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(i) In winter season the cambium is less active and forms fewer xylary elements that have narrow vessels / tracheids and this is called Autumn wood or lat wood.
(ii) They are thick walled. Autumn wood is darker in colour and has a higher density. This is covered by spring wood.
(iii) Thus the center part of wood is always dark.

Enzymes are globular proteins that catalyse the thousands of metabolic reactions taking place within cells and organism.

(i) No. there is no scientific proof for this statement. During day time photosynthesis takes place oxygen is evolved.
(ii) This reaction requires light hence the above statement is incorrect.

This is due to the immobile nature of minerals, Eg: Calcium.

(i) If the bark of a tree is damaged by the horn of a deer, the tree first seals the damaged region from microbial infection.
(ii) This happens by altering the chemistry of the affected area by forming a callus, which grows and covers the damaged area.

1. Genetic stability - Daughter cells are genetically identical to parent cells.
2. Growth - As multicellular organisms grow, the number of cells making up their tissue increases. The new cells must be identical to the existing ones.
3. Repair of tissues - Damaged cells must be replaced by identical new cells by mitosis.

Properties of Water
(i) Adhesion and cohesion property
(ii) High latent heat of vapori sation
(iii) High melting and boiling point
(iv) Universal solvent
(v) Specific heat capacity

60 years old - Age of the Tree.
Reason:
(i) In the cross section of the tree trunk, the lighter (spring wood) and darker (Autumn wood) rings appear in the form of concentric circles.
(ii) One spring wood circle and one autumn wood circle together constitute an annual ring.
(iii) Thus one dark and one light ring would have been formed every year.
(iv) 60 dark and 60 light rings indicate the age of the tree as 60 years.

Physiological effect:
1) Cytokinin promotes cell division in the presence of auxin (IAA).
2) Induces cell enlargement associated with IAA and gibberellins
3) Cytokinin can break the dormancy of certain light-sensitive seeds like tobacco and induces seed germination.
4) Cytokinin promotes the growth of lateral bud in the presence of apical bud.
5) Application of cytokinin delays the process of aging by nutrient mobilization.
6) It is known as Richmond Lang effect.
7) Cytokinin
(i) increases rate protein synthesis
(ii) induces the formation of inter-fascicular cambium
(iii) overcomes apical dominance
(iv) induces formation of new leaves, chloroplast and lateral shoots.
8) Plants accumulate solutes very actively with the help of cytokinins.

Because carbohydrates are partially oxidised to organic acid, particularly malic acid without corresponding release of CO₂ but O₂ is consumed. Hence the RQ value will be zero.
\(\underset { Glucose }{ 2{ C }_{ 6 }{ H }_{ 12 }{ O }_{ 6 }+3{ O }_{ 2 }\rightarrow } \underset { malic\quad acid }{ 3{ C }_{ 4 }{ H }_{ 6 }{ O }_{ 5 }+3{ H }_{ 2 }O+Energy } \)
RQ of glucose in succulents = \(\frac { Zero \ molecule \ of \ { CO }_{ 2 } }{ 3 \ molecules \ of \ { CO }_{ 2 } } \) = 0 (Zero)

C₄ plants are more advantageous than C₃ plants because increasing the proportion of C₄ plants on earth could assist biosequestration of CO₂ and represent an important cilmate change avoidance strategy.

(i) Nitrogen fixation process requires Nitrogenase enzyme complex, Minerals (Mo, Fe and S), anaerobic condition, ATP, electron and glucose 6 phosphate as H⁺ donor.
(ii) Nitrogenase enzyme is active only in anaerobic condition.
(iii) To create this anaerobic condition a pigment known as leghaemoglobin is synthesized in the nodules which acts as oxygen scavenger and removes the oxygen.

1. The discovery of enzyme phosphorylase in guard cells by Hanes (1940) greatly supports the starch-sugar interconversion theory.
2. The enzyme phosphorylase hydrolyses starch into sugar and high pH followed by endosmosis and the opening of stomata during light. The vice versa takes place during the night.

S.No	Nucleoside	Nucleotide
1	It is a combination of Nitrogenous base and sugar.	It is a combination of nucleoside and phosphoric acid
2	Eg: Adenosine = Adenine + Ribose.	Eg: Adenylic acid = Adenosine + Phosphoric acid

Ribonucleic acid (RNA): Ribonucleic acid (RNA) is a polymeric molecule essential in various biological roles in coding, decoding, regulation and expression of genes. RNA is single stranded and is unstable when compared to DNA.

