Blade Expansion Research Articles

Appearance and Growth of Individual Leaves as Affected by Semidwarfism in Isogenic Lines of Wheat

Two experiments were carried out with three isogenic lines (standard height, semi-dwarf and double dwarf) of wheat under field conditions without water and nutritional stresses, with the objective of assessing the effects of Rht1 and Rht2 leaf alleles on leaf appearance and leaf blade area development. Possession of dwarfing genes did not affect phenological development, final number of leaves nor the rate of leaf appearance on the mainstem. The relationship between number of appeared leaves and thermal time could be described by a bi-linear model with an inflection point at the sixth-leaf stages independently of any particular ontogenic stage. Rht alleles caused significant reduction in the growth of leaves and stems, but did not affect internode diameter. Rht alleles were also associated with decreased individual leaf blade area, mainly through reductions in leaf blade length caused by reduced rates rather than durations of extension. The data presented confirm that Rht alleles affect internode growth more than leaf blade expansion; two hypotheses are discussed.

Abnormal cell divisions in leaf primordia caused by the expression of the rice homeobox gene OSH1 lead to altered morphology of leaves in transgenic tobacco.

Transgenic tobacco plants were generated carrying a rice homeobox gene, OSH1, controlled by the promoter of a gene encoding a tobacco pathogenesis-related protein (PR1a). These lines were morphologically abnormal, with wrinkled and/or lobed leaves. Histological analysis of shoot apex primordia indicates arrest of lateral leaf blade expansion, often resulting in asymmetric and anisotrophic growth of leaf blades. Other notable abnormalities included abnormal or arrested development of leaf lateral veins. Interestingly, OHS1 expression was undetectable in mature leaves with the aberrant morphological features. Thus, OSH1 expression in mature leaves is not necessary for abnormal leaf development. Northern blot and in situ hybridization analyses indicate that PR1a-OSH1 is expressed only in the shoot apical meristem and in very young leaf primordia. Therefore, the aberrant morphological features are an indirect consequence of ectopic OSH1 gene expression. The only abnormality observed in tissues expressing the transgene was periclinal (rather than anticlinal) division in mesophyll cells during leaf blade initiation. This generates thicker leaf blades and disrupts the mesophyll cell layers, from which vascular tissues differentiate. The OSH1 product appears to affect the mechanism controlling the orientation of the plane of cell division, resulting in abnormal periclinal division of mesophyll cell, which in turn results in the gross morphological abnormalities observed in the transgenic lines.

Responses of shoot and root gas exchange, leaf blade expansion and biomass production to pulses of elevated C02in hydroponic wheat

Short-term effects of elevated CO 2 during the early life phase of plants may have long lasting consequences for growth and biomass in later periods. We exposed hydroponically grown wheat seedlings to 5 d pulses of elevated CO 2 while leaf expansion growth as well as shoot and root gas exchange were measured simultaneously and continuously. Shoot photosynthesis, night-time shoot respiration and below-ground respiration (largely by roots) roughly doubled when atmospheric CO 2 concentration was doubled. An interruption of CO 2 enrichment caused CO 2 assimilation and respiration to return to control levels. However, while the response of photosynthesis was immediate, that of respiration showed a hysteresis of about 3 d. Since shoot biomass increased at elevated CO 2 (with no change in allocation pattern) equal fluxes per shoot or root system after a return to control CO 2 concentrations indicate substantial downward adjustment of the capacity for CO 2 fixation and release in high-CO 2 grown plants. Leaf expansion growth was completely unaffected by CO 2 enrichment, whereas tiller initiation was significantly increased (doubled in 18 d). We conclude that leaf growth in these wheat plants was already carbon-saturated at ambient CO 2 concentration at optimum mineral nutrient supply. The stimulation of growth of whole plants was exclusively due to enhanced tillering during this very early part of the life of these wheat plants.

Callus Proliferation and Plant Recovery with Oxalis erosa Knuth Shoot Tip Cultures

A successful micropropagation method for Oxalis erosa Knuth is reported. The most suitable media contained Murashige and Skoog mineral salts and carbohydrates, including (M): 0.6 × 10(-6) thiamine-HCl, 4.8 × 10(-6) pyridoxine-HCl and 8.2 × 10(-5) nicotinic acid, and supplements of (M): 4.9 × 10(-7) IBA + 4.4 × 10(-6) BAP + 2.9 × 10(-7) GA(3) for callus induction, 2.2 × 10(-6) BAP + 2.9 × 10(-7) GA(3) for bud differentiation and shoot proliferation, 2.6 × 10(-6) GA(3) for internode elongation and leaf blade expansion, and the BM at half-strength + 2.5 × 10(-8) IBA, agar omitted, for the rooting of shoots.

