The effect of the original leaf area on growth of softwood cuttings and planting material of rose

Leaf area influences root formation and growth of single node softwood stem cuttings of rose. However, a complete assessment of the quantitative effect of the area of the original leaf on growth of cuttings and of derived planting material (rooted cuttings) is still lacking. Therefore, it was our aim to quantify the effect of the area of the original leaf of single node softwood cuttings on their growth until 10 weeks after severance. The concept of leaf area duration which accounts for the effects of leaf area and its persistence in time was used. In two experiments, the area of the original leaf of cuttings of Rosa hybrida Madelon(R) was reduced to different extent during the first 3 weeks of propagation. After 10 weeks, total plant dry weight, total leaf area and shoot length were proportional to the area of the original leaf but were not affected significantly by small reductions of leaf area. However, dry weight of roots was linearly related to the area of the original leaf, irrespective of the level of reduction. Three weeks after severance, total plant dry weight was linearly related with leaf area duration indicating a direct relation between the integral of photosynthesis and growth after the first 3 weeks. The moment of treatment had only a relevant effect on growth after 10 weeks when the original leaf area was reduced by more than 70%. Leaf removal during the first 7 days of propagation was the most critical for survival and growth because of stem black rot. We conclude that under our conditions the original leaf area of cuttings is a good indicator for growth of roots from cuttings and planting material which can determine establishment after transplantation. Leaf area is also a good indicator of growth potential of cuttings and planting material in case of severe reductions. (C) 2002 Elsevier Science B.V. All rights reserved.