Use Of Plant Growth Retardants Research Articles

Influence of Plant Growth Retardants and Nitrogen Doses on the Content of Plant Secondary Metabolites in Wheat, the Presence of Pests, and Soil Quality Parameters

Wheat is the cereal most susceptible to lodging, particularly during the flowering period and at the early ripening stage. The use of plant growth retardants (PGRs) is especially recommended when intensive nitrogen (N) fertilisation is applied, which increases the susceptibility of plants to lodging. This paper presents the results of tests into the effects of PGRs (PGR0—control; PGR1—chlormequat chloride (CCC) + trinexapac-ethyl (TE); PGR2—chlormequat chloride (CCC) + ethephon (ET)), and N dose—N0, N20, N40, and N60 [0, 20, 40, and 60 kg N ha−1] on the content of selected plant secondary metabolites (PSM) in the Indian dwarf wheat (Triticum sphaerococcum Percival) of the Trispa cultivar, and on the abundance of insect pests. In the developmental stage of wheat (BBCH 39), insects were collected with an entomological net. The study also investigated the effect of experimental factors on the physicobiochemical properties of the soil (pH in KC, granulometric composition, total organic carbon TOC, total nitrogen TN, fractional composition of humus, and the activity of enzymes). An increase in the plant secondary metabolite (PSM) and FRAP (ferring reducing ability of plasma) contents following the application of PGRs and N fertilisation already from as low a rate as 20 kg ha−1 was demonstrated. A significant positive correlation was noted between the abundance of Oulema spp. and the contents of total polyphenols, chlorogenic acid, and FRAP. No such relationship was noted for Aphididae or Thysanoptera. TOC content was higher on the plots on which N fertilisation was applied at the highest rate and after the application of PGRs. The factor determining the TN content was N fertilisation. Soil samples of the PGR0 N0 treatment were characterised by the greatest proportion of carbon in the humic and fulvic acid fractions and by the smallest proportion of carbon in the humin fraction. N fertilisation increased the proportion of carbon in the humin fraction on the plots on which no PGRs were applied. The study demonstrated an increase in the activity of oxidoreductive enzymes following the application of higher N rates. The application of PGRs resulted in no inhibition of enzymes in the soil compared to the control (PGRs0).

Cottonseed yield and its quality as affected by mineral nutrients and plant growth retardants

AbstractSeed quality is one of the most important factors for stand establishment in cotton (Gossypium sp.), and the use of good quality seeds is therefore essential to obtain an optimum plant population. Conditions prevailing during seed formation can affect the quality of seed produced, and hence crop establishment in the next growing season. These conditions can affect the germination of the seeds and the ability of the seedlings to emerge from soil, these being the most critical stages during the life cycle of cotton plant. Field experiments were conducted to investigate the effect of nitrogen (N), phosphorus (P), potassium (K), foliar application of zinc (Zn) and calcium (Ca), the use of plant growth retardants (PGR’s) [e.g. 1,1-dimethyl piperidinium chloride (MC); 2-chloroethyl trimethyl ammonium chloride (CC); or succinic acid 2,2-dimethyl hydrazide (SADH)], during square initiation and boll setting stage, on growth, seed yield, seed viability, and seedling vigor of cotton.

Response of different Bt cotton (Gossypium hirsutum L.) hybrids to canopy modification practices

A field investigation was carried out to characterize the growth and development of Bt cotton hybrids by detopping and use of plant growth retardants during the rainy (kharif) season of 2011 and 2012. The experimental site had loamy sand soils with normal in reaction. The experiment (split plot) involved three Bt cotton hybrids (MRC 7017, MRC 7031 and RCH 314) in main plots and growth regulation treatments (Mepiquat chloride (MC) @ 300 ppm, 2, 3, 5-tri iodo benzoic acid (TIBA) @ 100 ppm and Maelic hydrazide (MH) @ 250 ppm) in sub plots with four replications. Hybrid MRC 7017 produced significantly higher (p<0.01) seed cotton yield which was attributed to the maximum number of sympodial branches plant-1, total number of flowers and picked bolls plant-1. Application of MC @ 300 ppm, TIBA @ 100 ppm and MH @ 250 ppm reduced plant height, leaf area index and total dry matter accu-mulation than control. Detopping treatment significantly (p<0.01) reduced plant height than control but attained more plant height than all the PGRs. MC @ 300 ppm, TIBA @ 100 ppm and MH @ 250 ppm at 80 days after sowing had beneficial effect on seed cotton yield. Detopping done at 80 days after sowing failed to influence the seed cotton yield dur-ing both the years. The results revealed that foliar application of MC @ 300 ppm yielded more seed cotton by improv-ing the setting percentage and therefore, increased number of picked (open) bolls plant-1 without exhibiting any ad-verse effect on quality traits.

