Silver nitrate and adenine sulphate induced high regeneration frequency in the recalcitrant plant Cosmos bipinnatus using cotyledon explants

Plant regeneration ability was studied in the medicinal-ornamental plant, Cosmos bipinnatus ‘Sonata white’, which is a dicotyledonous recalcitrant plant to shoot induction. Cotyledons were used as sources of explants to investigate plant regeneration. High frequency of direct shoot induction was obtained when BA (5 mg/l) and AgNO₃ (5 mg/l) were used in combination with 20 mg/l adenine sulphate (73.8%) in Murashige and Skoog (MS) medium. The highest shoot number per explant (5.7) was induced on MS medium supplemented with 5 mg/l BA, 5 mg/l AgNO₃, and 40 mg/l adenine. Eight week-old shoots were transferred to root induction media containing MS and half-strength MS medium with different concentration of IBA. The highest rate of root induction (70.8%) was obtained on half-strength MS medium with 1.5 mg/l IBA within four weeks. The plantlets were transferred to pot and kept in the greenhouse condition. Seventy percent of the plantlets successfully acclimatised.

Abbreviations: BA, 6-benzylaminopurine; IBA, Indole-3-butyric acid; MS, Murashige and Skoog; PGRs, plant growth regulators.     

Application of 1-MCP as a liquid formulation prevents ethylene-induced senescence in Phalaenopsis orchid flowers and Kalanchoë blossfeldiana inflorescences

This study provides a very first report on the use of a sprayable formulation of 1-MCP, Harvista^TM, on ornamental plant species. Individual florets of Phalaenopsis and inflorescences of Kalanchoë blossfeldiana were sprayed with 1, 2, 4, or 6% Harvista^TM and this was compared to the commonly used 1-MCP formulation, SmartFresh^TM, which is administered as a powder releasing gas. Harvista^TM treatments for Kalanchoë were in addition also compared to plants treated with an alternative ethylene receptor blocker, STS, as well as with transgenic plants expressing the etr1-1 mutant gene of Arabidopsis thaliana.

In the presence of ethylene, Harvista^TM at all concentrations (except 1% for Kalanchoë), as well as the conventional SmartFresh^TM treatment, prevented wilting of florets and significantly extended their display life compared to that of control treatments: up to twofold for Kalanchoë and up to fourfold for Phalaenopsis. For Kalanchoë the best display life was, however, presented by etr1-1 transgenic plants. The efficacy and suitability of using Harvista^TM, a sprayable formulation of 1-MCP, was compared to using the gaseous application of SmartFresh^TM, or the environmental hazardous silver treatment, against having to consider expensive and lengthy genetic modification with etr1-1 as commercial alternatives to achieve protection against the detrimental effects of ethylene.

Abbreviations: 1-MCP, 1-methylcyclopropene; STS, silver thiosulfate     

First reported case of spontaneous hermaphrodism in female date palm (Phoenix dactylifera L.), cv ‘Alligue’

The date palm (Phoenix dactylifera L.) is dioecious with male flowers deficient in functional gynoecium and female flowers deficient in functional androecium borne on separate palms. The presence of male and female flowers on the same plant, a phenomenon known as monoecy, is unusual in male date palms.

This study reports for the first time on hermaphrodite (bisexual) flowers borne by two female date palms, ‘Alligue’, that were found growing in an open field in Degache, southern Tunisia. The observations on these two female palms were compared with hermaphrodite male date palms growing in the same location. Hermaphrodite female date palm inflorescence branches bear female flowers predominantly near their base, in contrast to the hermaphrodite flowers that are found primarily toward their upper part. The position of the hermaphrodite flowers in hermaphrodite male date palms is reversed: inflorescence branches bear male flowers toward the upper part while the hermaphrodite flowers are found at the base. Histological examination of female hermaphrodite flowers revealed that they had three carpels and 1–6 stamens. Hermaphrodite flowers on male plants were usually also composed of three carpels of variable size, and six stamens. Hermaphrodite flowers on both female and male palm trees turn generally into parthenocarpic fruits. The present data support the theory that dioecious plants are derived from a common hermaphrodite ancestor. Floral hermaphroditism in date palm should be investigated in relation to the in planta self-fertilization process to identify sex markers and genes that control sex organ development.     

