Chemical Plant Growth Regulators Research Articles

Improving yield and polyphenol content of Perilla frutescens (L.) by foliar methionine application

Perilla frutescens (L.) is a popular medicinal plant cultivated primarily for its pharmacological benefits. Research has recently focused on boosting crop yield without using excessive chemical fertilizers and plant growth regulators which could harm the environment and human health. One of them, methionine, has been discovered to play a crucial role in synthesizing growth-regulating compounds and accumulating secondary compounds in some plants. This study investigated the effects of methionine concentrations (0, 50, 100 and 150 mg/L) on the growth of Perilla frutescens. Agronomic, physiological and biochemical parameters were assessed. The results of the variance analysis show that spraying methionine increases the agronomic parameters. Additionally, methionine spraying increased photosynthetic and respiration rates. Compared to the control, spraying 150 mg/L of methionine increased phenolic and flavonoid accumulation by 89% and 115% respectively. These findings might provide a rationale from a scientific standpoint for cultivating Perilla frutescens to increase polyphenol content.

Chemical Characteristics and Plant Growth Regulators of Organic Waste as Liquid Organic Fertilizer

Abundant agricultural waste could be used to improve plant growth. This study was to obtain the nutrient characteristics and plant growth regulators (PGR) of organic waste (eggshells, banana peels, moringa leaves, onion peels, bean sprouts, and banana hump) which have the potential as liquid organic fertilizer (LOF). This research was conducted from July to August 2022 using a descriptive-analytic method. Organic waste was fermented anaerobically. The results showed that nitrogen content in banana peels, moringa leaves, onion peels, bean sprouts, and banana hump required the LOF standard (3-6%) and had the potential to be applied. In addition, eggshells had the highest calcium content (0.149%) compared to other organic wastes. Among the organic wastes, it was found that banana hump, moringa leaves, and onion peels had the highest PGR levels.

Height Control of Greenhouse-grown Pansy Using Colored Shade Nets

Pansy (Viola ×wittrockiana) is a greenhouse crop commonly grown under black shade net; it often requires the use of chemical plant growth regulators to maintain a compact growth habit. Nonchemical efforts to alter plant morphology, such as height, would provide a more sustainable solution than chemical application. The objective of these studies was to evaluate the effects of different colors of shade nets on controlling growth and flowering of pansy. In Expt. 1, ‘Clear Yellow’, ‘Buttered Popcorn’, and ‘Deep Orange’ pansy plugs were placed under 30% blue or black shade net or, as a control group, where grown with no shade net. In Expt. 2, the same three cultivars of pansy were grown under 50% black, red, pearl, or aluminized shade net. Data were collected on plant height, plant width, flower number, plant survival, soil plant analysis development chlorophyll meter (SPAD) readings, and light quality. In Expt. 1, the blue shade net reduced height to flower and height to leaves, but also decreased flower number and plant survival as compared with black shade net. All plants under no shade died. In Expt. 2, SPAD, an indicator of plant quality by estimating leaf greenness, was found to be lower under black shade net, whereas pearl shade net led to a decrease in plant height and no effect on the number of flowers. Light quality, including red-to-far-red ratio, varied among shade treatments, whereas light intensity was reduced under aluminized, black (50%), and red shade nets compared with other shade treatments. Blue and pearl shade nets both reduced plant height, but blue shade net also reduced plant survival and flowering.

Isolation, Screening, and Molecular Characterization of Rhizosphere Derived Potential Biofertilizer from Different Crops Land for Sustainable Agriculture and Environment

Overpopulation in world has created immense pressure on agricultural land to increase crops production by using excess chemical fertilizers, pesticides, and plant growth regulators. Nowadays, biofertilizer is one of the best concerns of research interest for sustainable development in agriculture and environment. About 30 soil bacteria were isolated from three different locations in Bangladesh by growing on nitrogen-free selective media and primarily had been categorized based on colony features. However, to short out the biofertilizer and biocontrol potential bacteria several assay had been conducted including nitrogen-fixing assay, ammonia production assay, phosphate solubilizing assay, IAA production assay, siderophores production assay, amylase production assay, biocontrol assay, and seed germination bioassay. Different species of Rhizobium, Bacillus, Paraburkholderia, Priestia, Arthrobacter, Pseudarthrobacter, Rhodanobacter, Flavobacterium, Mucilaginibacter, and Sphingomonas were identified by analyzing 16S rRNA gene partial sequence analysis by BLASTn that revealed many of these act as biofertilizer. Moreover, the antibiotic resistance tests of biofertilizer potential isolates and all others intensive data analysis in respect of biofertilizer functionality revealed that Paraburkholderia sacchari is the best while Priestia megaterium, Bacillus zanthoxyli, Arthrobacter globiformis, and Bacillus wiedmanni have also the potentiality to be biofertilizer. The outcome will help the researchers and industries to develop biofertilizer for crops plant.