Types of RNA:
1. mRNA (messenger RNA) - Single stranded, carries a copy of instructions for assembling amino acids into proteins. It is very unstable and comprises 5% of total RNA polymer. Prokaryotic mRNA (Polycistronic) carry coding sequences for many polypeptides. Eukaryotic mRNA (Monocistronic) contains information for only one polypeptide.
2. tRNA (transfer RNA) - Translates the code from mRNA and transfers amino acids to the ribosome to build proteins. It is highly folded into an elaborate 3D structure and comprises about 15% of total RNA. It is also called as soluble RNA.
3. rRNA (ribosomal RNA) - Single stranded, metabolically stable, make up the two subunits of ribosomes. It constitutes 80% of the total RNA. It is a polymer with varied length from 120 - 3000 nucleotides and gives ribosomes their shape. Genes for rRNA are highly conserved and employed for phylogenetic studies.

(i) Watson and Crick shared the Nobel Prize in 1962 for their discovery, along with Maurice Wilkins, who had produced the crystallographic data supporting the model. Rosalind Franklin (1920-1958) had earlier produced the first clear crystallographic evidence for a helical structure.
(ii) James Watson and Francis Crick of Cavendish laboratory in Cambridge built a scale model of double helical structure of DNA which is the most prevalent form of DNA, the B-DNA. This is the secondary structure of DNA.
(iii) As proposed by James Watson and Francis Crick, DNA consists of right handed double helix with 2 helical polynucleotide chains that are coiled around a common axis to form right handed B form of DNA.
(iv) The coils are held together by hydrogen bonds which occur between complementary pairs of nitrogenous bases.
(v) The sugar is called 2'-deoxyribose because there is no hydroxyl at position 2'.
(vi) Adenine and thiamine base pairs has two hydrogen bonds while guanine and cytosine base pairs have three hydrogen bonds.
(vii) As published by Erwin Chargaff in 1949, a purine pairs with pyrimidine and vice versa. Adenine (A) always pairs with Thymine (T) by double bond and Guanine (G) always pairs with Cytosine (C) by triple bond.

Photoperiodic induction
1) An appropriate photoperiod in 24 hours cycle constitutes one inductive cycle. Plants may require one or more inductive cycles for flowering.
2) The phenomenon of conversion of leaf primordia into flower primordia under the influence of suitable inductive cycles is called photoperiodic induction.
Example: Xanthium (SDP) - 1 inductive cycle and Plantago (LDP)- 25 inductive cycles.
Site of Photoinductive perception
1) Photoperiodic stimulus is perceived by the leaves.
2) Floral hormone is synthesised in leaves and translocated to the apical tip to promote flowering.
3) This can be explained by a simple experiment on Cocklebur (Xanthium pensylvanicum), a short day plant.
4) Usually Xanthium will flower under short day conditions. If the plant is defoliated and kept under short day conditions it will not flower.
5) Flowering will occur even when all the leaves are removed except one leaf.
6) If a cocklebur plant is defoliated and kept under long day conditions, it will not flower.
7) If one of its leaves is exposed to short day condition and rest are in long day condition, flowering will occur.

Plants which are growing in nitrogen deficient areas develop insectivorous habit to resolve nitrogen deficiency.
a. Nepenthes (Pitcher plant): Pitcher is a modified leaf and contains digestive enzymes. Rim of the pitcher is provided with nectar glands and acts as an attractive lid. When insect is trapped, proteolytic enzymes will digest the insect.
b. Drosera (Sundew): It consists of long club shaped leaves with tentacles which secrete sticky digestive fluid which looks like a sundew and attracts insects.
c. Utricularia (Bladder wort): Submerged plant in which leaf is modified into a bladder to collect insect in water.
d. Dionaea (Venus fly trap): Leaf of this plant modified into a colourful trap. Two folds of lamina consist of sensitive trigger hairs and when insects touch the hairs it will close and traps the insects.

S.No. Characters Dicot Stem Monocot Stem 1.  Hypodermis  Collenchymatous  Sclerenchymatous 2.  Ground tissue Differentiated into cortex, endodermis and pericycle and pith Not differentiated, but it is a continuous mass of parenchyma 3.  Starch Sheath  Present  Absent 4.  Medullary rays  Present  Absent 5. Vascular bundles  (a) Collateral and open  (a) Collateral and closed  (b) Arranged in a ring  (b) Scattered in ground tissue  (c) Secondary growth occurs  (c) Secondary growth usually does not occur.