Nigra Seedlings Research Articles

The effect of pollen irradiation on reproductive capacity, seedling growth, and variation of Betula nigra—II. Seedling growth and induced variation

Betula nigra seedlings were raised from controlled crosses made with pollen exposed to 0, 0·5, 1, 2, 4 and 8 kR of gamma radiation. Plants from the 8 kR treatment had poorer survival than those from all other treatments and were 11·5 per cent shorter than the controls. Their leaves also averaged 11·0 per cent smaller than those of the control plants but leaf length/width was unchanged. Dry weights of leaves, stems and roots after 8 kR were reduced to 79·7, 72·1 and 62·6 per cent, respectively, of those of the controls. Seedlings from this treatment also had the greatest shoot/root ratio. The 1 kR exposure appeared to have a stimulating effect on plant height, leaf size, and dry matter accumulation, but these increases were not statistically significant. Pollen irradiation had a pronounced effect on seedling variation. Plants with abnormal leaves occurred at a frequency of 11·5 per cent in the 8 kR population with asymmetry as the most common type of leaf abnormality. Seedlings with abnormal stems only were rare, whereas plants with various combinations of abnormal leaves and stems increased with the exposure level up to 24·7 per cent after 8 kR. In addition, this treatment level gave rise to 8·2 per cent dwarfs and to 7·7 per cent stunted plants. Thus, the 8 kR exposure resulted in 53·3 per cent aberrant plants, indicating that pollen irradiation should be an effective method of inducing and increasing variation in this species.

Accrescimento Delle Plantule Di « Pinus Nigra » Arn. Di Diversa Provenienza (Nota preliminare)

Abstract Growth of PINUS NIGRA Am. seedlings of different provenance. (Preliminary communication). — Pinus nigra seedlings from different provenance showed, during the first weeks of life, a different growth in height, irrespective of the photoperiod employed. Long night conditions were, on the whole, more favourable then short night conditions to their height growth. The test failed to show the existence of a significant interaction between photo-period and provenance.