Histological Characterization of Fraser Fir Abscission Zone

Histological characterization of Fraser fir abscission zone

Most conifers have the capacity to retain needles for several years losing them gradually in response to cold acclimation, a natural process referred to as needle abscission (NA). This process only involves a few layers of cells in predictable positions known as abscission zones (AZs).

NA is sometimes severely affected once a tree is cut, shipped and displayed in living rooms, common practices that North American Christmas tree growers and consumers know very well. Christmas tree growers recognize post-harvest needle abscission (PNA) as a common problem but changes in weather patterns and earlier harvest practices are increasing this phenomenon and highlight the need to identify trees with better adaptation.

Fraser fir branch with good needle retention phenotype
Fraser fir branch with poor needle retention phenotype
Fraser fir abscission zones after shedding

 

There is a growing demand for breeding Christmas tree varieties that hold their needles for longer periods of time to encourage more consumers to buy real Christmas trees instead of artificial trees. At the same time, there is a lack of methods that allow us to predict PNA as well as a limited knowledge of the histology and gene regulatory network that controls this important trait.

We are currently designing a system for the histological characterization of AZs in Fraser fir to complement our transcriptome data analysis to find putative control genes that play crucial roles during NA and PNA and could be used as molecular markers. The histological system includes fixation, staining and sectioning of AZs collected in the field and at different time points during indoor display followed by examination under bright-field and confocal microscopy. Using these approaches, we want to describe AZ development, identify potential anatomical differences between trees that retain their needles better and link physiological and transcriptome data in Fraser fir and other fir species

This project works with Marcela Rojas-Pierce in the NC State University Department of Plant & Microbial Biology.