Biology Chapter 9: Plant Nutrition

As light intensity increases, the rate of photosynthesis increases, while the rate of respiration remains largely constant. At low light intensities, respiration dominates, leading to a net uptake of oxygen and release of carbon dioxide. As light intensity increases, photosynthesis eventually surpasses respiration, resulting in a net uptake of carbon dioxide and release of oxygen. At the compensation point, the rates of photosynthesis and respiration are equal, and there is no net gas exchange.

During the night, plants exhibit a net uptake of oxygen and release of carbon dioxide. This is because photosynthesis ceases in the absence of light, while respiration continues, leading to the consumption of oxygen and production of carbon dioxide.

The compensation point is the light intensity at which the rate of photosynthesis equals the rate of respiration. This point is significant because it represents the minimum light intensity needed for a plant to maintain a stable supply of energy through photosynthesis and respiration.

<p>Factors such as carbon dioxide concentration and temperature, even when light intensity is high, can limit the rate of photosynthesis. Increasing carbon dioxide concentration can boost photosynthesis, but beyond an optimal level, further increases have little effect. Similarly, while increasing temperature can initially enhance photosynthetic rates, exceeding an optimal point may lead to a decline in activity due to enzyme denaturation.</p> Signup and view all the answers

<p>Plants rely on various structures for gas exchange. Lenticels, small pores in the bark, facilitate gas exchange between the interior of stems and the atmosphere. Roots also participate in gas exchange, absorbing oxygen for respiration and releasing carbon dioxide. The leaves, with their numerous stomata, are the primary sites of gas exchange during photosynthesis and respiration.</p> Signup and view all the answers

<p>Leaves are broad and flat to maximize surface area for gas exchange. They are also thin, reducing the diffusion distance for gases. The mesophyll cells have moist surfaces for gas dissolution, and there are air spaces within the spongy mesophyll for efficient gas diffusion. Stomata on the epidermis allow for gas entry and exit, and guard cells regulate the rate of gas exchange.</p> Signup and view all the answers

<p>Gases produced within the cells diffuse into neighboring cells and eventually reach the air spaces near the stomata. These gases then dissolve in the moist surfaces of the mesophyll cells and diffuse into the air spaces. Finally, gases from the air spaces diffuse out through the stomata into the atmosphere.</p> Signup and view all the answers

<p>Air spaces within the spongy mesophyll allow gases to diffuse freely within the leaf, facilitating efficient gas exchange between cells and the atmosphere. These spaces reduce the diffusion distance for gases, making the exchange process faster and more efficient.</p> Signup and view all the answers

<p>The adaptive features of leaves, including their broad and flat shape, thin structure, moist cell surfaces, air spaces, stomata, and controlled stomatal opening, collectively contribute to efficient gas exchange. These features create favorable conditions for gas diffusion, solubility, and regulation, maximizing the uptake of carbon dioxide for photosynthesis and the release of oxygen for respiration.</p> Signup and view all the answers

<p>Magnesium is a key component of chlorophyll, the pigment responsible for absorbing light energy during photosynthesis. A lack of magnesium restricts chlorophyll production, resulting in reduced photosynthetic activity and therefore a decline in plant growth. This is manifested by yellowing leaves as the plant loses its green pigment.</p> Signup and view all the answers

<p>The aluminium foil serves to block light and prevents algae from carrying out photosynthesis. This is crucial because algae would compete with the seedlings for the minerals in the solution and potentially clog the root hairs, interfering with the experiment's focus on the effects of specific minerals on plant growth.</p> Signup and view all the answers

<p>The cotton wool acts as a barrier, preventing contamination by bacteria or fungi that could enter the solution and potentially disrupt the plant's growth or introduce additional variables, interfering with the study of the mineral's effects.</p> Signup and view all the answers

<p>Young seedlings are preferred because their rapid growth rate allows for more prominent and readily observable results. Changes in their growth patterns due to mineral deficiencies or variations in nutrient solutions will be more noticeable and easier to quantify in a shorter time frame.</p> Signup and view all the answers

<p>The air bubbled into the solution provides oxygen for root respiration. Roots, like all living cells, require oxygen for respiration, which releases energy for their growth and function. Supplying carbon dioxide would not be beneficial as it is used during photosynthesis, a process that takes place in the leaves, not the roots.</p> Signup and view all the answers

<p>The nutrient solution needs to be renewed because the plants gradually absorb minerals from it over time. As the nutrients are depleted, the solution becomes less effective in supporting growth, and the plants may suffer deficiencies if the solution is not replaced.</p> Signup and view all the answers

<p>The palisade mesophyll is the layer of tightly packed, cylindrical cells located below the upper epidermis. These cells possess numerous chloroplasts, which are the sites of photosynthesis. The compact arrangement and high chloroplast content maximize the light absorption and energy conversion for photosynthesis, promoting efficient energy production for the plant.</p> Signup and view all the answers

<p>The cuticle, a waxy layer covering the epidermis of both the upper and lower leaf surfaces, acts as a protective barrier that minimizes water loss through transpiration. This is crucial for plant survival, especially in dry environments, as it helps maintain the plant's water balance and prevents dehydration.</p> Signup and view all the answers

<p>Photosynthesis</p> Signup and view all the answers

<p>Nitrogen, absorbed as nitrate or ammonium ions.</p> Signup and view all the answers

<p>It is required for the synthesis of nucleic acids and some enzymatic reactions.</p> Signup and view all the answers

<p>Potassium; deficiency causes poor growth and curled-up leaves with dark edges.</p> Signup and view all the answers

<p>By absorbing it from the soil.</p> Signup and view all the answers

<p>Plants synthesize organic substances from inorganic substances.</p> Signup and view all the answers

<p>Trace elements are minerals needed in small amounts for plant growth.</p> Signup and view all the answers

<p>It leads to poor growth and yellow leaves.</p> Signup and view all the answers

<p>lenticels</p> Signup and view all the answers

<p>photosynthesis</p> Signup and view all the answers

<p>compensation</p> Signup and view all the answers

<p>carbon dioxide</p> Signup and view all the answers

<p>roots</p> Signup and view all the answers

<p>magnesium</p> Signup and view all the answers

<p>chlorophyll</p> Signup and view all the answers

<p>poor</p> Signup and view all the answers

<p>aluminum</p> Signup and view all the answers

<p>cotton</p> Signup and view all the answers

<p>oxygen</p> Signup and view all the answers

<p>palisade</p> Signup and view all the answers

<p>cuticle</p> Signup and view all the answers

<p>chlorophyll</p> Signup and view all the answers

<p>photosynthesis</p> Signup and view all the answers

<p>ions</p> Signup and view all the answers

<p>nitrate</p> Signup and view all the answers

<p>nucleic acids</p> Signup and view all the answers

<p>photosynthesis</p> Signup and view all the answers

<p>yellow</p> Signup and view all the answers

<p>trace</p> Signup and view all the answers

<p>guard</p> Signup and view all the answers

<p>xylem</p> Signup and view all the answers

<p>dissolve</p> Signup and view all the answers

<p>moist</p> Signup and view all the answers

<p>epidermis</p> Signup and view all the answers

<p>opening</p> Signup and view all the answers

<p>stomata</p> Signup and view all the answers

<p>cork</p> Signup and view all the answers