Frond Elongation Research Articles

Impact of fruiting on gas exchange, water fluxes and frond development in irrigated date palms

The cultivation of date palms in Israel’s Arava Valley, which is characterized by a high evaporative demand, is widespread and exclusively depends on high-frequency irrigation. Fruit sets are usually thinned early in their development to produce large, high-quality dates. However, no effort has yet been made to comprehensively examine fruit load effects on date palm water use, CO2 fluxes and growth. The objective of this study was to investigate the effects of fruit load on these factors. Twelve date palms, six with fruit removed (“without fruit”) and six untreated (“with fruit”), were irrigated with equal amounts of water at sufficient levels for maintaining optimal soil water conditions. Sap flow and frond elongation were continuously measured. Gas exchange parameters (i.e., stomatal conductance and CO2 assimilation rate) and fruit growth (i.e., fruit size, mass, and sugar content) were monitored periodically. No significant differences were found in gas exchange, water consumption and frond elongation between the two treatments several weeks after the onset of the fruit load differentiation. However, a pronounced increase in stomatal conductance and CO2 assimilation rates in palms with fruit compared to those without fruit was identified during the sugar accumulation and post-harvest periods. Continuously increasing water consumption in palms with fruit was also observed during these periods, probably as a result of the progressive recovery of depleted carbohydrate and water storage in the tree. In addition, the frond elongation rate of palms with fruit was remarkably lower than those without fruit until the end of the harvest. It is concluded that crop load has a pronounced effect on physiological behaviors and water use of the cultivated date palm. Therefore, irrigation management must consider fruit load to achieve optimal yield.

A wireless device for continuous frond elongation measurement

Growth rate is one of the indicators for a plant’s physiological condition. Date palms are characterized by high frond elongation rates, which are mainly subjected to drought and salinity stresses. Thus, continuous measurement of these rates can provide real-time growth information, for assessing water status within the soil-plant-atmosphere continuum of cultivated date palms. This study introduces a novel device, the Palmeter, which continuously measures real-time date palm frond elongation. The Palmeter was calibrated in the laboratory and tested in a date palm orchard with a measurement resolution of 0.52mm. A field test indicated that the Palmeter could wirelessly transmit acquired data to a signal receiver over a distance of 100m with a success rate of more than 98%, facilitating the establishment of wireless sensor networks in date palm orchards. Neither temperature nor wind affected the Palmeter measurement within the orchard. The temporal patterns of the frond elongation measured by the Palmeter were found to be sensitive to various cultivation treatments, such as fruit load regimes, applied within a field study. Additionally, a six-volt power supply is recommended in order to reduce the Palmeter’s power consumption. The feasibility and robustness of the Palmeter system guaranteed the accurate measurement of the frond elongation under harsh field conditions. Therefore, the Palmeter can be potentially applied to measure the frond elongation of date palms and perhaps other palms, such as oil palms and coconut palms, for irrigation scheduling and cultivation management in large orchards.

Cell Division in the Absence of Mitosis: The Unusual Case of the Fucoid Ascophyllum nodosum (L.) Le Jolis (Phaeophyceae)

Fluorescence and electron microscopy were used to examine epidermal shedding in the fucoid alga, Ascophyllum nodosum. Mature meristoderm cells are ca. 50-100 x 30-40 and highly polarized, with a single nucleus and chloroplasts near the base of the cell. Nuclei in these cells undergo mitosis when they are dividing to form a new cortical cell towards the middle of the frond, or anticlinal divisions as part of frond elongation. However, cytokinesis also occurs regularly in these cells when a new periclinal wall is deposited at about 30% of the cell length from the apical end. The newly formed distal cells are anucleate and without chloroplasts. Following cytokinesis the tangential walls then break at the thinnest point. The whole process is synchronous in adjoining epidermal cells across large areas of the frond surface, and this layer dehisces from the thallus. This is the only known plant or algal system in which cytokinesis regularly occurs in the absence of mitosis. We consider this process a novel form of programmed cell death.

Comparative spatial distribution, size, biomass and growth rate of two varieties of bracken fern (Pteridium aquilinum L. Kuhn) in a neotropical montane habitat

A comparative field study of caudatum and arachnoideum, the two Pteridium aquilinum varieties of the caudatum subspecies known to grow in the neotropics, was performed in a montane savanna habitat of the Venezuelan Andes that was affected by wildfire. Frond size, ramet density and spatial distribution, blade and rhizome biomass, and frond elongation and expansion rates were measured in separate, isolated stands each containing only one bracken variety and covering approximately the same area (∼540 m2). In addition to clearly discernible morphological differences, caudatum and arachnoideum were found to possess distinct features: caudatum tends to develop open stands of relatively shorter blades of 76.6±0.89 cm (μ±SE) of rachis length and lower ramet density (1.6 fronds m-2, max.=7 fronds m-2) whereas arachnoideum grows into longer, more expanded fronds 124±1.6 cm tall and significantly higher ramet density (5.1 fronds/m2, max.=14.6 fronds m-2). The sum of aerial and underground biomass was found to be notably larger for arachnoideum (8522±614 Kg/ha) than for caudatum (1929±131 Kg ha-1) in stands growing under the same habitat conditions. Therefore the spatial distribution of arachnoideum appeared considerably more compact than that of caudatum. Blade growth rates and development time were also very different. Newly emerged caudatum croziers developed into mature blades within 42 to 48 days following an inverse exponential curve whereas arachnoideum blades required 70 to 75 days to reach maturity following a linear development. All the above dissimilarities are interpreted as the hitherto unreported indication of diverging growth strategies of two cohabitant bracken varieties following fire.

