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Some observations on the vital cycle of maize etioplasts I. Plants grown on an inorganic medium
Abstracts oJ' The X1V Congress of the Italian Socie O' oJElectrott Microscopy
140
endoplasmic r e t i c u l u m a n d the p r e s e n c e of n u m e r o u s large vesicles. The cont e n t of t h e s e v e s i c l e s , p r o b a b l y n r o t e i naceous, reveals a naracrystalline s t r u c t u r e in s o m e n o i n t s . The epithelial c e l l s a r e thus a c t i v e l y s e c r e t i n g materials in the l u m e n of the s e m i n a l receptacle. The fact that the typical spermatozoa of C o c h l o s t o m a montanum alr e a d y h a v e r i c h s u p m l i e s of g l y c o g e n w o u l d s e e m to e x c l u d e a n u t r i t i v e funct i o n for t h i s s e c r e t i o n I. Rather, the enithelial secretion could perhaps cont r i b u t e to the m a i n t e n a n c e of the p h y s i co-chemical conditions n e c e s s a r y to the v i t a l i t y of t h e s n e r m a t o z o a , j u s t as it could also constitute a k i n d of s p a t i a l matrix for the entire s~ermatozoan population. A l l the s p e r m a t o z o a in the s e m i n a l receptacle have the same spatial orientation: head pointed towards the epithelial c e l l s w i t h the t a i l t o w a r d s the c e n t e r of the lumen. T h e p a r t of the spermatozoon in the c l o s e s t c o n t a c t w i t h the e p i t h e l i a l c e l l s is the a c r o s o m e . T h e p l a s m a m e m b r a n e , w h i c h c o v e r s it, is r a i s e d to f o r m 1 0 n g d i g i t a t i o n s that s e e m to a d h e r e to the w a l l s of t h e e p i thelial cells. B e t w e e n the p l a s m a m e m b r a n e of the e p i t h e l i a l c e l l s a n d the m e m b r a n e c o v e r i n g the a o r o s o m e s t h e r e is a t h i n s p a c e c o n t a i n i n g a l a v e r of fibrillar, non-structured material. The specific attachment of the s n e r m a t o z o a to the e p i t h e l i a l cells could represent a mechanism a c q u i r e d to g u a r a n t e e t h e i r performance in l o c o f o r long n e r i o d s of time. 1.
M. G. Selmi and F. Giusti, in: "Atti IV Congresso S.M.I., Atti Accad. FisiocriticJ, Siena," ed. F. Giusti, 1(]80, pp. 115-47.
SOME OBSERVATIONS MAIZE ETIOPLASTS INORGANIC MEDIUM N. F.
O N T H E V I T A L C Y C L E OF I. P L A N T S G R O W N O N AN
R a s c i o , P. M a r i a n i , Dalla Vecchia
P.
Chitano
and
Istituto di B o t a n i c a e Fisiologia Vegetale, Universita di P a d o v a , Via Otto Botanico 15, 35100 Padova, Ital~
T h e p l a s t i d s of the h i g h e r p l a n t s g r o w i n g in the d a r k n e s s d i f f e r e n t i a t e as e t i o p l a s t s . These organelles contain protochlorophyll(ide) and tubular memb r a n e s a r r a n g e d in a t h r e e - d i m e n s i o n a l lattice named prolamellar body. We h a v e f o l l o w e d the w h o l e v i t a l
c y c l e of the e t i o m l a s t s in the s e c o n d l e a f of e t i o l a t e d m a i z e D e k a l b X L I 2 , c u l t u r e d on an i n o r g a n i c m e d i u m , in o r d e r to s t u d y t h e i r o n t o g e n e s i s and senescence matterns. D u r i n g the e a r l y s t a m e s of d i f f e r e n t i a t i o n the e t i o ~ l a s t s contain nrolamellar bodies with different membranal arrangements. In fact, t h e y m a y be o r g a n i z e d l o o s e l y a n d irregu l a r l y , or w i t h n u m e r o u s i n t e r c o n n e c t e d c e n t r i c u n i t s , or as p o l y h e d r i c lattices. By o p t i c a l d i f f r a c t i o n , the last arrangement a m p e a r s to be the m o s t r e g ular, s h o w i n g a c l e a r e x a g o n a l c r y s t a l line o r g a n i z a t i o n . T h i s e x a q o n a l arr a n g e m e n t is a l s o the m o s t f r e q u e n t in the m a t u r e e t i o n l a s t s , so it m i g h t be the f i n a l s t a g e of the n r o l a m e l l a r body differentiation. The etioplast senescence starts with a d e c r e a s e of the p r o t o c h l o r o n h y l l ( i d e ) content. Subsequently we can notice, in the e t i o n l a s t s t r o m a , an i n c r e a s e in the n u m b e r of the o s m i o p h i l i c globules, a mhenomenon k n o w n to h a n p e n a l s o in the l i g h t , d u r i n ~ the c h l o r o m l a s t s e n e s c e n c e . B e c a u s e of the p r e c o c i t y , in the e x a m i n e d leaf, of the f i r s t e v e n t (duri n g the s e c o n d w e e k of p l a n t life) as r e g a r d s the e x h a u s t i o n of the c a r y o p s i s reserves (occurring about four weeks after germination), the s e n e s c e n c e does n o t s e e m to be m e r e l y c o r r e l a t e d w i t h starvation mhenomena, but rather nredetermined in the p l a n t .
