Shoot

About: Shoot is a research topic. Over the lifetime, 32188 publications have been published within this topic receiving 693348 citations.

Formation of epicuticular wax and its effect on water loss in cabbage plants regenerated from shoot-tip culture

Abstract: Observation by scanning electron microscopy (SEM) revealed that cabbage plants in vitro had no structured epicuticular wax whereas plants grown in a growth chamber or in the greenhouse had consider...

Use of Rhizobacteria and Mycorrhizae Consortium in the Open Field as a Strategy for Improving Crop Nutrition, Productivity and Soil Fertility.

Abstract: Plant growth promoting rhizobacteria (PGPR) and arbuscular mycorrhizal fungi (AMF) are known for their beneficial effects. In recent years, more attention has been paid to their use as biofertilizers to reduce the use of chemical fertilizers causing significant damage to the environment. To have high plant yields, biofertilizers may not be able to sustain plant demands and could be used in combination with chemical fertilizers. However, the application of biofertilizers in the field such as rhizobacteria and AMF are understudied and powerfully needed. In this context, this study aims to evaluate the effect of inoculation with rhizobacteria and AMF and their potential to stimulate two of the most economically important crops in Mediterranean semi-arid areas (Vicia faba L. and Triticum durum L.). The effect of inoculation was studied in field experiment with six treatments: (i) the control without inoculation (C), (ii) PGPR alone (PG), (iii) rhizobia alone (R), (iv) the mixture of PGPR and rhizobia (PR), (v) AMF alone (M), and (vi) the mixture of PGPR, rhizobia and AMF (PRM). The inoculation with the consortium of PGPR-rhizobia-AMF (PRM) induced the greatest effect. This inoculation improved the growth parameters (dry weight of shoots and roots) of faba bean and wheat. An improvement of 130, 200, and 78% was observed in V. faba shoot and root dry weight, and the number of leaves, respectively. Similarly, shoot and root dry weight and number of leaves of T. durum were enhanced by 293, 258, and 87%, respectively. The inoculation improved the productivity of studied plants presented by the number and weight of bean pods (270 × 104 ha-1 and 30737.5 kg.ha-1) and wheat spikes (440 × 104 ha-1 and 10560 kg.ha-1). In addition, the mineral analyses showed that the inoculation with PGPR-rhizobia-mycorrhizae improved N, P, Ca, K, and Na shoots contents, as well as the contents of sugar and proteins. Finally, we revealed the positive impact of the tested biofertilizers and the interest of adoption of innovative practices improving crops productivity and soil fertility.

Uncoupling phosphate deficiency from its major effects on growth and transcriptome via PHO1 expression in Arabidopsis

Abstract: SUMMARYInorganic phosphate (Pi) is one of the most limiting nutrients for plant growth in both natural and agriculturalcontexts. Pi-deficiency leads to a strong decrease in shoot growth, and triggers extensive changes at thedevelopmental, biochemical and gene expression levels that are presumably aimed at improving theacquisition of this nutrient and sustaining growth. The Arabidopsis thaliana PHO1 gene has previously beenshown toparticipatein the transportof Pi fromroots toshoots, andthe null pho1 mutant hasall the hallmarksassociated with shoot Pi deficiency. We show here that A. thaliana plants with a reduced expression of PHO1in roots have shoot growth similar to Pi-sufficient plants, despite leaves being strongly Pi deficient.Furthermore, the gene expression profile normally triggered by Pi deficiency is suppressed in plants with lowPHO1 expression. At comparable levels of shoot Pi supply, the wild type reduces shoot growth but maintainsadequate shoot vacuolar Pi content, whereas the PHO1 underexpressor maintains maximal growth withstrongly depleted Pi reserves. Expression of the Oryza sativa (rice) PHO1 ortholog in the pho1 null mutant alsoleads to plants that maintain normal growth and suppression of the Pi-deficiency response, despite the lowshoot Pi. These data show that it is possible to unlink low shoot Pi content with the responses normallyassociated with Pi deficiency through the modulation of PHO1 expression or activity. These data also showthat reduced shoot growth is not a direct consequence of Pi deficiency, but is more likely to be a result ofextensive gene expression reprogramming triggered by Pi deficiency.Keywords: phosphate, PHO1, nutrient deficiency, signal transduction.INTRODUCTIONOf the macronutrients required for plant growth, phospho-rus is the least mobile in soil. Plants absorb phosphorusfrom the roots as orthophosphate (inorganic phosphate, Pi).Pi concentration in most soils is in the low micromolarrange, and may even drop to submicromolar levels at theroot/soil interface. Plants respond to growth in Pi-deficientenvironments with numerous changes at the biochemical,morphological, developmental and gene expression levels.For example, vacuolar Pi reserves are mobilized, phospha-tases are secreted to scavenge Pi from organic sources,phospholipids are replaced by sulfolipids and galactolipids,root hair density and length are increased, and growth ofsecondary roots is promoted (Poirier and Bucher, 2002).Microarray studies revealed that several hundreds of genesare either induced or repressed following Pi starvation(Misson et al., 2004; Morcuende et al., 2007; Mu¨ller et al.,2007). Collectively, all these changes are thought to help theplant improve the acquisition of this vital nutrient, therebysustaining growth and improving plant survival. From anagronomical point of view, the main deleterious effects ofPi deficiency is a strong reduction in shoot growth. The wideuse of Pi-containing fertilizers is aimed at compensating thislimitation, andthusassuringmaximumcrop yield.However,this agricultural practice is costly, non-sustainable and

