Sclereid Distribution in the Leaves of Pseudotsuga Under Natural and Experimental Conditions Author(s): Khalil H. Al-Talib and John G. Torrey Source: American Journal of Botany, Vol. 48, No. 1 (Jan., 1961), pp. 71-79 Published by: Botanical Society of America Stable URL: http://www.jstor.org/stable/2439597 . Accessed: 19/08/2011 13:16 Your use of the JSTOR archive indicates your acceptance of the Terms & Conditions of Use, available at . http://www.jstor.org/page/info/about/policies/terms.jsp JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact [email protected]. Botanical Society of America is collaborating with JSTOR to digitize, preserve and extend access to American Journal of Botany. http://www.jstor.org January, 1961] AL-TALIB AND TORREY-SCLEREID DISTRIBUTION 71 SMITH, G. H. 1926. Vascular anatomyof Ranalian flowers. Aquilegia formosav. truncata and Ranunculus repens. I. Ranunculaceae. Bot. Gaz. 82: 1-29. Univ. California Publ. Bot. 25: 513-648. 1928. Vascular anatomy of Ranalian flowers. II. TUCKER, SHIRLEY C. 1959. Ontogeny of the inflorescence Ranunculaceae (continued), Menispermaceae,Calycan- and the flowerin Drimys winteri v. chilensis. Univ. thaceae, Annonaceae. Bot. Gaz. 85: 152-177. California Publ. Bot. 30: 257-335. SNOW, MARY, AND R. SNOW. 1947. On the determination . 1960. Ontogeny of the floral apex of Micheiat of leaves. New Phytol. 46: 5-19. fuscata. Amer. Jour. Bot. 47: 266-277. SNOW, R. 1942. Further experimentson whorled phyllo- WARDLAW, C. W. 1949. Experimentaland analytical stud- taxis. New Phytol. 41: 108-124. ies of pteridophytes.XIV. Leaf formationand phyllo- STERLING, C. 1945. Growth and vascular developmentin taxis in Dryopterisaristata. Ann. Bot. (N.S.) 13: 163- the shoot apex of Sequoia sempervirens.II. Vascular 198. developmentin relation to phyllotaxis.Amer. Jour.Bot. 1957. On the organization and reactivityof the 32: 118-126. shoot apex in vascular plants. Amer. Jour. Bot. 44: TEPFER, S. S. 1953. Floral anatomy and ontogeny in 176-185. SCLEREID DISTRIBUTION IN THE LEAVES OF PSEUDOTSUGA UNDER NATURALAND EXPERIMENTALCONDITIONS' KHALIL H. AL-TALIB AND JOHN G. TORREY ABSTRA CT AL-TALIB, KHALIL H., and JOHN G. TORREY. (U. California,Berkeley.) Sclereid distributionin the leaves of Pseudotsuga under natural and experimentalconditions. Amer. Jour. Bot. 48(1): 71-79. Illus. 1961.-A studyof the distributionof sclereids in cleared leaves taken from1-, 2-, and 4-year-oldshoots of an adult tree of Pseudotsuga menziesii (Mirb.) Franco showed a repeated patternof sclereid distributionalong the shoot axis with many sclereids in the basal leaves grading into few or no sclereids in the terminal leaves of each year's growth. Attemptswere made to influencesclereid distributionby bud defoliationof attached branches with and without auxin treatmentand by testing the effectsof growth-regulatingsubstances on sclereid formationin leaves of excised buds of Pseudotsuga cultured in vitro. Whereas removal of the basal 84 of the leaves at the time of bud unfoldinghad no effecton bud, leaf or sclereid development,removal of the leaves of the upper half or complete defoliationled to prematureexpansion of next year's terminalbud with leaves developingin part from presumptivebud-scale primordia. Indoleacetic acid at 0.5% in lanolin paste applied to the defoliated region preventedthis prematurebud ex- pansion. Defoliation of the basal half did not affectsclereid formationin the terminal leaves. Sclereid developmentin leaves of prematurelyexpanded buds on defoliated branches was normal except in the few cases where bud expansion occurredin the presence of low-auxinconcentrations. Then, sclereid developmentwas inhibited. Sclereid formationin leaves of excised buds grown in nutrientculture was generally much less frequentthan in intact branches, and auxin treatment still furtherreduced the frequencyof sclereids. It was concluded that sclereid initiationand differ- entiationin the intact plant may well be under the control of hormonalfactors in the plant, one of which may be auxin. IN recentyears, sclerenchymatousidioblasts or tissues of various membersof the Coniferales. Allen sclereidshave been the subject of muchinvestiga- (1945) noted the occurrence of sclereids in the tionby plantanatomists. Their occurrence has been leaves of Pseudotsuga taxifolia. Sterling (1947) noted in leaves, stems,roots, fruitsand seeds of studied the ontogeny and morphology of the scle- angiosperms.Further, their morphologyand on- reids in the shoot of P. taxifolia and observed dif- togenyhave been studiedand theirtaxonomic im- ferences in the number of sclereids between indi- portanceevaluated (Foster, 