PHYSIOLOGICAL PROCESSES IN PLANTS 



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ning from the woody cylinder towards the surface through the 

 cortex. These connect with the root hairs on the rootlets, 

 and are modified cells that 

 form continuous hollow tubes. 

 They are known as fibrovascu- 

 lar bundles. 



3. Examine figure of across 

 section of a taproot (Fig. 16). 

 Note that the root hairs are 

 but hollow extensions of cells 

 (epidermal cells) on the outer 

 margins of roots or rootlets. 



Conclusions. 1. Which 

 part of a taproot contains 



Stored-up food (starch) ? Ex- FlG - 16. -Cross section of young root, 

 plain your answer. 



2. What seems to be the 



a, root hair; &, epidermis ; c, corti- 

 cal layer ; d, fibrovascular bundle. 



use of fibrovascular bundles in roots? 



c. Root Hairs (Optional Home Work) 



Observations. 1. Remove a geranium or other plant from the soil. 

 Pull the roots bearing root hairs through the hand m such a way that 

 the root hairs will be injured. Also allow some of them to dry. Repot 

 the plant and water it. Note the effect after a few hours. After a day 

 or so. 



2. Remove and repot another similar plant, taking care to keep root 

 hairs moist and uninjured. Water it. Note the effect as above. 



3. Which plant wilts more than the other ? Sooner than the other ? 



4. Do both plants regain their normal condition at the same time ? 

 Conclusion. What do you conclude is one function of root hairs ? 



d. How Root Hairs absorb Soil Water 

 1. OSMOSIS AND.EOOT HAIRS 



Note. The process by which two fluids or gases separated 

 by a membrane pass through the membrane and mix is called 

 osmosis. 



Method. Make an artificial root hair by emptying the coiv 



