Proteid- Synthesis involves further stages of formation of groups as (CHNH 2 ") 

 from CHOH groups and Nitrates, with subsequent introduction of S and Phosphoric 

 Acid, as also traces of Iron, to build more complex proteids, as in nuclei, before 

 plasma can be attained : little is known of such stages : substances found in plants 

 being molecular ends and de'bris of processes, rather than steps in actual metabolic 

 reactions. The elementary consideration of photosynthesis stops at carbohydrate 

 synthesis, though free energy of light is probably utilized all through ; but proteid- 

 synthesis can go on in the dark, as in growing roots or germinating seeds, other 

 energy being employed (katabolic). The entire sequence of events is termed assimi- 

 lation from the analogy of the animal, but may be conveniently distinguished as (i) 

 photosynthesis and (2) proteid-synthesis. 



Photosynthesis (='00,2 assimilation') thus involves the utilization of CO 2 of 

 the air, with consequent evolution of free O 2 , as a gaseous exchange. Other gaseous 

 exchanges are concurrently effected. 



Respiration : including gaseous exchanges as evidence of katabolism, the latter 

 involving oxidation-phenomena in the plasma, with evolution of CO 2 , in the normal 

 process of aerobic katabolism as utilized by animals and plants, in absence of light, 

 as the general method of obtaining energy for living processes. Hence in absence of 

 light, and in all parts not containing chlorophyll even in the light, normal respiratory 

 katabolism takes place. In this way living plants may be presenting a gaseous 

 exchange the reverse of that in photosynthesis, under certain conditions, as by night ; 

 and both actions may go on concurrently in green and non-green parts: the net 

 result of the exchange being the balance of two distinct processes. Active photosyn- 

 thesis is however normally several times (20-40) more intense than the respiratory 

 exchange, and may completely mask it by day. Hence respiratory activity is usually 

 studied in the case of seeds or non-green parts, and in the dark. Rarely does such 

 katabolism raise the temperature appreciably. (Antm-spadix, 105-112 F.) 



The ratio of CO 2 : 2 of respiratory exchange is normally less than unity, as 

 more oxygen is used in other reactions, and CO 2 is not the only product of such 

 oxidation, though the most highly oxidized form of carbon; e.g. the next most 

 highly oxidized carbon-compound is COOH COOH (Oxalic Acid), soluble in water, 

 and so retained in the plant, and poisonous. Hence this if neutralized by Ca. may 

 explain the common presence of Calc. oxalate crystals in actively metabolizing parts 

 of the plant. In extreme cases (some succulents) oxalate is formed in preference to 

 CO 2 . Katabolic processes taking place in absence of free oxygen, and expressed 

 in terms of other sources of chemical energy, are termed anaerobic (cf. Bacteria). 



Orientation : Elementary plasmatic organisms respond to changes in environ- 

 ment by form-alterations, originally the expression of modified surface-tension, giving 

 euglenoid and flagellar contractility. In more massive cellular organization form- 

 changes are effected by alterations in osmotic mechanism, as effecting turgidity and 

 growth of cell-units. Little movement is possible once the cellulose framework is 

 established. Such movements express ' Irritability ' in response to ' Stimulus ', i. e. 

 change ; or may be autonomous (spontaneous), i. e. without ascertainable cause. 



The most fundamental response is to sunlight, Heliotropism ; plant-shoots are 

 normally ' positively ' heliotropic, and tend to lie pointed in the direction of optimum 

 light-effect (orthotropic) ; leaves are * plagiotropic ', or tend to lie at right angles to 

 incident light. The movement is originally a general growth-response ; but may be 

 differentiated, as effected by the petiole to display the lamina, implying a certain 

 amount of conduction of stimulus, and foliage-leaves normally attain a fixed light- 

 position. 



In special cases movement is determined by a distinct ' pulvinus '-organ at the 

 base of the leaf or leaflet, and daily movements of presentation, or light-regulation, 

 are effected (cf. Robinia, Oxalis, and ' Sleep-movements '). In extreme cases the 

 mechanism is so delicate that it responds to other stimuli (electrical, or even a touch), 

 cf. Mimosa, leaves only displayed by excessive turgidity of pulvini, and hence ' sensi- 

 tive ' plant. 



All such mechanism of response, by turgid protoplasts, is subject to general tonic 

 actors, as temperature &c., and is only feebly expressed in these latitudes. For further 

 expression in warmer climate, cf. Sensitive Plant, and 'Praying Palm' (Bose, 1918). 



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