Nursery Production Of Seedlings Research Articles

Photosynthetic apparatus protection and drought effect mitigation in açaí palm seedlings by rhizobacteria

Water deficit sensitivity decreases the acai palm seedling production in nurseries. The goal of this study was to evaluate gas exchange, chlorophyll a fluorescence, lipid peroxidation and antioxidant enzymes in acai palm seedlings inoculated with rhizobacteria. Four rhizobacteria isolates (UFRA-58, UFRA-92, BRM-32111 and BRM-32113) and one control (without inoculation) were inoculated on acai palm seedlings at field capacity (FC) 100%, 75%, 50% and 25%. Water deficit reduced photosynthetic performance in all acai palm seedlings, but to a lesser extent in seedlings inoculated with rhizobacteria. At 75% FC, all inoculated seedlings maintained greater water potential, gas exchange and chlorophyll a fluorescence and, at 50% FC, only the seedlings inoculated with BRM-32111 and BRM-32113 were able to maintain these advantages in relation to the control. In 25% FC, no effect was observed for rhizobacteria inoculation. At 50% FC, the increase in catalase (CAT) enzymatic activity was induced by UFRA-58. The ascorbate peroxidase (APX) enzymatic activity was greater for UFRA-92, whereas superoxide dismutase (SOD) enzymatic activity was higher only for BRM-32113. The malonic aldehyde (MDA) content was greater only for control. Rhizobacterial inoculation in acai palm seedlings attenuates the water deficit effects by photosynthetic performance maintenance and antioxidant enzymes activation, contributing to decrease the seedling mortality rate in nurseries.

Biochar as a management tool for soilborne diseases affecting early stage nursery seedling production

Biochar is thought to have great potential as a supplemental amendment in nursery growing media. The knowledge of how to optimize the use of biochar in the nursery setting during the most vulnerable pre-emergence and early seedling stages of the plant, however, is underdeveloped. The current study involves pre-emergence trials in the Pythium aphanidermatum-cucumber pathosystem using a commercial nursery potting mixture amended with up to 3% w:w wood-derived biochar. The major questions were: (i) is pre-conditioning required to elicit suppression of pre-emergence damping-off disease in the Pythium-cucumber system; (ii) what are the changes in bacterial community composition and diversity due to pre-conditioning of the biochar-amended potting medium; and (iii) can the pre-conditioning stage be shortened from 45 days and still provide disease suppression. Pre-conditioning, consisting of pre-planting fertigation of the nursery medium, was found to be needed to achieve suppression of damping-off disease by biochar, with a reduction in pre-emergence damping-off caused by P. aphanidermatum by up to 71%. Illumina sequencing of 16s bacterial gene revealed a significant enrichment in the abundance of bacteria in general and potentially beneficial microorganisms in particular, as well as shifts in microbial community structure as a result of biochar addition. These changes may play an important role in the overall effects of biochar on disease suppression in young seedlings. A pre-conditioning period of only 14 days was found to be effective for disease suppression, which can substantially improve its practical utility for nurseries.

Deployment of olive-stone waste as a substitute growing medium component for Brassica seedling production in nurseries.

In the Mediterranean region, olive-stone waste (OSW) is accumulated and considered of environmental and human health constraints. In this study, OSW was used for peat (P) replacement in growing media for Brassica seedling production. Cauliflower, broccoli, and cabbage were seeded in growing media consisted of 0-20-40-60% OSW. The mixture of OSW with peat increased growing media bulk density and reduced the total pore space and available water and air at root system. A Considerable amount of minerals were provided into the growing media with the OSW, while their availability was increased with the raised pH values. Seed emergence percentage decreased with high ratio of OSW which also increased mean emergence time. The addition of OSW decreased plant height, leaf number, and fresh weight in all three examined species. The OSW decreased stomatal conductance (in cauliflower and cabbage) and chlorophylls content (including broccoli). The insertion of OSW affected the mineral accumulation in plants with decreases in nitrogen and sodium content and increases in potassium and calcium. OSW increased to some extent for cauliflower and broccoli or unchanged for cabbage polyphenolic content and antioxidant activity (ABTS, FRAP). Cellular damage was caused by the addition of OSW by increasing the lipid peroxidation and the production of hydrogen peroxide, and as a consequence, the plant antioxidative (catalase, superoxide dismutase) enzyme metabolism increased. The current study demonstrates that up to 20% of OSW can substitute peat for cauliflower, broccoli, and cabbage seedling production while cabbage was performed better under the increased OSW-caused stress.

