question: Since plants do not have muscle fibers, how do they get flaccid when deprived of water and stiff again when watered?
comment: Plant cells fill up with water when there's water around and lose water when there isn't. You know how when you blow up a balloon, its skin is rigid and you can bounce it off of things, but when you let all the air out it's just floppy and useless? Plant cells are basically like that, but they're filled with water instead. They're rigid when they're full of water and flaccid when they aren't.
passages: Osmotic pressure is the main cause of support in many plants. The osmotic entry of water raises the turgor pressure exerted against the cell wall, until it equals the osmotic pressure, creating a steady state.
  
  When a plant cell is placed in a solution that is hypertonic relative to the cytoplasm, water moves out of the cell and the cell shrinks. In doing so, the cell becomes "flaccid". In extreme cases, the cell becomes plasmolyzed – the cell membrane disengages with the cell wall due to lack of water pressure on it.
   Plants contain many hundreds of USP domains and genes. These genes are notably induced by environmental stresses such as drought. When a lack of hydration occurs, biochemical changes induced by the actions of USPs ensue. In response to drought, there is a reduction in photosynthetic carbon production as well as a reduction in energy metabolism. These actions are suggested to occur due to their implications in increasing energy conservation. Water limiting conditions are a common environmental pressure which plants will need to cope with on a regular basis, depending on their habitat. These resistant phenotypes will have an increased survival as they allow the plant to conserve energy in times of restricted water which is key to glucose production through photosynthesis.
   Most plants have the ability to close their stomata at the start of water stress, at least partially, to restrict rates of transpiration. They use signals or hormones sent up from the roots and through the transpiration stream. Since roots are the parts responsible for water searching and uptake, they can detect the condition of dry soil. The signals sent are an early warning system - before the water stress gets too severe, the plant will go into water-economy mode.
   Section::::Cultivation.:Diseases.:Phytoplasma.
  
  Overshooting is the term used when "Phytoplasma", a specialized bacterium, attacks the phloem of a plant. "Phytoplasma" infection is characterized by chlorotic small leaves, shortening of internodes, excessive lateral shoots and abnormal flowers. Although there have been reports of this disease within the passion fruit plant, many infected plants are affected without visible signs of disease. Although "Phytoplasma" can be spread through grafting, it can be inhibited by periodic inspection of plant nurseries and areas that have had past infections. Overshooting responds to treatment with tetracycline, a common broad-spectrum antibiotic.
  
  Section::::Cultivation.:Diseases.:Bacteria.
   In most cells, the cell wall is flexible, meaning that it will bend rather than holding a fixed shape, but has considerable tensile strength. The apparent rigidity of primary plant tissues is enabled by cell walls, but is not due to the walls' stiffness. Hydraulic turgor pressure creates this rigidity, along with the wall structure. The flexibility of the cell walls is seen when plants wilt, so that the stems and leaves begin to droop, or in seaweeds that bend in water currents. As John Howland explains
   Drought can cause plants to suffer from water stress and wilt. Adequate irrigation is required during prolonged hot, dry periods. Rather than shallow daily watering, during a drought water should be directed towards the roots, ensuring that the soil is thoroughly soaked two or three times a week. Mulches also help preserve soil moisture and keep roots cool.
   There have been many management solutions put forth, with the most important and widely used being the use of treated seeds. Growers should confer with the source of their seeds and as a second measure, check the weight of the seeds they receive. Lightweight seeds are typically infected. Seeds can also be treated to prevent pathogen activation. There are two options that have been found to be successful: hot water baths and chlorine treatments. However, one cannot be sure that the pathogen will be fully neutralized when subjected to these conditions.
   Necroses on green tissue are termed differently based on the nature of symptoms and the type of green tissue. The term, damping off refers to the sudden wilting and topping over of seedlings as a result of extensive necrosis of tender tissue of the roots and stem near the soil line, due to the attack of soil-borne pathogens such as fungus, "Pythium". This fungus is known to cause damping off in an assortment of seedlings such as that of brinjal, chilli, mung beans, tobacco, tomato, and "Cucurbita".
   If the plant shows dehydration tolerance, the environmental factor enters the plant tissues but the tissues survive, by e.g. maintaining turgor and osmotic adjustment.
  
  Section::::Mechanisms of Drought Resistance.:Escape.
  
  Dehydration escape involves e.g. early maturing or seed dormancy, where the plant uses previous optimal conditions to develop vigor.
  
  Dehydration Recovery refers to some plant species being able to recuperate after brief drought periods.
   The movement of this water can be explained by a water transport theory throughout a plant. This well-established water transport theory is called the cohesion-tension theory. In brief, it explains the movement of water throughout the plant depends on having a continuous column of water, from the leaves to roots. Water is then pulled up from the roots to the leaves moving throughout the plant's vascular system, all facilitated by the differences in water potential in the boundary layers of the soil and the atmosphere. Therefore, the driving force for moving water through a plant is the cohesive strength of water molecules and a pressure gradient from the roots to the leaves. This theory is still applied when the boundary layer to the atmosphere is closed, e.g. when plant stomata are closed or in senesced plants. The pressure gradient is developed between soil layers with different water potentials causing water to move by the roots from wetter to drier soil layers in a similar manner as when a plant is transpiring.
   Cytorrhysis of plant cells can be induced in laboratory settings if they are placed in a hypertonic solution where the size of the solutes in the solution inhibit flow through the pores in the cell wall matrix. Polyethylene glycol is an example of a solute with a high molecular weight that is used to induce cytorrhysis under experimental conditions. Environmental stressors which can lead to occurrences of cytorrhysis in a natural setting include intense drought, freezing temperatures, and pathogens such as the rice blast fungus ("Magnaporthe grisea").
  
