Question

A flowering plant is planted in an earthen pot and irigated. Urea is added in high amounts to make the plant grow faster, but after some time the plant died. This may be due to (a) exosmosis (b) endosmosit (c) water logging (d) suffocation

Short answer

Excessive urea creates a hypertonic environment, leading to exosmosis, which can dehydrate plant cells and cause the plant to die.

Step-by-step solution

Understand the Problem

The exercise presents a scenario where a flowering plant has died after being irrigated and given high amounts of urea. To find out the cause of the plant's death, it is essential to understand the effects of high concentrations of urea on plants and the potential outcomes.

Analyze the Options

Consider each of the given options and their relevance to the situation: (a) exosmosis is the movement of water out of a cell due to a hypertonic surrounding, which may occur if too much urea raises solute concentration outside plant roots; (b) endosmosis is the movement of water into cells, which is less likely in this case; (c) water logging concerns soil being too wet, inhibiting plant respiration, not directly linked to urea; (d) suffocation usually refers to lack of air, but excess urea isn't directly related to this.

Identify the Most Likely Cause

Considering the effects of excessive urea, it likely leads to a hypertonic environment around the roots, causing exosmosis - water moves out of plant cells, leading to dehydration and eventual death of the plant.

Key concepts

Exosmosis in Plants

Exosmosis is a critical physiological process affecting plants when they are exposed to hypertonic solutions. This process entails the movement of water from inside the plant cells to the outside environment, facilitated by a higher solute concentration in the surrounding medium. In simpler terms, it's similar to a sponge releasing water when it is placed in a saline solution.

One might wonder why this occurs. It boils down to osmosis – the natural tendency of water to move from an area of low solute concentration to an area of higher solute concentration in order to achieve equilibrium. When the external environment is hypertonic, or in other words, contains more solutes than the cell's interior, water moves out leading to the shrinkage of cells. This process can be detrimental to plants, as it can cause cells to become flaccid, interrupting vital functions like photosynthesis and nutrient absorption.

In our case, the addition of high amounts of urea created a hypertonic environment around the plant roots. As a result, water moved out of the roots' cells, causing the plant to dehydrate and eventually die. The prevention of such adverse plant responses is crucial for gardeners and agriculturists, as it directly impacts a plant's growth and survival.

Effects of High Urea Concentration

Urea is an inexpensive and widely used nitrogen fertilizer that can have profound effects on plant growth when used appropriately. However, when applied in high concentrations, urea can become a double-edged sword. The high urea concentration in the soil can initially give the impression of vigorous plant growth due to its rich nitrogen content, which plants use to synthesize proteins and other vital molecules.

Yet, excessive urea can disrupt the osmotic balance around the root zone. It increases the solute concentration of the soil solution, making it hypertonic when compared to the plant's internal cell sap. This situation forces the plant to undergo exosmosis, as discussed earlier. Continued exosmosis can run the plant dry and interrupt vital functions, leading to nutrient deficiencies, reduced vigor, and in severe cases, plant death, which is precisely the scenario exhibited in the exercise.

It is vital for those working with plants to understand the proper application rates of urea to avoid creating harmful hypertonic conditions. Advising moderation and following guidelines for fertilization can help protect plants from the unintentional consequences of excessive fertilizer use.

Plant Dehydration

Dehydration in plants can occur due to several factors, but in the case of our wilted plant, the excessive use of urea led to a detrimental loss of water. Plant dehydration is the result of inadequate water levels within plant tissues, essential for maintaining turgor pressure, which keeps the cells rigid and plants upright.

When a plant dehydrates, it can exhibit signs like wilting, curling of leaves, and stunted growth. The plant's stomata close to reduce water loss, which in turn reduces the carbon dioxide intake necessary for photosynthesis. Long periods of dehydration can lead to irreversible damage to the plant's structure and metabolism. The plant's ability to absorb nutrients becomes compromised, compounding the stress and accelerating its decline.

Preventing and addressing dehydration involves maintaining a balance in soil moisture levels and avoiding environmental conditions that promote excessive water loss. Understanding the unique water needs of each plant species, coupled with judicious application of fertilizers like urea, can help prevent dehydration through proper garden and agricultural management practices.