Contribution to the Anatomy of the Fruit of Peach. II. Crax and Wax Formation in Cell Walls of Epicarps

Abstract

Vanjska epiderma perikarpa breskve golice sadržava u vanjskoj membrani ispod kutikule kutikulame slojeve znatne debljine, a u bočnim membranama dobro razvijena kutikularna rebra. Zbog znatne napetosti, koja se stvara u epikarpu odraslih plodova, nastaje kidanje kutiniziranih dijelova membrane. Pri tom se stvaraju u mebranama dvije glavne forme pukotina: jedne, površinske pukotine, stvaraju se zbog kidan ja kutikule i kutikularnih slojeva i stoga su prema vani otvorene, a druge, unutrašnje pukotine, nastaju isključivo \u27zbog kidanja kutikularnih rebara, pa su zato zatvorene u unutrašnjosti membrane. Kad nastaju pukotine, one se ne proširuju u znatnijoj mjeri na susjedne nekutinizirane membranske dijelove, koji se odlikuju znatnom rastezljivošću, taiko da protoplasti epidermskih stanica ostaju i nadalje svagdje ovijeni membranom i zadrže, barem u većini slučajeva, sposobnost vršenja životnih funkcija. Unutrašnje i vanjske pukotine mogu se poslije ispuniti voskom. Voštane uklopine naročito su Česte u zatvorenim pukotinama, koje nastaju zbog poprečnog kidanja kutikulamih rebara. Te uklopine imaju karakterističnu strukturu. Čini se, da su izgrađene iz štapićastih elemenata, koji su većinom položeni paralelno s površinom ploda i paralelno sa smjerom, u kome se pružaju kutikulama rebra. Voštane uklopine jako su optički anizotropne. S obzirom na karakter dvoloma optički su negativne. Kod povišene temperature gube svojstvo optičke anizotropnosti, ali se to svojstvo ponovno vraća, kad se temperatura snizi.The outer epidermis of epicarp of Nectarine (Prunus per cica var. nucipersica C. K. Schneider) in the outer cell-walls below the cuticle contains cuticular laiyers of considerable thickness, and in the lateral walls well developed cuticular ribs (fig. 1). Because of considerable tension in epicarp of developed fruits the cutinised parts of the epidermal walls break up on many places. Two main forms of cracks are produced: the outer cracks (fig. 2f. and 3a) are produced because of the break of cuticle and cuticular layers and that is why they are open and ithe other, inner cracks (fig. lg, 2 d and 5c), are caused only by the break of cuticular ribs, and that is why they are closed in the inner of cell-walls. When the cracks are produced, they do not extend to a greater degree on the neighbouring uncut inised membrane parts which are characterised by considerable extensibility, so that protoplast of the epidermic cells remain everywhere wrapped by membrane and preserve, at least in most cases, their ability of fulfilling their vital functions. The inner and outer cracks can be filled up with wax. Wax inclusions are frequent especially in inner crack, which are caused by transversal rupture of cuticular rihs (fig. lg, 2e and 5c). Those inclusions have a characteristic structure. It seems that they are built by rod-shaped elements, which are mostly laid paralelly with the surface of fruit and paralelly with the direction in which the cuticular ribs are settled (fig. 1, 4b and 5c). Wax inclusions are optically anisotropic (Tab. I, fig. 3 and 4) and shine in polarised light between the crossed Nicols in many positions. The birefringence of the inclusions is negative. This negative birefringence disappear with rise of temperature, but it reappers on cooling