Oligonychus punicae as a pest of Eucalyptus urophylla in cultivation and potential new host species in Brazil

ABSTRACTThis study identified a mite species associated with Eucalyptus urophylla in clonal mini-garden of nursery seedling production and determined its instantaneous growth rate on several species of eucalypts. Mites were collected on the leaves of E. urophylla strains grown in clonal mini-garden and mounted on microscopy slides to species identification, while other were kept rearing on arenas. To determine the instantaneous growth rate of mites on Eucalyptus brassiana, E. urophylla, E. grandis, E. tereticornis, E. pellita and Corymbia citriodora grown on pots, arenas were assembled with Petri dishes containing foam, filter paper and leaf discs of each species of eucalypt and five adult mite females from the breeding colony. The “arenas” were kept in climatic chambers under controlled conditions. After 10 days the instantaneous growth rate was determined. The experiment was conducted in a completely randomized design with six treatments and six replicates. Data were submitted to Kruskal Wallis non-parametric test. The mite was identified as Oligonychus punicae. This is the first record of O. punicae associated with E. urophylla plants in clonal mini-garden of nursery seedling production. The instantaneous growth rate of O. punicae was positive in the six species of eucalypts suggesting the mite might damage clonal mini-gardens.

Nitrogen supplementation improves the high-light acclimation of Guazuma ulmifolia Lam. seedlings

High nitrogen supply prevents dynamic photoinhibition in Guazuma ulmifolia seedlings and improves their morphophysiological quality during the high-light acclimation in the nursery. Acclimation under full sun is an important step in the production of tree seedlings in nurseries because it increases plant resistance to stressful conditions. Thus, the development of management techniques that improve high-light acclimation could facilitate the production of higher-quality seedlings. Given the importance of nitrogen (N) for plant growth and photosynthetic metabolism, here we evaluated whether supplementation with high N levels (HN) could positively affect the high-light acclimation of seedlings of Guazuma ulmifolia Lam., a tree species widely used in reforestation programs in the neotropics. We compared the morphophysiological parameters of seedlings transferred from the shaded sector of the nursery to full sun that were supplemented with or without HN. HN supply prevented the midday depression of both photosystem II (PSII) activity and the CO2 assimilation rate, suggesting the avoidance of dynamic photoinhibition by HN. This effect was related to HN-induced increases in the electron transport rate of PSII, carboxylation efficiency and mesophyll conductance to CO2 and not to reduced stomatal limitation. A decrease in excess excitation energy in PSII resulting from energy-demanding N assimilation, as suggested by increases in the light saturation points of the CO2 assimilation and PSII electron transport rates, might also contribute to the protective effect of N. In addition, HN treatment increased seedling biomass accumulation and stem base diameter, enhancing the Dickson quality index of the acclimated seedlings. Overall, these results indicate that HN supply during high-light acclimation in the nursery improves the morphophysiological quality of G. ulmifolia seedlings.

Tento seed germination and seedling emergence (Ormosia paraensis Ducke – Fabaceae)

Ormosia paraensis Ducke, known as “tento”, has seeds used to make handicrafts and wood worked by furniture makers. Despite its importance in handcrafted, timber and for the recovery of degraded areas, there is little research on the physiology of its seeds in order to help the production of seedlings in nurseries. Thus, the purpose of this research was to determine the temperature and the best substrate for the germination of seeds, as well as the substrate and sowing depth for tento seedling emergence. The range of the optimum temperature for seed germination is between 25 and 35°C. Both sand and paper are suitable substrates for tento seed germination. Sowing depths higher than 2 cm are inadequate for Tento emergence. The most suitable substrates for seedling emergence in the nursery are sand, vermiculite and Plantmax.

Substrate and seed sowing position on the production of Plukenetia volubilis L. seedlings

ABSTRACT Plukenetia volubilis is a species native to the Amazonia and has economic potential due to the high contents of polyunsaturated fatty acids and vitamins of the seeds; however, information about production of seedlings in nursery is scarce. Factors that contribute to fast emergence and generation of vigorous seedlings are desirable for plant production in the nursery. Therefore, this study aimed to identify the most favorable substrate and seed position for the production of P. volubilis seedlings. The seeds were sown in the following four positions: hilum facing up, hilum facing down, seed lying on its cotyledon suture, and seed lying flat on one of its cotyledon faces. The substrates were sand, vermiculite and commercial substrate. Treatments were distributed according to a completely randomized design in a 4 × 3 factorial arrangement (seed position and substrate) with three replicates of 25 seeds each. The following variables were evaluated: emergence percentage; first count of seedlings; number, width and length of leaves; plant height; stem diameter; dry matter of shoots and roots. It was concluded that the production of P. volubilis seedlings is not affected by either substrate or seed position at sowing. The substrates most favorable to the quality of P. volubilis seedlings were the commercial substrate and vermiculite, always for the positions of seed lying on its cotyledon suture, with faces parallel to tube walls, and seed lying flat on one of its faces.

