Kaufmann M R
Department of Plant Sciences, University of California, Riverside, California 92502.
Plant Physiol. 1970 Dec;46(6):778-81. doi: 10.1104/pp.46.6.778.
The tensile force existing in the pericarp of a growing citrus (Citrus sinensis) fruit 17 to 19 centimeters in circumference was sufficiently high to cause a 3% shrinkage of the pericarp when it was excised. When a fruit was cut along the equator to the central axis, shrinkage of the pericarp resulted in the formation of a wedge-shaped gap at the cut. Stretch modulus of the pericarp was determined by measuring the force required to stretch excised strips of tissue to 1% longer than their excised length. Measurements were made on successive layers of pericarp tissue 5 millimeters wide and 1 millimeter thick taken from the fruit equator. All layers required more force for extension at lower temperatures and high water potentials than at high temperatures and low water potentials. The stretch modulus ranged from 0.88 to 2.16 kilograms per square millimeter depending upon the layer, temperature, and water potential. The inner layers, consisting primarily of mesocarp, had stretch moduli only 60 to 70% as great as the outer layer which consisted of exocarp tissue. Measurements of the stretch modulus of tissues from the pericarp support the hypothesis that changes in the tension existing in the pericarp depend upon conditions in the pericarp and are not related to changes in volume or pressure in the juice vesicles.
周长为17至19厘米的生长中的柑橘（甜橙）果实，其果皮中存在的拉力足够高，以至于在将果皮切除时会导致果皮出现3%的收缩。当果实沿赤道向中心轴切开时，果皮的收缩会在切口处形成一个楔形间隙。通过测量将切除的组织条拉伸至比其切除长度长1%所需的力来确定果皮的拉伸模量。对从果实赤道处取出的宽5毫米、厚1毫米的连续几层果皮组织进行了测量。与高温和低水势相比，所有层在较低温度和高水势下伸展时都需要更大的力。根据层、温度和水势的不同，拉伸模量在每平方毫米0.88至2.16千克之间。主要由中果皮组成的内层的拉伸模量仅为外层（由外果皮组织组成）的60%至70%。对果皮组织拉伸模量的测量支持了这样一种假设，即果皮中存在的张力变化取决于果皮中的条件，而与汁胞中的体积或压力变化无关。
