Production Of Healthy Seedlings Research Articles

Micropropagation from cotyledonary explants of grapefruit (<i>Citrus</i> <i>paradisi</i> Macf.) by indirect and direct organogenesis

Grapefruit (Citrus paradisi Macf.) is an economic fruit crop worldwide cultivated for its nutritional value, and aromatic flavours. However, the development of new varieties and high production of quality seedling constitutes a limit to improving grapefruit yields. An efficient regeneration protocol could be of great interest for grapefruit transformation, micropropagation, and germplasm conservation. In vitro plant regeneration systems of Citrus paradisi have been studied by using cotyledonary explants. Different concentrations of plant growth regulators were used to explore the organogenic potential of cotyledonary explants under laboratory conditions. For indirect organogenesis using cotyledon segment explants, a low concentration of 2,4-dichlorophenoxyacetic acid (2,4-D) lead to the formation of white callus, while a high concentration of 2,4-D induced brown callus and adventitious root differentiation. The best response for callogenesis was obtained on Murashige and Skoog (MS) medium supplemented with 2 mg/L of 2,4-D. Only brown callus cultured on MS added with 2 mg/L 6-benzylaminopurine (BAP) has regenerated shoots, but the percentage of callus producing shoots was very low (6.66 ± 2.68%). Regarding direct organogenesis from the cotyledonary node explants, the best response for shoot proliferation was observed on MS supplemented with 4 mg/L BAP (86.66 ± 12.58% of explants regenerating shoots, and an average number of 5.45 ± 0.45 shoots per explant). Low percentages of In vitro rooting of regenerated shoots were observed with different concentrations of α-naphthalene acetic acid (NAA) or indole-3-butyric acid (IBA). Nevertheless, the highest rooting percentage (13.33 ± 2.88%) was obtained on MS containing 2 mg/L NAA. These results provide new information for mass regeneration and the production of healthy seedlings, and can be applied in grapefruit improvement programs.

The use of near infrared spectroscopy to predict foliar nutrient levels of hydroponically grown teak seedlings

Due to a combination of durability, strength, and aesthetically pleasing color, teak ( Tectona grandis L.f.) is globally regarded as a premier timber species. High value, in combination with comprehensive harvesting restrictions from natural populations, has resulted in extensive teak plantation establishment throughout the tropics and subtropics. Plantations directly depend on the production of healthy seedlings. In order to assist growers in efficiently diagnosing teak seedling nutrient issues, a hydroponic nutrient study was conducted at North Carolina State University. The ability to accurately diagnose nutrient disorders prior to the onset of visual symptoms through the use of near infrared (NIR) technology will allow growers to potentially remedy seedling issues before irreversible damage is done. This research utilized two different near infrared (NIR) spectrometers to develop predictive foliar nutrient models for 13 nutrients and then compared the accuracy of the models between the devices. Destructive leaf sampling and laboratory grade NIR spectroscopy scanning was compared to nondestructive sampling coupled with a handheld NIR device used in a greenhouse. Using traditional wet lab foliar analysis results for calibration, nutrient prediction models for nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), sulfur (S), copper (Cu), molybdenum (Mo), magnesium (Mg), boron (B), calcium (Ca), manganese (Mn), iron (Fe), sodium (Na), and zinc (Z) were developed using both NIR devices. Models developed using both techniques were good for N, P, and K (R2 > 0.80), while the B model was adequate only with the destructive sampling procedure. Models for the remaining nutrients were not suitable. Although destructive sampling and desktop scanning procedure generally produced models with higher correlations they required work and time for sample preparation that might reduce the value of this NIR approach. The results suggest that both destructive and nondestructive sampling NIR calibrations can be useful to monitor macro nutrient status of teak plants grown in a nursery environment.