Simple bioreactors for mass propagation of plants

Abstract: Bioreactors provide a rapid and efficient plant propagation system for many agricultural and forestry species, utilizing liquid media to avoid intensive manual handling. Large-scale liquid cultures have been used for micropropagation through organogenesis or somatic embryogenesis pathways. Various types of bioreactors with gas-sparged mixing are suitable for the production of clusters of buds, meristems or protocorms. A simple glass bubble-column bioreactor for the proliferation of ornamental and vegetable crop species resulted in biomass increase of 3 to 6-fold in 3–4 weeks. An internal loop bioreactor was used for asparagus, celery and cucumber embryogenic cultures. However, as the biomass increased, the mixing and circulation were not optimal and growth was reduced. A disposable pre-sterilized plastic bioreactor (2–5-l volume) was used for the proliferation of meristematic clusters of several ornamental, vegetable and woody plant species. The plastic bioreactor induced minimal shearing and foaming, resulting in an increase in biomass as compared to the glass bubble-column bioreactor. A major issue related to the use of liquid media in bioreactors is hyperhydricity, that is, morphogenic malformation. Liquid cultures impose stress signals that are expressed in developmental aberrations. Submerged tissues exhibit oxidative stress, with elevated concentrations of reactive oxygen species associated with a change in antioxidant enzyme activity. These changes affect the anatomy and physiology of the plants and their survival. Malformation was controlled by adding growth retardants to decrease rapid proliferation. Growth retardants ancymidol or paclobutrazol reduced water uptake during cell proliferation, decreased vacuolation and intercellular spaces, shortened the stems and inhibited leaf expansion, inducing the formation of clusters. Using a two-stage bioreactor process, the medium was changed in the second stage to a medium lacking growth retardants to induce development of the meristematic clusters into buds or somatic embryos. Cluster biomass increased 10–15-fold during a period of 25–30 days depending on the species. Potato bud clusters cultured in 1.5 1 of medium in a 2-l capacity bioreactor, increased during 10–30 days. Poplar in vitro roots regenerated buds in the presence of thidiazuron (TDZ); the biomass increased 12-fold in 30 days. Bioreactor-regenerated clusters were separated with a manual cutter, producing small propagule units that formed shoots and initiated roots. Clusters of buds or meristematic nodules with reduced shoots, as well as arrested leaf growth, had less distortion and were optimal for automated cutting and dispensing. In tuber-, bulb- and corm-producing plants, growth retardants and elevated sucrose concentrations in the media were found to enhance storage organ formation, providing a better propagule for transplanting or storage. Bioreactor-cultures have several advantages compared with agar-based cultures, with a better control of the contact of the plant tissue with the culture medium, and optimal nutrient and growth regulator supply, as well as aeration and medium circulation, the filtration of the medium and the scaling-up of the cultures. Micropropagation in bioreactors for optimal plant production will depend on a better understanding of plant responses to signals from the microenvironment and on specific culture manipulation to control the morphogenesis of plants in liquid cultures.