REST IN BUDS OF WOODY PLANTS* 



R. M. SAMISH 



Division of Pomology and Viticulture, Agricultural Research Station, 



Faculty of Agriculture, Hebrew University, 



Rehovot (Israel) 



Continuing our previous discussion, it seems desirable to 

 define 'dormancy'. Dormancy in plants is a suspension of 

 visible growth accompanied by a slowing down of the rate of 

 metabolism. We should distinguish between two types of 

 dormancy. One, quiescence, is caused by unfavourable external 

 factors ; when these factors are removed growth is resumed. The 

 second type of rest may be defined as a suspension of growth 

 due to internal factors. Even if the plant is provided with 

 favourable conditions it will not resume growth, unless some 

 internal factor is changed or some block removed. 



Those of you who came here from Jerusalem enjoyed, no 

 doubt, the profuse bloom of plum trees in the hills, while you 

 may have noticed that the trees were still dormant in the coastal 

 plain. This is typical of Israel, where after the usual warm winter, 

 bloom in colder areas {i.e. at higher elevation and at greater 

 distance from the coast) occurs earlier than in the coastal plain. 

 Thus we see in Table I that the bloom of Santa Rosa plums at 

 Rehovot near the sea shore was later by 10 days than the bloom 

 at Jerusalem up in the mountains. These observations are not 

 in agreement with general phenological concepts, according to 

 which bloom occurs earlier in warmer spring weather. The 

 general phenological rule holds true for Israel after exceptionally 

 cold winters, as seen in the Table. Not only is the relative trend 

 as regards time of blossoming in warm and cool areas reversed 

 as compared with that after a warm winter (except for Rehovot), 

 but the average date of bloom is advanced by almost one month. 



* Publication of the Agricultural Research Station, Rehovot, 1960 Series, 



No. 337-E. 



