NIGHT AND DAY RATES OF ELONGATION OF 

 BANANA LEAVES 1 



By Sam F. Trelease 

 Of the Johns Hopkins University, Baltimore, Maryland 



It is well known that the aerial parts of plants usually enlarge 

 faster at night than in the daytime, if the temperature remains 

 about the same. Growing plant organs may even shrink during 

 the day instead of elongating. An example of this may be 

 taken from the results of a study of growth in Cestrum noctur- 

 tum, made by Brown and Trelease. 2 It was found that the 

 young shoots wilted and actually shortened during periods of 

 exposure to direct sunlight on dry days, but that they elongated 

 rapidly at night; they showed no elongation in the daytime 

 excepting in the late afternoon, after they had returned to 

 their early morning length. Measurable enlargement depends 

 principally upon an increase in the water content of enlarging 

 cells. The fact that the growth rate is usually higher for the 

 night than for the day is apparently related to a higher water 

 content of the plant as a whole in the night; 3 it is at least 

 safe to suppose that it depends upon a higher night water 

 content of the enlarging cells. 



The present paper aims to illustrate, by means of a series 

 of measurements, the relative elongation rates of leaves of a 

 banana [Mtisa sapientum Linn. var. cinerea (Blanco) Teod.], 

 locally known as latundan, by day and by night, and to present 

 some observations on variations in leaf position that appear to 

 be related to corresponding variations in foliar water content. 



1 Botanical contribution of the Johns Hopkins University, No. 73. 



3 Brown, W. H., and Trelease, S. F., Alternate shrinkage and elongation 

 of growing stems of Cestrum noctumum, Philip. Journ. Sci. § C 13 (1918) 

 353-360. 



• Livingston, B. E., and Brown, W. H., Relation of the daily march of 

 transpiration to variations in the water content of foliage leaves, Bot. 

 Gaz. 53 (1912) 309-330; Lloyd, F. E., Leaf water and stomatal movement 

 in Gossypium and a method of direct visual observation of stomata in 

 situ, Bull. Torrey Bot. Club 40 (1913) 1-26; Shreve, Edith B., The daily 

 march of transpiration in a desert perennial, Carnegie Inst. Washington 

 Pub. 194 (1914). 



