increases in straw and grain yield observed at Ca levels up to 300 ppm were linked to the Ca-enhanced activities of glutamine synthetase (GS), glutamate synthase (GOGAT), and ribulose 1, 5-bisphosphate carboxylase/oxygenase (Rubisco).

Phenology, early growth, and yield of planted and ratoon grain sorghum

Knowledge is limited on growth and development of ratoon grain sorghum [Sorghum bicolor (L.) Moench] in the field. In efforts to build simulation models of ratoon grain sorghum, modellers have assumed that the planted and ratoon crops grow similarily. This study was undertaken to document the growth of ratoon grain sorghum and test the hypothesis that growth and development of the ratoon crop is similar to the planted crop. Experiments were conducted from 1985 through 1987 under irrigated field conditions using nine hybrids of medium/medium-late maturity on a Houston Black clay: fine, montmorillonitic, thermic Udic Pellustert.In two of the three years, grain-yield of the planted crop exceeded the ratoon while grain-yield was equal in the other year studied. Rapid development of tillers produced much higher leaf-area indexes (L) and vegetative biomass early in the plant's ontogeny for the ratoon compared to the planted crop. Depending on hybrid and year, each primary shoot (PS) of the planted crop produced from 4 to 7 tillers within 20 days of harvest of the planted crop. At harvest, however, only 2–3 tillers/PS remained and only 1.7 tillers/PS (on average) produced grain.The planted crop allocated a higher proportion of its total above-ground biomass to grain than did the ratoon crop. Differences in the degree of tillering and partitioning of biomass to grain were found among hybrids. Yet, a significant hybrid×year interaction suggests that partitioning was dependent on the environment. Phenology of planted and ratoon crops were similar. Grain-forming tillers produced the same number of leaves as the primary shoot of the planted crop, and differences in time to anthesis between the planted and ratoon crops averaged approximately 100 of the 1000 heat units (7°C base temperature). Based on our observations, the assumption that growth of planted and ratoon grain sorghum are similar appears to be in error. However, the phenology of grain-forming ratoon tillers appeared to mimic the phenology of the planted crop's primary shoot.

Buvat, R. 1989. Ontogeny, Cell Differentiation, and Structure of Vascular Plants

Nordic Journal of BotanyVolume 9, Issue 5 p. 498-498 Buvat, R. 1989. Ontogeny, Cell Differentiation, and Structure of Vascular Plants Björn Walles, Björn WallesSearch for more papers by this author Björn Walles, Björn WallesSearch for more papers by this author First published: February 1990 https://doi.org/10.1111/j.1756-1051.1990.tb00540.xCitations: 1AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat No abstract is available for this article.Citing Literature Volume9, Issue5February 1990Pages 498-498 RelatedInformation

Variation in heteroblastic succession among populations of Crepis tectorum

Eleven populations of the monocarpic species, Crepis tectorurn (Asteraceae) in South Sweden differed in the extent to which different leaf characters changed during plant ontogeny. Multivariate analyses on sequences of leaf samples collected from greenhouse‐grown plants of different ages revealed a group structure of populations that was different from that revealed by analysing variation in leaves from adult plants. Ontogenetic data suggested that populations within a weed and an alvar ecotype constituted more natural groups than combinations of populations from both eco‐types that had similar leaves at adult stages, supporting the hypothesis that these ecotypes may have different migration histories in this area. Variation among the populations in leaf characteristics was partly due to differences that were present at all ontogenetic stages and partly due to variation in the rate of development of some of the leaf characters during plant ontogeny. Plants in some populations appeared to have more ‘juvenile’ leaves at adult stages than plants in other populations, at least in some characters.

Patterns of Plant Ontogeny that may Influence Genomic Stasis

Patterns of Plant Ontogeny that may Influence Genomic Stasis

Antibacterial activity of French tarragon (Artemisia dracunculusLinn.) essential oil and its constituents during ontogeny

SummarySteam distillation of the essential oil from French tarragon (Artemisia dracunculus L) yields a mixture of almost fifty different components. A set of ten bacterial species was exposed to the whole oil and several of its constituents, and the level of bacterial inhibition determined. Among the bacteria tested were several of public health significance, including Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus, Streptococcus faecalis and Yersinia enterocolitica. The most inhibitory compounds present in French tarragon essential oil were anisaldehyde, paracymene, eugenol, limonene, linalool, menthol, cis-ocimene, alpha-phellandrene, alpha-pinene and beta-pinene. The.antimicrobial activity of whole oil was also assessed at different stages during plant ontogeny.

