Biology subjects

Zuidema, P. A.

Publications and source records attributed to Zuidema, P. A..

2 recordsLinked to original sources

bioRxiv2023

Branching responses to pruning in cocoa

The branching pattern of a tree determines the efficiency of light interception and carbon assimilation. Pruning can modify the branching pattern, as a result of changes in physiological and environmental conditions, and ultimately pruning can have major effects on yield. For one of the major tropical tree crops, cocoa (Theobroma cacao), very little is known about branching response to pruning. To address this knowledge gap we performed a pruning experiment on young cocoa trees in Cote dIvoire. We applied five treatments: two heading treatments (the removal of the terminal apex or 66% of a branch) and two thinning treatments (the removal of 1 or 2 primary branches) and one unpruned control. The branching pattern of the primary branches was described by the number, position, and length of lateral branches right after pruning, and the same observations were repeated after a cycle of leaf production. The probability of branching and the length of lateral branches along a primary branch, in pruned and unpruned conditions, was analyzed using generalized mixed effect models. In unpruned conditions, the probability of branch presence was higher towards the middle of the primary branches and lower at the extremes. Branch length decreased going from the base to the tip of a primary branch. After one cycle of leaf production, new branches emerged preferentially on the distal section of a branch, but probability of branch emergence was reduced by the presence of other lateral branches. Pruning increased the probability of branch emergence mostly towards the tip of a branch, with heavy heading having the strongest effect. By contrast, heavy thinning increased branch emergence also toward the base of the branch. Our results can be applied to improve formation pruning, as this may trigger branching in different part of the crown, depending on the form of pruning. Our study also assists the development of three-dimensional tree models that could further our understanding of the impact of pruning on cocoa growth and productivity.

plant biology↗

bioRxiv2018

Low genetic variation in tolerance to defoliation in a long-lived tropical understorey palm

Defoliation is a ubiquitous stressor that can strongly limit plant performance. Tolerance to defoliation is often associated with compensatory growth. Genetic variation in tolerance and compensatory growth responses, in turn, play an important role in the evolutionary adaptation of plants to changing disturbance regimes but this issue has been poorly investigated for long-lived woody species. We quantified genetic variation in plant growth and growth parameters, tolerance to defoliation and compensatory responses to defoliation for a population of the understorey palm Chamaedorea elegans. In addition, we evaluated genetic correlations between growth and tolerance to defoliation.\n\nWe performed a greenhouse experiment with 731 seedlings from 47 families with twelve or more individuals of C. elegans. Seeds were collected in southeast Mexico within a 0.7 ha natural forest area. A two-third defoliation treatment (repeated every two months) was applied to half of the individuals to simulate leaf loss. Compensatory responses in specific leaf area, biomass allocation to leaves and growth per unit leaf area were quantified.\n\nWe found that growth rate was highly heritable and that plants compensated strongly for leaf loss. However, genetic variation in tolerance, compensation, and the individual compensatory responses was low. We found strong correlations between family mean growth rates in control and defoliation treatments. We did not find indications for growth-tolerance trade-offs: genetic correlation between tolerance and growth rate were not significant.\n\nThe low genetic variation in tolerance and compensatory responses observed here suggests a low potential for evolutionary adaptation to changes in damage or herbivory, but high ability to adapt to changes in environment that require different growth rates. The strong correlations between family mean growth rates in control and defoliation treatments suggest that performance differences among families are also maintained under stress of disturbance.

ecology↗