Compensatory growth and photosynthetic responses of Pharbitis purpurea seedlings to clipped cotyledon and second leaf

Institute of Grassland Science, Northeast Normal University, Changchun, 130024 China; Key Laboratory of Vegetation Ecology, Ministry of Education, Northeast Normal University, Changchun, 130024 China
Photosynthetica (Impact Factor: 0.86). 01/2011; 49(1):21-28. DOI:10.1007/s11099-011-0004-4

ABSTRACT Leaf tissue damaging to seedlings can limit their subsequent growth, and the effects may be more extensive. Compensatory photosynthesis
responses of the remnant cotyledon and primary leaf of Pharbitis purpurea to clipping and the effect of clipping on seedling growth were evaluated in a pot-cultivated experiment. Three treatments
were conducted in the experiment, which were clipped cotyledon (CC), clipped second leaf (CL), and control group (CG). The
area, thickness, mass, and longevity of the remaining cotyledon of CC exhibited over-compensatory growth. In contrast, seedlings
of CC had under-compensatory growth in seedling height, root length, seedling mass, and root to shoot ratio. However, the
traits of remnant cotyledon and seedling in CL treatment exhibited equal-compensatory growth. Net photosynthetic rate of the
cotyledon of CC was significantly higher than those of CL and CG treatments, and the diurnal changes in photosynthetic rates
showed significantly different patterns which were unimodal curve (CC) and bimodal curve (CL and CG), respectively. There
was no significant difference between CL and CG treatment. Net photosynthetic rate of the primary leaf of CL was significantly
higher than that of CG treatment. However, the photosynthetic rates of primary leaves of CL and CG treatments showed similar
photosynthetic patterns characterized by a bimodal curve. P. purpurea seedlings used a compensatory growth strategy in the remaining cotyledon or the primary leaf to resist leaf loss and minimize
any adverse effects.

Additional key wordsclipping–compensatory growth–photosynthesis–primary leaf–remnant cotyledon–seedling

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    ABSTRACT: Tissue damage to seedlings can limit their later growth, and the further effects may be greater with increasing seedling age. Seedlings, however, can minimize the effect of damage through compensatory growth. Seedlings of Pharbitis purpurea grow in frequently disturbed habitats and generally tolerate damage to leaf tissues. We evaluated the compensatory responses of the cotyledon to different levels of defoliation and their effect on seedling growth and development. We also examined the relationship between seeding depth and compensatory growth. We tested seven defoliation treatments with one or both cotyledons and/or the apical meristem of seedlings removed from seeds buried at a seeding depth of either 2 or 5 cm. We then measured 12 growth traits of the seedlings to assess development and growth compensation. The area, thickness, biomass, and longevity of the remaining cotyledon were also measured to quantify increased growth as result of treatment effects at both seeding depths. The results showed that defoliation reduced seedling height, belowground length, and total biomass significantly in subsequent growth in all treatments. However, defoliation treatments had direct positive impacts on growth at 2 cm depth compared with 5 cm depth. In contrast, the compensation of cotyledon area (C area), biomass (C mass), and thickness (C thickness) was greater at 5 cm depth than at 2 cm depth. The results thus indicate that P. purpurea seedlings adopted a compensatory growth strategy to resist leaf loss and minimize any adverse effects using the remaining cotyledon. Increasing seeding depth can aggravate the compensatory growth of remain cotyledon after partial defoliation.
    Ecological Research 27(3). · 1.55 Impact Factor