General Questions in English

(C) In addition to the $17$ essential elements,there are some beneficial elements such as sodium $(Na)$,silicon $(Si)$,cobalt $(Co)$,and selenium $(Se)$.
These elements are required by higher plants for various physiological processes,although they are not strictly essential for the completion of the life cycle.

(B) Justus von Liebig,often referred to as the Father of Agricultural Chemistry,was the first to systematically analyze plant ash and prove that plants contain a large number of minerals and elements. He proposed the Law of the Minimum and emphasized the importance of mineral nutrients for plant growth.

(A) The concentration of nutrients in a hydroponic solution is typically measured in parts per million $(ppm)$.
$1 \; ppm$ is defined as one part by weight of a mineral solute in one million parts of the solution.
This unit is equivalent to $1 \; mg$ of solute per litre of water $(1 \; mg/L)$.

(D) In hydroponics,various micronutrients (especially iron) are added to the nutrient solution. Chelating agents,such as $EDTA$,are added to keep these micronutrients in a soluble form so that they remain available for plant uptake and do not precipitate out of the solution. By ensuring the availability of these essential nutrients,chelating agents contribute to the overall nutrition,healthy development,and growth of the plants. Therefore,all the given options are correct.

(D) Humus is the dark-colored amorphous colloidal material that constitutes the organic component of soil.
It is formed by the decomposition of plant and animal remains and excrement,and it has a complex and variable chemical composition.
Being a colloid,it can hold water,therefore it improves the water-retaining properties of the soil.
It also enhances soil fertility,increases soil aeration,and improves soil porosity,which are all essential for healthy plant growth.

(A) In hydroponics,chelating agents (such as $EDTA$) are used to keep essential micronutrients,particularly iron $(Fe)$,in a soluble form.
These agents bind to metal ions to prevent them from precipitating out of the nutrient solution,thereby ensuring that the plants can effectively absorb the necessary minerals for their growth.

(B) When a plant is burnt,the organic matter (carbon,hydrogen,oxygen,nitrogen) is oxidized and released as gases like $CO_2$,$H_2O$,and $NO_x$.
What remains is the plant ash,which consists of non-volatile mineral salts absorbed by the plant from the soil.
Therefore,plant ash represents the mineral content of the plant.

(C) An ideal $pH$ range for most hydroponic crops is between $5.5$ and $6.5$.
This range is considered slightly acidic.
It is important because this $pH$ level optimizes the availability and absorption of essential mineral nutrients required for plant growth.

(C) Chelating agents are organic molecules that form stable complexes with metal ions,thereby keeping them in a soluble state and preventing them from precipitating or becoming fixed in the soil.
Assertion is incorrect because chelating agents are typically electron donors (ligands) that donate electron pairs to metal ions to form coordinate covalent bonds,not electron acceptors.
Reason is correct because chelating agents effectively increase the solubility and bioavailability of essential micronutrients (like $Fe$,$Zn$,$Mn$,and $Cu$) in soil,especially in alkaline or acidic conditions where these minerals might otherwise become unavailable to plants.

(C) The vegetation of any area is primarily determined by edaphic factors (soil factors) such as the $pH$ of the soil,the mineral composition of the soil,and the water-holding capacity of the soil.
These factors directly influence the nutrient availability and water accessibility for plants.
Weather conditions represent short-term atmospheric changes and do not determine the long-term vegetation patterns of a region as significantly as soil characteristics do.
Therefore,$I, II,$ and $III$ are the correct factors.

(C) The classification of soil based on the means of transport is as follows:
$1$. Water: Soil transported and deposited by water is known as Alluvial soil $(a-ii)$.
$2$. Air: Soil transported and deposited by wind is known as Eolian soil $(b-iii)$.
$3$. Gravity: Soil transported by gravity is known as Colluvial soil $(c-i)$.
Therefore, the correct matching is $a(ii), b(iii), c(i)$.

(A) Soil porosity refers to the volume of pores or spaces between soil particles.
$A$. Sandy soil: Composed of large particles,resulting in large pore spaces,which makes it highly porous and loose.
$B$. Clay soil: Composed of very fine particles. While it has many small capillary pores,the total volume of large pores is lower compared to sandy soil.
$C$. Silt: Intermediate in particle size between sand and clay.
$D$. Loam: $A$ mixture of sand,silt,and clay,providing moderate porosity.
Therefore,sandy soil exhibits the maximum porosity due to the large size of its particles.

(D) According to the $NCERT$ textbook for Class $11$ Biology,Chapter $12$ (Mineral Nutrition),it is stated that out of the $105$ elements discovered so far,not all of them are necessary for plants. Only $60$ or more elements have been found in different plants.

(D) The toxicity of micronutrients is defined as any concentration of a mineral ion in tissues that reduces the dry weight of tissues by $10$ percent. This threshold is used to identify levels of minerals that are harmful to plant growth and development.

(D) Minerals are essential for the growth and development of plants.
Plants obtain their mineral requirements from the soil through their roots.
The soil acts as a reservoir of essential elements.
These elements are derived from the rocks through the processes of weathering and breakdown,which release soluble ions and inorganic salts into the soil,making them available for plant uptake.
Therefore,all the given statements are correct.

(B) The soil texture is defined by the relative proportion of different particle sizes,such as sand,silt,and clay,present in the soil.
Since the property is based on the size of its particles,it is referred to as soil texture.
Other options like colour,field capacity,and water-holding capacity are influenced by texture but are distinct properties.