Poor Seedling Growth Research Articles

Loss of LEUCINE CARBOXYL METHYLTRANSFERASE 1 interferes with metal homeostasis in Arabidopsis and enhances susceptibility to environmental stresses

The biochemical function of LEUCINE CARBOXYL METHYLTRANSFERASE 1 (LCMT1) is to transfer a methyl group from the methyl donor S-adenosylmethionine (SAM) to the catalytic subunits of PROTEIN PHOSPHATASE 2A (PP2Ac), PP4 and PP6. This post-translational modification by LCMT1 is found throughout eukaryotes from yeast to animals and plants, indicating that its function is essential. However, Arabidopsis with knocked out LCMT1 still grows and develops almost normally, at least under optimal growth conditions. We therefore proposed that the presence of LCMT1 would be important under non-optimal growth conditions and favoured plant survival during evolution. To shed light on the physiological functions of plant LCMT1, phenotypes of the lcmt1 mutant and wild type Arabidopsis were compared under various conditions including exposure to heavy metals, variable chelator concentrations, and increased temperature. The lcmt1 mutant was found to be more susceptible to these environmental changes than wild type and resulted in poor growth of seedlings and rosette stage plants. Element analysis of rosette stage plants mainly showed a difference between the lcmt1 mutant and wild type regarding concentrations of sodium and boron, two-fold up or halved, respectively. In both lcmt1 and wild type, lack of EDTA in the growth medium resulted in enhanced concentration of copper, manganese, zinc and sulphur, and especially lcmt1 growth was hampered by these conditions. The altered phenotype in response to stress, the element and mRNA transcript analysis substantiate that LCMT1 has an important role in metal homeostasis and show that functional LCMT1 is necessary to prevent damages from heat, heavy metals or lack of chelator.

Effect of soil biota on growth and allocation by Eucalyptus microcarpa

We examined growth of Eucalyptus microcarpa seedlings in soil collected from four sites in southeastern Australia, in which retired pasture land has been revegetated with mixed plantings of Eucalyptus and Acacia species. Revegetation of farm land in southeastern Australia is an area of major investment. The focus of the study was to examine the influence of soil biota on seedling growth and its possible interaction with soil enrichment from a legume (Acacia) and decomposition rates. We used a soil freezing treatment (−80°C for 3 days) to retard the soil biota, with the expectation that invertebrates in particular would be killed. Soil freezing did not cause a nutrient pulse, but did reduce the level of ammonium in soil. Nitrate levels increased with time in pots, regardless of the soil treatment. Decomposition rates measured using cellulose substrate were significantly reduced by the freeze treatment, but only for approximately 90 days. Eucalyptus microcarpa seedlings grown in freeze-treated soil were approximately 40% smaller (total biomass), had marginally lower LAR (leaf area ratio), and significantly lower LMA (leaf mass per area). Low LMA indicates that leaves are either thinner in cross-section or less dense. We hypothesise that both the poor growth of seedlings and production of less robust leaves are consequences of reduced availability of soil nutrients due to the diminished soil biota after freeze treatment. Litter under Acacia was richer in nitrogen than litter under Eucalyptus but there was no difference in nitrogen content of soil, and consequently no soil source effects on plant growth or decomposition. We suggest that variation in the soil biota has the potential to greatly enhance or hinder the success of revegetation on retired agricultural land, but enrichment of soil by decomposition of nitrogen rich litter in these sites requires longer than the 8–15 years since they were revegetated.

Refinement of potting medium ingredients for production of high quality seedlings of sandalwood (Santalum album L.)

Summary This study was undertaken in order to refine the potting medium and improve seedling growth of Santalum album L. in root trainers. The potting medium ingredients, including sand, soil, compost, cocopeat, burnt rice husk and charcoal, were tested in fourteen combinations in 270 mL block-type root trainers using Cajanus cajan as a pot host. A medium consisting of sand, soil, compost, burnt rice husk (BRH) and charcoal in the ratio of 25:15:50:5:5 favoured overall seedling growth in terms of height, collar diameter, shoot dry weight, root dry weight, total dry weight, root fibrosity and quality index at age 6 mo. The next best medium was a mixture of sand, soil and compost in the ratio 35:15:50. Where rice husk and charcoal are not available, this second medium may be used to produce good quality seedlings. The best potting medium for sandalwood had up to 60% organic matter mixed with sand and soil. This medium had low bulk density, good aeration and water-holding capacity, encouraged lateral root formation, and ensured good plug formation and easy plug removal. A high proportion of sand, soil or organic matter caused poor seedling growth.

Fertilization in Icelandic Afforestation: Evaluation of Results

Limited research has been done on nutrient application to trees in Iceland, and little attention has been given to its possible role in alleviating plantation establishment problems. High mortality and poor growth of seedlings has been observed at many sites. Since 1995, fertilization trials have been established, addressing forest survival and initial growth. Results from trials established in 1995 revealed positive effects of fertilizer application both to survival and growth. Both, slow-release fertilizer and easily soluble fertilizers (N, NP or NPK) had a positive effect. Application of large doses of N (5.6 g N/plant), either alone or in combination with P and K resulted in increased mortality in the first growth period. N and P in combination were essential for successful establishment. Liming, K and P alone, showed no significant effect on survival or growth. Future research needs are discussed.