y y Geotropismo Positivo: si los órganos de la planta van en dirección al centro de la tierra; tal es el caso de las El geotropismo es un tipo de tropismo, propio de las plantas, que se refleja en un El gravitropismo se ve definido por la concentración diferencial de auxina. fototropismo em plantas EFECTOS FISIOLÓGICOS DE LAS AUXINAS: FOTOTROPISMO Y GRAVITROPISMO Existen tres sistemas principales de control de.
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New insight into how thigmomorphogenesis affects Epipremnum aureum plant development. Climbing Epipremnum aureum plants develop larger leaves than unsupported, hanging plants. This effect may be regarded, in part, as a thigmomorphogenic response, but gravimorphogenetic effect may also be involved, since polar auxin transport is known to be negatively affected in plants with horizontal or hanging stems, which may result in an altered hormone balance at the whole plant level.
The present work was aimed at studying how exogenous auxins and cytokinins may influence growth of E. Rooted cuttings of E. All leaves of each plant were sprayed to run-off at sunset with four indoleacetic acid IAA doses 7 days after transplanting and one week later, with four benzylaminopurine BAP concentrations, rendering 16 hormone combination treatments. The application of IAA or BAP at 50 mg L -1 to creeping and planats plants significantly promoted growth but, in climbing plants, a negative effect was generally observed.
Changes in net assimilation and photosynthetic rates, together with modified allometric coefficients, accounted for these responses. The higher growth promotion by exogenous growth regulators gravitropismk in creeping or hanging plants compared to climbing plants, may be interpreted mostly as a gravimorphogenetic response.
Estacas enraizadas de E. The Golden Pothos Epipremnum aureuma naturally variegated plant, is a tree-climbing vine native to the Solomon Islands.
Golden Pothos varieties are among the most popular tropical ornamental hanging basket crops for interior landscape. However, plants used for interior landscape purposes usually have heart-shaped leaves that rarely exceed 15 cm in length.
Leaf size depends, among other factors, on how vines are trained. When plants grown in pots under commercial facilities are vertically supported, leaf size significantly increases in comparison to leaves from basket hanging plants Di Benedetto et lpantas. Native shade planats environments are characterized by a low light intensity, and for this reason, carbon gain is an important aspect of plant performance. A strategy for maximizing light capture in several shade-adapted plants consists of exploring the vertical environment through the anchorage to an adjacent surface such as host plants, rocks or walls.
These changes in plant growth habit modify, in turn, enn shoot and root growth Di Benedetto et al. The climbing vine finds anchorage with adventitious aerial geavitropismo roots appraised to an adjacent surface of host plants, rocks or walls. They suggested that the morphological differences between climbing and grxvitropismo hanging plants represent thigmomorphogenic responses of climbing plants to a mechanical stimulus generated by the contact of the stem with the support surface.
However, when comparing climbing plant with plants hanging freely from a pot, an alternative or complementary explanation of the morphologic responses gravitroopismo Golden Pothos to vine orientation may be given. Gravimorphic responses are associated with modified auxin flux, which is known to be inhibited by placing stems in horizontal or downward, instead of upward position.
Auxins normally move in a polar manner from shoot to root apices, but in downward-pointing shoots, auxins accumulate near the shoot tip Lovisolo et al. Auxins play key roles in organ development.
Auxins are known to promote the differentiation of gravjtropismo roots as well Pacurar et al. The latter is a very important control point of plant growth, since root apices are the main source of cytokinins. In turn, cytokinins, graviyropismo are transported via xylem to the shoot apex, exert a multiple-faced ,as promoting action in the aerial part of the plant. Thus, inhibition of polar auxin transport in horizontally or downwardly oriented stems may ultimately result in a decreased whole-plant growth Keller, Gravimorphism and thigmomorphism may influence growth at the same time; for example, Steinitz et al.
Previous reports have shown that leaf size, leaf number Di Benedetto et al. Leaf area and whole-plant biomass accumulation increased with relatively low BAP application mg L -1while mg L -1 BAP generally appeared as a supra optimal concentration. In these works, BAP-driven growth promotion was associated with increased net assimilation rate NAR and net photosynthetic rate. Exogenous sprays of indole acetic acid on E.
Since both creeping and climbing plants may be considered as thigmo-stimulated, differences in growth patterns between them may be solely attributed to gravity. If departure from upward position results in decreased growth due to an impaired auxin transport to the root system, then exogenous auxin and cytokinin application to the foliage should be a straightforward manner to overcome such restriction. The aim of this work was to study E. At the transplant stage, cuttings had an average 3.
Ca nitric acid, lsa acid, potassium nitrate and calcium nitrate via overhead irrigation water. Plants were cultivated either climbing supported through an upright wooden board 5 cm in width and cm in poantas, coated with black polyethylenecreeping on the glasshouse bench or hanging from a basket, to obtain three different platas habits. Both climbing and creeping plants were assumed thigmo-stimulated, being their aerial roots in contact with the respective surfaces either wooden board or bench surface.
Care was taken to ensure similar light exposure to the plants regarding the training system employed. Daily mean temperatures ranged between Seven days after transplantation, all leaves of each plant were sprayed to run-off at sunset with IAA solutions 0, 5, 50, or mg L -1followed 7 days later by sprays with BAP solutions 0, 5, 50, or mg L -1rendering 16 hormone combination treatments.
Chemicals were of highest purity Sigma-Aldrich Co. No surfactants were used. Ten plants, either climbing, creeping or hanging, randomly distributed within each greenhouse block, were sprayed with each of the 16 gravitropisml regulators combinations tested. At 0, 60, 90, and days after transplanting, two plants per block treated with each combination of growth regulators under each training system were destructively sampled.