Oxylipin affects ethylene metabolism and ethylene receptor gene expression levels in peach fruit (Prunus persica L. Batsch)

The effects of two oxylipins – jasmonic acid (JA) and 9, 10-ketol-octadecadienoic acid (KODA) – on ethylene metabolism and ethylene receptor genes were examined in peach fruit (Prunus persica L.) harvested at 88 days after full bloom (DAFB), in the pre-climacteric stage, and at 102 DAFB, at the beginning of the climacteric stage. Immediate post-harvest applications of either n-propyl dihydrojasmonate (PDJ) (a JA analog) or KODA stimulated ethylene production and 1-aminocyclopropane-1-carboxylate (ACC) concentrations in fruit that were harvested at 88 and 102 DAFB. KODA application significantly increased levels of ACC oxidase (PpACO1) expression at 5 and 8 days after treatment (DAT) in 88-DAFB-harvested fruit, and at 1 DAT in 102-DAFB-harvested fruit. Expression levels of ethylene response factors (PpERS1) were not influenced by either PDJ or KODA applications at 88 or 102 DAFB. In contrast, levels of ethylene-receptor-coding genes (PpETR1) expression in 88-DAFB KODA-treated fruit increased at 8 and 14 DAT. Expression levels of constitutive triple response (PpCTR1) in the untreated control fruit decreased with DAT in both 88- and 102-DAFB-harvested fruit.

These results suggest that certain oxylipins may promote ethylene production in peach fruit, and that PpETR1 and PpCTR1 may be associated with the autocatalytic system of ethylene production.     

Transpiration,photosynthetic responses,tissue water relations and dry mass partitioning in Callistemon plants during drought conditions

Callistemon is an Australian species used as ornamental plant in Mediterranean regions. The objective of this research was to analyse the ability of Callistemon to overcome water deficit in terms of adjusting its physiology and morphology. Potted Callistemon laevis Anon plants were grown in controlled environment and subjected to drought stress by reducing irrigation water by 40% compared to the control (irrigated to container capacity). The drought stress produced the smallest plants throughout the experiment. After three months of drought, the leaf area, number of leaves and root volume decreased, while root/shoot ratio and root density increased. The higher root hydraulic resistance in stressed plants caused decreases in leaf and stem water potentials resulting in lower stomatal conductance and indicating that water flow through the roots is a factor that strongly influences shoot water relations. The water stress affected transpiration (63% reduction compared with the control). The consistent decrease in g_s suggested an adaptative efficient stomatal control of transpiration by this species, resulting in a higher intrinsic water use efficiency (P_n/g_s) in drought conditions, increasing as the experimental time progressed. This was accompanied by an improvement in water use efficiency of production to maintain the leaf water status. In addition, water stress induced an active osmotic adjustment and led to decreases in leaf tissue elasticity in order to maintain turgor. Therefore, the water deficit produced changes in plant water relations, gas exchange and growth in an adaptation process which could promote the faster establishment of this species in gardens or landscaping projects in Mediterranean conditions.     

Response to water stress of some oleander cultivars suitable for pot plant production

Oleander (Nerium oleander L.) is an evergreen shrub of great ornamental interest which, in recent times, has been increasingly used as a flowering pot plant. Plants grown in pots undergo more frequent water stress conditions than those grown in the soil, due to the limited volume of substrate available for the roots. Oleander is a species adaptable to dry conditions and able to survive long periods of drought. It is well known that under water stress conditions all plants reduce photosynthetic activity, resulting in reduced plant growth. In case of severe water stress, leaves undergo strong wilting and senescence resulting in the loss of ornamental value. In the present work, a study was conducted to evaluate the ecophysiological response to water stress in four oleander cultivars previously recognised (on the basis of traits such as size, habit, earliness, abundance and duration of flowering, aptitude for cutting propagation and rapidity of growth) as suitable for pot plant production. Our data confirm the high drought tolerance of oleander. In the studied cultivars, plants submitted to water stress showed only minor variations in leaf gas exchange parameters [transpiration (E), stomatal conductance (g_s) and CO₂ net assimilation (A)] for at least 10 days without a change in leaf water content [assessed as relative water content (RWC)] for 22 days from the beginning of the stress treatment. During this period, non-irrigated plants maintained the same water status as control plants and were visually undistinguishable from them. Moreover, plants survived without water supply for one month. Following the supply of water again, they were able to restore RWC, gas exchange parameters and instantaneous water use efficiency [A/E ratio (WUE_inst)] to the values of control plants. Furthermore, if at the end of the stress period plants appeared withered and were pale green in colour, they regained their normal appearance after they were irrigated again. Although the four studied cultivars showed some minor differences in leaf gas exchange parameters and in the manner in which the latter parameters changed after irrigation was stopped, the response to water stress was essentially the same. Therefore, as far as drought tolerance is concerned, all these cultivars have a good aptitude for use as flowering pot plants.     

