Histological Development of the Green Bean Pod as Related to Culinary Texture.

摘要

SUMMARY—The basic pattern of tisue origins is well established in the bean pod when the unopened flower bud is less than 3.0 mm long. An outer epidermis (protoderm) with many hair‐like outgrowths forms the outermost tissue of the young pod. A subjacent layer one cell deep forms a hypodermis. Inwardly, a zone 8 to 10 cells deep of enlarging and vacuolating cells forms the young outer parenchyma of the growing pod. Within the innermost half of this zone, the meristematic stage of vascular tissues (procambium) is differentiated.An inner epidermis (protoderm) and an ill‐defined hypo‐dermis line the pod cavity. The young inner epidermis is continuous with the outer epidermis of the young seed (ovule). Cell divisions in the inner epidermis and its hypo‐dermal layer initiate an inner parenchyma and fiber sheath, respectively, approximately at the end of flowering. The inner parenchyma becomes extensive in early post‐floral stages. At the same time, the initials of the fiber sheath become sharply differentiated by cell elongation at a 45° angle to pod length, and assume the characteristics of young fiber cells (sclereids).Cell divisions cease first in the outer parenchyma, and most post‐floral growth of this tissue is by cell enlargement. Cell divisions persist through early post‐floral growth in the inner parenchyma, young fiber sheath, procambial tissues and outer epidermis. These differences in origin and rates of early development of pod tissues foreshadow marked differentiation and structural specializations that are significant to textural qualities at cul