|Abstract or Summary
- The physiological condition of a seedling often determines its ability to survive when planted. However, physiological damage is difficult to determine from external measurement or observation, because a healthy looking seedling can be of poor quality (quality is defined as the ability of a seedling to survive when outplanted). Methods currently used to assess quality rely primarily on the growth performance of a seedling. The most widely used quality evaluation method tests a seedlings ability to initiate and elongate roots, commonly called root growth potential (RGP). Other evaluation methods measure seedling frost hardiness, plant water potential, and speed of bud break. However, these indirect measurements of seedling physiology are often
inaccurate evaluators of quality and are slow to yield results. To obtain a direct measure of the physiological condition of seedlings, and hence a direct measure of seedling quality, biochemical markers were sought for Douglas-fir [Pseudotsuga menziesii
(Mirb.) Franco] plants of varying vigor.
Markers of field survival, growth room survival, RGP (number and total length of
new roots), exposure to freezing and drying conditions, and time of lifting were
identified by measuring a large number of compounds from methanol extracts of the apical shoots of 300 seedlings using high performance liquid chromatography (HPLC).
Data were acquired and processed on a computer, and analyzed with five different
multivariate statistical techniques. Principal component analysis was used as an
exploratory technique to investigate the structure of the data. Stepwise multiple
regression and cluster analysis were used to explore grouping among the treatments and
to identify markers The nature of many of the resulting clusters was not easily
determined using this method. Unknown factors in addition to survival, RGP, and exposure to freezing and drying conditions, appeared to control treatment similarity.
However, it was possible to cluster treatments accurately based on the time seedlings were lifted from the nursery.
Results from stepwise and canonical discriminant analysis imply that markers
identified with these procedures are capable of separating treatments of varying field
survival, growth room survival, RGP, or time of lift. Markers were unable to confirm a
clear separation between seedlings that had been damaged by exposure to freezing or
drying conditions. A strong relationship was observed between survival and RGP as
indicated by shared markers. Biochemical markers can be used to predict the survival of seedlings by classifying plants of unknown survival into predetermined groups. This technique promises to be a rapid, reliable, and quantitative means of evaluating seedling quality.