Date of Award:

1990

Document Type:

Dissertation

Degree Name:

Doctor of Philosophy (PhD)

Department:

Natural Resources

Department name when degree awarded

Range Science

Advisor/Chair:

Christopher A. Call

Abstract

Controlled environment experiments were designed to study the germination, seedling development, and defoliation responses of Chrysopogon aucheri and Cymbopogon jwarancusa to better understand their xv autecology and potential use in range improvement programs in Baluchistan.

In experiment 1, Cymbopogon jwarancusa had greater seed fill and viability than Chrysopogon aucheri. When incubated at six different alternating temperature regimes, seeds of Cymbopogon jwarancusa had greater cumulative germination at five temperature regimes and faster germination at the colder temperature regimes than Chrysopogon aucheri.

In experiment 2, seedling shoot and root development was characterized at 15-day intervals over a 60-day period. Seedlings of both species had a "panicoid'' type seedling morphology. Chrysopogon aucheri and Cymbopogon 􀁛warancusa developed comparable numbers of leaves and tillers per plant during the 60-day period. Chrysopogon aucheri had a greater number, length, and dry weight of primary and seminal roots than Cymbopogon jwarancusa at 30 and 60 days, respectively. Adventitious root length was also higher for Chrysopogon aucheri than Cymbopogon jwarancusa at 60 days. Seedlings of both species had similar shoot:root ratios and relative growth rates. In experiment 3, seedlings of both species were planted in rnonocultures and in a 50:50 mixtures. Defoliation treatments, implemented 32 weeks after emergence, included: equally clipping all plants of both species zero, one, two, or three times (at 4-week intervals) in monoculture and mixture; and clipping one species zero, one, two, or three times (at 4-week intervals) without clipping the associated species in mixture. Both species remained vegetative and did not differ in leaf and tiller development until about 32 weeks after emergence. During later growth, Chrysopogon aucheri reproduced while Cymbopogon jwarancusa remained vegetative. cymbopogon jwarancusa produced more tillers on control plants and defoliated plants (mainly in monoculture). At lower frequencies of defoliation Chrysopogon aucheri produced more shoot and root biomass than Cymbopogon jwarancusa (mainly in mixture). In 50:50 mixtures when one species was defoliated and the other not, both species were comparable in shoot dry weight; however, Chrysopopgon aucheri was superior to Cymbopogon jwarancusa in root dry weight at all defoliation regimes. The initial standing crop and subsequent regrowth of Chrysopogon aucheri were comparable or higher in crude protein and digestibility than Cymbopogon jwarancusa.

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