（201）富田絹子：発芽，生育，貯蔵に於ける1］諸成分の変化（第5宰即，貯蔵時の成分変化，酸酵工学，28，440
−444（1950）…
（202）冨田絹子：Amylase作用力に及ぼすVitamin C其他の影轡，醗酵工学，29，157−142（1951）．
（205）塚本洋太郎：挿木繁殖に関する研究，第1報 発根の肝易と含有物質との関係，閲研集録，4，51−59
（1949）．
（2∩4）突永−・枝：作物の生育に対する土壌水分の影響に就いて（第一・報），農学会報，（519），229−244（1929）．．
（205）樋 国珍：小麦の生育…収鼠に及ばす土壌水分の影響誓に就いて，日作紀，15，2占7−270（1942）…
（20占）楠田宰相‥土壌水分が秋蒔大麦及び小麦の生育孟をびに収穫物に及ぼす影響（預報），】ヨ作紀，5，5−50
（1955）．．
（207）横間肇朋：光線の強度がノ」＼麦の生育に及ぼす影響に就いて■，日作紀，10，99−118（1958）‖
（208）植田宰怖：ニヒ壊水分並匿敷藁が拘前の生育に及ぼす影幣に就いて，日作紀，12，5る0−572（1941）．
（209）植田宰椰：土壌水分が大豆の生育並匿収私物に及ぼす影響（要旨），日作紀，21，125−12占（1952）．．
（210）渡辺 斉：苗床の条件とトマト，胡瓜苗の光合成作用について，千葉大開平軋（5），74−85（1957）．
（211）WERNER，H．0一．：The effect of temperature，photoperiod and nitrogenlevelupon tuberization in the potato，PYOC・。Amer．．Soc．丑）ri．Sci．，52，507（1954）．
（212）軌王1貞治郎，林 武，中川一・郎，村山 発：1］」譜搾ナーlの利用（其の1），農及閲，18，927−928（1945）．
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（215）山崎 僻：畑作物の湿害に関する土触化学的並紅植物生理学的研究，農技柳平軋 B，（1），1−92（1952）い
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（219）ZIMMERLE￥，H．H．：The effect of the NpP−K fertilizer ratio on the shape of the Porto Rico SWeet pOtatO，ProcいAmel… Soc．Hort．Sci‖，52，498〜501（1954）．
ー88−
PhysiologicalStudies on the Growing Process of Sweet Potato Plants
Junzaburo NAKA
Sofaras the authorisaware，fewdetailedaccountsseemtohavebeenpublishedhitherto on the physiologlCalan．d ecologicalnaturesof sweetpotatoplants・pIn thehopeofgalrllng some董undamer］talinformationfortheimprovement of their cultivationaI】dutilization，the present study on the process o王thelife cycle was carriedout；SpeCialattention was paid to the metabolism of sweet potato plants throughout the storage，nurSery，tuber forming and developmentalstages．Moreover，the growlngStatuS and metabolism under various circumstances were also traced．The principalresults obtained aIe aS follows：
During the storage stage．the contents of carbohydrate and nitrogen・COmpOund at the
parts of apex，Center and tailin both pith and cortex of seed tubers showed the fluctua−
tion relating closely to the physiologicalfunction of each tissue，Such fluctuationis
SuppOSed to be concerned with the development of bud and root primordia．
In the nuヱSery Stage，the reseIVe materials were transIocated from seed tubers to buds
Where they were consumed remarkably fo工the development of new sprouts＝ Upon attain−
ing thelater stag−e，the re−aCCumulation of assimilation materials at and near the cortex
Of seed tubers was observed．On the other hand，the contents of carbohydrate andI】itro−
gen COmpOundiI〕Vines were ratherlarge at the sprouting Stage，and thereafter they declined with the development of sp工OutS巾However，afteIVines attained their autotrophic
phase，the rate of decline of these contents dec工eaSed gradually，董01lowed by a slight re‑accumulation of assimilates in vines
When the higher temperature suitable董orthe emergenceof buds was main．tained at the
earlier part of nursery stage，the growth of sprouts was considerably better than that of
thelow temperature plotin．which buds were hardly able to emeIge．Tn this case，the
COnSumption of reserve materialsin seed tubers of thehightemperatureplot，WaS earlier
than that of thelow temperature plot．The contents of sugar and soluble−Nin sprouts of
the high tempeIature plot werelarger than those of thelow temperature plot，While the
COntentS Of starch and protein／N showed the reverse teIldencies．
The grOWth of sprouts of the heavy nitrogen plot was considerably better than that of
the no nitrogen plot at the nursery stage．The contents of reserve materialsin seed
tubers of both plots decreased duIing theimbeddi工〕g al］d sprout developiI】g Stage．Inthe later stage When sprouts had become vigorous，the coI】tentS Of carbohydrate andl】itrogen COmpOund contrarilyincreased more evidently not onlyin seed tubers，butalsoin sprouts Of the heavy rlitrogen plot，thanin those o董the no nitrogen plot．
When the sufficient soilmoisture was maintained at the nursery stage，the emergence
Of buds and the growth of sprouts were better than those ofthein，Sufficientsoilmoisture
plot．In this case，the consumptioI〕Of reserve materialsin seed tubers which were cuト
turedin the suf董icient soilmoisture plot，WaS reCOgnized earlier than that of seed tubers
岬89 −
Culturedin theinsufficient soilmoisture plot．In thelater stage，however，the re・aCCu−
mulation of assimilation materials began earlier in seed tubers of the sufficient soil moisture plot thanit didin those of theinsufficient soilmoisture plot．At the same time，the highsugar content and the somewhatlow content ofmitrogen compound were
recognizedin vines of the sufficient soilmoistueplot；thisfindi皿gindicates thevigorous
growth of vines．