Photosynthetic capacity, irradiance and sequential senescence of sugar beet leaves

In field-grown sugar beet plants (Beta vulgaris L. cv. Dobrovicka A), each of66 successive leaves produoed in the course of the vegetation period was different with respect to its photosynthetic capaoity (Pc), life span, duration of leaf area expansion, and longevity after its maximum leaf area (Amax) has developed. The proportionality between the seasonal changes in these characteristics was not the same if the sequential senescence of leaves was taken into account. With aging of individual leaves, Pc increased with the leaf area expansion having attained the peak value between 75% to 100% of Amax The rate of ontogenetic changes in Pc of each leaf was specified by the rate of its growth and development so that even at comparable ages the successive leaves constituted a series of different physiological units. The seasonal changes in quantum irradiance (PAR) were found to be responsible for differences in the growth characteristics between the successive leaves: Leaf expansion period was related with daily integrals of the incoming PAR (Io), while leaf longevity, after the Amax had been attained, was closely linked with PAR intercepted by the canopy (I). Pc expressed per the total leaf area of the plant was significantly correlated withI, while Pc calculated per unit leaf area of the plant was related toI o Leaf potential to adapt Pc correspondingly to changes in PAR was greatest during leaf blade expansion; after the leaf had ceased to expand, changes in Pc were independent of differences in leaf irradiance. The results stress, at least for field conditions, the inadmissibility of the extrapolation of attributes from one leaf to the other ones sequentially senescing on the plant.

Ontogeny of Photosynthetic Performance in Fragaria virginiana under Changing Light Regimes

Apparent photosynthesis and dark respiration were followed during development in four light environments of leaves of Fragaria virginiana Duchesne. Leaf expansion was completed more rapidly the higher the growth photon flux density and leaves senesced more quickly in high light. Maximum photosynthetic capacity coincided with the completion of blade expansion and declined quickly thereafter. Leaves were transferred from high to low and low to high photon flux densities at several stages during expansion. Leaf photosynthetic performance and anatomy were subsequently analyzed. Leaf anatomy and apparent photosynthesis per unit dry weight can be modified during expansion to reflect the predominant light conditions. Adaptive potential is greatest early in blade expansion and decreases as expansion is completed.

Calcium nutrition of the sugarbeet

Abstract When sugarbeet seedlings are transferred from a complete nutrient solution to one from which Ca has been withheld, the rootlets and tops fail to develop. The same transfer at the eight‐leaf stage causes the rootlets to become stubby and swollen at the tips and blade expansion becomes modified; particularly the upper portions of the blades attaining nearly full development, which pucker and often develop a cupping or hooding effect; a unique symptom characteristic of Ca deficiency. As each new leaf develops, the blade area becomes smaller until only a black tip remains at the apex of the petiole, which is the symptom referred to as tip‐burn for this petiole and the successively . shorter petioles formed as Ca deficiency increases in severity. Strangely, these symptoms also appear during periods of rapid growth when the nutrient solution contains as much as 10 to 28 milliequivalents per liter of Ca or when soils are high in Ca. This implies that Ca absorption and possibly translocation limits the C...

Calculated Leading-Edge Bluntness Effect on Transonic Compressor Noise

Theme A METHOD was developed for calculating forwardradiated shock waves and expansion regions of cylindrically blunted straight-entrance transonic compressor blades within constant-annulus inlet ducts. Tone noise at blade passing frequency and its subharmonics, caused by shock waves produced by blade curvature and nonuniformity, could be avoided in concept if all blades were precisely sharp, precisely straight, and precisely positioned. However, leadingedge thickness would necessarily be many orders of magnitude larger than the mean free path in air. Each blade, therefore, must support a detached curved wave that decays from a normal shock towards a Mach wave. It was shown by Morfeyl that if a transonic compressor generated a periodic pressure system, the upstream asymptotic pressure field was a periodic sawtooth pattern whose strength was independent of blade shape and initial shock wave strength. This prediction has been validated analytically2 and by numerical experiments3 for sharp, curved blades. It was not obvious how, or if the pressure pattern generated by straight, parallel, very slightly blunted blades would approach the same amplitudes. Contents An earlier solution4 had assumed that each detached shock wave had the shape of a hyperbola asymptotic to a Mach wave. In this solution, the strong inner-portion of each shock wave is approximated by a hyperbola with steeper asymptote. The hyperbola is matched to an isolated-blade weak-shock outer solution obtained from sonic boom theory5 for blunt two-dimensional shapes. The expansion field produced by an isolated blade's leading edge is distorted by the entropy gradient downstream of the curved strong shock. Each blade's expansion field was calculated from the sonic boom solution and corrsponds to a centered expansion whose hypothetical origin is significantly downstream of the leading edge. These portions of the solution were validated by comparisons with wind-tunnel data for isolated blunt flat plates at low supersonic speeds. Compressor cascades were represented by starting with isolated-blade shock waves and expansion regions and then calculating the upstream propagation. At moderate distances ahead of the cascade leading edge plane, the variation of static pressure with distance is given by a shock-wave compression, a linear expansion to the pressure ahead of the shock, and a region of constant pressure. Eventually each blade's shock wave overtakes the aft end of the preceding blade's expansion and the pressure pattern becomes a sawtooth waveform. As upstream distance is increased, the flowfield occurring within the expansion region. That is, the

Photomorphogenesis in Sinningia speciosa, cv. Queen Victoria I. Characterization of Phytochrome Control

The morphological development of Sinningia speciosa plants that were exposed to supplementary far red light was very different from that of plants receiving dark nights. After several nights of such irradiation, stems and petioles were elongated, petioles were angulated, leaf blade expansion was inhibited, plants were chlorotic and the accumulation of shoot dry weight was retarded.Red reversibility of the morphological changes potentiated by far red light indicated control by the phytochrome system. A high P(FR) level during the last half of the night inhibited stem elongation and promoted leaf blade expansion, but both of these processes were hardly affected by the P(FR) level during the first half of the night. Thus sensitivity to P(FR) was cyclic.The interpretation of our experiments was complicated by quantitative morphological differences resulting from long, as compared to short, far red irradiations.