SOME OBSERVATIONS MAIZE ETIOPLASTS: WITH SACCHAROSE F. M a r i a n i , N. a n d P. C h i t a n o
ON T H E V I T A L C Y C L E OF II. P L A N T S S U P P L I E D
Rasc±o,
F.
Dalla
Vecchia
Istituto di B o t a n i c a e Fisioloqia Vegeta!e, Universit~ di P a d o v a , Via Otto Botanico 15, 35700 Padova
We have previously o b s e r v e d t h a t in the e t i o n l a s t s differentiated in l e a v e s of m a i z e g r o w n in the d a r k n e s s on ino r g a n i c m e d i u m the s e n e s c e n c e symptoms s t a r t e a r l y d u r i n g the p l a n t life. T h i s study has been carried out with etiolat e d m a i z e c u l t u r e d on a m e d i u m a d d e d with saccharose, in o r d e r to d e t e c t the nutritional involvement in the s e n e s cence phenomenon. The observations on the s e c o n d leaf show that the added saccharose does not c h a n g e the o n t o m e n e t i c p a t t e r n of the etiomlasts. In the j u v e n i l e s t a g e s of differentiation it is m o s s i b l e , in fact,
140
endoplasmic r e t i c u l u m a n d the p r e s e n c e of n u m e r o u s large vesicles. The cont e n t of t h e s e v e s i c l e s , p r o b a b l y n r o t e i naceous, reveals a naracrystalline s t r u c t u r e in s o m e n o i n t s . The epithelial c e l l s a r e thus a c t i v e l y s e c r e t i n g materials in the l u m e n of the s e m i n a l receptacle. The fact that the typical spermatozoa of C o c h l o s t o m a montanum alr e a d y h a v e r i c h s u p m l i e s of g l y c o g e n w o u l d s e e m to e x c l u d e a n u t r i t i v e funct i o n for t h i s s e c r e t i o n I. Rather, the enithelial secretion could perhaps cont r i b u t e to the m a i n t e n a n c e of the p h y s i co-chemical conditions n e c e s s a r y to the v i t a l i t y of t h e s n e r m a t o z o a , j u s t as it could also constitute a k i n d of s p a t i a l matrix for the entire s~ermatozoan population. A l l the s p e r m a t o z o a in the s e m i n a l receptacle have the same spatial orientation: head pointed towards the epithelial c e l l s w i t h the t a i l t o w a r d s the c e n t e r of the lumen. T h e p a r t of the spermatozoon in the c l o s e s t c o n t a c t w i t h the e p i t h e l i a l c e l l s is the a c r o s o m e . T h e p l a s m a m e m b r a n e , w h i c h c o v e r s it, is r a i s e d to f o r m 1 0 n g d i g i t a t i o n s that s e e m to a d h e r e to the w a l l s of t h e e p i thelial cells. B e t w e e n the p l a s m a m e m b r a n e of the e p i t h e l i a l c e l l s a n d the m e m b r a n e c o v e r i n g the a o r o s o m e s t h e r e is a t h i n s p a c e c o n t a i n i n g a l a v e r of fibrillar, non-structured material. The specific attachment of the s n e r m a t o z o a to the e p i t h e l i a l cells could represent a mechanism a c q u i r e d to g u a r a n t e e t h e i r performance in l o c o f o r long n e r i o d s of time. 1.
