Mesocotyl elongation in Digitaria sanguinalis during seedling development

The mesocotyl is an embryonic organ present in Poaceae that plays an important role in seedling emergence. The elongation of this first internode contributes decisively to the coleoptile reaching the soil surface. This study examines the process of mesocotyl elongation under controlled conditions in three caryopsis collection sites of Digitaria sanguinalis (L.) Scop. originating from Spain (Barcelona and Girona) and Argentina that may have two patterns of germination: radicular or coleoptilar. The frequencies of the two germination patterns varied significantly depending on the origin. Light inhibited the elongation of the mesocotyl drastically, resulting in maximum lengths of 3.5mm, while in darkness the maximum length was 57mm. The time-course evolution displayed under dark conditions was quite similar for all sites of origin and both germination patterns; the growth rate ranged from 0.23 to 0.30mmh21. Within localities, caryopses with a coleoptilar pattern of germination showed a lower growth rate than those with a radicular one.Postprint (author's final draft

Functional characterization of two plant type I MADS-box genes in Arabidopsis thaliana : AGL40 and AGL62 : a thesis presented in partial fulfilment of the requirements for the degree of Master of Science in Plant Biology at Massey University, Palmerston North, New Zealand

MADS-box transcription factors (TF) are a family of evolutionary conserved genes found across various eukaryotic species. Characterized by the conserved DNA binding MADS-box domain. MADS-box TF has been shown to play various roles in developmental processes. MADS-box genes can be based on MADS-box structural motifs divided into type I and type II lineages. In plants very limited functional characterization have been achieved with type I genes MADS-box genes. In this project we attempted to functionally characterize 2 closely related members of the type I lineage MADS-box genes AGL40 and AGL62 and give further support to the hypothesis that plant type I MADS-box genes are also crucial to normal plant development. Based on our expression domain characterization assay using AGL62: GUS fusion construct, we have shown expression of AGL62 in various tissues but especially strong in developing seeds, pollen and seedling roots and shoots. The web based microarray data suggesting that AGL62 may have a function in seed, pollen and seedling development backed up this result. Interestingly when we carried out PCR based genotyping with segregating population of heterozygous AGL62 T-DNA insertion lines (agl62/+) to identify the homozygous T-DNA insertion lines we detected no homozygous T-DNA insertion line indicating loss-of-function of AGL62 may be lethal to plant. With reference to the AGL62 expression in pollen, seed and seedling root and shoot, we carried out phenotypic assay on each of these tissues in agl62/+ background to investigate whether there was any phenotypic defect observed. Significant reduction in number of seeds was observed in agl62/+ indicating possible role of AGL62 in seed development. Our microscopic observation of seeds from agl62/+ plants showed defective embryos and confirmed that AGL62 plays a role in seed development. Our data on AGL62 is the first report that confirms AGL62's involvement in plant development and can be a ground work for further works on functional characterization of other members of plant type I MADS-box genes

The COP9 SIGNALOSOME is required for postembryonic meristem maintenance in Arabidopsis thaliana

Cullin-RING E3 ligases (CRLs) regulate different aspects of plant development, and are activated by modification of their cullin subunit with the ubiquitin-like protein NEDD8 (NEural precursor cell expressed Developmentally Down-regulated 8) (neddylation) and deactivated by NEDD8 removal (deneddylation). The CONSTITUTIVELY PHOTOMORPHOGENIC9 (COP9) signalosome (CSN) acts as a molecular switch of CRLs activity by reverting their neddylation status, but its contribution to embryonic and early seedling development remains poorly characterized. Here, we analyzed the phenotypic defects of csn mutants and monitored the cullin deneddylation/neddylation ratio during embryonic and early seedling development. We show that while csn mutants can complete embryogenesis (albeit at a slower pace than wild type) and are able to germinate (albeit at a reduced rate), they progressively loose meristem activity upon germination, until they become unable to sustain growth. We also show that the majority of cullin proteins is progressively neddylated during the late stages of seed maturation and becomes deneddylated upon seed germination. This developmentally regulated shift in the cullin neddylation status is absent in csn mutants. We conclude that the CSN and its cullin deneddylation activity are required to sustain postembryonic meristem function in Arabidopsis

Effect of substrates on germination and seedling emergence of sunflower (Helianthus annuus L.) at the Yongka Western Highlands Research/Garden Park, Bamenda-Cameroon