The effect of water deficit stress on the growth,yield and composition of essential oils of parsley

Three parsley cultivars (plain-leafed, curly-leafed and turnip-rooted) were grown under conditions of 35–40% and 45–60% water deficit in order to evaluate the effect of this form of stress on plant growth, essential oil yield and composition. Plant growth (foliage and root weight, leaf number) was significantly reduced by water stress, even at 30–45% deficit. Water stress increased the yield of essential oil (on a fresh weight basis) from the leaves of plain-leafed and curly-leafed, but not turnip-rooted, parsley. However, on a m² basis foliage oil yield increased significantly only in curly-leafed parsley. Water stress also caused changes in the relative contribution of certain aroma constituents of the essential oils (principally 1,3,8-p-menthatriene, myristicin, terpinolene + p-cymenene), but these changes varied between cultivars. The oil yield of roots was low and water deficit stress had relatively little effect on the root oil composition. It is concluded that because the biomass of plants subjected to water deficit is reduced, it is possible to increase the plant density of plain-leafed or curly-leafed parsley, thereby further increasing the yield of oil per m². However, the application of water deficit stress to parsley essential oil production must also take into account likely changes in oil composition, which in turn relate to the cultivar.     

Effects of diluted and undiluted treated wastewater on the growth,physiological aspects and visual quality of potted lantana and polygala plants

In many nurseries in the Mediterranean area irrigation water supply is a major problem due to climatic conditions, and it is important to evaluate alternative water resources, such as treated wastewater, for ornamental plant production. For this reason, a nursery study was conducted in order to determine: (1) the effect of irrigation with a saline reclaimed wastewater (reused water) on the growth and visual quality of Lantana camara and Polygala myrtifolia, and (2) the effectiveness of the mixing the same water with canal water to reduce any negative effects observed with the reused water. Potted plants were irrigated with reused water, canal water and reused water diluted 50% with canal water. The results suggest that polygala can be irrigated with reused water since visual damage is minimal and growth reduction very slight, which seems to be related with the plant's low accumulation of saline ions. In lantana, reused water led to an excessive uptake of chloride, sodium and boron in the leaves, which was associated with defoliation, leaf burn, leaf chlorosis and damage to the photosynthetic apparatus, diminishing both growth and its aesthetic value. The dilution of reused water alleviated some negative effects in lantana, but not sufficiently to avoid a significant loss of plant quality.     

Influence of paclobutrazol and substrate on daily evapotranspiration of potted geranium

The application of plant growth regulators and the use of different culture media are common practices in potted ornamental crops. We report the results of a study to evaluate the effect of two substrates (peat moss or coconut fiber) and spraying 30 ppm paclobutrazol (PAC) on water resource management of zonal geranium (Pelargonium × hortorum L.H. Bailey) seedlings growing in a greenhouse during spring–summer. Growth, water consumption, leaching, evapotranspiration rate (ET), water use efficiency (WUE) and leaf water potential were determined. Plant growth was greater in peat moss (peat) than in coconut fiber (coconut), while the use of PAC decreased plant growth in both substrates, although more markedly in peat. Coconut produced a higher leaching fraction than peat in both PAC-treated plants and non-treated plants, although PAC application increased the leaching fraction in both substrates. Water consumption was lower in coconut than in peat and decreased in response to PAC. Peat was more effective at improving the water-use efficiency and increased the electrical conductivity in the leachate, while PAC decreased the latter in this same substrate. Daily ET showed a maximum of 200 mL/pot in peat and a minimum of 60 mL/pot in the coconut-PAC treatment. During the experimental period, accumulated ET values were higher in peat than in coconut, while the application of PAC reduced the value in peat but increased it in coconut. The evolution of ET per hour during the day showed that the highest rate (23 mL/h) was registered at midday in peat, while about 90% of ET occurred between 10 and 18 h in all treatments. When a cycle of water stress and recovery was applied, the peat induced the highest ET values of all treatments during the first days of drought, but the lowest ET after a week of drought. PAC modified this response, favoring a more balanced behavior of ET, although after the second cycle of drought this effect disappeared. Based on these results, the best strategy in normal irrigation conditions would be to use coconut fiber and not apply PAC, because this provides plants of excellent commercial quality with low water consumption. In plants at moderate water deficit PAC played a more important role than the substrate, improving the water status of plants with both substrates used. However, in the face of severe water stress the effect of PAC disappeared and peat acted as a better substrate than coconut fiber.     