Fresh weights FW of the different aerial parts i. The relative rate of leaf area expansion RLAE was calculated as the slope of the regression of the natural logarithm ln of total leaf area versus time in days. Relative growth rate RGR was calculated as the slope of the regression of the ln DW whole plant versus time in days.
Mean net assimilation rate NAR was calculated as:. RGR days -1 ; A 0: Since in most treatments plant biomass accumulation approached a plateau towards the end of the experiment, the last sampling days after transplant was not included for performing this analysis, which is best suited for plants growing exponentially.
Specific leaf area SLA was calculated as the ratio of individual leaf area to leaf DW average of all plant leaves. Samples of young fully expanded leaves were collected to examine leaf anatomy i.
Data presented are the means of three leaves per treatment using ten leaf cross-sections per leaf. Quantitative anatomical data were obtained using Image Pro Express version 6. The experiment was arranged in a three-way factorial design with four concentrations of IAA, four concentrations of BAP and three plant training systems. Least significant differences LSD values were calculated.
The application of IAA or BAP at any concentration, either in single or combined manner, led to a significant increase in final FW in creeping and hanging plants, but not in climbing ones. Plants were grown under climbing Acreeping B or hanging C training systems. Buenos Aires, UBA, There were no significant differences in dry matter content among training systems or hormone treatments data not shown.
In untreated controls, climbing plants had significantly higher DW-based RGR than either creeping or hanging ones.
Combined hormone application gravktropismo all combinations promoted RGR of creeping plants. Plahtas the other hand, in hanging plants, the most effective hormone combinations were the and mg L -1 IAA-BAP treatments, although several other treatments also had an effect on RGR.
In untreated controls, differences in RGR among training systems could be attributed more due to differences in NAR than to variation in LAR, although differences in NAR between climbing and creeping plants were not significant.
Similarly, growth regulators-driven decrease in RGR of climbing plants was generally associated with a decrease in NAR, and conversely, the increase in RGR of growth regulators-treated creeping or hanging plants was associated with a significant increase in NAR.
Variation in LAR was in general low, climbing plants tend to present higher values than either creeping or hanging ones.
función y relación
LAR was rather unaffected by growth regulator treatments but in the few treatments in which significant growth regulators effects were found i. The root versus shoot allometric analysis of untreated controls showed a trend for higher root vs. The net photosynthetic rate of young, gravitropimso expanded leaves of untreated plants showed a similar pattern to that of biomass allocation, this is, higher values in climbing plants than in creeping ones, fravitropismo higher values in creeping plants than in hanging ones Figure 2 A-C.
Plants were grown under climbing Acreeping B and hanging C training systems.
Meaning of “fototropismo” in the Spanish dictionary
Conversely, in creeping and hanging plants, a significant increase of net photosynthetic rate was observed when exogenous IAA and BAP, either in single or combined manner, were applied. Trends for plant total leaf area of untreated controls at the end of the experiment, as well as for the relative rate of leaf expansion RLAEwere similar to those found for FW and DW accumulation, this is, significantly higher values for climbing plants than for creeping or hanging ones Table 3.
Both larger individual leaf area and higher rate of leaf appearance in climbing plants than in either creeping or hanging ones accounted for such differences. Conversely, SLA values of climbing plants were lower than in creeping ones, and they were also lower in creeping than in hanging ones. In creeping plants, single BAP sprays at 5 or 50 mg L -1 resulted in increased values, being the concentration of mg L -1 supra-optimal, while in hanging plants all concentrations were promotive particularly the highest one.
On the other hand, IAA sprays on creeping plants significantly promoted total leaf area only at the lowest concentration tested 5 mg L -1 ; while on hanging plants, all IAA concentrations were similarly effective.
Up to a large extent, differences in RLAE among training systems for each growth regulators combinations treatment accompanied those found for total leaf area at the end of the experiment. In climbing plants, the growth regulators-induced decrease in both variables measuring total leaf area accumulation, could be ascribed to a reduced RLA rather than to a decrease in individual leaf area, since growth regulators sprays at any combination in comparison with untreated controls, did not significantly affect the latter.
Growth regulators treatments generally had no significant effect on SLA values of climbing plants. Conversely, most growth regulators combinations i. In creeping plants, results were more variable: Control, untreated climbing plants had thicker leaves than creeping and hanging ones. On the other hand, no significant effect could be observed in climbing plants. In untreated climbing plants, the epidermal cell layer represented a larger fraction of leaf cross-section than in either creeping or hanging ones.
Growth regulators applications tended to reduce this contribution in climbing plants and to increase it in hanging ones, while no clear trend was observed in creeping plants Figure 3 B-D. The intercellular space fraction occupied a relatively low proportion of leaf cross-sections i. In most cases, growth regulators supply led to an increase in this fraction, particularly in climbing and creeping plants.
On the other hand, no clear trends regarding the parenchymatous layer were found. Plants were grown under climbing Bcreeping C and hanging D training systems.
Bar indicates least significant difference LSD. In the present work we show that leaves from climbing E. These differences ultimately lead to a decreasing foliage production i.
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These effects were also accompanied with an increasing dry mass partitioning towards the root system, from climbing to hanging plants Table 2.
However, an even more important effect of training system on plant performance was that of carbon assimilation, being both the calculated NAR and measured photosynthetic rates higher in climbing plants than in creeping ones, and higher in creeping plants than in hanging ones Table 3Figure 2. This effect led to important differences among training systems in RGR, which decreased together with departure from upward growth position Table 1.
Growth regulators-treated plants also showed higher RGR values, which could be explained mainly because of a strong promotion in NAR by both auxin and cytokinin.