At the stages of the rooti工Ig Of cuttings and of theIOOt tuberfo工mation，Strikingaccu−
mulations of carbohydrate and nitrogencompoundtookplaceinthe basalpartsofcuttings；
such accumulation seems to be due to the translocation of assimilates from leaves to those
pa工■ts．
C／N ratio of the apicalparts．of vines，aS Wellas ofleaf−blades and petioles attached to them waslow for twenty or thirty days a董ter planting，When thelateralshoots began to emerge，butit was highiust before and afterthisstage．Onthe contrary，C／Nratios Of the basalparts of vines and of rootsincreased gradually．C／N ratios of petioles and Ofleaf−blades attached to the basalparts of vines were highrespectively on the twenti−
eth or fortieth day afteIplanting，When the formation of root tubers was found to start．
So，it seems reasonable to assume that the vaIiations of chemicalcomponentsin shoots
androots，inother wordshighC／Nratios，areintimatelyrelated totherootingof cuttings，
the development of vines，the g工OWth oflate工alshoots and the root tubeIformation・
Moreover，the accumulation of ca工bohydratein tuberous roots may be assumed to proceedin parallelwith theIOOt tuber formation；the carbohydrate contentin the di畠tal
Part Of tuberous roots was almost similar to thatin fibrous roots．In company with the
accumulation of carbohydratein roots，the differencei皿 aCtivities of amylase and of Phosphorylasein tuberous and fib工OuS rOOtS WaS reCOgnized，Which was closelyrelatedto the root tuber foImation．
The quantities of nitrogen and potassium fertilizers supplied to the soil are reflected in the numbers and the weigts of root tubers obtained on the fortieth day after planting．
Inleadin yield was the heavy potassium plot．Followlngln Order were the nomitrogen
plot and the controlplot，then the heavy nitrogen and heavy potassium plot，but no Sign of root tuber formation was recognizedin the heavy nitrogen plot．C／N ratio of the
no nitrogen plot was theユargest throughout allparts of theplants，While theratiosin the
heavy nitrogen plot and in the heavy nitrogen and heavy potassium plot weIe generally
Small．C／N ratios of the controland of the heavy potassium plot stood between the above two g工OupS．
The numbers and the weights of root tubers obtainedin theinsufficient soilmoisture plot on the foItieth day after planting, were consideIably inferioI to those of the control
Plot・From the viewpoint of chemicalcomponentsin the plants，C／Nratiosof every partOf the plantsin theinsufficient soilmoisture plot werelarger than thosein the controI
Plot．These facts show that the shortage of water supply to the soilcaused the retarda−
tion of assimilates translocation which in turn made the unfavourable condition foI the root tuber formation．
ー90−
Bylimiting the oxygen supply to the soilduring forty days after planting，the root
tuber formation was also checked，and C／N ratios obtained from diffeIent PartS Of such
plants were smaller than those of the controlplants．
Thelow soiltemperature during forty days after planting did not appear to affect the
numbers of root tubers，but the weights of root tubers raised under thelow soiltemper−
ature condition were greater than those of the controlplot．C／N ratios of different parts
Of the treated plants except fibrous roots，Were higher than those of the controlplantsu
When the short day treatment throughout forty days after planting was made，the numbers and the weights of root tubers of the treated plants were smaller than those of
the controlplants．C／N ratios of different parts of the treated plants except vines and root tubers，Werelower than those of the controlplants．
In the developmentalstage of root tubers，StarCh contentsin both pith and cortex at thecentralzone of roottubersinc工eaSedwith the tuber development and then a slight decrease was observed at thelater stage．Such variationsin starch contents progressed
contrary to those of sugar and moisture contents
As regards the behavior of translocation and storage of nitrogen compound at the cen−
tIalzone of developlngrOOt t11bers，1arge amounts of soluble−N and protein−N wereIeCOg−
nized at the earlier stage of root t11beIdevelopment，but they display a tendency to
decrease concomitant with the march of their development．Finally，aCCOmPanied with the attainment of maturity of root tubers，SuCCeSSiveincreases of both soluble−N and protein・・N contents were ascertained．
Throughout the entire stageof root tuber development，the totalcontent o王carbohydrate
WaS the most abundantin root tubers．Followlngln Order were the contentsin the basal
parts of vines，fibrous roots，the apicalparts of vines，1eaf−blades，and finallyin peti−
01es．Moreover，the totalcontents of carbohydydratein root tubers，the basal parts of