Growth regulation by air stream-based mechanical stimulation in tomato (Solanum lycopersicum L.) – Part II: Phenotypic and physiological responses

Plant responses to mechanical stimulation have a great potential for growth control of ornamentals plants and vegetable seedlings and is a major requirement to ensure plant compactness and stability. 21 days old tomato (Solanum lycopersicum cv. ‘Romello’) plants were exposed to regularly applied mechanical stimuli for 14 days by applying of a defined air stream through a custom-built air stream applicator. Air stream application gradually reduced total plant leaf area by 14% and promoted radial growth relative to internode length compared to the untreated control, resulting in a more compact and stable plant phenotype, which was also related to an increased stem dry matter content of the air stream-treated plants. The reduction in total plant leaf area was compensated for the translocation of proportionally more assimilates to light-harvesting tissues and to stems at the expense of dry mass accumulation in petioles. Total stem, leaf and root dry mass of air stream-treated plants were unaffected. The specific leaf area of the air stream treated plants was reduced compared to the control, resulting in an increased relative leaf greenness and consequently in an 8% higher net carbon assimilation rates on average compared to the control. Thereby, air stream-treated plants were able to maintain overall biomass accumulation at the same level as the control. Leaf transpiration rate of air stream treated plants was not markedly affected in the long-term. The technique presented should be easily transferable to other plants, such as ornamentals where the application of chemical plant growth regulators is still the most common technique for plant growth control.

Evaluation of energy use and carbon dioxide emissions from the consumption of fossil fuels and agricultural chemicals for paste tomato cultivation in the Bursa region of Turkey.

This study was aimed to determine the fossil fuel consumption, energy use, and carbon dioxide (CO2) emissions in per unit production area (ha) considering the petroleum products (PP) directly used and the chemical fertilizers and pesticides for the cultivation of paste tomatoes in open-field conditions in Bursa region of Turkey. The primary data of the study consisted of data collected by making face-to-face surveys with the producers of paste tomatoes in the Bursa region. The direct energy inputs and CO2 emissions related to diesel fuel and lubricant oil consumptions of engines of agricultural tractors for cultivation operations and the indirect energy inputs and CO2 emissions related to the manufacturing of chemical fertilizers and plant growth regulators used for plant nutrition and pesticides used for plant protection were determined for paste tomato cultivation. A total of 288.6 L diesel fuel and 0.067 L lubrication oil are consumed per hectare when using tools and machinery in paste tomato production. A total of 408 kg of chemical fertilizers and 15.5 kg of pesticides are used per hectare in paste tomato production in the Bursa region of Turkey. A total of 2343.45 MJ/ha and 2700.5 MJ/ha indirect energy is used in the application of chemical fertilizers and pesticides, respectively. A total of 792.43 kg and 0.189 kg CO2 is released as a result of diesel fuel and lubricant oil consumptions. For the production of one kilogram of paste tomato, 2.68 grams (g) diesel fuel and lubricating oil, 175.02 kilojoules (kJ) of energy is consumed, and 15.88 g CO2 is released in the Bursa region of Turkey.

Overexpression of the Brassica rapa SRS7 gene in pot-type chrysanthemum [Chrysanthemum morifolium Ramat] reduces plant height

