Seedlings from seeds that have been produced in green-house environment and in outdoor conditions, respectively, will be grown in the following temperature-drought conditions in the phytotron at the department of forest genetics: The seeds are sown in tubular plastic containers, diameter 30 mm, length 150 mm, filled with granulated pumice. This particular root substrate has proven suitable for studying drought stress in a series of experiments.

To create different levels of water stress, the tubes containing substrate and seedlings are soaked in nutrient solution with differing intervals. By regular weight measurement of the total box, watering will be done whenever the boxes have reached a threshold value for water content. The plants exposed to water stress thus receive nutrient solution about every second week, while plants grown under no water stress are watered every other day. The water treatments, normal watering and drought stress, respectively, will be repeated in a series of different growth temperatures: 17o, 20o and 23o centigrades. A total of 30 families have been selected. Each family has been produced in nursery environment and in field conditions, respectively.

Each of the climate chambers in the phytotron has a capacity of 1920 plants, distributed over 16 mobile growth-units, each containing 120 plants. In one chamber, equal to one temperature treatment, plants from the two seed-environments will be subjected to normal watering and drought stress treatment. Each temperature/water-stress treatment in a chamber thus comprises 15 plants per family. To ensure sufficient statistical accuracy of estimated parameters, each treatment in a chamber is repeated once to yield a total of 30 seedlings per family per treatment. In each treatment, the plants will be grown for two growth periods, covering a total period of 12 months

Measurements

The phenology of each family is recorded by observation of bud-stage at the end of each growth period and at the beginning of second growth period. At the end of each growth period the height of the plants is registered, and at harvest, the pumice is washed away from the roots and fresh weight as well as dry weight of shoot and root separately are recorded

• Protocolls of plant performance, for full-sib families that have been produced in different environments, will be recorded in three different temperature/drought climates
• Protocolls of genetic differences between identical full-sib families will be quantified by genetic variance components for growth characters and growth rhythm in the different temperature/drought treatments in the phytotron
• Response curves along the environmental gradient and estimates of genotype x environment interaction caused by ranking shifts between families