Vines and fibrous roots showed highvalues at the middle stage of root tuber development，
While thosein the apicalparts of vines andinleaf−blades attached to themdecreased at the same stage．At the finalstage of roottuberdevelopmenta considerablylargeamount Of totalcarbohydrate was found to be containedin fibrous roots．Butin petioles attached to the apicalparts of vines，nO remarkable changeincarbohydrate content wasrecogmized throughout allstages of their development．
As to the totalcontent ofmitrogen compound throughout allstages of root tuber de−
Velopment，inlead was the contentinleaf・blades attached to the apicalparts of vines；
followingln Order were the contentsin petioles，the apicaland basalpartsofvines，and
finallyin fibrous roots and root tubers．At the same time no remarkable differencein
the totalcontent ofmitrogen compound between fibrous roots and root tubers was found．
Moreover，it may be pointed out that the totalcontents of nitrogen compoundsin almost allparts of the plants were highat the early and finalstages of the development of
root tubers，Showing alittle depressionin the middle stage of root tuber development．
As for the physiological interrelationship between the accumulations of carbohydrates
in fibrous，penCil−1ike and tuberous roots at various developmentalstages，and the
一 91−
activities of phosphorylase and phosphatase，increase of such enzymatic activities were
recognized with the growthin thickness of roots．In regard to amylase，thelowest ac−
tivity was observedinfibrous roots，and the highestin pencil−1ike roots，With thatin tuberous工00tSintermediate between the two．In this case a negative correlation was
recognized between the amylase activity and the degree of growth in thickness of root
tubers．The totalcontents of ascorbic acid and carbohy drate were thelowestin fibrous，
intermediatein pencil−1ike，and the highestin tuberous roots．In thelast casethetotal
SugarCOntentdecreasedand starchcontentincreased withthe growthinthicknessofroots．
When heavymitrogen or heavymitrogen and heavy potassium fertilizers were supplied at the stage of root tuber development，the most vigorous growth of top was foundin
the heavy nitrogen and heavy potassium plot，theleastin the controIplot，and the intermediate growthin the heavy nitrogen plot．On the other hand，the numbers and the
Weights were the greatestin the controlplot，intermediatein the heavy nitrogen and
heavy potassium plot，and theleastin the heavy nitrogen plot．Under such conditions，
the carbohydrate contentin theheavymitrogen and heavy potassium plot was higherin
the apicalparts of vines andleaf・blades attachedtothemthanthatintheheavynitrogen
plot．The carbohydrate contentsin the basalparts of vines andinroottubersintheheavy
nitrogen and heavy potassium plotweremoresimilar to thatinthecontrolplotratherthan
thatin the heavy nitrogen plot．On the other hand，the totalcontent of nitrogen com−
POundin every part of the plants was the highestin the heavy nitrogen plot，intermedi−
atein the heavy nitrogen and heavy potassium plot，and thelowestin the controlplot．
Excessive soilmoisture was found to be harmfulfor the growth of top and the root
tuber development．Thus the carbohydrate contentsin the apical parts of vines，leaf−
blades and petioles attached to them，aS Wellasin the basalparts of vines and．fibrous
rootsintheexcessivesoilmoistureplot werehigher thanthoseinthe controlplot，Whereas
the carbohydrate contentin root tubersin the excessive soilmoisture plot wasless than
thatinthe controlplot．Moreover，thetotalmitrogencontentsinthe apicalparts of vines，
1eaf−blades and petioles attached to them，aS We11asin the basalparts ofvines，fibr−
OuS rOOtS and root tubersin the excessive soilmoisture plot werelower than thosein
the controlplot．However，the protein−N contentin root tubersin the excessive soil
moisture plot was rather higher than thatin the controlplot．These facts seem to offer
themost reasonabIe expIanation for the harmfuleffectof excessive soilmoisture upon the growthin thickness of root tubers of sweet potato plants．Uuder such a condition the Carboydrates stagnateinIeaves due to theinhibition of smooth translocation of assimi−
1ates fromleaves to root tubers，and at the same time the formation and accumulation of starch in root tubers are much retarded owing to the shortage of oxygen supply to the
SOil．
By shading the sunlight during the entire stage of root tuber development，the more Vigorous growth of top was found，but the numbers and the weights of root tubers were
COnSiderably smaller than those of the controIplot．In the shaded plot，the contents of
Carbohydrate and of nitrogen compoundinleaf−blades attached to the apicalparts of
ー92−