Quantitative effects of field water deficits on N2(C2H2) fixation in selected legumes grown in the Indian desert

The nitrogenase activity of irrigated and rainfed plants of mung bean, cluster bean and moth bean was studied throughout the growth period in order to estimate the reduction in the potential nitrogen fixation (C2H2 reduction) rate due to field water deficits. Nitrogenase activity followed a similar trend in all crops and was dependent on both plant ontogeny and soil moisture levels. The loss of activity due to water deficits varied from 13% to 100% at different growth stages and was related to the plant water potential. The specific activity was directly correlated with the plant water potential under both the treatments. The average loss of nitrogen fixation rate during the season did not differ markedly among crops. There was an accumulation of ureides in the nodules with increasing field moisture stress in mung bean and moth bean while no such effect was found in cluster bean. The significance of these results is discussed in the N-economy of these legumes grown in the drought-prone areas of the Indian desert.

Growth Patterns of Gemmlings of Lycopodium lucidulum

Knowledge of branching patterns in Lycopodium is often based on herbarium specimens of mature plants or parts of plants. Comparative studies of the architecture and chronological events have received little attention. Most information concerns the mode of dichotomy or stelar structure in plant parts of different age (Ogura, 1972). Primack (1973) compared shoot growth patterns in five species of Lycopodium. Investigations of the ontogeny of young plants and their changes as they reach maturity are limited by the difficulties in collecting gametophytes and young sporophytes of different age. There are few references to the growth pattern of vegetatively propagated plantlets and their chronological development (Bruchmann, 1898; Troll, 1937, for L. selago). The present study of Lycopodium lucidulum Michaux is concerned with the method of elaboration of a mature plant from a single gemma. As L. lucidulum grows and branches very slowly in time, plants of different age had to be compared to analyze ontogenetic changes.

The dynamics of the flavour precursors, the S‐alk(en)yl‐L‐cysteine sulphoxides, during leaf blade and scale development in the onion (Allium cepa)

This study was undertaken to determine the patterns of accumulation and loss of the flavour precursors. (+) S‐1‐propyl‐L‐cysteine sulphoxide, (+) trans‐S‐1‐propenyl‐L‐cysteine sulphoxide, and (+) S‐1‐methyl‐L‐cysteine sulphoxide, during the development and senescence of the leaf blades and scales of a brown onion (Allium cepa L. cv. Pukekohe Longkeeper).The levels of the flavour precursors were related to the ontogeny of the individual leaf blade and scale, and the ontogeny of the entire plant. Leaf blades which developed on a young or bulbing onion contained all 3 flavour precursors (total of about 50–70 mg leaf−1); but as each attached scale developed, the leaf blades lost their flavour precursors. All 3 flavour precursors increased in the developing scales and decreased in the senescing scales. Leaf blades which developed on an older, ripening onion contained, and then lost, only (+) S‐1‐propyl‐L‐cysteine sulphoxide, whilst the scales accumulated only (+) S‐1‐propyl‐L‐cysteine sulphoxide; (+) S‐1‐methyl‐L‐cysteine sulphoxide and (+) trans‐S‐1‐propenyl‐L‐cysteine sulphoxide were minimal. In the main scales of the onion, which did not senesce during ripening, there was a transition between these two patterns. These scales accumulated all 3 flavour precursors with (+) S‐1‐propyl‐L‐cysteine sulphoxide remaining constant at about 30 mg/scale; however there was a 10 fold loss of the other 2 flavour precursors (from 20 to about 2 mg/scale). The base plate (true stem) contained mainly (+) S‐1‐propyl‐L‐cysteine sulphoxide, which increased 5 fold in amount during bulbing. The other 2 flavour precursors were present at much lower levels.A recycling of flavour precursors is suggested, with the leaf blades supplying flavour precursors to scales, and in turn older senescing scales recycling their flavour precursors to developing younger scales.

Changes in relative growth rate with plant ontogeny in spring wheat genotypes grown as isolated plants

For a better insight in the effect of wide spacing on the outcome of plant selection in spring wheat, the growth of free-grown individual plants was followed in time for each of 12 cultivars. As time proceeded, the cultivar differences for per-plant weight showed progressively less relation with those for seedling weight. At anthesis, the genetic correlation with seedling weight was still about 0.80, but at final harvest it was only 0.06. This contrasted with the genetic correlation between seedling weight and final biomass in closely planted mixtures which was on the average 0.77. The outcome of selection of genotypes in isolation is therefore expected to deviate substantially from that of selection in densely planted segregating populations where the differences in initial size tend to be maintained in time.