1944, 1945, 1946, 1947, vidual branches. He also observed that sclereids in 1955a, 1955b,1956; Bloch,1946; Bailey and Nast, the cortex were less abundant but were larger than 1948; Rao, 1951). those in the pith. Griffith(1950) reported the In gymnosperms,sclereids have been less in- presence of numerous crystalliferous idioblastic tensivelystudied; theyhave been shownto occur, sclereids in the leaves of certain species of Arau- however,in both the vegetativeand reproductive caria. Sacher (1954) found that sclereids occur in the cortex of shoots of Pinus ponderosa, extending 1 Received for publication April 25, 1960. up to within 2 mm. of the shoot apex. Kitamura This work was supported in part by Research Grant (1956) studied the distributionof foliar sclereids Health Serv- RG 2861, National Institutesof Health, Public verticillata and found that various ice. The authors express their appreciation to Dr. A. S. of Sciadopitys Foster and Dr. L. Machlis for helpful advice. zones of the leaf differin the number of sclereids 72 AMERICAN JOURNAL OF BOTANY [VO1. v l j S &0 ' f: ? t . , , .. ,.,.. ....- . :.x : . j::: fi .;,-: . ' '' ... .... :.; . ., .-. : .... r . , .. .: . .. !o- :.. .. - : ........... .1w . ... I . r .. I ' : . :. ,., ......... ' 1 .:: ' . : . ': j : : . ! .l ;> ,' '.'.'.',.'' . .. ,<. .: . , ' :Ri < . .. : .: : : ',:.,s,. 1.: ' . t . .:: . u .: .: . ', S .. d C 00000X ff SE ;j {0000nDS00; 0 " 0 aV0000- 0,0f'0,j,'"'00000 M\\s'S} wi} . _ !; ' - W.t, ^;7 t j ,' t50'; y< t X1i; 011'f' f ' 'Ds y \ . \ 111|0f'leg * . ,. .i . : . : S1: 42 i3-;itv ... * _ .r : . I S .. ........ .. _l | i| S I __ i l l I l * - 1@ ...............................| l|. I!, i1l-I1 | ,_-- ._ : January, 1961 1 AL-TALIB AND TORREY-SCLEREID DISTRIBUTION 73 TABLE 1. Sclereid distributionin leaves along the shoot axis ziesii in natureand an accountof certainexperi- of 1- and 2-year-oldbranches of Pseudotsuga menziesii ments designed to affectthe regular patternof sclereidformation. A. 1-year-oldbranch (1954) MATERIALS AND METHODS.--Freshleaves and buds Segmentnumber Averagenumber of were obtained froma single old tree of P. menziesii, (15.leaves per Numberof sclereids sclereids per approximately50 ft. tall and 1 ft. in diameterat segment) per segment leaf and S.E. the base, growingin the BotanicalGarden, Univer- 1 (Terminal) 32 2.13 ? 0.41 sity of California,Berkeley. Preservedspecimens 2 128 8.53 ? 0.72 of P. menziesii, P. macrocarpa, P. glauca and P. 3 228 15.20 ? 0.82 sinensis were obtained from the Herbarium of the 4 338 22.53 0.79 ? of 5 (Basal) 286 19.07 ? 2.95 University California. The freshmaterial was collectedat monthlyin- B. 2-year-oldbranch tervalsfrom October 1953 to June1957, was killed 1954 and fixedin formalin-aceticacid-alcohol (FAA) Averagenum- withaspiration and was thenstored in freshFAA Number of ber of sclereids untilneeded. For thestudy of sclereiddistribution, Segment leaves in Total number per leaf and number segment of sclereids S.E. large numbersof leaves frombranches at various levelson the treewere collected, marked according 1 (Terminal) 20 31 1.55 ? 0.27 2 19 158 8.33 ? 0.62 to theirlocation along a branchand thencleared 3 15 245 16.33 ? 0.65 as wholeleaves in sodiumhydroxide. 4 16 428 26.75 ? 0.95 For clearing,the leaves werefirst boiled in 70% 5 (Basal) 18 450 25.0 ? 2.28 ethylalcohol to removepigments (several hours forold leaves fromthe intact plant; 30-60 min.for 1953 1 (Terminal) 15 34 2.27 ? 0.35 leaves fromcultured buds). Afterwashing in water, 2 17 99 5.82 ? 0.38 the leaves were placed in sodium hydroxide solu- 3 18 228 12.67 ? 0.72 tion (5% for old leaves; 2.5/o for young leaves 4 19 356 18.74 ? 0.59 from cultured buds) and placed in an oven at 35- 5 15 258 17.20 ? 1.87 40?C. Several changes of sodium hydroxide solu- tion were needed to complete clearing in some cases. Afterwashing with water again, the leaves were de- presentwith the highest number of sclereidsoccur- hydrated through an ethyl alcohol series to 70%, ringtoward the tip of the leaf. Withthe exception at which stage they were stained with safranin. De- of the studyby Kitamura,there appears to be no hydration was then completed through to absolute quantitativestudy of sclereiddistribution in plants. ethylalcohol, followedby 2 washes of absolute ethyl Duringa preliminarystudy of the occurrenceof alcohol-xylene (1:1) and finallywith pure xylene, sclereids in the leaves of Pseudotsuga menziesii then mountingin piccolyte. In cleared preparations (Mirb.) Franco2 (Douglas fir), therewas noteda of this type, cellular detail is quite evident and the ratherstriking and distinctivepattern of sclereid large