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Titre : SEED COATING HISTOLOGY, GERMINATION, DORMANCY AND SEEDLING DROUGHT TOLERANCE OF LEHMANN LOVEGRASS, ERAGROSTIS LEHMANNIANA, NEES.

Auteur : Brauen, Stanton E. (Stanton Elwood)

Université de soutenance : University of Arizona

Grade : Doctor of Philosophy (PhD) 1967

Résumé
The objectives of this study were to study the pattern and degree of seed (caryopsis) dormancy of Lehmann lovegrass and develop the optimum germination environment. Investigations were pursued to identify and characterize seed dormancy and to relate seed dormancy to seedling drouth tolerance. Germination experiments were conducted in Stults Da-lite germinators in petri dishes with crimped cellulose as germination substrate. Sixteen hours of darkness were concomitant with the 20 C temperature and eight hours of light with the 30 C temperature. Laboratory germination of all accessions was compared with germination in Mohave clay loam soil under greenhouse conditions. Thirty-seven seed sources were collected, repre senting several phenotypes. Seed of stoloniferous accessions were dormant immediately following harvest. Germination of the standard type increased linearly after harvest up to 100 weeks. Maximum germination was reached at 150 weeks after harvest. Seed of bunch grasses were of dormant or non-dormant types immediately after harvest. Dormancy was partially or wholly removed in some accessions by 24 hours of dark imbibition and accessions varied in the degree of germination response to light or dark. Dark imbibition never inhibited germination when applied for less than 24 hours. Dark treatments of greater than 24 hours inhibited germination of some accessions. Several filter paper substrates inhibited germination. Eaton and Dikman No. 617, Whatman No. 2 and Kimpak gave the highest germination but they were not different significantly from one another. Germination, was highest at alternating 20-30 C and was greater significantly than at the constant 15 or 20 C temperatures. Series of treatments with gibberellic acid, thiourea, kinetin, IAA, extended prechill, potassium nitrate, gamma radiation and radio frequency electrical fields did not effect germination of the standard source. However, sodium hydroxide, sulfuric acid and water were effective in increasing germination. Swirling seed in an abrasively lined cylinder removed seed dormancy. Eight to ten seconds of scarification broke seed dormancy on freshly harvested seed lots of all but three accessions. Scarifi cation was partially effective on these three accessions. Dark induction was not required for germination of scarified seed.

Mots clés : Love grass — Seeds. ; Seeds — Development.

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