SEED DEVELOPMENT IN PISUM - THE LH(I) ALLELE REDUCES GIBBERELLIN LEVELS IN DEVELOPING SEEDS, AND INCREASES SEED ABORTION

The lh and lh(i) alleles have been shown previously to reduce the leve l of endogenous gibberellin A1 (GA1) in shoots of pea (Pisum sativum L .), resulting in a dwarf phenotype compared with the wild type, cv. To rsdag (Lh). In addition, plants homozygous for the lh(i) allele have r educed seed yield compared with Lh (tall, wild type) and lh (dwarf) pl ants. In this paper we show that the lh(i) mutation is expressed in de veloping seeds and pods. Comparison of GA levels in young shoots and d eveloping seeds of genotypes lh and lh(i) demonstrates that the relati ve severity of the two mutations varies in different tissues. Homozygo us lh(i) seeds have reduced GA levels, weigh less, and are less likely to develop to maturity when compared with Lh seeds. However, fertiliz ation of lh(i) plants with Lh pollen increases seed GA levels, seed we ight and seed survival, indicating that an increase in seed GA levels due to the presence of the Lh allele can restore normal seed growth. P ods developing on self-pollinated lh(i) plants are shorter than pods o n Lh (wild type) plants, although this may be an indirect effect of th e increased seed abortion of lh(i) plants. Based on these results we s uggest that endogenous GAs play an important role in the development o f seeds of P. sativum L.