Aspects of the Comparative Physiology of Ranunculus bulbosus L. and Ranunculus repens L.: I. Response to Nitrogen

Ranunculus bulbosus and R. repens are closely related taxonomicallyand coexist in the same general habitat but differ in that R.bulbosus only exceptionally shows vegetative multiplicationcontrasting with R. repens which reproduces extensively by meansof long branched stolons which root and form new daughter plantsat the nodes. The response of these two species to nitrogen was similar inthat an increase from 10 to 50 ppm nitrogen gave rise to greatlyincreased total dry weight and higher shoot to root ratios,whereas further nitrogen increase from 50 to 200 ppm had littleeffect. However, they differed in that at low nitrogen levelsthe perennating organ (corm) took priority in R. bulbosus withsexual reproduction assuming greater importance at the highernitrogen levels, whereas in R. repens the main storage organ(the stock) was not especially favoured at low nitrogen levelsreflecting perhaps the differences between this structure andthe corm in R. bulbosus. In R. repens the greatest responseto nitrogen was shown by the stolons although this was due toincreased branching and a higher dry weight per unit lengthat the higher levels of nitrogen (50 and 200 ppm). Primary stolonlength was not greatly affected by nitrogen level. Dry weightsof flowers and fruits in R. repens were very much lower thanin R. bulbosus. It is suggested that in R. bulbosus the emphasis lies firstin replacement of the parent at approximately the same siteby a daughter from the new corm and secondly in sexual reproductivespread. In R. repens lateral spread by vegetative propagationtakes precedence over all else and under low nitrogen conditionsbranching is sacrificed and energy is diverted to maintaininglong primary stolons. These, in turn, have the potential forproducing daughter plants at some distance from the parent andthis may be of considerable importance in field situations sincethe daughter may come to occupy more favourable sites than theparent.