A study was carried out at the Yongka Western Highlands Research Garden Park, Nkwen­Bamenda in Cameroon to evaluate the effect of substrates on the germination and seedling emergence of sunflower (Helianthus annuus L.). Seeds of African Giant variety were used with six substrate media (sawdust, sand, soil, sawdust­sand, sawdust­soil and sand­soil). The experiment was laid out in a Randomized Complete Block Design in three replications. Germinated seeds were counted daily for a 15 days period. To estimate seedling emergence from two Weeks After Sowing (WAS) up to four WAS, data on seedling height and number of leaves were recorded. The results showed that germination started 8 days after sowing for all substrates. Germination rate was significantly affected by the substrates but the rates were less than 80%. The highest germination rate was recorded on the soil substrate (75%) while the lowest rate (25%) was recorded on the sawdust substrate. Seedlings on the sawdust substrate were also less vigorous and had less leaves (12.67 cm height and 4.7 leaves) than those on other substrates at four WAS (50–63 cm and 12.6–15.3 leaves). Based on the results, it is recommendable to use the soil substrate to nurse African Giant seeds

Imbibition, germination, and early seedling growth responses of light purple and yellow seeds of red clover to distilled water, sodium chloride, and nutrient solution

The seeds of red clover are heteromorphic and two color morphs can be visually recognized, light purple and yellow, resulting from heterozygosity and recessive homozygosity at two loci. Here, we report the responses of seed imbibition, seed germination, and early seedling growth of the two morphs to distilled water, sodium chloride, and complete nutrient solution. The sensitivity of red clover seeds to treatments increased with the stage of development in what seems to be a cumulative process. No differences were found in seed imbibition between morphs or between treatments. In seedling growth, on the contrary, treatments were always effective, but differences between morphs were only observed in seeds that were treated with nutrient solution, whereas in the intermediate stage of seed germination, the effects by treatments were observed together with the appearance of differences between morphs in distilled water and in the treatment by sodium chloride solution. Simultaneously, the superior performance of the yellow morph that was found in germination, which appears to be a trait stable across cultivars of red clover seeds, turned into a superior performance of the light purple morph in seedling growth

Seed factors involved in early seedling establishment of Festuca arundinacea (tall fescue) : a thesis presented in partial fulfilment of the requirements for the degree of Master of Science in Plant Biology and Biotechnology at Massey University, New Zealand

New Zealand pastures are commonly based on vigorously growing Lolium (ryegrass) species. In many situations, however, it is often advantageous to combine the vigorous qualities of Lolium species with the versatility of other species such as Festuca arundinacea (tall fescue) to result in a pasture which is high in quality all year. F. arundinacea, however, has poor seedling vigour which places it at a competitive disadvantage when sown with Lolium. During seedling establishment, the seedling is dependent upon the food reserves present in the seed. The nature and amount of these reserves and the ability of the seed to mobilise them are therefore likely to have an affect on seedling perfonnance. While much knowledge exists about the processes involved in seed reserve mobilisation in some cereals, little information is available for pasture grasses. An in depth investigation of the behaviour of one seed lot of F. arundinacea was undertaken in order to gain a more detailed understanding of germination, reserve mobilisation and establishment processes in pasture grasses and how they relate to the processes of seedling growth. Comparisons between this species and Lolium multiflorum (Italian ryegrass) were undertaken throughout the study. Germination and seedling growth of the F. arundinacea seed lot was found to be heterogenous and slower than in L. multiflorum due to later radicle emergence. Mobilisation of reserves and the onset of α-amylase activity correlated well with the utilisation of reserves in L. multiflorum. In both prechilled and non prechilled F. arundinacea seeds, however, anomalies were identified in the process which indicated that reserve mobilisation was less tightly coupled to seedling growth in F. arundinacea. Reciprocal plot analyses indicated that the beneficial effects of prechilling in most seeds of the F. arundinacea seed lot were not related to residual dormancy but were a thermal time benefit. It appears prechilling was allowing rate limiting steps in embryo growth to be advanced before visible germination. Apart from this, no real differences were detected in the way the two species mobilised reserves. Differences in the appearance of α-amylase isoenzymes of F. arundinacea at different times during germination indicated that gene expression may be under some complex differential control mechanisms during germination and reserve mobilisation. Prechilling was not found to change the spectrum of isoenzymes, but merely to advance the time-course in which different isoenzymes appeared. There were also distinct differences in α-amylase isoenzyme patterns between F. arundinacea and L. multiflorum, and also wheat. Preliminary studies indicated that exogenous gibberellic acid was more effective in promoting α-amylase production in L. multiflorum than in F. arundinacea. However, α-amylase production in F. arundinacea was more susceptible to promotion by prechilling. This study has identified a wide range of variables impacting on germination and seedling establishment in F. arundinacea. This, together with the lack of previous detailed studies on grass seed germination and seedling growth and the lack of literature on F. arundinacea germination in particular, highlights the enormity of the task ahead of extending key areas of this study to different seed lots and species

