Respiration of the field crop. -- By changing the temperature in the plant
chambers in the field, while covered with black plastic, a relationship
between the rate of respiration of the aerial parts of the tulip and
temperature was established. The respiration increased exponentially
between 7 and 30°C (Fig. 4). This is general for most crops (e.g. James,
1953;De Wit, 1966). The Q10 values for the measured range were calculated
for the 2 consecutive seasons. Both Q10 and the respiration rate reached
their maximum value at anthesis. Before flowering, the values of Q~0 were
above 2, while afterwards the values dropped below 2. Where the values had
been determined at the same development stage in the 2 consecutive years,the
agreement was very close. Only the low value of Q~0 in the week after removal
of the flower needs further observation. The drop in Q~0 is correlated with the
development and age of the crop. When the aerial parts of the tulip plant are
still growing Q~0 is above 2, while later in the season when nearly no growth
occurs in the flower stalk with leaves Ql0 is below 2. A similar phenomenon
was observed with Scolopendrium scolopendrium Karst. fronds (Belehr~dek
and Belehr~idkov~, 1929). Here Ql0 dropped from 3.5 for the young fronds
to 1.7 for the older fronds. James (1953) and Forward (1960) also mention
a correlation between development stage and Ql0.