PLANT MORPHOGENESIS FOR SCIENTIFIC MANAGEMENT OF RANGE RESOURCES 



43 



as for Dollard at ambient. Dollard was superior 

 to the MD. Syn-1 at 10°, but no plants survived 

 at 32°. 



In 1969, when spaced plants of red clover and 

 timothy were placed in bare soil and in different 

 sections of each temperature plot, performance 

 was different than in 1968. Without strong com- 

 petition from the timothy sward, all clover plants 

 survived (table 5). At 32°, crown and root 

 growth of Dollard changed very little through- 

 out the season while the growth of MD. Syn-1 

 increased. Weights for both clovers increased at 

 21°, 10° and ambient soil temperatures, with MD. 

 Syn-1 being superior in each case. 



Crown and root growth of Climax increased 

 most at 10°, followed by 21°, ambient, and then 

 32°. Preselected plants were dug at the end of 

 each month. Half were placed in a dark growth 

 chamber where etiolated growth was measured 

 (13) and crown and root weights were deter- 

 mined on the remainder. Regrowth potential in- 



Table 5. — Effect of soil temperature on crown 

 and root growth of red clover and timothy and 

 on etiolated growth of timothy, 1969 



Soil 











Etiolated * 



temper- 











growth 



ature 



Date 



Dollard 



MD. Syn-1 



Climax 



of Climax 



Ambient 



7-14 



3.51 



2.89 



8.68 



0.68 





8-15 



5.33 



5.78 



15.69 



1.83 





9-22 



6.09 



9.40 



11.54 



1.69 



Average 





4.98 



6.02 



11.97 



1.40 



32° C. 



7-14 



4.94 



3.70 



6.83 



1.08 





8-15 



3.17 



4.00 



9.53 



0.92 





9-22 



4.32 



6.30 



9.59 



0.89 



Average 





4.14 



4.67 



8.65 



0.96 



21° C. 



7-14 



3.73 



3.72 



8.19 



1.06 





8-15 



6.94 



5.77 



14.45 



0.89 





9-22 



8.43 



11.96 



22.29 



1.67 



Average 





6.37 



7.15 



14.98 



1.21 



10° C. 



7-14 



4.56 



7.36 



10.73 



1.09 





8-15 



9.32 



5.90 



10.69 



2.76 





9-22 



9.31 



9.58 



29.68 



4.20 



Average 





7.73 



7.61 



17.03 



2.68 



'Technique suggested by Burton (IS). 



creased markedly throughout the season at 10°, 

 but dropped at 32°. It was relatively low at am- 

 bient and 21°, changing little during the season. 



Tiller numbers per plant, although not shown 

 here, followed a similar pattern to that shown 

 for solid stands (table 3). Tiller and leaf growth 

 were followed closely on both species through- 

 out the season. A "leaf development" index was 

 recorded twice each week on all plants using 

 techniques suggested by Carlson (15) for clover 

 and Higgins and others for grasses (30). Al- 

 though there was a direct relationship between 

 soil temperature and leaf development (lower 

 temperature-higher index), correlations between 

 indices and forage yields were extremely low and 

 variable even when calculations were made with- 

 in temperatures. Low temperatures stimulated 

 greater leaf initiation, especially during hot sum- 

 mer weather, but this did not necessarily mean 

 extra forage yields. 



Findings in these studies as well as other re- 

 search have established the fact that, with cool- 

 season grasses, tiller development is enhanced by 

 cool soil temperatures and high light and that 

 associated with high tiller production is a cor- 

 respondingly high level of soluble carbohydrates. 

 However, Sheard (58) suggested that without 

 a high level of nitrogenous compounds within the 

 plant for rapid sj'nthesis of new protoplasm along 

 with the high carbohydrate level, maximum 

 growth will not result. 



Tillers of perennial grasses must be considered 

 as parts of the whole with varying degrees of 

 independence. This makes the grass plant, then, 

 a system rather than an entity. It seems that the 

 primary function of tillers is to perpetuate the 

 species and not necessarily to produce more 

 leaves, dry matter, and so forth, although this 

 may occur. Plants respond to environment in a 

 way that favors survival. Pere'nniality depends 

 upon the perpetuation of a process, not an entity. 

 and soil temperature plays a major role in this 

 process. 



Soil samples were taken at the end of each ex- 

 periment to determine changes in soil aggrega- 

 tion and organic matter caused by differences 

 in soil temperature. Some of these data are pre- 

 sented in table 6. In the spring of 1969, the sur- 

 face soil (10 cm.) from all temperature treat- 

 ment plots within a replication was thoroughly 



