A researcher wanted to study light reaction during photosynthesis by blocking photosynthetic electron flow using the herbicide, dichlorophenyldimethylurea (DCMU) and paraquat. The researcher listed the following observations:

A. Both DCMU and paraquat block the electron flow in Photosystem II.

B. Both DCMU and paraquat block the electron flow in Photosystem I.

C. DCMU blocks electron flow in Photosystem I while paraquat blocks in Photosystem II.

D. DCMU blocks electron flow in Photosystem II while paraquat blocks in Photosystem I.

Which of the following combinations of the above statements is INCORRECT?

• A, B, and C

• A, B, and D

• A, C, and D

• B, C, and D

A leaf appears green in daylight. If this leaf were observed in red light, what colour would it appear to have?

• green

• black-brown

• red

• blue

143.

The photon intensity captured by green plants is used in the following processes:

(i) Photosynthesis

(ii) Generation of heat.

(iii) Production of toxic products such as superoxide, singlet oxygen etc.

(iv) Damage to D1 protein of PSII.

Based on the above facts, photoinhibition will happen when the

• entire photon intensity is used for photosynthesis.

• excess photon intensity is completely used for heat generation

• excess photon intensity is used for heat generation and formation of toxic products

• excess photon intensity leads to the damage of D1 protein.

Given below are some statements on secondary metabolites in plants.

A. Glucosinolates are synthesized by elongation in the length of side chains of their precursor amino acids.

B. All terpenes produced in herbs and spices are sticky, oily liquids which reduces the palatability (edible value) of these plants.

C. Cyanogenic glycosides are produced and stored in a toxic form in plants and are therefore more effective in defense against invading pathogens and herbivores.

D. The defense molecules, alkaloids (or their precursors), are gathered from plants and used by some insects for their own protection against predators.

Which one of the following represents correct statements?

• B and C only

• A and B only

• C only

• A and D only

Which one of the following is NOT a phenotype of dark-grown seedlings that are etiolated?

• Short hypocotyls

• An apical hook

• Closed cotyledons

• Non-photosynthetic proplastids

The plant hormone, Gibberellic acid is generally not associated with

• stem elongation

• parthenocarpy

• parthenogenesis

• malt production

Which one of the following statements is NOT correct for the Casparian strip?

• It breaks the continuity of water movement through the apoplast pathway.

• It is formed in the growing part of the root.

• It is formed several millimetres or several centimetres behind the root tip.

• It is a band within the radial cell walls of the endodermis that is impregnated with lignin.

Which one of the following statements is true about xylem in plants?

• It is characterized by the presence of tracheary elements responsible for the conduction of water in vascular plants.

• It is responsible for the transport of water and characterized by sieve elements like parenchyma cells and sclerids.

• It is responsible for the transport of assimilates in the vascular plants and characterized by tracheary elements.

• It is responsible for the transport of assimilates in both vascular and non-vascular plants.

Which one of the following secondary metabolites is characterized by the presence of a central carbon atom that is bound by a sulphur to a glycone group, and by a nitrogen to a sulfonated oxime group?

• Alkaloids

• Terpenes

• Phenolics

• Glucosinolates 

Dark grown Arabidopsis seedlings show ‘triple response’ when exposed to ethylene hormone. Which one of the following options is characteristic of ‘triple response’? 

• Reduced shoot elongation, increased shoot thickness and tightening of apical hook

• Reduced shoot elongation, reduced shoot thickness and loosening of apical hook

• Increased shoot elongation, increased shoot thickness and loosening of apical hook

• Increased shoot elongation, reduced shoot thickness and tightening of apical hook.