Retardation of plant growth is important in horticultural plant production and is generally achieved through the application of various chemical plant growth regulators (PGRs). Chrysanthemum plants grown in pots (pot-mums), are typically treated with PGRs to produce a compact form; however, these compounds can be hazardous to the environment and human health. In an effort to develop a method to produce compact chrysanthemum plants without using PGRs, we introduced the BrSRS7 gene from Brassica rapa L. ssp. pekinensis into chrysanthemum with its expression controlled by the promoter of the chrysanthemum actin gene (CmActin). As a first step, we evaluated the regeneration capacities of seven pot-mum cultivars and identified the Peace Copper (PC) cultivar as having the best regeneration efficiency. After transformation of the BrSRS7 gene into PC followed by selection and 5 rounds of vegetative subcultivation, 11 transgenic lines were identified for analysis. Internode lengths were reduced in all lines compared to control plants, but plant heights of some lines were similar to those of control plants. Four transgenic lines were selected for a sixth round of subcultivation and for further study. We determined the relative expression levels of gibberellin- and auxin-related genes in the four transgenic lines. Of the auxin-related genes, ARF2 and YUCCA10 showed higher expression in the transgenic lines than in the control. The expression levels of GA-related genes decreased overall in P-33, which showed the greatest decrease in height. Subjecting the transgenic lines to a dwarfing treatment with the PGR B9 showed that the plants could be reduced to actual marketable size with only a single dwarfing treatment. Our results demonstrate the possibility of using the BrSRS7 gene to produce compact chrysanthemum plants with reduced or no use of PGRs.

In vitro Shoot Multiplication of Curcuma xanthorrhiza with Coconut Water and Banana Extract Nutrient

Curcuma xanthorrhiza is a medicinal plant, commonly used for spices, growth by rhizome, which is as its main product. Its rhizome demand both quantity and quality are increasing every year. Tissue culture techniques can achieve the efforts for providing plant materials massively in the short-term time with free from pest. In vitro, multiplication is an alternative production method. However, it is still limited by high chemical cost and plant growth regulators. Moreover, various natural materials can be used as a substitute for plant growth regulators, such as coconut water extract and various organic materials. The purpose of this study is to assess the response of Curcuma xanthorrhiza explants with coconut water, and Cavendish bananas extract by in vitro. The experiments conducted in February until May 2016 in the Laboratory of Plant Physiology and Biotechnology, Faculty of Agriculture, Sebelas Maret University Surakarta. A completely randomized design was applied with two factors: the first factor was the four concentrations Cavendish banana fruit extract: 0 g/l, 50 g/l, 100 g/l and 150 g/l. The second factor were the 4 concentrations coconut water: 0 ml/l, 100 ml/l, 150 ml/l, and 200 ml/l. The observed variables were the period of shoots to appear, the period of leaves to appear and the period of roots to appear, the number of shots, the number of leaves, the number of roots, the height of shoots, the length of leaves and the length of roots. Observed data analyzed by descriptive and variance analysis continued with Duncan Multiple Range Test (DMRT). Research results showed that there were some effects on coconut water and Cavendish banana extract treatment toward the average time of shoots appear, number of shoots, number of leaves and length of leaves. The best treatment for this research is a combination of coconut water at 150 ml/l and 100 g Cavendish banana extract.

Using Light Quality for Growth Control of Cucumber Seedlings in Closed-Type Plant Production System.

During seedling production, growth control of seedlings is an important problem because the overgrowth of seedlings causes a decrease of seedling quality and has disadvantages after transplanting. In this study, we aim to evaluate the possibility of replacing chemical plant growth regulators using light quality in a closed-type plant production system (CPPS) for cucumber seedling production. We used various light treatments, such as monochromatic or combined red (R) and blue (B), and combined R and B with UV-A or Far-red (Fr) light, to compare with a chemical plant growth regulator conventionally using in nursery farms. The combined R and B treatment decreased stem elongation and increased dry matter and compactness. UV-A treatment increased compactness but did not significantly affect the stem elongation or dry matter. Fr increased stem elongation and stem diameter and decreased compactness and dry matter. In leaf growth, combined R and B treatments and UV-A treatments increased leaf area, specific leaf weight, and SPAD value, and decreased leaf shape index. Fr treatments increased leaf area and leaf shape index and decreased specific leaf weight (SLW) and SPAD values. Cucumber seedlings have many different morphological changes, and R5B5 light quality was more effective in growth control due to higher compactness than chemical plant growth regulators. Also, R5B5 light quality has increased seedling quality, such as dry matter and SLW compared with fluorescent lamps. Thus, the use of light quality is a possible alternative to a chemical plant growth regulator.

Rhizogenic agrobacteria as an innovative tool for plant breeding: current achievements and limitations.