Are plant growth retardants a strategy to decrease lodging and increase yield of sunflower?

One of the major disadvantages of sunflower cultivation is the increased plant height, making it prone to the lodging. The use of plant growth retardants can be an alternative strategy to reduce plant height; however, these compounds may affect productivity. The aim of this study was to evaluate the effects of plant growth retardants on sunflower development and yield. Four treatments were studied: 1- control; 2- gibberellic acid (GA) 10 mg L−1; 3- trinexapac-ethyl (TE) 5 mL L−1, and 4- maleic hidrazide (MH) 8 mL L−1. TE and MH decreased plant height (16.9 and 35.9%, respectively); however, only TE positively influenced capitulim diameter and dry mass (46.7 and 311%, when compared to control) at 60 days after planting (DAP). At 81 DAP, dry mass of capitulum did not differ among control and TE-treated plants. On the other hand, MH impaired diameter and dry mass of capitulum (92.9 and 74.7%, respectively). It can be concluded that the application of TE is a potential strategy to decrease lodging probability without affecting sunflower yield. Furthermore, although MH negatively affected sunflower development, its use on the crop cannot be excluded since other doses, frequencies and moment of application can be studied.

The Effect of Nitrogen and Phosphorus Ratios and Electrical Conductivity on Plant Growth

Environmental concerns surround the use of plant growth retardants (PGRs) for plant height control, and non-chemical alternatives to PGRs can be labor intensive and expensive. Macronutrient modification is a little-studied, yet potentially effective method of controlling plant height. A number of studies have suggested that phosphorus (P) limitation may restrict plant height. Anecdotal evidence also suggests that using nitrate (NO3-), rather than ammonium (NH4+), as the principal nitrogen (N) source may help control plant height. The primary objective of this study was to evaluate different ratios of NO3-/ NH4+, NO3-/P and NH4+/P as well as electrical conductivity (EC) on plant height and growth. This was tested in a hydroponic system using marigolds, sunflowers and tomatoes. Initially, different ratios were tested at an EC of 1.2 dS·m-1, followed by using the same ratios at four ECs (0.6, 1.2, 2.2 and 4.0 dS·m-1) as a second objective. Although ratios did, at times, limit plant height, responses were season and species dependent, suggesting that modifications in plant nutrition, at the ratios used in this study, may not effectively control plant height in hydroponic systems. More consistent, yet species specific, height control was achieved by increasing EC level.

Paclobutrazol or Ancymidol Effects on Postharvest Performance of Potted Ornamental Plants and Plugs

Effects of paclobutrazol and ancymidol on postharvest performance and growth control of potted sunflower (Helianthus annuus L.), zinnia (Zinnia elegans Jacq.) and marigold (Tagetes erecta L.), petunia (Petunia ×hybrida Vilm.) plugs, respectively, were studied. Paclobutrazol was applied as a drench at 0, 1.0, 2.0, or 4.0 mg of a.i. per 15.2-cm pot for sunflower and 0, 0.5, 1.0, or 2.0 mg per 12.5-cm pot for zinnia, while ancymidol was applied at 0, 40, 80, and 160 mg·L−1 with a volume of 0.21 L·m−2 as a foliar spray for marigolds or petunia plug crops. With an increase in paclobutrazol dose or ancymidol concentration, plant growth (plant height and diameter, shoot fresh or dry weight) was controlled for all species tested. Use of 1.0–2.0 mg paclobutrazol per pot produced 21% to 28% shorter plants with 12% to 15% smaller plant diameter, 13% to 19% less shoot fresh weight, 15% to 21% less dry weight, and darker green foliage color for potted sunflower than nontreated plants. Treatment with 1.0–4.0 mg paclobutrazol per pot delayed first wilting by 0.7–1.4 days compared with nontreated plants. For zinnia, 0.5–1.0 mg paclobutrazol controlled plant growth, produced dark green foliage, and extended shelf life by delaying first wilting by 2.6–3.9 days and second wilting by 1.4–2.0 days than nontreated plants. For marigold and petunia plugs, 40–80 mg·L−1 ancymidol provided ample growth control with darker green foliage; however, postharvest longevity was extended only when plugs were sprayed with 160 mg·L−1 ancymidol. During simulated storage and shipping, plant growth retardants maintained darker green foliage for potted sunflower, zinnia, and marigold plugs and prevented postharvest stem elongation of petunia plugs. In summary, use of plant growth retardants effectively controlled excessive plant growth and extended shelf life of potted plants and plugs.

