Morphology and Growth in Seedlings of Several C4, Perennial Grasses

Abstract

Establishment of forage grasses depends upon their ability to compete for resources in the critical seedling establishment phase. Desirable native grass species are generally considered to be more difficult to establish from seed than the introduced Old World bluestems (Bothriochloa spp.), although comparative data are generally lacking. This study compared the responses of morphological attributes commonly associated with seedling vigor and some growth parameters in 17 perennial, C4 grasses including 5 native and 12 Old World bluestems. Plants were grown in a greenhouse under well-watered and limited watering regimes. The objective was to document differences in morphology and growth among these grasses from emergence through 7 weeks post emergence. The Bothriochloa species generally rated higher than the native species in morphological characters commonly associated with seedling vigor. The exotics produced as much or more biomass and had more leaf area per plant, more tillers, and leaves per tiller than the natives. Although the native grasses produced less leaf area, the cost of these leaves in terms of biomass per unit area was higher than in the introduced grasses. The natives tended to partition relatively more biomass aboveground and more of this to leaves, rather than sheaths plus stems, than the Old World bluestems. However, partitioning of total plant biomass among roots, sheaths plus stems, and leaf blades was remarkably insensitive to water stress in all entries. Approximately one-third of total biomass was partitioned among leaf blades, sheaths plus stems, and roots, respectively, with sheaths+stems tending to be a slightly smaller fraction than the other 2 components. Recurring water stress cycles reduced most parameters significantly and generally accentuated the normal ontogenetic decline in relative growth and unit rates. Across all entries, total plant biomass and leaf blade area were reduced over 40% by a limited watering regime. Although water stress reduced the size of the assimilatory surface, the remaining leaves were more efficient in the production of new biomass. This response correlated with an increase in specific leaf weight under water stress.