Q. Illustrate Physiological Evidence ?

Physiological and biochemical evidence is providing data of increasing importance to plant systematic. Recently, it has become apparent that a syndrome of anatomical and physiological features related to a high efficiency carbon fixation process occurs in a large number of plants. This syndrome has been called the Kranz syndrome or C4 photosynthesis. In algae, mosses, most ferns, gymnosperms and many families of flowering plants C3-photosynthesis is the only known carbon fixation cycle. C4-photosynthesis occurs in approximately 10 unrelated families of monocotyledons and dicotyledons. Krariz syndrome has proved useful in characterising Panicum and . other taxa in the grass family. In the dicotyledon genus Euphorbia (Euphorbiaceae) C3, C4 and CAM (Crassulaceas Acid Metabolism) species are known. Both C3 and C4 carboxylation occurs in zygophyllum (zygophyllaceae) and in Atriplex (chenopodiaceae).