EFFECT OF MODERATE AND SEVERE DROUGHT STRESS ON THE PREANTHESIS DEVELOPMENT AND YIELD FORMATION OF OATS

Greenhouse experiments were conducted at the University of Helsinki, D epartment of Crop Husbandry in 1989 and 1990 to provide information on the effects of drought stress on the developmental rate of the panicl e, formation and abortion of florets, and formation of yield component s in two oat cultivars, both adapted to the northern marginal growing conditions. Moderate water deficit and severe drought stress did not a ffect the developmental rate of the panicle, but the pre-anthesis and post-anthesis architecture changed considerably; leaves unrolled later , the number of green leaves was lower, the internodes lengthened less , and the inflorescence was shorter as a consequence of water deficit. Drought stress decreased the number of fertile florets in the panicle significantly, in the lower clusters of branches in particular. In th e cultivar "Puhti", 57 % of the fertile florets aborted as a consequen ce of moderate drought stress and 89 % as a result of severe drought s tress when compared to well-watered individuals, while in "Virma", a c ultivar of significantly higher yield potential, 80 % and 90 % of the fertile florets wilted, respectively. In addition, water deficit cause d considerable losses in all the morphological characteristics measure d. Further implications of these results for yield formation are discu ssed.