Effects Of Defoliation On Clonal Growth In Potentilla Anserine L.

This article took the rosaceae plant Potentilla anserina L. as the main research object,studied the effects of defoliation on the growth characteristics and the shape characteristicsas well as the patition of the energy, also studied the physioecological response of Potentillaanserina L. This research has selected the field experimental simulation mothed. Theexperiment was conducted from June to Octomber, 2008 in the JilinUniversity, China (N44°16',E 125°47'). Vegetative plant materials of Potentilla anserina L. was transplanted ineach plot (0.75m*0.75m each) on June 25, 2008, and were watered daily during the initial10 days after transplantation. The plants were defoliated originally in August 27, 2008. Allplants were manually cut and left 3/4 leaves and 2cm stubbles. The experiment werecomposed of 4 treatments (every treatment with 3 replicates ). Defoliation periodicity was 7,14, 21and 28 days (i.e. D7, D14, D21 and D28). There was also another treatment (i.e. CK)with no defoliation(5 replicates) . The measurements commenced on August 27 andcontinued to Octomber 8, and modules densities and shape character were measured on eachweekend.On Octomber 9, all of the plants were removal from the fiels for subsequentmeasurements of biomass and caloric value of modules. The main results were summarizedas the following:1.There was a significant positive correlation between the leaf density of Potentillaanserina and the growth days (p<0.05), the moderate defoliation not only can promote thegrowth of leaves, but also can prolong the growing season. The average RGR (relativegrowth rate) difference of the growing season between each treatment was smaller thanAGR (absolute growth rate) difference, almost no difference. Under the moderate cuttingconditions, Potentilla anserina could continue to grow within a certain period of time, to extend the growing season. Density of leaves tended to be highest in D21, generallyfollowed by D14, CK, D28 and D7, which can explained as follow: moderate defoliationfrequency (D21, D14) improved light environment in the sward growth of new leaves andphotosynthesis rate of Potentilla anserina, which was in favor of plant growth and leavesdensity increase. However, when the defoliation frequency overtook a certain rage, theweakening of Potentilla anserina accumulation of nutrients and the growth of new leaves,resulted in lower leaves density.2.The new leaves quantity which have been defoliated was significantly higher thanthe control group. The defoliation can stimulate the growth of new leaves, in thisexperiment, the medium frequency defoliation had the strongest effect on newleaves'growth. The new leaves density had a significant positive correlation with thegrowth days (p<0.05), the number of new leaves increased first and then decreased. Withthe increase of defoliation frequency, the new leave proportion of the total leave increasedfirst then decended. The moderate defoliation could substantial increase the proportion ofnew leave, in comparison, the high frequency defoliation could increase the proportionmore. There was a significant positive correlation between the number of death leave andthe growth days (p<0.05) except D7 treatment. The death rate descended significantly afterdefoliation, so defoliation has benefits on plant growth.3. Compared to the control treatment, defoliation made a serious impact on the leafcharacteristics of the treatment groups, the average seasonal leaf areas were quite differentbetween each group. LAI (leaf area index) depended primarily on density rather than thesize of the average leaf area. Moderate defoliation interference could improve the LAI,promoted the plant photosyhthesis, then increased the production.4. The petiole length turned short after defoliated, it made the growth model of leafturn to small and more from large and little. This is a form of expression of morphologicalplasticity in Potentilla anserina.5. The results showed that defoliation treatment on Potentilla anserina significantlyaffect petiole diameter. After mowing treatment, leaf petiole was significantly larger indiameter. The more defoliation frequency made the larger petiole diameter. It could be explained that the defoliation stimulated the growth of new leaves which petiole more stoutthan the old leaves, the greater the frequency of mowing, the higher the proportion of newleaves, the more stout petiole.6. Whether defoliated or not, the angle between leaf and ground changed along withthe number of transplant days and had the basic synchronization with the growing season.After mowing, this angle size of average season tally with the order D21> D14> CK> D7>D28, moderateintensitymowing made this angle larger, while too high or too lowfrequncy will lead to the small angle. This angle had a significant positive correlation withleave density (p<0.001) and showed exponential growth with the leave density increased.7. Module and total plant yields were affected remarkably by defoliation frequency(p<0.05). Compared with the CK, total production of every treatment exhibited overcompensation,and the compensation was most significant in D21 and D14 because of thecompensatory growth of the underground accumulated biomass.8. Following longtermdefoliation, caloric values of leaves and roots wereremarkable higher than unclipping control. The caloric value of roots improved greater thanleaves. As to the energy accumulation, D21 exhibited overcompensatory while D7 and D28exhibited full compensation. The results showed that defoliation was in favor oftransporting the higher energy to the roots, the root percentage of energy rised while theleave percentage declined with the defoliation frequency increased.