Frond development and phenology of Thelypteris limbosperma, Athyrium distentifolium, and Matteuccia struthiopteris in Western Norway

Odland, A. 1995. Frond development and phenology of Thelypteris limbosperma, Athyrium distentifolium, and Matteuccia struthiopteris in Western Norway. — Nord. J. Bot. 15: 225–236. Copenhagen. ISSN 0107–055X.The pattern of growth and phenology of Thelypteris limbosperma, Athyrium distentifolium, and Matteuccia struthiopteris fronds has been investigated, with particular emphasis on height increments of the sporophytes and the development of fertile fronds. In order to study both interspecific and intraspecific differences, fern stands along altitudinal gradients have been monitored. To investigate the initiation of fertility, fronds representing different developmental stages have been sampled. Climatic data have been collected with a data‐logger during the study periods.The ferns show significant differences in growth pattern and phenology. Matteuccia struthiopteris has a growth curve that is best described as monomolecular, characterised by high growth rates during the early developmental stage, while the development of Thelypteris limbosperma and Athyrium distentifolium follow a logistic growth curve. The species need different periods of time to develop their fronds. The main frond elongation does not start before soil temperature has reached 7 C. After that, the growth is mainly controlled by air temperature. Within the interval when mean maximum temperatures are 8–20 C, all three ferns showed increased growth rates with increasing air temperatures, but the increase was greatest in M. struthiopteris. At higher temperatures, the growth rate of M. struthiopteris and T. limbosperma decreased. Athyrium distentifolium is characterised by producing sori at an early developmental stage. Fertile Matteuccia strurhiopteris fronds are developed at a much later developmental stage. Thelypteris limbosperma needs a longer period of time to produce mature fronds than the other species. The investigation indicates that plant growth and development are determined by both internal and external factors. It is concluded that growth rate, phenology, and the ability of ferns to produce mature fronds reveal close similarities with their response to environmental variables, and hence with their broad‐scale geographical distributional patterns.

Growth and production of the red alga Gelidium sesquipedale off the Basque coast (northern Spain)

Several aspects of the growth of the agarophyte Gelidium sesquipedale Clemente (Thuret) were studied in sublittoral populations of the Basque coast (northern Spain) from 1981 to 1986. The standing stock of the populations varied greatly with season. During two consecutive years, 60 to 70% of summer biomass had been lost by the end of the unfavourable period of year to growth (autumn and winter). The decline in biomass was mainly due to partial losses of branches, with more branches being lost from larger fronds. Yearly variations in the standing stock were also recorded. Production estimates obtained by a destructive sampling method were not satisfactory because of the spatial heterogeneity of the populations at the three locations studied. Indirect estimation of production by measuring the growth of marked fronds in a control quadrat gave more reliable estimates. Production values of ∼622±124, 735±147 and 615±123 g dry wt m-2 yr-1 were obtained at the three locations, respectively. Frond elongation rates of 7.5, 6.1, 7.5 and 7.9 cm yr-1, respectively, were recorded during four consecutive years. In winter elongation rates of fronds were rather low. Elongation did not seem to be affected by frond length, the self-shading effect of the canopy, or changes in depth. Cuts resulting from grazing were frequent on fronds through the year, decreasing significantly with increasing depth. Sheared fronds regenerated promptly, independent of season or height at which the cut was made. For commercial purposes the best season for harvesting is summer, which is the period of maximum standing stock, infertility, and calm warm waters that provide easier working conditions for divers.

Frond elongation rates of shallow waterMacrocystis pyrifera (L.) Ag. In northern Baja California, Mexico

Macrocystis pyrifera (L.) Ag.frond elongation rates were measured during autumn-winter, spring and summer in a shallow water (7.5 m depth) kelp bed in Bahia Papalote, northern Baja California. Frond elongation was maximum during spring and minimum during winter. Frond growth was significantly correlated with solar radiation, and was highest in the smallest size fronds (0–2 m). Average frond elongation rate varied between 0.3–11% d−1 during the study period. The relationship between average frond length and elongation rate followed an exponential curve with a negative slope during autumn-winter and summer, but was best described by a straight line during spring. Standard growth rates were obtained by a graphic method. Standard growth rates had intermediate values between those reported for southern California and southern Baja California.M. pyrifera growth cycle shows a different trend from what has been previously reported.