Differential Effects of Increasing Salinity on Germination and Seedling Growth of Native and Exotic Invasive Cordgrasses

Soil salinity is a key environmental factor influencing germination and seedling establishment in salt marshes. Global warming and sea level rise are changing estuarine salinity, and may modify the colonization ability of halophytes. We evaluated the effects of increasing salinity on germination and seedling growth of native Spartina maritima and invasive S. densiflora from wetlands of the Odiel-Tinto Estuary. Responses were assessed following salinity exposure from fresh water to hypersaline conditions and germination recovery of non-germinated seeds when transferred to fresh water. The germination of both species was inhibited and delayed at high salinities, while pre-exposure to salinity accelerated the speed of germination in recovery assays compared to non-pre-exposed seeds. S. densiflora was more tolerant of salinity at germination than S. maritima. S. densiflora was able to germinate at hypersalinity and its germination percentage decreased at higher salinities compared to S. maritima. In contrast, S. maritima showed higher salinity tolerance in relation to seedling growth. Contrasting results were observed with differences in the tidal elevation of populations. Our results suggest S. maritima is a specialist species with respect to salinity, while S. densiflora is a generalist capable of germination of growth under suboptimal conditions. Invasive S. densiflora has greater capacity than native S. maritima to establish from seed with continued climate change and sea level rise.Ministerio de Educación, Cultura y Deporte (FPU14/06556

Attainment of reproductive competence, phase transition, and quantification of juvenility in mutant genetic screens

Plant development between seedling emergence and flowering is characterized by a series of successive qualitative phases: (1) a post embryonic photoperiodinsensitive phase, during which plants are insensitive to photoperiod; (2) a photoperiod- sensitive inductive phase, in which plants require a number of short day (SD) or long day (LD) inductive cycles, depending on their age for rapid flowering, and (3) a photoperiod-insensitive post-inductive phase, in which plant development is no longer influenced by photoperiod (Figure 1; Matsoukas et al., 2013)

Fertirrigação e regulador de crescimento na produção de mudas de café em tubete

The use of quality seedlings is important in establishing a productive coffee crop. However, the most widely used method to produce coffee seedlings is time consuming (6-12 months) and lacks new production technologies. This study aimed to assess the use of fertigation and a growth regulator in the production of coffee seedlings, in order to develop a system faster than the conventional method. For that, Topázio coffee cultivar seeds were pre-germinated and planted in tubes flled with substrate (composted pine bark), in a protected nursery. A randomized block design was used, in a 4 x 2 (fertigation levels x the use or not of growth regulator) factorial scheme, with four replications. Daily fertigation positively influenced all the growth variables evaluated. The foliar spraying of the growth regulator had little effect on seedling growth. When compared to the conventional system described in the literature, the coffee seedling production system described here reduced, by around 60 days, the production time and enables a largescale productionA utilização de mudas de boa qualidade é importante para a formação de uma lavoura produtiva de café. Entretanto, o método mais utilizado atualmente para a produção de mudas de cafeeiro é demorado (6-12 meses) e carece de novas tecnologias de produção. Objetivou-se avaliar a utilização de fertirrigação e regulador de crescimento na produção de mudas de cafeeiro, com vistas ao desenvolvimento de um sistema mais rápido que o sistema convencional de produção. Para isso, sementes da cultivar Topázio foram pré-germinadas e plantadas em tubetes com substrato (casca de pinus compostada), em viveiro coberto. Adotou-se o delineamento de blocos ao acaso, em esquema fatorial 4 x 2 (níveis de fertirrigação x utilização ou não de regulador de crescimento), com quatro repetições. A fertirrigação diária influenciou positivamente em todas as variáveis de crescimento analisadas. A pulverização foliar do regulador de crescimento apresentou pouco efeito sobre o crescimento das mudas. Quando comparado ao sistema convencional descrito na literatura, o sistema de produção de mudas de cafeeiro descrito neste trabalho reduziu, em cerca de 60 dias, o tempo de produção e permite a produção em larga escala.info:eu-repo/semantics/publishedVersio

Evidence-based target characteristics for seedlings: Experimental design, initial results from field trials and future research

Low seedling quality is a pervasive problem for smallholder forestry in the Philippines. Intervention measures to improve seedling quality are being examined in a research project funded by the Australian Centre for International Agricultural Research. Field trials have been established as part of this ‘seedling enhancement project’ to compare performance on outplanting of Gmelina arborea when imported, selected and non-selected seeds are used. Itis expected that this research will provide important information for the development of evidence-based guidelines for seedling quality, and assist in refining the best practice manuals for seedling production