不同灌水量对三种园林植物生长的影响

以2a生的臭柏、榆叶梅、山桃为试材,采用盆栽法,将土壤水分梯度分为4个处理等级(即各处理土壤含水量基本保持在田间持水量的15%～25%(T1)、35%～45%(T2)、55%～65%(T3)和不灌水仅靠天然降雨(CK)),分析不同灌水条件对3种园林植物苗木生长的影响。结果表明:3种植物各处理下的生物量均比对照组有所增加,在T3处理时生物量达到最大值,即臭柏为895.28g、山桃为492.01g、榆叶梅为421.86g。各处理条件下臭柏根冠比均无显著性差异;山桃根冠比大小为:CKT1T2T3;榆叶梅根冠比除对照外,随着灌水量的增加而显著减小。3种植物的株高和地径增量随灌水量的增加而增大;并且都在T3处理下增大最为显著。经综合评价,3种园林植物的抗旱能力大小为:臭柏山桃榆叶梅。土壤水分控制在田间最大持水量的55%～65%有利于3种植物的生长,其生物量、地径和株高增加普遍显著好于其它处理,有利于在干旱环境下保持正常生长,为3种园林植物的节水和栽培提供了参考。     

Regulated deficit irrigation in potted Dianthus plants: Effects of severe and moderate water stress on growth and physiological responses

The purpose of this study was to analyze the physiological and morphological response of carnation plants to different levels of irrigation and to evaluate regulated deficit irrigation as a possible technique for saving water through the application of controlled drought stress. Carnations, Dianthus caryophyllus L. cultivar, were pot-grown in an unheated greenhouse and submitted to two experiments. In the first experiment, the plants were exposed to three irrigation treatments: (control); 70% of the control (moderate deficit irrigation, MDI) and 35% of the control (severe deficit irrigation, SDI). In the second experiment, the plants were submitted to a control treatment, deficit irrigation (DI, 50% of the control) and regulated deficit irrigation (RDI). After 15 weeks, MDI plants showed a slightly reduced total dry weight, plant height and leaf area, while SDI had clearly reduced all the plant size parameters. RDI plants had similar leaf area and total dry weight to the control treatment during the blooming phase. MDI did not affect the number of flowers and no great differences in the colour parameters were observed. RDI plants had higher flower dry weight, while plant quality was affected by the SDI (lower number of shoots and flowers, lower relative chlorophyll content). Leaf osmotic potential decreased with deficit irrigation, but more markedly in SDI, which induced higher values of leaf pressure. Stomatal conductance (g_s) decreased in drought conditions more than the photosynthetic rate (P_n). Osmotic adjustment of 0.3 MPa accompanied by decreases in elasticity in response to drought resulted in turgor less at lower leaf water potentials and prevented turgor loss during drought periods.     

Improved water-use efficiency by deficit-irrigation programmes: Implications for saving water in citrus orchards

Water efficiency is a key concept to solve water-shortage problems in semiarid areas. Deficit irrigation (DI) in many crops has frequently proved to be an efficient tool to optimise water-use efficiency. Three different DI strategies were studied for commercial orchards of mature sweet orange (Citrus sinensis L. Osbeck, cv. Salustiana and cv. Navelina) from 2006 to 2008: sustained deficit irrigation (SDI), regulated deficit irrigation (RDI), and low-frequency deficit irrigation (LFDI) all defined physiologically with stem-water potential thresholds. The experimental research plots were located in the Guadalquivir river basin, SW Spain. The effects of DI treatments on the fruit yield and on the crop-water status, by the integrated stem-water potential (Ψ_int) were analysed. Also, the benefits of DI in terms of agricultural water-use efficiency (WUE_agr) and financial water-use efficiency (WUE_f) were estimated for each irrigation strategy. Different relationships were estimated between these parameters and irrigation and total water applied, in order to establish the best irrigation strategy for different irrigation regimes. Yield and Ψ_int showed significant differences consistent with the water amounts applied, although the crop response was influenced by other parameters such as crop variety and irrigation strategy. In this sense, treatments with similar irrigation rates and Ψ_int resulted in different yield values, evidencing the importance of these factors. Regarding the crop variety, the results showed that cv. Salustiana responded better than cv. Navelina to DI, from the physiological and agricultural perspectives. In terms of water savings, the RDI and LFDI reduced water use by between 1000 and 1250 m³ ha⁻¹, respectively, with similar yields in comparison to the fully irrigated treatment, significantly improving the WUE. Consequently, the WUE_f, and WUE_agr were more strongly affected by deficit-irrigation strategy rather than the total water supplied. Thus, the amount of irrigation water would have a relative importance but other variables such as the irrigation strategy, would decidedly influence prudent water management in semiarid areas.     

