Compensatory growth response of the legume, Medicago sativa, to defoliation and denodulation

Abstract

A laboratory study was conducted to determine the effects of defoliation and denodulation on compensatory growth of Medicago sativa (L.). Plants grown hydroponically in clear plastic growth pouches were subjected to 0 and 50% nodule pruning, and 0, 25, 50, and 75% defoliation by clipping trifoliate leaves. An additional experiment was conducted to determine if clipping leaves simulated herbivory by Hypera postica (Gyllenhal) larvae. Previously, we determined that nodule pruning accurately simulated herbivory by Sitona hispidulus (L.) larvae (Quinn & Hall, 1992). Results indicated that denodulation stimulated nodule growth and caused exact compensation in standing and total number of nodules per plant within 15 days and in standing nodule biomass within 22 days of treatment. Denodulation caused a significant reduction (13%) in final shoot biomass, but did not affect significantly final root biomass. Percentage of change in number of trifoliate leaves per plant increased with the level of defoliation. Within 22 days of treatment, total number of trifoliate leaves per plant was similar to controls. However, final standing shoot biomasses were significantly less that controls, indicating undercompensatory growth. Shoot biomasses of the 25‐, 50‐, and 75%‐defoliated plants were 18, 20, and 36% lower than controls, respectively. Nodule biomass per plant was reduced by 24 and 32% in 50‐ and 75%‐defoliated plants, respectively, but was not affected significantly by 25% defoliation. Root biomass was affected by all levels of defoliation. Clipping trifoliate leaves accurately simulated defoliation by H. postica larvae. Our results indicated that partial defoliation affected shoot, root, and nodule biomass of M. sativa, but that partial denodulation only affected shoot biomass.

The Use and Usefulness of Artificial Herbivory in Plant-Herbivore Studies

“…The effects of European pine sawfly Neodiprion sertifer on the growth of lodgepole pine (Britton 1988) and the effects of gastropod damage on the growth of the kelp Laminaria hyperborea (Toth and Pavia 2002) were similar to the effect of artificial damage. Quinn and Hall (1996) could artificially simulate the defoliation and denodulation of the legume Medicago sativa by alfalfa weevil Hypera postica and Hodge et al (2000) showed that artificial damage and herbivory of Cleora scriptaria¸ a geometrid moth, had the same effect on leaf loss of Macropiper excelsum. In some of the studies, the lack of significant differences may be due to low sample size and few and insensitive response variables compared to mammalian studies.…”

A comparison of artificial defoliation techniques using canola (Brassica napus)

“…The majority of these studies reported detrimental effects on components of plant fitness, such as reduced shoot and root biomass (Knapp 1986;Quinn and Hall 1996;Wirf 2006), decreased flower, fruit, or seed production (Obeso 1993;Domínguez and Dirzo 1994;Koptur et al 1996;Genter et al 1997), and decreased seed size (Sackston 1959;Rockwood 1973;Koptur et al 1996). On the other hand, some studies have demonstrated compensatory or even beneficial, overcompensatory effects of herbivory (McNaughton 1983;Karban and Myers 1989;Paige 1994;Lennartsson et al 1998;Marshall et al 2005; but see Belsky 1986 andBelsky et al 1993) or variable effects, depending on whether defoliation occurred naturally or was achieved artificially (Gedge and Maun 1992;Nowatzki and Weiss 1997).…”

“…removed (Escarré et al 1996;Quinn and Hall 1996;Susko and Lovett-Doust 1999). The effect of an additional factor, the pattern of tissue removal, has only been considered on a few occasions (Mauricio et al 1993;Coleman and Leonard 1995;Morrison and Reekie 1995;Gavloski and Lamb 2000;Macedo et al 2007), but it has obvious implications for assessing the impacts of different herbivores with different feeding habits or foraging patterns.…”

“…The effects of herbivory are dependent upon a number of factors, including the extent of plant tissue damage (Obeso and Grubb 1994;Koptur et al 1996;Quinn and Hall 1996;Susko and Lovett-Doust 1999), the developmental stage of a plant at the time of assault (Hare 1980;Obeso and Grubb 1994;Escarré et al 1996;Lennartsson et al 1998;Marshall et al 2005), prevailing environmental conditions when herbivory occurs (Lee and Bazzaz 1980;Maschinski and Whitham 1989;Escarré et al 1996;Mabry and Wayne 1997), and the type of plant tissue (i.e., leaves, meristems, reproductive structures, roots, etc.) removed (Escarré et al 1996;Quinn and Hall 1996;Susko and Lovett-Doust 1999).…”

Effects of initial N reserve status and residual leaf area after cutting on leaf area and organ establishment during regrowth of alfalfa

“…Usually, a close relationship is reported between plant leaf area and DM accumulation (Sharratt and Baker 1986;Quinn and Hall 1996). When leaves had been kept, plants had a very branched architecture with small leaves.…”