20640
Drought and heat resulted in the down - regulation of photosynthetic linear electron transport in the leaves , although only a slight decrease in variable fluorescence ( Fv ) / maximal fluorescence ( Fm ) was observed , indicating that the chloroplast was protected by mechanisms that dissipate excess excitation energy to prevent damage to the photosynthetic apparatus .
 None
Given options, please tell me the categories of all the listed entity words.Output format is "type1: word1; type2: word2". 
Option: Chemical 
Text: {0} 
 Entities:  
Answer:
 None