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Cell Disruption
Published in Pau Loke Show, Chien Wei Ooi, Tau Chuan Ling, Bioprocess Engineering, 2019
Turgor pressure (ranging from 2–6 atm) is necessary for the cells to remain intact and is directly related to the elasticity of cell membranes (Ruiz et al., 2006). However, if the environmental conditions are altered, this pressure varies, which affects the cell’s elasticity and in turn the size of pores present in the cell membrane. Variation in pore size causes the release of intracellular contents. In this process, cells are first exposed to hypertonic solution (salt or sugar solution) for them to shrink; then the cells are treated using hypotonic solution (cold water) for the shrunk cells to swell. The shrinking and swelling of cells during hypertonic and hypotonic treatments, respectively, affects the intactness of the cell membrane, thus increasing the pore size. Increase in pore size causes the release of periplasmic proteins, leaving the cytoplasmic contents intact. This is the major advantage of this method. It is more suitable for gram negative bacteria and also mammalian cells. The method’s efficiency is reduced, however, for cells that have tougher cell walls. Sometimes enzymatic treatment methods are initially applied followed by osmotic shock process, which increases the efficiency of the disruption process (Ramanan et al., 2010; Shehadul Islam et al., 2017). The process of osmotic shock is illustrated in Figure 1.5.
Emerging Nature-Based Materials and Their Use in New Products
Published in Graham A. Ormondroyd, Angela F. Morris, Designing with Natural Materials, 2018
Many biological materials are not static, whether this is muscle-controlled motion in animals, or moisture actuated movement such as the opening and closing of flowers, or angling of leaves in plants. In many cases, these rely on live tissue to respond to metabolic signalling. Plant movement can be nastic (response to non-directional stimulus) or tropic (such as the phototropic growth response towards directional light, Figure 9.40a). Nastic movements include the thigmonastic response to touch of mimosa, where the plant defines the direction of movement, or the whirling, searching movement made by growing vine seedlings until the find a support to twine around (Figure 9.40b). The thigmotropic reaction of the seedling to the presence of a support is defined by the contact with the support. Turgor pressure is an important factor in the majority of plant motions, whether this is localised to a few cells, such as in the control of stomata, or readjusting the whole stem in response to light or gravity (Forterre 2013). Plant cells are commonly at high pressures of 0.4 to 0.8 MPa, when fully hydrated, and can reach 4 MPa in specific tissues such as the guard cells of stomata (Tomos and Leigh 1999; Franks et al. 2001; Taiz and Zeiger 2002). Cells can be considered to act as hydrostats, as was introduced in ‘Cells: Containing and Using Hydrostatic Pressure’ section.
Plant Responses and Tolerance to Salt Stress
Published in Hasanuzzaman Mirza, Nahar Kamrun, Fujita Masayuki, Oku Hirosuke, Tofazzal M. Islam, Approaches for Enhancing Abiotic Stress Tolerance in Plants, 2019
Babar Shahzad, Shah Fahad, Mohsin Tanveer, Shah Saud, Imtiaz Ali Khan
The initial effect of salt stress on plant growth is a limitation of water availability called osmotic stress (Munns, 2005; Rahnama et al., 2010). High concentration of salt in the root zone limits the water potential of the soil solution, which strictly reduces root water conductivity (Munns and Tester, 2008). As a result, cell membrane permeability drops and the influx of water to the plant is greatly reduced (Munns, 2002). In jute, relative water content, leaf water potential, water uptake, transpiration rate, water retention and water use efficiency reduced under salt stress (Chaudhuri and Choudhuri, 1997). Salt-stress-induced osmotic stress reduces turgor pressure and forces stomata to close following this decline in photosynthetic activity (Munns, 1993). Moreover, cell division and cell elongation were badly affected by the loss in turgor pressure (Shannon et al., 1998). Different studies revealed that cell growth is primarily correlated with turgor potential, and reduction in turgor pressure is one of the major causes of inhibition of plant growth under saline conditions, e.g., maize (Cramer et al., 1996), rice (Moons et al., 1995) and Shepherdia argentea (Qin et al., 2010). The adverse effect of salinity in the form of osmotic stress at the cellular level is well documented in a number of comprehensive reviews (Hasegawa et al., 2000; Munns, 2005; Munns and Tester, 2008). However, the extent of growth inhibition due to salt-induced osmotic stress depends on the type of plant tissue and the concentration of salts present in growing medium. In view of the aforementioned reports, it is clear that salinity causes osmotic stress to plants, but the extent of the effect of this stress varies from species to species. It is therefore necessary to understand the molecular mechanisms responsible for the salinity tolerance to find out whether their growth is limited by salt-induced osmotic stress or by the toxic effect of the salt within the plant.
Learning solar energy inspired by nature: biomimetic engineering cases
Published in European Journal of Engineering Education, 2021
J. M. Delgado-Sanchez, I. Lillo-Bravo
More specifically, the analogy of the olive tree was presented to the students, which is one of the most abundant trees in our neighbour landscape. The olive tree is often regarded as a stationary organism. However, most plants have very active motions where leaves and even stems can change their physical position when they are properly stimulated. Plants, unlike animals, lack both centralised control structures such as the central nervous system, and specialised effector structures such as muscles, so instead, they depend on a localised simple mechanism for generating movements. The primary mechanism is the adjustment of cell hydration to increase or decrease water pressure (turgor pressure) within the individual cells. Leaves can for instance bend towards the sun utilising special motor cells in the hinge of the leaf petiole (pulvinus); if cells on the upper side of the pulvinis dehydrates, they become less rigid; while cells on the under side hydrates and thus become more rigid, the leaf will bend upwards (Lenau and Hesselberg 2014).
Exploring design principles of biological and living building envelopes: what can we learn from plant cell walls?
Published in Intelligent Buildings International, 2018
Yangang Xing, Phil Jones, Maurice Bosch, Iain Donnison, Morwenna Spear, Graham Ormondroyd
In non-lignified plant tissues, it is the internal pressure of the cell contents that allows plants to maintain their upright stance. The cell wall enables plant cells to develop high turgor pressure (typically 0.3–1 MPa), important for the structural stability of the cells within plant tissues (Cosgrove 2009). The turgor pressure also influences the water relations and water economy of plants; the loss of turgor pressure, that is, when the rate of loss of water from the plant is greater than the absorption of water in the plant, for instance, due to drought stress, causes wilting. To resist internal hydrostatic pressure, the microfibril alignment in the primary cell wall is optimized to achieve hoop strength of the cell (Wainwright 1970). This is different to the load-bearing role of the secondary cell wall discussed in the section ‘Structure, composite, form and functions’. This combined action of the cells under hydrostatic pressure within a closed cell foam can provide significant hydraulic support to plant tissues. In addition, control of hydrostatic pressure by osmosis allows response to stimuli and nastic movements as mentioned above, with leaf angle or flower head tilting being a result of short-term alterations in the turgor pressure. The touch response of Mimosa pudica is a well-known example (Volkov et al. 2010). Here the shape and location of the parenchyma cells within pulvini govern the range of movement, and the electrical signalling mechanism allows rapid response by the leaflets. Tropic movement, by adjustment of cell growth in response to light or gravity, also overcomes some of the limitations of the sessile nature of plants, allowing growth into adjacent spaces as a response to changes in the canopy or competitor plants. These responsive structures provide inspiration for mechanical devices and actuators within buildings, as will be discussed in the section ‘Key novel design principles and related attempts’.