Controlled Water Deficit as an Alternative to Plant Growth Retardants for Regulation of Poinsettia Stem Elongation

Production of poinsettias (Euphorbia pulcherrima) often involves intensive use of plant growth retardants (PGRs) to regulate height. Height control is necessary for visual appeal and postharvest handling. Since PGRs do not always provide consistent height control and can have unwanted side effects, there is interest in alternative methods of height control. Since turgor potential drives cell expansion, and thus stem elongation, drought stress has potential for regulating plant height. Through soil moisture sensor-controlled irrigation, the severity of drought stress can be both monitored and controlled. The objective of our study was to compare poinsettia ‘Classic Red’ height control using PGRs (spray, mixture of daminozide and chlormequat at 1000 mg·L−1 each and drench, 0.25 mg·L−1 paclobutrazol) with the use of controlled water deficit (WD). Graphical tracking of plant height, using a final target height of 43.5 cm, was used to determine when to apply PGR or controlled WD. In the WD treatment, substrate volumetric water content (θ) was reduced from 0.40 to 0.20 m3·m−3 when actual height exceeded the expected height. PGR applications (spray or drench) reduced poinsettia height to 39 cm, below the final target level of 43.5 cm. WD resulted in a height of 44.5 cm, closest to the target height, while control plants were taller (49.4 cm). There was no effect of PGR drenches or WD on bract size, while spraying PGR reduced bract size by ≈ 40%. Bract chroma was unaffected by WD or PGR treatments. There was no difference in shoot dry weight between PGR- and WD-treated plants. Lateral growth was reduced by the PGR treatments, but not by WD. These results indicate that controlled WD can be used to regulate poinsettia height.

Induction of dwarfing in bougainvillea cv Mahara by use of growth regulators

Bougainvillea (Bougainvillea spectabilis) is a very popular evergreen landscape plant in tropical and subtropical areas. Because of the vigorous growth habit, bougainvillea needs a lot of labor-intensive pruning when being used as a potted plant. PGRs could be alternatives to frequent pruning on bougainvillea to reduce labor costs. But, little research has been carried out on the use of plant growth retardants (PGRs) for controlling the growth and flowering. The present investigations were carried out to study the effect of growth regulators mainly; paclobutrazol, daminozide and maleic hydrazide on bougainvillea cv Mahara to induce dwarfing. The experiment was laid out in completely Randomized Block Design with 11 treatments and four replications. The rooted cuttings of bougainvillea were planted on 7 July 2012 in earthen pot (10” diameter) containing potting media consisting of sand: soil: FYM in a ratio of 1:2:1. The plants were pruned to a uniform height of 10+2 inches on 3rd September 2012. The growth regulators were applied in the form of foliar spray or drench and data was recorded for vegetative and flowering traits. After 14 weeks, it was observed that there was a significant reduction in plant height and plant spread when paclobutrazol was applied in the form of spray or drench. However, application of maleic hydrazide inhibited the plant growth, on the contrary increased plant height and plant spread over control (Distilled water spray) was observed with 5000 ppm Daminozide (B-9) application. Drench application of paclobutrazol @30 ppm resulted in highest flower index as compared to other treatments.

Cottonseed yield and its quality as affected by mineral fertilizers and plant growth retardants

The increase in the population in Egypt makes it imperative to explore promising approaches to increase food supply, including protein and oil, to meet the needs of the Egyptian people. Cotton is the principal crop of Egyptian agriculture, it is grown mainly for its fiber, but cottonseed products are also of economic importance. Cottonseed is presently the main source of edible oil and meal for livestock in Egypt. Economic conditions in modern agriculture demand high crop yields in order to be profitable and consequently meet the high demand for food that comes with population growth. Oil crop production can be improved by development of new high yielding varieties, and the application of appropriate agronomic practices. There is limited information about the most suitable management practice for application of N, P, K, Zn, Ca and PGRs in order to optimize the quantity and quality of oil and protein of cottonseed. In maximizing the quantity and quality of a crop’s nutritional value in terms of fatty acids and protein, field experiments were conducted to investigate the effect of nitrogen, phosphorus, potassium, foliar application of zinc and calcium, the use of plant growth retardants (Pix, Cycocel or Alar), on cottonseed, protein, oil yields, and oil properties of Egyptian cotton. From the findings of this study, it seems rational to recommend that application of N, P, K, foliar application of Zn and Ca, the use of PGRs (Pix, Cycocel or Alar), could bring about better impact on cottonseed yield, seed protein content, oil and protein yields, oil refractive index, unsaponifiable matter, and unsaturated fatty acids in comparison with the ordinary cultural practices adopted by Egyptian cotton producers.

