Planta

Ptanta t44, 205-207 (1979)

9 by Springer-Verlag 1979

Short Communication

The Role of Leaves in Sex Expression in Hemp and Spinach M . K h . C h a i l a k h y a n a n d V.N. K h r y a n i n K.A. Timiriazev Institute of Plant Physiology, Academy of Sciences of USSR, Botanicheskaya ul. 35, Moscow, USSR 127106

Abstract. W h e n s h o o t s o f y o u n g p l a n t s o f h e m p (Cannabis sativa L.) a n d s p i n a c h (Spinacea oleracea L.) were c u l t u r e d as c u t t i n g s a n d a l l o w e d to regenerate a d v e n t i t i o u s roots, ca, 8 0 - 8 5 % b e c a m e f e m a l e ( f o r m e d pistillate flowers) r e g a r d l e s s o f w h e t h e r the leaves were left o n the p l a n t s o r were cut o f f (except for the 2 - 3 u p p e r m o s t ones) after the b e g i n n i n g o f a d v e n t i t i o u s - r o o t f o r m a t i o n . But w h e n the leaves were cut off a n d the cuttings t r e a t e d with gibberellic acid ( G A 3 , 25 mg/1) ca. 7 7 - 8 0 % o f the p l a n t s b e c a m e male ( f o r m e d s t a m i n a t e flowers). T h e result was quite s i m i l a r w h e n r o o t s a n d leaves o f y o u n g h e m p p l a n t s were r e m o v e d at the same time a n d the cuttings t r e a t e d with G A 3. It is suggested t h a t the leaves p l a y an essential role in sex e x p r e s s i o n in h e m p a n d spin a c h a n d t h a t this role is related to gibberellin synthesis in the teaves. Key words: Cannabis - F l o w e r s (sex) - G i b b e r e l l i n Sex e x p r e s s i o n - Spinacia.

In p r e v i o u s p a p e r s ( C h a i l a k h y a n a n d K h r y a n i n , 1978b, c) it was s h o w n t h a t the r o o t system p l a y s a n essential role in sex e x p r e s s i o n in h e m p a n d s p i n a c h a n d t h a t this role is b a s e d u p o n synthesis a n d e x p o r t o f c y t o k i n i n s by roots. In the e x p e r i m e n t s to be r e p o r t e d in the p r e s e n t p a p e r we l o o k e d into the role o f the leaves in m a l e sex expression a n d into the q u e s t i o n which h o r m o n e s are i n v o l v e d in this role. W e c o n d u c t e d e x p e r i m e n t s with the s h o r t - d a y p l a n t , h e m p (Cannabis sativa L., cv. U S - 6 ; seeds f r o m the I n s t i t u t e o f F i b e r C r o p s , G l u k h o v , U S S R ) a n d the l o n g - d a y p l a n t , s p i n a c h (Spinaeia oleracea L., cv. V i c t o r i a ; seeds f r o m Soyuzsortsemovoskch, Ministry of Agriculture of USSR, M o s c o w , U S S R ) . P r o c e e d i n g f r o m the facts t h a t gibberellic acid ( G A 3 ) c o n s i d e r a b l y increases m a l e sex