MODELING THE GROWTH OF EUCALYPTUS PLANTS BASED ON THE THERMAL SUM

ABSTRACT Among the environmental variables that affect the growth and development of plants, the air temperature is of great importance. In this context, the objectives of this work were to model the growth of eucalyptus seedlings in terms of accumulated degree-days during the production process and model validation. The study was conducted in the forest research nursery of the Department of Forestry, located in Viçosa (MG), during the periods of 08/02/2011 to 28/04/2011 and 03/08/2012 to 01/11/2012, making it possible to contemplate seasonal variations in the production cycle. The monitored variables were shoot height, stem diameter, leaf area, root length and fresh and dry biomass. Results showed that it took 1065 degree-days for the production of seedlings and sigmoidal models obtained showed high correlation and Willmott coefficients, indicating good performance for estimating the growth and development of eucalyptus seedlings. This tool has great potential for planning and monitoring the production of eucalyptus seedlings in nurseries.

English

Eucalyptus cultivation has expanded considerably in Brazilian systems, leading to the current search for technologies to optimize growing conditions and the production of seedlings in nurseries. Based on the understanding that the development of tree species such as Eucalyptus sp. can be influenced by endophytic fungi that act directly as plant growth-promoting species, cloned seedlings of Eucalyptus grandis x Eucalyptus urophylla hybrids grown from minicuttings we stimulated with three species of endophytic fungi and the effects of inoculation on seedling growth was evaluated. Strains of Trichoderma sp., Fusarium sp. and Papulaspora sp. were forced to colonize the root system of the plants, which were continuously maintained under protected cultivation. Inoculation of the symbionts had positive effects on stem length, stem diameter and the fresh and dry biomass of the treated plants. Non-inoculated plants presented a shorter stem length than the plants treated with any of the endophytic species. The cloned seedlings inoculated with Trichoderma sp. exhibited the greatest stem measurements at 120 days after transplanting. The seedlings inoculated with Fusarium sp. displayed a greater number of leaves than the other seedlings as well as greater amounts of fresh and dry biomass. The authors also conducted quarterly evaluations of the increment in seedling growth promoted by the inoculants, which were more effective in the early stages, up to 60 days after transplanting. Keywords: Inoculants, microorganisms, minicutting, tree species

Physiological, physical, and morpho-anatomical changes in Libidibia ferrea ((Mart. ex Tul.) L.P. Queiroz) seeds after overcoming dormancy

Seed dormancy is a phenomenon that affects the distribution of plant species in time. However, it may slow germination and consequently hinder seedling production in nurseries. Many seeds of forest species of the Fabaceae family, such as Libidibia ferrea (Brazilian ironwood), have physical dormancy caused by impermeability of the seed coat to water. Therefore, the aim of this study was to evaluate the physiological, physical, and morpho-anatomical characteristics of L. ferrea seeds before and after application of different treatments for overcoming dormancy. We evaluated the imbibition curves, germination percentage, germination speed index (GSI), the force required to puncture the micropylar region, and morpho-anatomical changes through images obtained from a scanning electron microscope (SEM) before and after application of treatments for overcoming dormancy. L. ferrea seeds immersed in sulfuric acid show a triphasic pattern of imbibition. The required force to puncture the micropylar region of L. ferrea seeds is less for both the treatment with boiling water and for treatments with sulfuric acid. In addition, the required force to puncture the micropylar region decreases during imbibition of the seeds after application of sulfuric acid. The time of application of sulfuric acid influences the thickness of the material removed from the macrosclereid layer of the seed coat.