Review on application of plant growth retardants in medicinal plants cultivation

Plant growth retardants are widely used in cultivation of medicinal plant, but there is still lack of scientific guidance. In order to guide the use of plant growth retardants in medicinal plant cultivation efficiently and reasonably, this paper reviewed the mechanism, function characteristic, plant and soil residue of plant growth retardants, such as chlorocholine chloride, mepiquat chloride, paclobutrazol, unicnazle and succinic acid, and summarized the application of plant growth retardants in medicinal plants cultivation in recent years, with focus on the effect of growth and yield of the officinal organs and secondary metabolites.

Direct and residual effects of plant nutrition’s and plant growth retardants, on cottonseed

Seed quality is one of the most important factors for stand establishment in cotton (Gossypium Sp.), and the use of good-quality seeds is therefore essential to obtain an optimum plant population. Conditions prevailing during seed formation can affect the quality of seed produced, and hence crop establishment in the next growing season. These conditions can affect the germination of the seeds and the ability of the seedlings to emerge from soil. Field experiments were conducted to investigate the effect of nitrogen (N), phosphorus (P), potassium (K), foliar application of zinc (Zn) and calcium (Ca), and the use of plant growth retardants (PGR) [e.g., 1, 1-dimethyl piperidinium chloride (MC); 2-chloroethyl trimethyl ammonium chloride (CC); or succinic acid 2, 2-dimethyl hydrazide (SADH)], during square initiation and boll setting stage, on growth, seed yield, seed viability, and seedling vigor of Egyptian cotton (G. barbadense). Dry matter yield, total chlorophyll concentration, K, Zn and P-uptake plant-1, were increased with the addition of K, foliar application of Zn, and different concentrations of P (576-1728 g·ha-1 of P). Seed yield plant-1 and plot-1, seed weight, seed viability, seedling vigor, and cool germination test performance increased as a result of the addition of the high N-rate (142.8 kg·ha-1 N), the high P-rate (74 kg·ha-1 P2O5), K (47 kg·ha-1 K), and from application of Zn, and Ca and the PGR. From the findings of the present study, band application of such treatments showed improved cotton-seed yield and affected the quality of seed produced, and hence crop establishment in the next growing season.

Artificial light from light emitting diodes (LEDs) with a high portion of blue light results in shorter poinsettias compared to high pressure sodium (HPS) lamps

Strict control of morphogenesis is essential in production of potted poinsettia. Commonly, this is obtained by the use of plant growth retardants (PGRs), often in combination with early morning temperature drops. Due to negative effects on human health and the environment, the use of PGRs is becoming restricted. Also, energy-saving growth regimes and periods of high temperatures limit effective use of temperature drops. In the present study the use of a high proportion of blue (B) light provided by light emitting diodes [LEDs, 20% blue (B), 80% red (R)] was compared with traditional high pressure sodium (HPS) lamps (5% B) providing similar phytochrome photostationary state to produce compact poinsettia plants. Both in the greenhouse and growth chamber, all cultivars were 20–34% shorter for LED compared to HPS grown plants. Also, leaf and bract area as well as chlorophyll content and total dry matter accumulation were lower under LED. The LED did not delay bract color formation, visible cyathia and flowering compared to HPS, and no difference in post production performance (cyathia/bract abscission or necrosis) between the two light treatments was found. The effect of end of day-red (EOD-R) lighting combination with LED and HPS supplemental lamps during the photoperiod in the greenhouse was also investigated. Reduced stem extension (13%) was observed under HPS only and for one of the two cultivars tested, whereas under the LED regime, there was no effect of EOD-R lighting.

