MISCELLANEOUS PUBLICATION 1271, U.S. DEPARTMENT OF AGRICULTURE 



mental interaction (table 3). Adventitious bud 

 formation apparently was not related to root 

 growth, root size, or carbohydrate content of the 

 root tissue. Environmental conditions that re- 

 duced top growth, or defoliation, had a physio- 

 logically favorable effect on adventitious bud for- 

 mation, suggesting a possible involvement of 

 auxin or some analogous growth substance in the 

 formation of these adventitious buds. 



A further indication that endogenous growth 

 substances may be involved in tiller development 

 in alfalfa was reported by Cowett and Sprague 

 (7). In their studies, number of stems per plant 

 increased when the plants were treated with anti- 

 auxin, triiodobenzoic acid, while an auxin, 

 naphthaleneacetic acid, reduced stem number. En- 

 vironmental conditions of light intensity, tem- 

 perature, soil moisture, and fertility influenced 

 the number of stems per plant primarily by af- 

 fecting plant vigor. Plants exposed to full sun- 

 light and grown at low plant densities had the 

 highest number of stems per plant. 



Vegetative growth of perennial herbage grasses 

 consists almost entirely of leaf and sheath tissue. 

 Thus, environmental effects on the vegetative 

 development of herbage grasses involves the num- 

 ber of tillers per plant or unit area, rate of leaf 

 appearance, and rate of leaf expansion. In an un- 

 disturbed condition, tiller number increases dur- 

 ing the spring and fall seasons. During the sum- 

 mer period when stem elongation occurs, tiller 



LIGHT INTENSITY - K LUX 



Figure 6. — Dry weights of alfalfa plants grown at two 

 light levels and three temperatures, averaged over 

 varieties and growing periods (9). 



and others (5) found that the number of adven- 

 titious buds produced was greater when the plants 

 were grown at warm temperatures (18° to 24°C.) 

 and short day lengths (10 to 14 hr.) than when 

 the plants were grown at cool temperatures (10° 

 to 18°) and long day lengths (16 hr.). Specific 

 clones were more responsive to day length than 

 others suggesting an important genetic-environ- 



Table 3. — Adventitious bud formation in roots of creeping - 

 rooted alfalfa clones grown at two temperatures and day 

 lengths (5) 



Temperature 







Number 



of buds 1 







and day 



























length 



CHa 2 



CHb 



CMa 



CMb 



CLa 



Mean 



Warm (18° to 24°) 













20.2 



Long (16 hr.) 



31.0 



1.3 



7.3 



22.0 



1.7 



12.6 



Short (10 to 14 hr.) 



38.3 



33.7 



9.7 



49.7 



7.0 



27.7 



Cool (10° to 18° C.) 







__ 















5.1 



Long (16 hr.) 



6.3 



1.0 



1.0 



2.0 



1.3 



2.3 



Short (10 to 14 hr.) 



6.7 



11.0 



2.3 



16.7 



3.0 



7.9 



1 The value 1 was added to the observation of each pot to eliminate all 

 zero observations for statistical purposes. 



2 The letter "a" refers to plants defoliated four times and "b" refers to 

 plants defoliated three times during a 116-day period. 



