Any producer or importer whose total sales of flowers and plants do not exceed $100,000 during a twelve consecutive month period prior to the date an assessment is due and payable shall be exempt from assessments under this chapter under such conditions and procedures as may be prescribed in the order or rules and regulations issued thereunder and shall not vote in any referendum under this chapter: Provided, That the Floraboard shall have the discretion to make annual adjustments in the level of exemption to account for inflation. For the purpose of this section, a producer’s or importer’s total sales shall include, in those cases in which the producer or importer is an individual, sales attributable to such person’s spouse, children, grandchildren, and parents; in those cases in which the producer or importer is a partnership or a member of a partnership, sales attributable to the other partners; and, in those cases in which the producer or importer is a corporation, sales attributable to any corporate subsidiaries of which such corporation owns 50 per centum or more of the stock, or if such subsidiaries are not corporations, subsidiaries which are controlled by such corporation. In addition, in determining a producer’s or importer’s total sales, the sales of any corporation in which such producer or importer owns 50 per centum or more of the stock shall be attributed to such producer or importer. For these purposes stock in the same corporation which is owned by such producer’s or importer’s spouse, children, grandchildren, parents, partners, and any corporation 50 per centum or more of whose stock is owned by the producer or importer shall be treated as owned by the producer or importer.