DISCUSSION

 Total weight data in Table 1 indicate that plants in Experiment 1 added 8 to
 10% weight in one week following estimated optimum maturity. Trimmed weight in
 Experiment 1, declinedone week after optimum maturity and increased in Experiment
 2. When number of pithy petioles per plant found after field trimming in both
 experiments are taken into consideration (Table 2), one can only conclude that
 plants harvested one week after optimum in Experiment 2 were not as severely
 stripped. This is further borne out by the differences in weight of waste found
 between the two experiments for the last harvest. Pithy petioles usually stand
 out from the plant and most are trimmed off in making a compact plant for market.
 Consequently, total weight along with the development of the physiological dis-
 orders, is a better criteria for judging relative maturity in this instance than
 yields of trimmed weight.

 As in previous experiments, physiological disorders of nodal cracking, pith,
 feather leaf, increased in a linear manner with maturity. However, dry weight
 of plant tissue significantly increased with maturity. Previous studies with
 outer petiole tissue only, have shown linear decreases in dry weight with maturity.
 Why the reversal in these two experiments is not exactly known.

 Total nitrogen, protein nitrogen, phosphorus and potassium content of all
plant parts tested, decreased significantly with increasing maturity. We have
shown previously that it decreased in outer petiole tissue.

 Differences in calcium and magnesium content of the various plant parts
were generally highly significant. However, they did not follow the strict de-
creasing pattern of the other nutrients determined. In the data previously
reported, calcium content of outer petiole tissue decreased significantly with
maturity while magnesium content increased.

 Some of these differences might be explained by the fact that none of the
plants in the earlier experiments showed a tendency toward bolting, regardless
of the age of the plants. While no plants in these experiments used for plant
tissue sampling showed signs of bolting, it is possible that in some of these
plants bolting had been initiated but was not yet evident.

 SUMMARY

 Plants harvested after estimated optimum market maturity continued to increase
in total weight while marketable celery decreased because of pith development,
increased nodal cracking and feather leaf incidence. Dry weight increases with
maturity were contrary to previous findings, and might possibly be connected with
the tendency of the plants in these experiments to bolt as opposed to former
experiments. Nitrogen, phosphorus, potassium tended to decrease in all parts of
the plant with maturity. Most differences in calcium and magnesium contents were
significant at the various stages of maturity but did not follow the same linear
patterns as in previous experiments.



EES 70-11


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