Some Anatomical Effects of Moisture Stress in Nursery Seedlings of Guayule

Abstract

1. Sections of root-crown, young stem, and leaf of nursery plants of guayule that had been subjected to three levels of moisture stress were examined anatomically. 2. Under the conditions of the experiment, moisture stress had no effect on the thickness of the cork, the width of the vascular rays, the length of cells in the cortex or epidermis, the width of cells in the cork or rays, or on the number of cells along a diameter of the pith. 3. Low moisture stress leads to increased cambial activity, resulting in greater xylem and phloem areas with correspondingly longer vascular rays. The diameter of the pith and the size of its cells are also greater under low moisture stress. 4. At the intermediate moisture stress, the development of xylem appears to have priority over the development of phloem. 5. High moisture stress leads to increased deposition of rubber and lignin and to considerable enlargement of the resin canals. 6. In general, low moisture stress leads to enlargement of the tissues of the plant w...