Question 1

The site of perception of light in plants during photoperiodism is :

Accepted Answer

The site of perception of light in plants during photoperiodism is leaf.

Question 2

Which one of the following is a long day plant?

Accepted Answer

d) Long-day plants usually flower in the spring or early summer; they flower only if the light periods are longer than a critical length, which is usually 9-16 hours. For example, wheat plants flower only when light periods exceed fourteen hours.

Question 3

In short day plants, flowering is induced by

Accepted Answer

(b) A plant that requires a long period of darkness is termed a “short-day” (long-night) plant. Short-day plants form flowers only when day length is less than about 12 hours. Many spring- and fall-flowering plants are short-day plants, including chrysanthemums, poinsettias and Christmas cactus.

Question 4

Phytochrome is found in

Accepted Answer

Phytochrome is a photoreceptor, a pigment that plants (and some bacteria and fungi), use to detect light. The most important plant responses regulated by the phytochrome system include photoperiodic induction of flowering. As angiosperms are the flowering plants, the phytochromes are present in angiosperms.

Question 5

Pick up the correct match -

Accepted Answer

Short day plants (SDP) require long period of darkness and short period of light to flower. Long day plants (LDP) will flower when they are exposed to short period of darkness and long period of light. Long day plants flower in summer and short day plants flower in spring. Day neutral plants (DNP) do not depend upon the amount of darkness or daylight hours. Examples of day neutral plants are sunflower, cucumber, tomato. Examples of short day plants are rice, tobacco, cotton, xanthium. Examples of long day plants are lettuce, wheat, spinach, potato, radish.

Question 6

The long-day plant is

Accepted Answer

Long day plants are those plants that begin flowering when the days are longer than their critical day length. They will flower when they are exposed to short period of darkness and long period of light. Long day plants flower in summer and short day plants flower in spring. Examples of long day plants are lettuce, spinach, potato.Thus, the correct answer is option D.

Question 7

In short day plants, flowering is inhibited by

Accepted Answer

Short day plants (SDP) are those plants that begin flowering when the days are shorter than their critical day length. They require a long period of darkness and short period of light to flower. Flash of white or red light in dark thus inhibits flowering in short day plants.Thus, the correct answer is 'Interruption of dark by white or red light'.

Question 8

The plant which requires an exposure to light for a period greater than critical day length is

Accepted Answer

The effect of photoperiods or daily duration of light hours (and dark periods) on the growth and development of plants, especially flowering, is called photoperiodism. Photoperiodism was first studied by Gamer and Allard (1920) in 'Maryland mammoth' a variety of Tobacco.Long Day Plants (LDPs) flower when they receive long photoperiods or light hours which are above a critical length, e.g., henbane, wheat oat sugar beet, spinach (Spinacia oleracea), radish, barley, larkspur, lettuce.So the correct answer is 'long day plants'.

Question 9

If the dark period is interrupted by flashes of light, short day type plant will not flower.

Accepted Answer

Short day plants such as canabis or cotton flower during the late summer or fall in the northern hemisphere when days get shorter. Periods of darkness longer than that of light are needed for the plants to flower. if the plants are exposed to light, their photoperiodism is disturbed and the plants do not flower.

Question 10

Which of the following factors influence the process of flowering?

Accepted Answer

In photoperiod, a duration of day length suitable for flowering, plants secrete Florigen. Florigen induces flowering in angiospermic plants. Florigen is the hypothesized hormone-like molecule responsible for controlling and triggering flowering in plants. It is produced in the leaves and acts in the shoot apical meristem of buds and growing tips. It is known to be graft-transmissible, and even functions between species.So, the correct answer is 'Photoperiod'.

Question 11

Flowering is influenced by

Accepted Answer

Photoperiodism is the phenomenon in which formation of flowers in plants depends on the relative length of photoperiod, that is length of day and night. Short day plants are those plants that require long period of darkness and short period of light to flower. Long day plants are those plants that will flower when they are exposed to short period of darkness and long period of light. Thus, the correct answer is option C.

