448 PLANT PHYSIOLOGY 



into the ripening grain ceases. At the same time, the delivery 

 of water is Hkewise inhibited, the grain dries, and ripening 

 occurs prematurely. It is important to note that after the dry 

 wind has ceased, the wind-burned plants are no longer capable 

 of restoring the normal supply to the seeds because of some 

 irreversible changes that are not understood as yet and have 

 not been investigated. 



ShriveUng may be the result not only of a disturbance in 

 water supply of the plants; rust and other parasitic fungi, 

 utilizing the carbohydrates elaborated by the leaves and thus 

 inhibiting their translocation into the grain, also cause a shrink- 

 age of the grain. The same results are produced by the parasitic 

 higher plant Orohanche, which develops on the roots of sunflowers. 

 A sharp diminution of the assimilating leaf surface from defoha- 

 tion caused by caterpillars, locusts, and other insects leads to 

 analogous consequences. 



Premature ripening because of wind burn is also accompanied 

 by changes in the chemical composition of the grain. As it 

 desiccates in its early stages of development, the processes of 

 transformation of soluble carbohydrates into starch are not 

 completed, and consequently instead of a starchy grain whose 

 cells are filled with starch, there results grain with a glassy 

 fracture, in which the starch grains are held together in a horny 

 mass by dextrines. The accumulation of proteins is reduced 

 less than that of carbohydrates. Hence, wind-burned grain is 

 relatively richer in proteins than well-filled grain. But though 

 it may contain a higher percentage of proteins yet per 1,000 

 grains, it is considerably poorer in nitrogen. 



In arid regions, especially on shghtly saline soils, when the 

 conditions of water supply are not favorable on account of the 

 high osmotic pressure of the soil solution, the ripening of grain 

 even in the most favorable years always proceeds under condi- 

 tions that impede its filhng, and the grain is somewhat poorer in 

 starch but relatively richer in proteins than in more humid 

 regions. Such a change in the chemical composition of the grain 

 of arid regions makes it especially valuable for baking bread and 

 especially for macaroni production. The wheat from the semi- 

 arid regions of the lower Volga in Russia and from the Dakotas 

 has been highly esteemed in Italy and other European countries 

 and has formed the chief supply for macaroni. 