Influence of stratification, light, and planting depth on rabbitbrush seed germination and emergence

Rubber rabbitbrush ( Ericameria nauseosa (Pall. ex Pursh) G.L. Nesom & Baird) [Asteraceae]) has potential for use as an effective element of water-conserving landscapes. To enhance availability of this species, it is important to optimize nursery seedling production. Our objectives were to determine the influence of 1) stratification (cold-moist); 2) light exposure; and 3) planting depth on germination and emergence of seeds collected from diverse populations of rubber rabbitbrush. Seeds representing a range of environments were collected from Idaho and Utah and were cleaned, sorted, and exposed to germination-enhancing treatments. Following stratification, seeds of 3 of 4 rabbitbrush populations responded with a statistically significant increase in germination percentage. More significant, stratification increased the germination rate, reducing time to culmination from 4 or more wk to 1 wk or less. Compared with seeds germinated in the dark, exposure to sunlight increased germination percentage 1.5- to 3-fold, depending on population. Any amount of seed burial markedly decreased seedling emergence for all 4 populations. Six wk after planting, removal of all but a few mm of soilless substrate resulted in emergence of a portion of the buried seeds, indicating induction and release of conditional dormancy (possibly quiescence) due to a lack of light or other factors. Responses to stratification, light, and seed burial varied by population, thus confirming previously described variability that exists among rubber rabbitbrush populations. Results of this study will help nursery growers provide optimal conditions for producing nursery stock of rubber rabbitbrush.

Growth of mycorrhizal jack pine (Pinus banksiana) and white spruce (Picea glauca) seedlings planted in oil sands reclaimed areas

The effectiveness of ectomycorrhizal inoculation at the tree nursery seedling production stage on growth and survival was examined in jack pine (Pinus banksiana) and white spruce (Picea glauca) planted in oil sands reclamation sites. The seedlings were inoculated with Hebeloma crustuliniforme strain # UAMH 5247, Suillus tomentosus strain # UAMH 6252, and Laccaria bicolor strain # UAMH 8232, as individual pure cultures and in combinations. These treatments were demonstrated to improve salinity resistance and water uptake in conifer seedlings. The field responses of seedlings to ectomycorrhizal inoculation varied between plant species, inoculation treatments, and measured parameters. Seedling inoculation resulted in higher ectomycorrhizal colonization rates compared with non-inoculated control, which had also a relatively small proportion of roots colonized by the nursery contaminant fungi identified as Amphinema byssoides and Thelephora americana. Seedling inoculation had overall a greater effect on relative height growth rates, dry biomass, and stem volumes in jack pine compared with white spruce. However, when examined after two growing seasons, inoculated white spruce seedlings showed up to 75% higher survival rates than non-inoculated controls. The persistence of inoculated fungi in roots of planted seedlings was examined at the end of the second growing season. Although the inoculation with H. crustuliniforme triggered growth responses, the fungus was not found in the roots of seedlings at the end of the second growing season suggesting a possibility that the observed growth-promoting effect of H. crustuliniforme may be transient. The results suggest that the inoculation of conifer seedlings with ectomycorrhizal fungi could potentially be carried out on a large scale in tree nurseries to benefit postplanting performance in oil sands reclamation sites. However, these practices should take into consideration the differences in responses between the different plant species and fungal strains.

Premature shoot growth termination allows nutrient loading of seedlings with an indeterminate growth strategy

Nutrient loading of nursery seedling stock of species with an indeterminate growth strategy is challenging and poorly understood. Here, we explore the use of two potential techniques for nutrient loading of trembling aspen (Populus tremuloides Michx.) seedlings: (1) exponential fertilization and (2) early shoot growth termination in order to divert assimilated nutrients and carbon to storage rather than to growth. In the first study, aspen seedlings were treated with either exponential or constant fertilization rates, both of which supplied the same amount of nutrients over the growing season. Exponential fertilization resulted in overall poor planting stock form (stunted seedling growth and weak root development) and produced only marginal improvements of nutrient status. As a result, the exponential fertilization regime studied cannot be recommended as a treatment for aspen seedlings. In the second study we treated seedlings with a 2 × 2 factorial combination of fertilization and shoot growth inhibitor (SGI) applications with the fertilizer treatments varying in terms of mid-season fertilizer concentrations. Seedlings with SGI application had much higher tissue nutrient and carbon reserve concentrations than seedlings without a SGI application. In addition, nutrient uptake appeared to be more efficient in SGI treated seedlings, which could potentially result in significant reductions of nutrient application rates during aspen seedling production in nurseries. Overall, early shoot growth termination using a SGI appears to be an effective technique to produce nutrient loaded aspen seedlings.

