For the purpose of assessing compensation and damages, the right to them accrues at the date of issuance of the summons, and its actual value at that date is the measure of compensation of the property to be actually taken, and the basis of damages to property not actually taken but injuriously affected in the cases where the damages are allowed. If an order is made letting the plaintiff into possession, as provided in AS 09.55.380, the compensation and damages awarded shall draw lawful interest from the date of the order. Improvements put upon the property after the date of the service of summons may not be included in the assessment of compensation or damages.