Frond elongation rates of shallow waterMacrocystis pyrifera (L.) Ag. In northern Baja California, Mexico

Frond elongation rates of shallow waterMacrocystis pyrifera (L.) Ag. In northern Baja California, Mexico

Regrowth after experimental harvesting of the agarophyteGelidium pristoides(Gelidiales: Rhodophyta) in the eastern Cape Province

Rate of regrowth of Gelidium pristoides after experimental harvesting did not show significant difference between tufts cut with shears and those picked by hand. Harvested tufts grew back to the same size and biomnss as control tufts within 3–4 months after harvesting in early spring, and 4–5 months after harvesting in late autumn. Frond elongation rates showed marked seasonality, with optimum growth during the summer season. Regrowth of sheared tufts was much faster in the lower eulittoral zone. After 12 months there was no recruitment of G. pristoides in quadrats from which all visible plants had been removed, stressing the importance of vegetative regeneration in the short-term maintenance of natural populations after harvesting. The results lead to the following recommendations for commercial harvesting: (i) the period between successive harvestings should be sufficient for regrowth of individual tufts, (ii) excessive damage to the regenerative holdfast is to be avoided and (iii) harvesting should be ...

Effect of frond age on frond elongation, gas exchange, and water relations in the ostrich fern (Matteuccia struthiopteris)

The effect of frond age in the ostrich fern (Matteuccia struthiopteris) upon changes in frond elongation, frond water status (osmotic, pressure, and total water potential), and gas exchange (diffusive resistance, net photosynthesis rate, and dark respiration rate) was examined. The maximum elongation rate in the youngest fronds was 2.83 mm h−1 and occurred between 1500 and 2100 hours. Growth of individual fronds was completed in ca. 16–20 days after emergence from the apical bud. As a frond approached final length, both the dark respiration rate and rate of daily elongation decreased. Compared with mature fronds, young fronds (5 to 8 days old) had higher dark respiration rates and lower net photosynthesis rates. They also had higher osmotic potentials and lower pressure potentials and predawn diffusive resistances. In the youngest fronds (3 and 6 days old) the fastest elongation rates occurred at the lowest water potentials. This phenomenon may be an example of "growth-induced water potential." The increase in pressure potential and decrease in osmotic potential as the frond approached full expansion on day 16 indicates an "apparent" osmotic adjustment which was probably due to a decrease in the yielding properties of the cell walls while solutes continued to accumulate in the tissue. At full expansion further accumulation appeared to stop, suggesting that the frond had increased net solute export.

Differential Response in the Water Status of Immature and Mature Fronds of the Ostrich Fern (Matteuccia struthiopteris [L.] Todaro) to a Mild Water Stress

Experiments were conducted in growth chambers to examine the effect of a mild water stress (-200 kilopascals polyethylene glycol) on frond elongation and water status of the ostrich fern (Matteuccia struthiopteris [L.] Todaro). Measurements were taken for two days, starting one day after the application of polyethylene glycol. Total water potential in control (well-watered) plants was always significantly higher in immature fronds than in mature fronds. The osmotic potential in mature fronds was always significantly lower (about 800 kilopascals) than in immature fronds in both control and stressed plants. In immature fronds, the stress decreased elongation and total water and pressure potentials, while in mature fronds it increased total water and pressure potentials. The decreases in total and pressure potentials in immature fronds were approximately equal to the increases in mature fronds.

Morphological and growth responses of geographically isolated Macrocystis integrifolia populations when grown in a common environment

Changes in blade morphology and growth characteristics of Macrocystis integrifolia Bory from four geographically separated populations grown in a common environment were followed over two growth seasons. Initial differences in blade morphology and rate of biomass change became increasingly similar over time, indicating a plastic phenotypic response to the environment. In contrast, frond elongation and the rate of frond initiation appeared to be genotypically controlled.

Growth and utilization of internal nitrogen reserves by the giant kelp Macrocystis pyrifera in a low-nitrogen environment

An adult giant kelp plant (Macrocystis pyrifera), moved from an inshore kelp forest to an offshore, low-nitrogen environment near Santa Catalina Island, California (USA), maintained growth for 2 wk on internal nitrogen reserves. Frond elongation rates decreased significantly during the third week, and plant growth rate (wet wt) dropped from an initial inshore rate of 3.6 to 0.9% d-1. During this 3 wk period, nitrogen contents and free amino acid concentrations decreased, while mannitol and dry contents increased in frond tissues. After depletion of internal nitrogen reserves, the nitrogen content of lamina and stipe tissues averaged 1.1 and 0.7% dry wt, respectively. The experimental plant was exposed to higher ambient nitrogen concentrations during the last 2 wk. Rates of frond elongation and plant growth increased, but nitrogen content and amino acids in frond tissues remained low. Of the total nitrogen contained in frond tissue of the plant before transplantation, 58% was used to support growth in the absence of significant external nitrogen supply. Amino acids constituted a small proportion of these internal nitrogen reserves. Net movement of nitrogen occurred within large fronds, but not between different frond size classes. The nitrogen content of holdfast tissue remained relatively constant at 2.4% dry wt and accounted for 18 to 29% of the total nitrogen. Holdfast nitrogen was not used to support growth of nitrogen-depleted fronds. In comparison to Laminaria longicruris, which is adapted to long seasonal periods of low nitrogen availability, M. pyrifera has small nitrogen-storage capacity. However, internal reserves of M. pyrifera appear adequate to make nitrogen starvation uncommon in southern California kelp forests.