The formation and significance of Carboniferous coal balls

Coal balls (exceptionally preserved calcareous permineralized peat), widely described from tropical Carboniferous Euramerian coal seams, have yielded diverse data on the biology, ontogeny and ecology of swamp plants and ecosystems. Probably over 75% of the swamp taxa may have been preserved, in contrast to probably less then 10% in other contemporaneous environments, but the assemblages are species-poor and represent an evolutionarily conservative assemblage. The in situ nature of coal ball peats allows ecological changes to be identified from vertical profiles. Major changes in plant communities both within individual seams and between seams appear to reflect both local and widespread climatic changes, particularly in rainfall. The preservation of cell contents, plant apices, gametophytes, etc., demonstrates the contemporaneous or early diagenetic formation of coal balls. Their common association with marine sediments has supported arguments for a marine source for the carbonate. Stable oxygen and carbon isotope studies suggest a meteoric origin for some carbonate. No current model for the formation of coal balls completely explains their occurrence and rarity outside the Upper Carboniferous of Eurameria.

Diurnal and Seasonal Variation in Dinitrogen Fixation (Acetylene Reduction) Rates by Field–Grown Soybeans1

AbstractNo data exist that represents in situ, continuous observations under field conditions of changes in dinitrogen fixation potential through diurnal cycles. Acetylene reduction responses of soybean [Glycine max(L.) Merr.] plants to changes during the diurnal cycle and during seasonal developmental changes were monitored using a continuous flow system with very low acetylene concentration. These data were used to assess the relative effects on acetylene reduction rates of environmental and plant ontogeny variables. During the diurnal cycle, acetylene reduction rates generally peaked late in the afternoon and then declined through the night. However, the night rates did not fall below half of the daily maximum. Within individual days, rates were more closely correlated with soil temperature than with photosynthetically active radiation. A consistent link was not observed between acetylene reduction rates and any particular stage of ontogeny. These results, and a reexamination of published reports, suggest that dinitrogen fixation rate in soybeans is not closely coupled to current photosynthetic rates under field conditions.

NON‐PHOTOSYNTHETIC FIXATION OF CARBON DIOXIDE AND POSSIBLE BIOLOGICAL ROLES IN HIGHER PLANTS

Summary1. Non‐photosynthetic fixation of CO2/HCO3‐ occurs both under light and dark conditions and involve the addition of carbon to substrates which in higher plants are derived originally from carbon reduced to carbohydrates during photosynthesis. Despite the endergonic nature of these carboxylations, the advantages offered seem to be sufficient to outweigh the disadvantages of energy loss.2. Non‐photosynthetic carbon incorporation into metabolism is dealt mainly in relation to PEP carboxylase, acetyl‐CoA carboxylase, carbamoyl phosphate synthetase and phosphoribosylaminoimidazole carboxylase while other carboxylases await further characterization or discovery. The extent to which a carboxylase participates depends upon the need for products of its activity in metabolism.3. Non‐photosynthetic carbon fixation is intricately involved in several pathways of metabolism throughout the ontogeny of plants. The roles in relation to leaf carbon metabolism, respiratory metabolism, nitrogen metabolism, lipid and isoprenoid biosynthesis, purine and pyrimidine metabolism and metabolism associated with the action of growth regulators have been described. The fixation reactions appear to be largely concerned with the production of intermediary metabolites, circumvention of energy barriers in metabolism and regulation of plant metabolism. In addition, the activity of PEP carboxylase is involved in ionic balance and pH‐stat.4. Malate derived by way of PEP carboxylase and NAD‐malate dehydrogenase acts as an effective osmoticum and a counter‐ion for K+ accumulation in actively growing plant cells. In addition, malate may enter the TCA cycle or can be decarboxylated by cytoplasmic NADP‐malic enzyme converting NADH to NADPH. Wherever it has been sought in different plant tissues, some evidence for PEP carboxylase and metabolism of malate has always been found.5. Almost every plant process spanning from seed development and germination to flowering and fruit‐set requires the essential participation of non‐photosynthetic carbon fixation in regulating certain metabolic and cellular functions but it does not contribute in a major way to the carbon nutrition of plants. It is largely the tissue type that appears to determine which of the roles is predominant at any one time.