WATER REQUIREMENTS OF Dipteryx alata VOGEL SEEDLINGS AT DIFFERENT SOLAR RADIATION LEVELS IN CERRADO-AMAZON TRANSITION

<p><strong>Background. </strong>Water and energy availability are factors that determine the maintenance, growth and development of plants and, consequently, affect its productivity. knowledge what water requirements of forest species during the initial growth stage under different energy levels are essential for technical and economic planning and the proper management of irrigation in forest nurseries, aiming at the production of healthy seedlings. <strong>Objective.</strong> The evapotranspiration potential (ETc) and crop coefficients (Kc) of baru plants (<em>Dipteryx alata</em> Vogel) were set at the early plant development stage, at increasing shading (black polyolefin screens) and spectral solar radiation levels (colored polyolefin screens), in order to subsidize irrigation and management projects focused on forest nurseries. <strong>Methodology</strong>. The experiment was conducted in the Center-Northern region of Mato Grosso State, during the dry season (from June to October 2017), for 125 days. ETc was measured through capillary lysimeters, whereas reference evapotranspiration (ETo) was set through the <em>FAO-56 Penman</em><em>-</em><em>Monteith equation</em> - Kc values were defined through the ETc/ETo ratio. Destructive growth analysis was performed 125 days after transplantation in order to determine the morphometric variables of the plants. <strong>Results.</strong> Increased shading levels decreased ETc, Kc and seedling stem diameter, besides increasing the leaf area. The herein adopted quantitative and spectral shading levels did not affect growth (in height) and dry mass accumulation in different <em>D. alata </em>seedling partitions. <strong>Implications.</strong> The results obtained allow defining improvements in the management of irrigation of forest nurseries. The adoption of irrigations systems with design errors and/or with water requirements inadequate for the production of forest seedlings may lead to yields lower than the genetic potential of the species, favor the establishment of diseases increased the consumption of nutrients and water. <strong>Conclusion.</strong>The production of <em>D. alata </em>seedlings depends on the cost-benefit ratio of shading screens and local water availability - production in full sun condition is recommended whenever water is not a limiting factor.</p>

Modelling seedling development using thermal effectiveness and photosynthetically active radiation

Seedling quality is a prerequisite for successful field performance and therefore influences crop yields. Temperature and illumination are two major factors affecting seedling quality during nursery propagation. Suboptimal temperature or light of nurseries generally result in leggy or weak seedlings and great economic loss. However, production of healthy seedlings is challenging due to the lack of knowledge in systemic management of nursery environments. In this study, we have established simulation models to predict how temperature and illumination coordinately influence the growth of tomato and cabbage seedlings. Specifically, correlation between seedling quality characteristics (root-shoot ratio, G value (growth function: defined as ratio of whole plant dry weight to days of seedling), healthy indexes) and TEP (thermal effectiveness and photosynthetically active radiation) were explored to establish the models, which were validated with independent test data. Our results suggested that the curve of healthy index 1 (HI1) and TEP fitted well with high coefficient of determination (R2) in both species, indicating that the model is highly reliable. The HI1 simulation models for tomato and cabbage are HI1=0.0009e0.0308TEP–0.0015 and HI1 = 0.0003e0.0671TEP–0.0003, respectively, which can be used for predicting vigors of tomato and cabbage seedlings grown under different temperature and light conditions.

Seed longevity, germination and seedling vigour of Rheum australe D. Don: A step towards conservation and cultivation

A 60 months study was carried out to assess the seed longevity and effect of duration of storage period on viability, germination and seedling vigour in Rheum australe D. Don. (rubarb), a highly valued medicinal herb. The species is in high demand and has endangered status therefore, required conservation/cultivation interventions. The study was carried out using seeds of same lot after storage of every six months (0, 6, 12, 18 and so on) till complete loss of seed viability. Freshly harvested seeds exhibited high seed viability (94%) and were non-dormant; above 80% germination occurred within a week. The above status was completely retained till 12 months storage. Beyond this period both seed viability and germination declined consistently with the progression of storage period. A complete loss of viability was observed beyond 60 months storage. Seed pre-treatments tested namely, GA3, KNO3 and chilling neither affected significantly the final germination of fresh seeds (86, 80 and 78%, respectively) nor differentially stored seeds. However, GA3 (1mM) and chilling significantly reduced the time required for germination. The seed longevity (time taken for 50% decline in seed viability) of R. australe was about 45 months, but a storage period of no longer than 24 months can be recommended. During 24 months storage period the seed viability and germination were reasonably high and resulted in the production of healthy seedlings with high survival rate. The outcome was favourable for the conservation/cultivation of the species.