Question 12

Etiolation occurs when plants

Accepted Answer

Etiolation is a process which is seen in flowering plants that are grown in partial or complete absence of light. It is characterized by slender yellowish stems, smaller yellowish leaves due to longer internodes, subterminal hook and chlorosis due to lack of chlorophyll. The growing tips are attracted towards light and will elongate towards it.Thus, the correct answer is 'Are grown in dark'.

Question 13

How is the movement of leaves of sensitive plant different from the movement of a shoot towards light?

Accepted Answer

The type of movement of leaves of the sensitive plant is known as a nastic movement.  This type of movement does not depend on the direction of stimuli. The movement of shoot towards light is known as a tropic movement. This movement depends on the direction of light. This is known as phototropism. This type of movement is directional and growth development.

Question 14

Define photoperiodism, and discuss its relationship to flowering in certain plants.

Accepted Answer

Photoperiodism is the physiological reaction of organisms to the length of day or night. It occurs in plants and animals. Photoperiodism can also be defined as the developmental responses of plants to the relative lengths of light and dark periods.  On the basis of photoperiodism the plants are classified in two classes:    • Short Day plants: A plant that requires a long period of darkness, is termed a "short day" (long night) plant. Short-day plants form flowers only when day length is less than about 12 hours. Many spring and fall flowering plants are short-day plants, including chrysanthemums, poinsettias, and Christmas cactus.    • Long day plant: Long-day plants require less darkness to generate the reaction needed for production. These plants need about eight hours of darkness to start flowering. The long-day flowers that grow well in the home garden are lettuce (Lactuca sativa), spinach (Spinacia oleracea) and petunias (Petunia x hybrids).

Question 15

Assertion :In short day plant, day length should be less than critical day length. Reason :Long night should be continuous.

Accepted Answer

In short day plants, day length must be shorter than a certain critical duration. The night must also be continuous. Thus, both Assertion and Reason are correct, but Reason is not the correct explanation for Assertion.

Question 16

Assertion :In short day plant, day length should be less than critical day length.Reason :Long night should be continuous.

Accepted Answer

Short Day Plants are the plants which flourish when the duration of daytime is shorter. Thus, obviously the nights should be longer.

Question 17

In short day plants (SDP), flowering is induced by

Accepted Answer

Short-day plants (also called as long-night plants) flower when the night length is equal to or greater than some critical period. Thus, short-day plants detect the lengthening nights of late summer or fall. There are two kinds of short day plants: qualitative and quantitative. In qualitative short-day plants, flowering occurs only in short days; in quantitative short day plants, flowering is accelerated by short days. The initiation of flowering in short-day plants is not due to the shorter period of day light but to the long, uninterrupted period of darkness. The minimum critical night length varies considerably from one plant species to another but falls between 12 and 14 hours for many. Examples of short-day plants are florists chrysanthemum, cocklebur and poinsettia, which typically flower in late summer or fall.Thus, the correct answer is option C.

Question 18

Effect of the day length duration on plant development and flowering is

Accepted Answer

Effect of the day length duration on plant development and flowering is called photoperiodism. Photoperiodism can also be defined as the developmental responses of plants to the relative lengths of light and dark period.Plants have been classified under three groups according to photoperiods. They are short-day plants, long-day plants and day-neutral plants.So, the correct answer is 'Photoperiodism'.

Question 19

Photoperiodism influences

Accepted Answer

Photoperiodism is the phenomenon in which formation of flowers in plants depends on the relative length of dark or light periods. It also influences growth, seed germination, fruit development, the onset of winter dormancy. Short day plants are those plants that require long period of darkness and short period of light to flower. Long day plants are those plants that will flower when they are exposed to short period of darkness and long period of light.Thus, the correct answer is 'Seed germination'.

Question 20

Which of the following is a day neutral plant?

Accepted Answer

Photoperiodism is the physiological reaction of organisms to the length of day or night. It occurs in plants and animals. Photoperiodism can also be defined as the developmental responses of plants to the relative lengths of light and dark periods. A plant that flowers regardless of the length of the period of light it is exposed to, is called as day neutral plant. For example- Rice, corn and the cucumber are day neutral plants.

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Solution for Class 11, Biology, Plant Growth and Development

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