Study On Determinate And Indeterminate Growth Habit Of Cultivated Alfalfa(Medicago) Stem

Under irrigation and semi-drought cultivated conditions,it was found that there was determinate, indeterminate and intermediate growth habit type of alfalfa stems.Overlapping period of vegetative organ growth and reproductive organ growth in indeterminate types was longer than that of determinate types,and these two periods competed intensely for photosynthates,however it was reverse in determinate types.When nutrition growth was to end and supplied with sufficient water and fertile,the old branch of indeterminate alfalfa crown would form new growing point again,continued to develop and taking dominant possession;but the new branch of determinate alfalfa crown would develop quickly and formed configuration of new branch mixed old one.Under condition of drought,the growth habit of a typically intermediate tested material was determinate,While,under condition of enough water and fertilizer,which was indeterminate habit.Based on growth trait of typical cultivars of Alfalfa growth habit type,We firstly found that 8 indexes,including proportion of growth-end top stem in mature period,quantity and height of new twig at shoot base,the proportion of nutrition organ to reproductive organ at four growth stages and the length of the longest secondary adnation branch could be chosen as the identification indexes for alfalfa stem growth habit type.Based on this indexes and the stem growth trait of typical cultivars of alfalfa, we classified the alfalfa stem growth habit type using cluster analysis and discriminatory analysis.The results showed that 40 alfalfa varieties were divided to 3 clusters,in which 12 varieties belong to indeterminate type,19 varieties belong to Intermediate type,and 9 varieties belong to determinate type with accurate ratio of 97.5%.It was proposed that indexes could reflect different aspect growth habits of Alfalfa,but the optimal time for determining need to study further.We determined root system characters in green returning period of 40 tested materials which was planted in last autumn,and found the main root diameter of indeterminate habit type was less than that of intermediate type and determinate type by 32.43%and 34.43%.The number of lateral root of indeterminate type was less significantly than intermediate type and determinate type by 83.87%and 71.68%.But the length of main root and the number of hair root among the three growth types were not significant.When growth season was to end,we found the root could be divided by ramification root form,lateral root form,hair root form,transversal branch form and other forms.Analyzing the co-relation between root system type of early growth stagy and stem growth habit,the independence test was x² =42.72＞x²_0.995(6) =16.812 with significant difference(p=0.05),showed that different growth habit have different proportional of root forms. From study of plant characters and growth types,it was found that there was some roles on plant height and growth rate among different growth types(including regeneration grass),which reflected the growth habits of each growth habits.The relative plasma membrane permeability,proline content in the leaf and water content in root were measured both for field and nutrition soil cultivated plants,and these indexes were not significantly different among habit types.Whether the physiology and biochemistry indexes were affected or not by the difference of growth period between determinate and indeterminate habit type need further investigation.The relationship research between plant character and growth type showed that the growth rate was higher in determinate type(including regeneration grass) than that of indeterminate type during vegetative period,and significantly higher at some growth stage(p≤0.05).This study indicated that growth habit of Alfalfa stem is an important ecological character,which was controlled by water factor mainly and other cultivated conditions.Distinctions of Alfalfa growth habit characters will helpful for us to make appropriate measurements to cultivated utilization and field management corresponding to different growth habit type,made advance study on seed breeding and hybrid vigor utilization..