Biomass allocation, regrowth and root carbohydrate reserves of chicory (Cichorium intybus) in response to defoliation in glasshouse conditions

Abstract

Three glasshouse experiments were conducted between 14 September 1993 and 9 January 1996 at the Plant Growth Unit, Massey University, Palmerston North, New Zealand. Experiment 1 studied the effects of cutting height on the regrowth and biomass allocation of chicory (Cichorium intybus L. cv. Grasslands Puna), Expt 2 investigated the biomass allocation and root carbohydrate reserves of three chicory cultivars (Puna, PG90 and Orchies) in response to defoliation, and Expt 3 studied the morphological characteristics and persistence of Puna under extreme defoliation.

Cutting height had no significant effect on accumulated secondary leaf and stem masses in Expt 2, but affected secondary leaf mass in Expt 1. However, cutting height significantly reduced root size after two cuttings in both Expts 1 and 2. Three severe cuttings (removing all shoots including visible buds >5 mm on crown) killed 73% of plants, whereas 96% plants survived under lax cutting (100 mm) in Expt 3. Orchies had the highest total reducing sugar concentration in its taproot (56·6%), whereas PG90 had the lowest (32·1%). Therefore, Orchies was the most persistent but had the slowest growth rate, and PG90 the least persistent with the highest growth rate. The performance of Puna was intermediate.

It is concluded that the persistence of Puna would be more sensitive to cutting frequency than cutting intensity due to its medium level of root carbohydrate reserves. In contrast, PG90 could be defoliated frequently, but not closely. However, Orchies with its thick taproot was insensitive to cutting intensity and would also be insensitive to cutting frequency due to its larger root carbohydrate reserves. It is suggested that to improve the persistence and enhance the leaf production of Puna by plant breeding the emphasis should be on increasing taproot size without unduly prejudicing herbage production.