Influence of water deficit and low air humidity in the nursery on survival of Rhamnus alaternus seedlings following planting

Summary

The effect of irrigation and air humidity on the water relations and root and shoot growth of Rhamnus alaternus L. during the nursery phase was considered to evaluate the resulting degree of hardening obtained by these treatments. R. alaternus seedlings were pot-grown in two greenhouses of equal characteristics. In one of these greenhouses air humidity was controlled using a dehumidifying system, while in the other one the environmental conditions were not artificially modified. In each greenhouse, two irrigation treatments were used. Thus, four different treatments were applied during the nursery phase (January-May): 1) control air humidity + control irrigation; 2) control air humidity + deficit irrigation; 3) low air humidity + control irrigation; 4) low air humidity + deficit irrigation. In May, plants of all treatments were transplanted and grown in good environmental and irrigation conditions for one month (17 May–20 June), after which they received no irrigation until the end of the experiment (14 July). Low air humidity and water deficit reduced all shoot growth parameters during the nursery phase, however the root growth was not significantly affected by air humidity and even increased under the water deficit. The reduction in leaf water potential under water stress was induced by tissue dehydration since leaf turgor potential also decreased and non-osmotic adjustment was observed. The drought effects on water relations were similar in both low and high air humidity. The leaf stomatal conductance was also reduced by both types of stress, leading to a decrease in the rate of photosynthesis at the end of the nursery phase. Both water deficit and low air humidity showed their value as nursery acclimation processes, improving the survival of seedlings following transplanting and non-irrigation conditions (establishment phase). The stomatal regulation and a shift in the allocation of assimilates from shoot to root were the acclimation mechanisms showed by R. alaternus under both types of stress. The accumulated effects in low air humidity and water deficit plants could explain the highest percentage of survival at the end of the establishment period (97%) for the combined treatment.     

Daily and seasonal variation of water relationship in sugar apple (Annona squamosa L.) under different irrigation regimes at semi-arid Brazil

In the northeast of Brazil the drought period determines the yield period of the sugar apple (Annona squamosa L.). As a result, the use of irrigation is essential to stagger production over the course of the year. The results shown here represent an analysis of water status levels in sugar apples in daylight and seasonal periods in semi-arid regions. Two plant groups were studied: one without irrigation and the other with irrigation during drought months. This study showed that younger leaves displayed greater stomatal conductance and transpiration. In drought months, even in irrigated plants, the high air moisture deficit had a strong influence on the stomatal closure, which did not translate into a reduction in transpiration. Over the same period, the leaf water potential was −1.8 and −2.9 MPa at mid-day in irrigated and non-irrigated plants, respectively, and only the irrigated plants could recover their leaf hydration level at night. With a water deficit, plants showed greater control of transpiration through stomatal closure, with a linear relationship between stomatal conductance and transpiration.     

Effect of nursery regimes and establishment irrigation on root development of Lotus creticus seedlings following transplanting

Summary

The influence of irrigation and temperature regimes in the nursery on the dynamics of root development after being transplanted with minimum management conditions was investigated in Lotus creticus. In the nursery period (three months), plants were pot-grown in greenhouses, heated and unheated, located on the Southeast Mediterranean coast of Spain. Drip irrigation was used, with three irrigation treatments: T-6, plants watered 6.d a week at the water-holding capacity; T-3, plants watered 3.d a week; and T-2, plants watered twice a week. The total water applied over the whole nursery period was (in litres per plant): T-6, 7; T-3, 3.5; and T-2, 2.3. After the nursery period, plants were transplanted in a growth chamber into transparent containers (round acrylic tubes 8.cm diameter and 100.cm tall) and just one establishment irrigation was applied. Three treatments were applied, using three different amounts of water in the establishment irrigation: 10, 30 and 60.mm. The containers were kept in the growth chamber for one month, until the end of experiment. The harsher the conditions after transplanting (less water in the establishment irrigation) the more evident was the positive effect of hardening in the nursery. The regime involving least water and lowest temperature in the nursery period produced plants best adapted to stress at transplanting: a greater root length:shoot length ratio, higher percentage of brown roots and lower fresh weight:length ratio in shoots. All the plants survived transplanting. The most stressed plants in the nursery (least water and no heating) showed greater and more rapid root growth than the less stressed plants, especially when soil moisture was low.