Compact plant growth is an economically important trait for many crops. In practice, compactness is frequently obtained by applying chemical plant growth regulators. In view of sustainable and environmental-friendly plant production, the search for viable alternatives is a priority for breeders. Co-cultivation and natural transformation using rhizogenic agrobacteria result in morphological alterations which together compose the Ri phenotype. This phenotype is known to exhibit a more compact plant habit, besides other features. In this review, we highlight the use of rhizogenic agrobacteria and the Ri phenotype with regard to sustainable plant production and plant breeding. An overview of described Ri lines and current breeding applications is presented. The potential of Ri lines as pre-breeding material is discussed from both a practical and legal point of view.

Рeculiarities of development of potato diseases Alternaria solani and Phytophthora infestans when applying various types of plants protection

The article observes peculiarities of the development of Alternaria solani and Phytophthora infestans potato pathogens for the use of chemical and biological agents and plant growth regulators (PGR) under laboratory conditions. All fungicides of chemical origin — Consento 450 SC, Acrobat MC, Centurion, Anthracol 70 WP, for efficiency were equivalent and showed high efficacy (100%) in laboratory conditions in terms of limiting the development of pathogens of leaf diseases potatoes. The use of biological preparations reduced the development of pathogens of fungi, indicating their effectiveness. The best effect was shown by Phytosporin — M, n — on the 14th day of the experiment, the development of diseases (diameter of the colony on the nutrient medium) was 71.1 and 19.3 mm, which is higher than control at 22.8 and 27.9 mm, respectively. Among PPPs, the most effective for the development of Phytophthora infestans was Gumysol, And in relation to Alternaria solani — Gumysol, Rh. And Poteitin.

A Review of Root Pruning to Regulate Citrus Growth

Root is the important plant organ hiding below the soil that serves as plant supporting structure, water and nutrient supplier and assimilates storage. Root growth occurs in turn with shoot part, forming repeated cyclic pattern because of the photosynthate competition. Root growth regulation is one of the promising practices to boost the yield of fruit tree, especially citrus that is economically important and highly demanded fruit. Root pruning varied based on the scale of intensity and plant growth stage, including air root pruning, knife root pruning and modern pruning using root pruner machine mounted to a tractor. Root pruning to induce the growth of more fi brous root system and to correct root deformation at seedling stage have potentials to improve post-transplant growth. Besides, it has a potential to replace the use of chemical plant growth regulator for a more environmentally friendly practice. The pruning of root impeded the canopy growth, altered the plant water status leading to fl ower promotion. In addition, it is also a promising practice to overcome the alternate bearing on fruit tree, including citrus, through the suppressing of excessive growth and restricting the high fruit load during the ‘on year’ and allowing a better carbohydrate storage for the improvement of yield during the ‘off year’.

Morphology and growth of ornamental seedlings grown under supplemental light-emitting diode lighting and chemical plant-growth regulators

Morphology and growth of ornamental seedlings grown under supplemental light-emitting diode lighting and chemical plant-growth regulators

Chemical plant protectants and plant growth regulator effects on annual bluegrass survival of ice cover

AbstractAnnual bluegrass (Poa annua L; ABG) is susceptible to damage from ice cover. Effects of chemical treatments on ice survival under low temperature growth chamber conditions were studied. Field putting green plots of ABG were treated in the fall of 2014 and 2015 with Civitas, mefluidide, propiconazole or trinexapac‐ethyl (TE) at label rates. After acclimation, turfgrass cores from each plot were transferred to a low temperature growth chamber, received ice or no ice treatment and were sampled at 0, 20, 40 and 60 days. Ice was applied by misting plants at low temperature. In 2014, Civitas‐, mefluidide‐ and propiconazole‐treated plugs had the greatest amount of regrowth after ice and no ice treatments on most days; comparable results were found in 2015 but fewer statistical differences were detected. TE‐treated plants were no different from the untreated controls on most days in either year. Plants that were treated with mefluidide, propiconazole and Civitas had more polyunsaturated fatty acids (FA) in crown tissue, with linoleic acid approximately 50% greater compared to TE and untreated samples. Civitas, mefluidide or propiconazole treatments improved ABG survival of simulated ice conditions, which could be associated with the changes to saturated and unsaturated FA ratios that were observed in this study.

