Tag: significance of transpiration

The leaves are covered with waxy cuticle but roots do not possess any cuticle. Cuticle helps in preventing loss of water from the surface of the leaves. Since roots are present underground immersed in the soil they do not show transpiration and hence no cuticle is present. 

Charles Darwin and Francis showed  the presence of the phototropic stimulus at the tip of the plant and that the apical region communicates with the cell of elongation zone. The Danish plant physiologist Boysen-Jensen experimentally showed that the apex cells communicate with the the cell of elongation zone via chemical passing down from the tip of the coleoptile. Lamarck gave the theory of inheritance of acquired characters that explains evolution as the inheritance of acquired characters under influence of needs as posed as changing environmental conditions. Thus, the correct answer is option B.

W. Ruhland (1912) and Hoffman (1925) put forth the ultrafiltration theory and describe that small pores are found on the membrane of the molecules, which are small in size than pores of the membrane are only passed through membranes.

• Monocots have scattered vascular bundles, while dicots have a continuous ring arrangement of vascular bundles. In a dicot stem, after a few years of growth, phloem is present as a single continuous layer or sheet on the outer side as a constituent of bark. 
• It can be easily removed because it is present as a continuous sheet. In a similar manner phloem cannot be removed in a monocot stem, because of the scattered arrangement, some of the vascular bundles might be present near the surface and some embedded deep inside. 
• Removing phloem from each of the bundles individually is not possible. The girdling experiment is used to identify the tissue through which food is conducted. In this experiment, a ring of phloem is removed from the woody plant. 
• Hence girdling experiments cannot be performed on a monocot stem-like sugarcane.

There will be loss of water through the leaves if the beaker is kept covered. Otherwise direct evaporation of water from free surface will also happen. The purpose of this experiment is to demonstrate transpiration, which is loss of water through leaves of plants in vapour form.

Traube (1867) proposed his ''Haftdruck'' or retention pressure theory. According to this theory, the permeation of solutes through a membrane depended on their relative affinity towards the membrane substance as compared to that of water.

In the atmosphere, plants prepare food due to photosynthesis and release oxygen and animals release carbon dioxide by respiration. Animals inhale oxygen released by plants and plants use carbon dioxide for the process of photosynthesis. Hence balance of carbon dioxide and oxygen is maintained by photosynthesis. Plants use energy from sunlight to turn water and carbon dioxide into an energy-rich sugar called glucose.which is stored as starch inside the plant body. Plants provide food in the form of carbohydrates(glucose and starch).