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EFFECT OF HIGH ROOT TEMPERATURE AND 

 EXCESSIVE INSOLATION UPON GROWTH. 



By WINIFRED E. BRENCHLEY, D.Sc. 

 (Rothamsted Experimental Station.) 



ASSISTED BY 



KHARAK SINGH, M.A. 



{Punjab Agricultural College, Lyallpur.) 



(With 2 Text-figures.) 



In an earlier paper (3) it was demonstrated that the reduction of hght 

 due to the over- crowding of barley plants brings about a condition of 

 light starvation which has a harmful effect upon growth, even when an 

 abundance of food and water is supplied to the roots. The suggestion 

 was made that this factor of light competition might be equally or even 

 more important in the case of broad-leaved plants, as greater overshadow- 

 ing might occur. 



To test this water culture experiments were repeated several times 

 with peas at different seasons, 64 plants being closely crowded in a solid 

 square, and 64 others having abundant room to prevent any shading of 

 one another. The nutrient solutions were changed frequently and the 

 tendrils of the peas were cut off as early as possible to prevent damage 

 from one plant clinging to its neighbour when being moved. 



Sutton's ^ Harbinger peas were used throughout. 



In a test carried on from September 10th to December 21st, 1920, 

 the prevaihng conditions were : 



Average weekly maximum temperature of house 9-26° C. 



„ „ minimum ,, ,, 2-11° C. 



Total hours of sunshine per week ... ... 45-9-48 



Temperature and sunhght both fell off considerably during the latter 

 half of the experiment. 



1 We are indebted to Mr Martin Sutton for the gift of all the seeds used in these 

 experiments. 



