Root starch storage and allocation patterns in seeder and resprouter seedlings of two Cape Erica (Ericaceae) species

Abstract

Post-fire sprouting of dormant buds in resprouter plants is facilitated by stored carbohydrate reserves, with starch being the critical reserve. Starch is mainly stored in xylem parenchyma ray tissue of woody underground organs, such as burls, lignotubers, and roots. We carried out a comparative analysis of the pattern of starch storage and the proportion of parenchymatic ray tissue in the upper root or cotyledonary region of seedlings from seeder and resprouter forms within two Cape Erica (Ericaceae) species: E. coccinea L. and E. calycina L., which were raised in the greenhouse under controlled irrigation. We also explored the root-to-shoot allocation patterns of seeder and resprouter seedlings in these two species. Resprouter seedlings of both species showed higher relative amounts of upper-root starch and upper-root storage tissue as well as a higher root-to-shoot allocation than their seeder counterparts. Pronounced swelling of the upper root region suggests ontogenetic development of a lignotuber in the resprouter forms of the two Erica species. The distinct allocation of starch in roots seems to be genetically determined and would account for the apparent differences in the root-to-shoot allocation patterns between both regeneration forms from the early seedling stage.

Root traits explain different foraging strategies between resprouting life histories

“…most branches emerging from the main axis) is expected in plants developing roots that function as storage organs or to obtain deep resources . Thick storage roots, like those of R+, tend to have more parenchymatic cells and consequently higher storage capacity, which is developed early in seedling ontogeny (Verdaguer and Ojeda 2002). However, thick roots have low surface:volume ratio (SVR) and offer higher resistance to the radial flow of water, both causing lower root absorption potential (Larcher 1995;Huang and Eissenstat 2000).…”

Nonstructural Carbon in Woody Plants

“…Resprouting in trees after low but pervasive levels of disturbance is supported by both below-and aboveground reserves, whereas resprouting in shrubs and trees subject to frequent, severe disturbance is supported by belowground reserves (93). Mediterranean woody shrubs in fire-prone heathlands allocate and accumulate more NSC belowground than sympatric, obligate seeders do (6,58,140). Here, starch reserves have been identified as critical for resprouting and are stored in xylem parenchyma ray tissue of woody underground organs, such as burls, lignotubers, and roots (6,140).…”

“…Mediterranean woody shrubs in fire-prone heathlands allocate and accumulate more NSC belowground than sympatric, obligate seeders do (6,58,140). Here, starch reserves have been identified as critical for resprouting and are stored in xylem parenchyma ray tissue of woody underground organs, such as burls, lignotubers, and roots (6,140). Similarly, savanna trees, which persist through repeated top kill by resprouting, also store large amounts of NSC (e.g., sugars plus starch = 28-30% mass) belowground in specialized organs (i.e., lignotubers) (49,144).…”

Morphological traits and water use strategies in seedlings of Mediterranean coexisting species

“…Species show different aboveground and belowground characteristics responsible for their survival, growth, and reproduction in different habitats. There is broad evidence supporting a correspondence between the various root system traits developed by species in drought-prone ecosystems and their performance (Davis et al 1999;Bell 2001;Verdaguer and Ojeda 2002), with important implications on the extent of fluctuations in water status of species (Fleck et al 1995(Fleck et al , 1998. In addition, it has been reported that the first summer rainless period after seedling establishment is a major limiting factor when seedling roots are not fully developed (Vallejo et al 1999;Pratt et al 2007).…”