86 PHOTOCONTROL OF GROWTH 



a growth inhibitor and also interference with gaseous exchange. Light 

 is apparently necessary to enable the embryo to overcome this inhibit- 

 ing effect of the pericarp and endosperm. 



A study of the growth inhibitors in Acer pseudoplatanus in relation 

 to day length conditions seems to indicate that more inhibitor is pro- 

 duced in the leaves under short days than under long days, suggesting 

 that onset of dormancy of the short apices in response to short days is 

 due to the accumulation of inhibitor in this region under such day 

 length conditions. 



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germination in Betula pubescens Ehr. Physiol. Plantarum, 8, 300-16. 



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