PLANT MORPHOGENESIS FOR SCIENTIFIC MANAGEMENT OF RANGE RESOURCES 



105 



Total yield 



9 First harvest yield 



■ Shoot recovery 



100 



5 6 7 8 9 10 11 12 13 14 15 16 

 Weeks after emergence 



Figure 5. — Bulrush millet. Recovery after defoliation at 

 different stages of development. (After Begg, 7.) 



sidual level of nutrients following removal of 

 the large main tillers. Later, as growth rates 

 declined, some new tillers developed from basal 

 buds and rapidly became reproductive and pro- 

 duced infloresences. 



Grazing experiments of Norman and Begg 

 (30) showed that the highest cattle gains per 

 hectare and per head were obtained from bulrush 

 millet when cattle were put on early — that is, 

 during the vegetative stage of growth. 



Trifolium subterraneum L. (subterranean 

 clover), a cool season Mediterranean annual leg- 

 ume with a prostrate habit, is of potential value 

 as a pasture plant on 3.5 million ha. in southern 

 Australia (27). Aitken(7) described the develop- 

 ment of the growing point in subterranean clover. 

 Rate of leaf and node production, about the same 

 for each variety or cultivar of subterranean 

 clover, varies with temperature and is higher in 

 autumn than in winter. Lateral growing points 

 are formed in the axils of the young leaves and 

 may develop into lateral shoots. Those formed 

 at some distance from the apical growing point 

 are vegetative and those in the axils of the young- 

 est leaf may form flower panicles. As in temper- 

 ate grasses the change from vegetative to flower- 

 ing state is accompanied by elongation of the 

 lower nodes of the stem. Early flowering varieties 

 initiate floral primordia and develop flowers at 

 low nodes, while late flowering varieties flower 

 at high nodes. Tallarook, a late flowering cultivar 

 sown in early April, initiated flowers in early 



September and flowered in October at the 18th 

 node. Dwalganup, an early variety sown at the 

 same time, initiated flowers in early June and 

 flowered in September at the 9th node. Again as 

 in annual grasses, time for floral initiation de- 

 creased with lateness of sowing. The node at 

 which the first flowers are formed on lateral 

 stems is lower than that at which flowers develop 

 on main stems (2). 



Weight of seed per unit area was 27 percent 

 higher from clover defoliated in July, or in July 

 and September, than from uncut controls. Cutting 

 in July also increased the number of seeds per 

 burr (34). With progressively later defoliations 

 at flowering and seed setting, seed weights fell 

 to the control level and finally to 15 percent below 

 it. A single cut in mid-September — that is, at 

 flowering — reduced seed yields by 33 percent. 

 Early defoliations, after floral induction but be- 

 fore flowering, increased the number of seeds per 

 unit area by 40 percent. The increase was due to 

 the large number of inflorescences on early cut 

 plants. Later defoliations reduced seed numbers 

 to the level of the uncut control. Rossiter (34) 

 concluded that hard grazing of clover swards 

 before flowering would increase seed yields. Mow- 

 ing for hay after flowering would decrease seed 

 yields but, by reducing competition from grasses, 

 might increase the proportion of clover in mixed 

 swards the following year. 



Growth of swards of subterranean clover is 

 described by Davidson and Donald (14)- 



Medicago spp. (barrel, strand, and burr med- 

 ics) are sown and naturalized Mediterranean an- 

 nual legumes. The structure and development of 

 the growing point in annual medics are similar 

 to subterranean clover (3). Commercial barrel 

 medic has a maturity grading like that of the 

 subterranean clover cultivar, Yarloop. Barrel 

 medics, like clover, flower at their lowest nodes 

 when sown in winter and at their highest when 

 sown in summer — that is, when sown early they 

 are vegetative for a longer period, presumably be- 

 cause of high temperatures and diminishing pho- 

 toperiods. As for clover, the time between sowing 

 and flowering in Medicago species was shortest 

 for winter sowings. 



Stylosanthes humilis (Townsville stylo) is a 

 sown and naturalized tropical annual legume. 

 Torsell and others (46) established that the 