The long-term ambient storage-induced alterations in seed viability, germination and seedling vigour of Saussurea costus, a critically endangered medicinal herb of North West Himalaya

Saussurea costus (Falc.) Lipschitz (Asteraceae), an economically important medicinal herb, is categorized as critically endangered. The plant is cultivated in some parts of Lahaul (Himachal Pradesh, India) in North West Himalaya. However, in the recent past, the cultivation has declined owing to an array of reasons including a long cultivation cycle, greater profits from other cash crops (mainly pea, potato, hops) and formalities to be completed in obtaining the export permits. Therefore, the possibilities of ex situ (in areas other than Lahaul) cultivation/conservation needs to be explored. In this context, the understanding of seed physiological characteristics would be of immense help. Since there is a dearth of information concerning the storage-depenedent changes in seed physiological status of S. costus, we have analyzed these aspects for a long-term ambient storage (66 months) in a population from Lahaul. The freshly harvested seeds exhibited high viability (95%) with 65% germination that could be enhanced through GA3 and chilling pre-treatments. During storage, the seed germination increased after 12 months suggesting the seeds to be partially dormant that required an after-ripening prior to the commencement of germination. GA3 and chilling treatments appeared to substitute such requirement. Further, the seed viability was completely maintained at least for 18 months and even after 30 months storage, 82% viability retention associated with the production of healthy seedlings was evident. However, beyond 30-month-storage, both seed viability and germination declined substantially. Maintenance of reasonably high viability status, germination and seedling vigour even after substantial storage of seeds under ambient conditions suggests the suitability of seeds for regeneration/cultivation of this species.

Survey of the entomofauna through luminous trap

The demand for forest-based raw materials for energy, construction, paper pulp and the pressure to comply with legal requirements concerning environmental legislation, for example, the replacement of the permanent preservation area, legal reserve and recovery of degraded area, leads to encourage the production of healthy seedlings in a health status to do not compromise their future production. The present study aimed to survey the entomofauna population using the “Luiz de Queiroz” model of luminous trap, with white and red fluorescent lamps. The experiment was conducted at the nursery “Flora Sinop” in Sinop – MT. The survey was conducted weekly between the months of April to July 2010, totaling 4 months sand, 32 samples collected. The orders Hemiptera and Coleoptera showed the highest number of individuals captured, either in attraction with white or red light. It was captured 10.089 individuals, 9.339 collected under the influence of white light, representing 92,56%, and 750 with red light, only 7,44% of the total. The white light luminous trap possessed greater efficiency in the attraction of insects when compared with the red light trap.

The effects of single species, dual species and indigenous mycorrhiza inoculation on citrus growth and nutrient uptake

The objective of this study was to evaluate the effects of selected single arbuscular mycorrhiza (AM) species, dual species inoculations and indigenous mycorrhizae (IM) inoculations, using specific growing media (GM), on the growth and nutrient uptake of sour orange (Citrus aurantium L.) seedlings. Five mycorrhiza species and their dual species inoculations, one commercial and one indigenous (multiple species) mycorrhizae were investigated using two growing media, GM1 (andesitic tuff + peat (1:1, V:V)) and GM2 (andesitic tuff + peat + soil (4 + 5+1, V: V:V)), under controlled greenhouse conditions. The experiments were conducted over 12 months. Mycorrhizal inoculation increased certain plant growth parameters such as shoot height, diameter, and shoot and root dry matter. Generally, mycorrhiza species and their dual species inoculations exerted different responses on plant growth. In GM1, Funneliformis mosseae, Rhizophagus clarus and indigenous mycorrhiza (IM) species were the best inoculants to increase citrus growth, root colonization and nutrient uptake; however, in GM2, Fu. mosseae and IM were the best inocula. Fu. mosseae + R. clarus was the most efficient dual species inoculation in GM1, whereas in GM2 the most efficient combination was Fu. mosseae + Fu. caledonium. The beneficial effects of AM fungi and the dual species inoculation with IM was also significant. Citrus seedlings grew much better in GM1 than in GM2. Root colonization was also increased with dual species inoculation and IM. In addition, the plant phosphorus and zinc content increased with mycorrhizal inoculation. Our results reinforce the efficiency of IM and mycorrhizal inoculations as being as effective as exotic AM fungal isolates. Dual species inoculation and IM show promise in the production of healthy seedlings, using several growing media.