M. G. Selmi and F. Giusti, in: "Atti IV Congresso S.M.I., Atti Accad. FisiocriticJ, Siena," ed. F. Giusti, 1(]80, pp. 115-47.
SOME OBSERVATIONS MAIZE ETIOPLASTS INORGANIC MEDIUM N. F.
O N T H E V I T A L C Y C L E OF I. P L A N T S G R O W N O N AN
R a s c i o , P. M a r i a n i , Dalla Vecchia
P.
Chitano
and
Istituto di B o t a n i c a e Fisiologia Vegetale, Universita di P a d o v a , Via Otto Botanico 15, 35100 Padova, Ital~
T h e p l a s t i d s of the h i g h e r p l a n t s g r o w i n g in the d a r k n e s s d i f f e r e n t i a t e as e t i o p l a s t s . These organelles contain protochlorophyll(ide) and tubular memb r a n e s a r r a n g e d in a t h r e e - d i m e n s i o n a l lattice named prolamellar body. We h a v e f o l l o w e d the w h o l e v i t a l
c y c l e of the e t i o m l a s t s in the s e c o n d l e a f of e t i o l a t e d m a i z e D e k a l b X L I 2 , c u l t u r e d on an i n o r g a n i c m e d i u m , in o r d e r to s t u d y t h e i r o n t o g e n e s i s and senescence matterns. D u r i n g the e a r l y s t a m e s of d i f f e r e n t i a t i o n the e t i o ~ l a s t s contain nrolamellar bodies with different membranal arrangements. In fact, t h e y m a y be o r g a n i z e d l o o s e l y a n d irregu l a r l y , or w i t h n u m e r o u s i n t e r c o n n e c t e d c e n t r i c u n i t s , or as p o l y h e d r i c lattices. By o p t i c a l d i f f r a c t i o n , the last arrangement a m p e a r s to be the m o s t r e g ular, s h o w i n g a c l e a r e x a g o n a l c r y s t a l line o r g a n i z a t i o n . T h i s e x a q o n a l arr a n g e m e n t is a l s o the m o s t f r e q u e n t in the m a t u r e e t i o n l a s t s , so it m i g h t be the f i n a l s t a g e of the n r o l a m e l l a r body differentiation. The etioplast senescence starts with a d e c r e a s e of the p r o t o c h l o r o n h y l l ( i d e ) content. Subsequently we can notice, in the e t i o n l a s t s t r o m a , an i n c r e a s e in the n u m b e r of the o s m i o p h i l i c globules, a mhenomenon k n o w n to h a n p e n a l s o in the l i g h t , d u r i n ~ the c h l o r o m l a s t s e n e s c e n c e . B e c a u s e of the p r e c o c i t y , in the e x a m i n e d leaf, of the f i r s t e v e n t (duri n g the s e c o n d w e e k of p l a n t life) as r e g a r d s the e x h a u s t i o n of the c a r y o p s i s reserves (occurring about four weeks after germination), the s e n e s c e n c e does n o t s e e m to be m e r e l y c o r r e l a t e d w i t h starvation mhenomena, but rather nredetermined in the p l a n t .
SOME OBSERVATIONS MAIZE ETIOPLASTS: WITH SACCHAROSE F. M a r i a n i , N. a n d P. C h i t a n o
ON T H E V I T A L C Y C L E OF II. P L A N T S S U P P L I E D
Rasc±o,
F.
Dalla
Vecchia
Istituto di B o t a n i c a e Fisioloqia Vegeta!e, Universit~ di P a d o v a , Via Otto Botanico 15, 35700 Padova
We have previously o b s e r v e d t h a t in the e t i o n l a s t s differentiated in l e a v e s of m a i z e g r o w n in the d a r k n e s s on ino r g a n i c m e d i u m the s e n e s c e n c e symptoms s t a r t e a r l y d u r i n g the p l a n t life. T h i s study has been carried out with etiolat e d m a i z e c u l t u r e d on a m e d i u m a d d e d with saccharose, in o r d e r to d e t e c t the nutritional involvement in the s e n e s cence phenomenon. The observations on the s e c o n d leaf show that the added saccharose does not c h a n g e the o n t o m e n e t i c p a t t e r n of the etiomlasts. In the j u v e n i l e s t a g e s of differentiation it is m o s s i b l e , in fact,