Stomatal Density and Responsiveness of Banana Fruit Stomates

Abstract

Receivcel May 5, 1963. S'umu,arv. Determiiniationi of stoniatal (leinsities of the banana l)eel (Mlusa a(cLl iniiitia L. var Hort. Valery) 1w micros co)ixc ol)servations showed 30 timiies fewer stonmates o01 frulit el)idermuis thani found on1 the banlana leaf. (O)bservations also showed that peel stomiatel were nlot lai(l dowA-ln in a liniear l)atterli as onl the leaf. It was (lemollstrate(d that .tonmatal reslpolnses occurred in banaall fruiit. Specific coii-ditionis of hig,h humidity and light were necessary for stonliatal opening: low hutimiditv and darkness were neciessarv for cloutire. Responsiveness of the stomates cointinuiie(l for a considerable length of timiie after thie frutit had been severedl fromii the lhost. Althotilgh stu(lies hia-e been llla(le of the distribu-tiol lpatterils ail(l fulinctioIns of stomilates onl gyreeni leaves (2. 5. 7.) relatively little work has been (loie oni stomiiates of fruiit. It hals leeln noted in the literattlure that stomates exist on somile fruits. but it lhas been assunle(l that they probably were 1o longer functional (1. 8). Th'le commercial iniportance of banana frulit and its ili:v ill transit an(l storage instigate(l the fol-lowvimg investigation of the natuire of .tomiates on banana lpeels. Materials and Methods 'T'lle following work emp)e(l greenll frulit of .1/ tos (W1I/linl(t(L. v-ar. lIort. \Valery. a conmmercil1v imi-portalt variety. Stomatal dleisities wxere (letermined(l by milicirscop)ic ol)servations uisinlg siliconie rulbber impressions (Gen-eral Electric RTV-1 1) (6) of siurfaces of-reenihouse-gOrowni friuit. This comipound. wvhich vuilcanlizes at roomii tenpl)erature, gives a l)erfect niegative impres-sionl of a suirface vithout any physical damilage to that suirface. At each stage of maturity. the central finiger of the ouiter friuit row of a haid, located about lhalfwvav up the stein, was chosen. Duplicate imlpres-SiOl0s were made fromii 4 of the faces of each finger. Clear nail polish. l)ainte(l on these ipll)ressionss to create a positive l)rinlt. was l)eele(d off whenl (Ir-an(floate(d onito microsli(des and the stomates. couitite(l. The generanl appearance of banana leaf and fruit sutrfaces u.ingi this techliii(itle is-shownii ill figure 1. T'lhe ability of stomiiates to op)eln and close in re-sponlse to light and (larkiuess was investigate(l with fruit of 3 categories: inltact hangin, fruit ill tile Presenit address: College of T'ropical Agriculture, t1iiiversity of Hawaii, Hotnoluiltu, Hawaii.-Present addIress Departmiient of Agronomy and(Plant (;enIetics, University of Mfinnesota, St. Pauil, Min-iesota. FT(;. 1. Positive prinits of epiderimial surfaces takeni troiil silicone rubber impil)ressio Ins. .\. laniana leaf siur-face. B. Baalniaa peel surface. (Both l>)iotogral)lpe(l at sam11e imiagniificationi.) greenhouse: freshly picked greenhouse fruit; and 10-day-old fruit harvested ill the tropics and shiipped on the hanid throughll lnormiial commiiiiercial channels. Although silicone rubber imlpressions Nvere effective for counltinig stomiiates, the degree of stoniiatal opening was (lifficuilt to ascertaini. Tlherefore. relative sto-matal opening was dletermiinie(l every 15 minutites after exl)osure to light or (larkness b)-y a chloroplast-bleaching tecllhniquie uising-chlorinie gCas (4). Previously. thi.s technii(qtue was used onl g,reeni leaves wherein it w as foutii(I that portions of leaves with open stomates bleached to a l)ale yellov after exposure to chlorinie ga(IS for a few secon(lss: portions (If leaves wvith closed stomates. however. remiiainie(d greenl after at least I hioturs exl)osure. Results A sIimilary of the stom.atal (lensitv counits and(I the statistical variation is griven in table 1. Tlhese dlata show fewer stomates oii the lIel tlhani Sktitclh () fouln(d o il banatna leaves. His c(tiiCtllts avera-e(d 99