  Section::::Mechanisms of avoidance.
   As a cover crop, "Vigna hosei" is susceptible to the fungus disease "Rhizoctonia solani", which causes wilting of large patches of leaves. Wet weather favors the spread of the disease. "Vigna hosei" is also one of many plants able to be infected by the cucumber mosaic virus.
  
  Section::::Uses.
   About 15 million km2 of the land surface is covered by crop-land, and about 16% of this area is equipped for irrigation (Siebert "et al." 2005). Thus, in many parts of the world, including the United States, plants may frequently encounter dehydration stress. Rainfall is very seasonal and periodic drought occurs regularly. The effect of drought is more prominent in sandy soils with low water holding capacity. On such soils some plants may experience dehydration stress after only a few days without water.
   Though often referred to as hydraulic lift, movement of water by the plant roots has been shown to occur in any direction. This phenomenon has been documented in over sixty plant species spanning a variety of plant types (from herbs and grasses to shrubs and trees) and over a range of environmental conditions (from the Kalahari Desert to the Amazon Rainforest).
  
  Section::::Causes.
   Bacterial wilt is a disease of the vascular tissue. When a plant is infected, "E. tracheiphila" multiplies within the xylem, eventually causing mechanical blockage of the water transport system. The first sign of infection, which appears about five days after acquisition, is the wilting of individual leaves on a single stem. However, the disease will soon spread down the runner and then infect the whole plant, causing it to shrivel and die. 
   Lake model parameters were provided by Dave Kramer in 2004. Since then, Luke Hendrickson has provided simplified lake model parameters that allow the resurrection of the parameter NPQ, from the puddle model, back into the lake model. This is valuable because there have been so many scientific papers that have used NPQ for plant stress measurement, as compared to papers that have used lake model parameters.
  
  For an in-depth overview of quenching, refer to the OSI quenching application note.
   Mesophytes are plants living in lands of temperate zone, which grow in well-watered soil. They can easily compensate the water lost by transpiration through absorbing water from the soil. To prevent excessive transpiration they have developed a waterproof external covering called cuticle.
  
  Section::::In animals.
   The ability of plants to access water depends on the structure of their roots and on the water potential of the root cells. When soil water content is low, plants can alter their water potential to maintain a flow of water into the roots and up to the leaves (Soil plant atmosphere continuum). This remarkable mechanism allows plants to lift water as high as 120 m by harnessing the gradient created by transpiration from the leaves.
   Breeding for drought stress tolerance
  
  Breeding for drought resistance is the process of breeding plants with the goal of reducing the impact of dehydration on plant growth.
  
  Section::::Dehydration stress in crop plants.
  
  In nature or crop fields, water is often the most limiting factor for plant growth. If plants do not receive adequate rainfall or irrigation, the resulting dehydration stress can reduce growth more than all other environmental stresses combined.
   Typically any indoor plant disease rarely affects "D. reflexa" var. "angustifolia". The most common issue it suffers from is a result of improper watering. Improper watering can be either too much or too little, but a majority of the time is due to over-watering. When the soil is over-watered, root rot can occur on the leaves because the soil is unable to properly drain. This can lead to discoloration and droopy leaves.
  
  Section::::"Dracaena reflexa" var. "angustifolia".:Uses.
   There are many factors which affect water availability, which is the major limiting factor of seed germination, seedling survival, and plant growth. These factors include infrequent raining, intense sunlight and very warm weather leading to faster water evaporation. An extreme environmental pH and high salt content of water also disrupt plants' water uptake.
  
  Section::::Types.
   Brown and Pezeshki devised an experiment in which many "S. alterniflora" individuals were put under situations of increased salinity, increased water stress, and then a combined treatment. They found that those plants that experienced the combined treatment exhibited an increase in water stress, where plants are unable to get a sufficient amount of water from the soil, a decrease in photosynthetic activity, and ultimately death (Brown & Pezeshki 2007).
   Section::::Symptoms of potassium deficiency.
   Pressure potential is based on mechanical pressure, and is an important component of the total water potential within plant cells. Pressure potential increases as water enters a cell. As water passes through the cell wall and cell membrane, it increases the total amount of water present inside the cell, which exerts an outward pressure that is opposed by the structural rigidity of the cell wall. By creating this pressure, the plant can maintain turgor, which allows the plant to keep its rigidity. Without turgor, plants will lose structure and wilt.
   Watering frequency and amount is determined by many factors, including temperature and light, the age, size and stage of growth of the plant and the medium's ability to retain water. A conspicuous sign of water problems is the wilting of leaves. Giving too much water can kill cannabis plants if the growing medium gets over-saturated. This is mainly due to oxygen not being able to enter the root system. Anaerobic bacteria start to accumulate due to waterlogged, stale conditions. They begin to consume plant roots, beneficial(aerobic) bacteria, as well as nutrients and fertilizer. When using soil as a growth medium, the soil should be allowed to dry adequately before re-watering.
  
raw_presuppositions: Muscle fibers are necessary for plants to get flaccid or stiff. Muscle fibers are needed to become flaccid and stiff.
raw_corrections: Plants cells get flaccid or stiff when they lose or fill up with water. Muscle fibers are not necessary to be rigid or flaccid.