Thigmomorphogenesis – Control of plant growth by mechanical stimulation

Abstract Controlled regulation of plant growth is a general prerequisite for the production of marketable ornamental plants. Consumers as well as retailers prefer stronger, more compact plants with greener leaves as these not only better meet a certain desired visual quality but also allow for a maximization of production per unit area as well as facilitation of packaging and transport. The same applies for the production of young vegetable plants. Special attention is paid to solid, compact and resilient plants that survive transport and planting without any problems. During the last decades plant growth control has mainly been achieved through the application of chemical plant growth regulators that generally interfere with the function of growth regulating hormones. However, there is an increasing demand to replace chemical treatments by other means such as the modulation of growth conditions, including temperature, light and fertilization. Alternatively, the application of mechanical stimulation has been shown to induce plant responses that yield some of the commercially relevant phenotypes including increased compactness, higher girth, darker leaves and a delay in flowering. The ability of plants to sense and respond to mechanical stimuli is an adaptive trait associated with increased fitness in many environmental settings. Mechanical stimulation in nature occurs e.g. through wind, rain, neighboring plants or predatory animals and induces a range of morphogenic responses that have been summarized under the term thigmomorphogenesis. We are only just about to begin to understand the molecular mechanisms underlying mechanosensing and the associated morphogenic changes in plants. However, a number of examples suggest that mechanical stimulation applied in a greenhouse setting can be used to alter plant growth in order to produce marketable plants. In this review will briefly summarize the current knowledge concerning the biological principles of thigmomorphogenesis and discuss the potential of mechanical growth regulation in commercial plant production especially with respect to organic horticulture.

EFFECTS OF AGRICULTURAL PRACTICES ON SOIL FAUNA COMMUNITIES IN KIWIFRUIT PLANTATIONS

Kiwifruit is intensively produced in Galicia (NW Spain) by either conventional (CONV) or organic (ORG) farming practices. In the former case, large amounts of chemical fertilizers, pesticides, herbicides and plant growth regulators are applied, whereas the ORG systems rely on natural amendments to minimise the adverse impacts on the environment. Soil fauna play a critical role on soil organic matter transformations and hence, any alteration in the structure of their communities could have important implications for soil fertility. Therefore, in this study, we compared the abundance and diversity of macrofauna (earthworms and macroarthropods) and mesofauna (enchytraeids, mites and collembolans) in organically and conventionally produced kiwifruits crops. Replicate soil samples (PVC cores: 83 cm2 and quadrats: 2500 cm2) were collected from CONV and ORG plots monthly from March 2013 to February 2014 and the soil organisms from each extracted, identified and counted. Results showed that management significantly affected total soil fauna abundances, with a 31% reduction in CONV treatments when compared to the ORG ones. Furthermore, agricultural practices also had a significant effect on the community structure and while earthworms were negatively affected by CONV treatments (76% reduction), mesofauna clearly benefited from these practices. In contrast, the soil communities under ORG systems were less diverse than those under the CONV ones. In conclusion, agricultural practices profoundly affect the numbers and kinds of organisms by altering their densities and the ratios of the different groups. In particular, larger bodied earthworms appeared to be the most sensitive organisms to external agricultural inputs.

Determining the Effect of Carrier Water pH and Bicarbonate Concentration on Final pH of Plant Growth Regulator Solutions

Chemical plant growth regulators (PGRs) are important tools in greenhouse ornamental crop production because growers must increasingly meet specifications for plant shipping and marketability. However, the role of water quality parameters such as pH or alkalinity (bicarbonate in this study) on final PGR solution pH is not well documented and could impact efficacy. We assessed the interaction of PGR type and concentration on the final spray solution pH when combined with carrier water of varying pH and bicarbonate concentration. Eleven PGRs commonly used in floriculture (ancymidol, benzyladenine, chlormequat chloride, daminozide, dikegulac-sodium, ethephon, flurprimidol, gibberellic acid, gibberellic acid/benzyladenine, paclobutrazol, and uniconazole) at three concentrations (low, medium, and high recommended rates for each product) were added to reverse osmosis (RO) carrier water adjusted to four pH (5.3, 6.2, 7.2, 8.2) levels or added to tap carrier water adjusted to four bicarbonate concentrations (40, 86, 142, 293 mg·L−1 of CaCO3). Resultant solution pH levels were measured. Plant growth regulators were categorized as acidic, neutral, or basic in reaction based on the change of the carrier water pH on their addition. Benzyladenine, chlormequat chloride, gibberellic acid, and gibberellic acid/benzyladenine acted as weak acids when added to RO water, whereas daminozide, ethephon, and uniconazole reduced final solution pH from 1.25 to 5.75 pH units. Flurprimidol and paclobutrazol were neutral in reaction with final solution pH being similar to that of the RO carrier water before their addition. Ancymidol and dikegulac-sodium were basic in reaction, increasing final solution pH in RO carrier water up to 2.3 units. There was an interaction between chlormequat chloride concentration and RO carrier water pH on change in pH. When added to tap carrier water, final solution pH increased for all except the stronger acids, daminozide, ethephon, and uniconazole, where it decreased up to 3.5 units, and benzyladenine, where it decreased 0.35 units at 40 mg·L−1 bicarbonate. There was an interaction between PGR concentration and bicarbonate concentration in tap carrier water for daminozide and ethephon. The magnitude of change in pH (final solution pH minus initial carrier water pH) with the addition of each PGR was greater for RO than for tap water containing 40 to 293 mg·L−1 bicarbonate for all 11 PGRs tested.