Observations of Forestry Seedling Production Systems in Thailand and Vietnam

Visits to forestry agencies and seedling nurseries in Thailand and Vietnam revealed an impressive level of progress in regard to both industrial and small-scale forestry. In both countries, reforestation is accorded high priority, the government is a major player in nursery seedling production, and a high level of technology is used in producing seedlings. Universities also play an active role in forestry seedling production. The visit provided valuable lessons for seedling production systems in the Philippines, including information about the roles of government versus private nurseries and about seedling quality and nursery accreditation.

Standardization of Inoculum dose of an AM Fungus for Prosopis cineraria seedlings

To examine the critical level of arbuscular-mycorrhizal (AM) fungi for Prosopis cineraria under nursery seedling production, Glomus sp. was used at different spore levels (0, 100, 200, 300, 400, 500, 600, 700, 800 and 900 spores per seedling per polybag). Mycorrhizal inoculation increased plant height, dry matter yield, root length and per cent root infection. Eighty five per cent infections were found to be sufficient for optimum response by P. cineraria seedling. The critical level of spores was found to be 400 per polybag (1 kg soil).

Effect of nursery irrigation regimes on vegetative growth and root development of Silene vulgaris after transplantation into semi-arid conditions

SummaryThe influence of irrigation regimes during nursery production of seedlings on development of the aerial parts and root system after being transplanted into semi-arid conditions was investigated in Silene vulgaris (Moench.) Garcke. This Mediterranean native herb is of interest for phytoremediation of contaminated soils and for edible and medicinal uses. During the 35 d nursery period, seedlings were grown in polystyrene trays. Three irrigation treatments were used throughout the nursery period:WI, well-irrigated seedlings; MS, moderately-stressed seedlings; and HS, highly-stressed seedlings. In all treatments, seedlings were overhead irrigated on 2 d per week, and the total amounts of water applied (per tray of 176 seedlings) over the whole nursery period were:WI, 16.10 l; MS, 10.75 l; and HS, 4.50 l.After the nursery period, WI and MS plants were transplanted into transparent containers (cylindrical acrylic tubes, 8 cm in diameter and 100 cm tall) and into the field, where mini-rhizotrons were used to evaluate root system dynamics. Plants transplanted into containers were watered with two irrigation regimes: normal irrigation (NI) and deficit irrigation (DI), with 0.90 or 0.45 l plant–1 week–1, respectively. All plants transplanted into the field were watered equally, with 1.16 l plant–1 week–1. Post-transplantation growth of aerial parts and roots was studied over 120 d in the transparent containers and over 60 d in the field. MS and HS treatments during the nursery period produced seedlings that showed lower midday leaf water potential and greater root:aerial parts fresh weight (FW) ratios than the WI treatment. The MS treatment produced seedlings with the greatest length and FW of roots and with the highest quality. The HS treatment produced seedlings which were too small and over-hardened. The latter were therefore not used for post-transplantation experiments. After transplantation into transparent containers, MS seedling-derived plants showed greater root growth than WI-derived plants, especially when the water content of the substrate was low (DI treatment). Also, mini-rhizotrons allowed observation of more active root growth in MS seedling-derived plants than in WI seedling-derived plants after transplantation into the field, especially in the deepest layer of soil (50-75 cm). WI-derived and MS-derived plants, under NI or DI post-transplantation treatments, showed similar FWs and dry weights (DWs) of their aerial parts, but MS-derived plants showed greater leaf:stem FW and DW ratios than WI-derived plants under DI conditions.

Beneficial Effects of Moist Chilling on the Seeds of Black Spruce (Picea mariana [Mill.] B.S.P.)

Moist chilling (cold stratification) is well-known as a simple and effective means of overcoming physiological seed dormancy and enhancing germination of many temperate tree and shrub species. However, the apparent activation of intracellular repair mechanisms in non-dormant black spruce (Picea mariana) seeds following moist chilling, has not previously been reported. The present contribution records the beneficial effects of moist chilling after accelerated ageing (40°C/98% relative humidity) for 3–10d of black spruce seeds. This treatment was maximally effective after 7d of accelerated ageing, increasing germination from 43 to 61%. Ultrastructural examination of embryo cells indicated that intracellular activation occurred during moist chilling even when seeds had not been subjected to accelerated ageing, and that the increasing levels of damage accumulating over the 3–7d period of ageing were substantially reversed during subsequent moist chilling. The results of cold stratification of non-dormant seeds are discussed in terms of the value of this practice in nursery seedling production from seeds that are of less than the highest quality.