5th Class Science Plants Photosynthesis

           Photosynthesis

 

Photosynthesis is derived from two words, photo + synthesis. 'Photo' means light and 'synthesis' means manufacturing, i.e. manufacturing food in the presence of light.

 

All green plants prepare its own food with the help of carbon dioxide and water in the presence of chlorophyll and sunlight.

In this process solar energy is converted into chemical energy.

The function of chlorophyll is to absorb solar energy.

 

Absorption of carbon dioxide and evolution of oxygen takes place through the leaves.

 

Water is obtained from the soil through the roots and transported to leaves for photosynthesis. Food prepared in the leaves transported to all the parts of the plants. Both the process are carried out with the help of veins.

Roots absorb water from the soil

 

Path way of carbon dioxide and oxygen in and out of the plant body:

 

Oxygen is a byproduct in the photosynthesis process that leaves the plant body through the stomata, which is present in the leaves., also enters the body through the stomata.

Mushrooms are grown in the dark places. It doesn't undergo photosynthesis process, rather it feeds on dead and decayed organic matter.

 

Mushroom obtains its food from dead decayed plant product

 

Some plants are parasitic in nature. They eat insects trapped by them. Such types of plants are called insectivorous plants, e.g. sundew, venus fly trap, pitcher plant etc.

Insectivorous plants appear very attractive as they need to attract insects. They can even trap frogs, birds etc.

                                                          

   Venus fly trap                                     Pitcher plant                                          Sundew  

 

         Respiration in Plants

Like animals, plants also need energy; but to a little extent. Because plants don't have to move from one place to another in search of food like animals. This energy comes from the oxidation of the food prepared by leaves. Hence we can say that in the presence of oxygen food is broken down into CO₂ and H₂O along with the release of energy. Photosynthesis is a synthesis process and respiration is a breaking down process. Respiration is an opposite process of the process of photosynthesis.

 

     

 

         Adaptations in Various Plants

Adaptations are favorable changes that enable an organism to increase its chances of survival.

     

  

 

 

 

 

           Water and carbon dioxide combine to form glucose and oxygen In the process of photosynthesis. What is the role of chlorophyll?

(a) To absorb solar energy

(b) To look beautiful

(c) To excite water molecule

(d) To break water and carbon dioxide into oxygen

(e) All of these

 

Answer: (a)

Explanations

Chlorophyll receives sunlight to initiate the photosynthesis process.

Therefore, option (A) is correct and rest of the options is incorrect.

 

 

         Consider the following statements:

Statement X: Xerophytes plants are tall and have large leaves.

Statement Y: Hairy and spiny plants are an adaptation to disperse the seed from one place to another.

Which one of the following is correct about the above statements?

(a) Statement X is true

(b) Statement Y is true

(c) Both X and Y are true

(d) Both X and Y are false

(e) None of these

 

Answer: (b)

Explanation

Xerophytes plants are short and leaves modified to spines to prevent water loss through transpiration. Hairy and spiny plants get stuck to the animal's body and hence dispersed from one place to another.

Therefore, option (B) is correct and rest of the options is incorrect.

 

 

       Seed

Seed is a part of the flower which gives birth to a new plant. It is surrounded or protected by seed coat that contains food in it. It is the result of fusion of male and female sex gametes. Embryo develops inside it. Seed enclosed in an ovary is an essential feature of the flowering plant.

Look at the following picture of internal parts of seed:

 

             Embryo

Immature plant from which new plant is grown is called embryo. Embryo consists of precursor tissues for the leaves, roots, stems etc. it has cotyledons, radical and plumule.

 

             Cotyledons

It provides food thus this is the first photosynthetic organ of the plants.

 

           Radicle

Radicle develops into root system so called - ve phototrophic, or + vely geotropic.

 

           Plumule

Plumule grows into shoot system thus called + vely phototrophic or –vely geotropic.

Seed is protected by seed coat which is called as testa. It is usually hard and tough.

 

         Micropyle 

 

Micropyle allows the pollen tube to enter the ovuie for fertilization. Water also enters into the seed through the micropyle for germination. Germination is defined as the growing and developing of embryo into a mature plant.

See the given picture of growth of embryo into a mature plant:

 

     

 

           Essential Condition for Germination

Water

Air

Warmth

Food (Which comes from cotyledons)

 

           Dispersal of Seeds

Seed dispersal means transportation of seeds from one place to another.

 The following agents help in the dispersal of seed:

(a) Wind

(b) Animals

(c) Water

(d) Birds

(e) Explosion method

Dispersal of seeds avoid gathering of many plants to grow at one place. Nature has developed mechanism to scatter the seeds of plants to different places to ensure proper water, sunlight and soil etc to the developing seeds.

 

         Seeds Dispersed by Wind

Winged seeds can be easily carried by the wind. e.g. maple, pine.

Seeds have hairs that help in dispersing through wind e.g. dandelion, poplar etc.

                                                

           Dandelion                                               Maple                                                           Orchid  

 

          Seeds Dispersed by Water

A type of seeds floats in water so called buoyant seeds. E.g. water lily.

These seeds are dispersed by the water bodies. E.g. coconut has fibrous outer covering that helps in floating from one place to another. Other examples are milkweed mangrove, palm trees etc.

                                     

         Milkweed                                                  Palm                                                       Water lily  

 

           Seeds Dispersed by Animal

Seeds which dispersed by animals are brightly colored.

It has tasty pulp, e.g. raspberry

It has spines or hooks, which get stacked on the animal's body, e.g. date, goose grass.

Girds and monkeys eat different types of seeds at one place and leave its seeds on some other places, e-g. fig, strawberries, etc.                                              

                  Raspberry                                    Fig                                                       Strawberry  

 

        Explosive Mechanism of Seed Dispersal

Certain fruits explode on becoming dry. This explosion flies away seed with great force at places away from the mother plant. E.g. balsam, pea, geranium, touch me not, cucumbers etc..

                                                                        

           Exploding geranium                        Exploding balsam                     Cucumber ready to explode    

 

         Oil and Fiber Producing Seeds

Some seeds are oil producing, e.g. sunflower, mustard, groundnut etc. And some seeds are fibre yielding, e.g. cotton, jute etc.

                                       

     Oil producing                                   Fibre yielding seed    

 

 

 

 

     Find the statement which is not true about seed.

(a) Gymnosperms have seeds enclosed in an ovary

(b) Embryo is the baby plant inside the seed

(c) Germination is the process of growing baby plant from the embryo

(d) Maize has one cotyledon in the seed

(e) All of these

 

Answer: (a)

Explanation

Gymnosperms have naked seeds. Hence, the statement which is given in the option (A) is incorrect. Therefore, option A is correct and rest of the options is incorrect.

 

 

       Ayush had to submit germinated seed to his science teacher Diuya madam as a project. But he couldn't submit the project as his seeds were not germinated. What could be the possible reason for this?

(a) Ayush's mother kept the soaked seed in a moist cloth in the kitchen

(b) Ayush's mother kept the soaked seed in the dark room'

(c) Ayush's mother kept the soaked seed in a dry cloth

(d) Ayush's mother kept the soaked seed in an air tight container

(e) All B, C and D

 

Answer: (e)

Explanation

Several factors are essential for the germination process. These are water, oxygen, temperature and light. Absence of any of these factor could lead to stoppage of germination process. Therefore, option (E) is correct and rest of the options is incorrect.