Development of Specific Inhibitors of CYP707A, a Key Enzyme in the Catabolism of Abscisic Acid

Abscisic acid (ABA) is a plant hormone involved in stress tolerance, stomatal closure, seed dormancy, and other physiological events. Although ABA is registered as a farm chemical (plant growth regulator), its practical use has been limited, mainly due to its weak effect in field trials, which is considered to be due to its rapid inactivation through biodegradation. Catabolic inactivation of ABA is mainly controlled by ABA 8'-hydroxylase (CYP707A), which is the cytochrome P450 catalyzing the C8'-hydroxylation of ABA into 8'-hydroxy-ABA and its more stable tautomer, phaseic acid, which has much lower hormonal activity than ABA. Thus, a specific inhibitor of CYP707A is promising not only as a chemical probe for the mechanism of ABA action, but also because of its potential use in agriculture and horticulture. This review article focuses on our recent research on the development of two types of specific inhibitors of CYP707A: the ABA analogue-type inhibitors that were designed on the basis of differences between the structural requirements for CYP707A and for ABA activity, and the azole-type P450 inhibitors that were developed by conformational restriction or enlargement of the plant growth retardant uniconazole.

Far-red light filtering by plastic film, greenhouse-cladding materials: effects on growth and flowering in Petunia and Impatiens

SummaryPhotoselective plastic films with low transmission to far-red (FR) light (700–800 nm) are now available so that plants grown in greenhouses clad with such plastics exhibit reduced stem extension and, consequently, plant height. Here we compare the action of three FR-absorbing polythene films on extension growth of Petunia (Petunia hybrida) cv. ‘Express Blue’ and Impatiens walleriana cv. ‘Accent Deep Pink’ with plants grown under a control polythene film (standard UVI/EVA film). Half of the plants under the control film were treated with a chemical plant growth regulator (PGR; diaminozide, B-Nine) and half were sprayed with water alone. Possible negative effects of such film plastics on flowering, and on fresh and dry weight accumulation, were also quantified. Plants were harvested destructively when all plants in each treatment had reached the first open flower stage. In Petunia, plant height was reduced by all three FR-filtering films and by PGR-treatment. The FR-filtering films giving the highest R:FR ratios also reduced plant height in Impatiens. Leaf number, leaf area and total dry weight in both species were greatest in the controls and smallest under films with the lowest PAR transmission. The film giving the highest R:FR ratio and PAR transmission also produced the most compact Petunia plants; while the film with the lowest PAR transmission produced the least compact plants in both species. There was no significant effect of treatments on time to first flower in Impatiens. However, Petunia plants under low PAR transmission films took longer to flower. Plastic films which filter out FR light to increase the R:FR ratio, combined with high PAR transmission, can therefore be used as an alternative to conventional PGRs.

PHENOTYPIC CHARACTERIZATION OF PETUNIA PLANTS EXPRESSING AN INDOLEACETIC ACID (IAA)-LYSINE SYNTHETASE TRANSGENE DRIVEN BY A SHOOT SPECIFIC PROMOTER

ISHS XXVI International Horticultural Congress: Biotechnology in Horticultural Crop Improvement: Achievements, Opportunities and Limitations PHENOTYPIC CHARACTERIZATION OF PETUNIA PLANTS EXPRESSING AN INDOLEACETIC ACID (IAA)-LYSINE SYNTHETASE TRANSGENE DRIVEN BY A SHOOT SPECIFIC PROMOTER