GROWTH RESPONSE OF SUGAR BEET 351 



Table 3 



The effects of watering on the growth of previously droughted sugar beets (B) in 

 comparison with freely watered plants (A) 



* Assuming transmission of glasshouse = 70%. 



that the difference in leaf area may have been important (the after effect has 

 only been observed in crops with L less than 2-5), it cannot be the main 

 factor otherwise a large after effect would have been observed in i960 

 (maximum L 1-3). 



The maximum after effect of the 1959 B treatment on E (112%) was 

 somewhat smaller than that originally described by Owen and Watson 

 (1956) (182%), although L, the drought effect on L, and the effective 

 radiation (taking the transmission of the glasshouse as 70%) were closely 

 similar in the two experiments. 



Owen and Watson's plants were growing in an open field on hght, 

 sandy soil and so are not strictly comparable with those in my experiments. 

 Further, the hght transmission of the Dutch-hght structure was not 

 accurately known and may have been overestimated, so the large after- 

 effect they obtained may have been caused by a greater radiation intensity. 