End-of-day Lighting with Different Red/Far-red Ratios Using Light-emitting Diodes Affects Plant Growth of Chrysanthemum × morifolium Ramat. ‘Coral Charm’

Controlling plant height without the use of plant growth retardants is one of the goals in future production of potted plants. Light quality with a low red to far-red ratio (R:FR) increases plant height. In this trial, the effects of light quality [R:FR ratio of 0.4, 0.7, and 2.4 (R = 600–700 nm, FR = 700–800 nm)] at the end of day were investigated on potted chrysanthemums using growth chambers. After a 9-h photoperiod, the 30-min end-of-day lighting was provided by light-emitting diodes at low irradiance by maintaining either red = 1 μmol·m−2·s−1 (Rcon) or far-red = 1 μmol·m−2·s−1(FRcon). After 3 weeks of end-of-day lighting, plants given the lowest end-of-day ratios (R:FR of 0.4 or 0.7) were taller than control plants (R:FR = 2.4). For low ratios of R:FR (0.4), the actual intensities of R and FR did not affect plant height, whereas for higher ratios of R:FR (0.7 and 2.4), plant height was greater for FRcon than for Rcon. Leaf area of the lateral side shoots was lower for plants treated with an R:FR of 0.4 compared with those of controls. Dry weight, stem diameter, number of internodes, and number of lateral branches were unaffected by the end-of-day ratio.

Height Control of Picea spp. and Chamaecyparis lawsoniana with Uniconazole and 6-Benzyladenine

Abstract The use of plant growth retardants (PGRs) could benefit conifer growers by enabling them to produce more uniform, live tabletop Christmas tree specimens. We applied two PGRs to determine effectiveness on height control and terminal bud density for the following species of conifer seedlings: Black Hills spruce (Picea glauca var. densata), Serbian spruce (P. omorika), Colorado blue spruce (P. pungens), and Port Orford cedar (Chamaecyparis lawsoniana). The chemicals were applied at 2-week intervals throughout an 8-week period for a total of four applications. Uniconazole was applied as a foliar spray and soil drench (5 and 1 ppm, respectively), 6-benzyladenine (BA) was applied as a foliar spray (500 and 1000 ppm), and the control did not receive a PGR application. Uniconazole was generally effective on the spruces but not on Port Orford cedar, whereas BA reduced height of all species and increased spruce bud densities. However, BA treatments were phytotoxic in all species tested. The drench of uniconazole caused minor phytotoxicity in Black Hills spruce, whereas foliar applications to Port Orford cedar had minor phytotoxic effects.

Storage of Chrysanthemum (Dendranthema grandifiorum (RAMAT.) KITAMURA) Plantlets in vitro

Plant tissues or plantlets can be stored in vitro by the two methods; show growth or cryopreservation. The former is known as a useful method for short or medium term storage of shoot cultures.In this study, the slow growth of chrysanthemum was studied in several ways: (1) by maintaining the cultures at 10°C, that is a temperature much lower than the optimal culture temperature, (2) by supplying carbon source at levels either above or blow those generally considered to be optimal, (3) by inducing osmotic stress by the addition of osmotica, (4) by the use of plant growth retardants. The cultures were incubated on a medium containing 0.3% Hyponex (6.5-6-19) and 2% sucrose at 25 or 10°C at a constant 1, 500lux.The growth of chrysanthemum plantlets and the absorption of N, P and K at 10°C was slower than that at 25°C. The plant cultured at 10°C showed short internodes and lobated mature type leaves. When sucrose was reduced or mannitol was added at the level of 2-8% in the medium, the growth of chrysanthmum plantlets was significantly reduced. The plant growth retardants were also effective in the reduction of growth.These experiments have shown that chrysanthemum can be successfully maintained in vitro for one year or more without transfer to fresh culture medium by culturing on the sucrose free medium at 10°C.

Book Reviews

Book reviewed in this article:A revised Handbook to the Flora of Ceylon. Volume I. Ed. by M. D. Dassanayake and F. R. FosbergResults and Problems in Cell Differentiation. Volume 10. Chloroplasts. Ed. by J. Reinert.Plant Disease. An advanced treatise. Vol. V. How Plants Defend Themselves. Ed. by J. G. Horsfall and E. B. Cowling.Recent Developments in the Use of Plant Growth Retardants. Ed. by D. R. Clifford and J. R. LentonQuaternary Palaeoecology. By H. J. B. Birks and Hilary H. Birks.Seeds and Their Uses. By C. Duffus and C. Slaughter.Studies in Biology no. 124, Light and Plant Life. By Jean M. Whatley and F. R. Whatley.