e x p r e s s i o n w h e n a p p l i e d t h r o u g h the r o o t C h a i l a k h y a n a n d K h r y a n i n , 1978a) a n d t h a t gibberellins a r e f o r m e d in the leaves (see reviews by C h a i l a k h y a n , 1958, 1968) we tested the effect o f G A 3 on sex expression in d e f o l i a t e d h e m p a n d s p i n a c h cuttings. The plants were grown in boxes with soil in a greenhouse on long days (18 h daylight extended with light from xenon-arc lamps, DKSTW 6000, Moscow, USSR; 0.009 W cm-2). Hemp was used when the plants had formed the third visible pair of leaves, spinach upon appearance of the third visible leaf. At these stages the plants were cut off at the root-shoot juncture and the shoots placed with their cut ends in containers, at first with water and then with Knop nutrient solution, in a controlled-environment cabinet under 16-h photoperiods (light from fluorescent lamps; LBZ 80, Baku, USSR; 0.002 W cm -2) at 20~ C and 80% relative humidity. The plants were divided into three groups. In all groups adventitious roots were allowed to develop while the leaves (except the 2-3 uppermost ones) were removed in the 2nd and 3rd group at the very beginning of root regeneration, in hemp after 10 12 d and in spinach after 3-6 d, and the cuttings of group 3 were placed with their ends into a 25 mg/l GA3 solution for 28 h. Thus, the experiments consisted of three treatments: 1) cuttings with roots and leaves (control), 2) with roots but with the leaves removed, 3) as 2) but with GA 3 treatment (the GA3, was from Sigma Chemical Comp., St. Louis, Mo., USA). The hemp plants formed flower buds 17-19 d and the spinach plants 9-11 d after the beginning of the experiment. The growth of the adventitious roots in groups 2 and 3 was somewhat delayed, most probably because of the absence of leaves. F r o m T a b l e 1 a n d F i g u r e s 1 a n d 2 can be seen that, as in earlier e x p e r i m e n t s , in h e m p a n d s p i n a c h p l a n t s in which b o t h leaves a n d a d v e n t i t i o u s r o o t s were p r e s e n t ( g r o u p 1) the sex r a t i o in b o t h types o f p l a n t s s h o w e d a shift to the female side (82.4 a n d 84.7%, respectively). A similar shift t o w a r d the female side was o b s e r v e d in g r o u p 2 where a d v e n t i t i o u s r o o t s were a l l o w e d to d e v e l o p while the leaves were r e m o v e d after the a p p e a r a n c e o f a d v e n t i t i o u s r o o t s (80.0 a n d 86.1%, respectively). In g r o u p 3, which was t r e a t e d like g r o u p 2 b u t in a d d i t i o n received G A 3

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206

M. Kh. Chailakhyan and V.N. Khryanin: Leaves in Sex Expression in Hemp and Spinach Table l. Sex expression in hemp and spinach plants with and without leaves and the effect of GA 3 treatment Treatment

Fig. 1. The influence of gibberellic acid on sex expression in hemp plants. From left to right: plants with adventitious roots and leaves; with adventitious roots, without leaves; with adventitious roots, without leaves, treated with 25 rag/1 GAs for 28 h Fig. 2. The influence of gibberellic acid on sex expression in spinach plants. From left to right, 3 plants each: with adventitious roots and leaves; with adventitious roots without leaves; with adventitious roots, without leaves, treated with 25 mg/l GAa for 28 h

for 28 h, m o s t of the plants were f o u n d to be male (80.9% in hemp, 76.7% in spinach). The experiment thus shows that in the presence o f roots the sex is shifted t o w a r d the female side in plants both with and without leaves (groups 1, 2), but if GA3 is applied while the leaves are r e m o v e d the sex is shifted toward the male side (group 3). A n even stronger effect was obtained in an experiment with hemp. This experiment was quite similar to the previous one, but the leaves (expect the 2-3 u p p e r m o s t ones) in the 2nd and 3rd g r o u p were r e m o v e d immediately after the shoots had been cut off the roots, and GA3 applied to the plants of the 3rd g r o u p at the same time. R o o t regeneration in the 2rid and 3rd groups began only 24 d after the start o f the experiment and the roots failed to grow. Flower buds appeared in the 3rd g r o u p after 9 d while in the 1st and the 2rid groups they appeared after 17 and 21d. As can be seen in T a b l e 2 the majority o f the plants in group 3 became male (89.5%) while in g r o u p l, where the adventitious roots and the leaves were allowed to develop, the majority o f plants became female (86.2%). In g r o u p 2, where the adventitious roots were present and the leaves removed immediately after the cuttings were prepared, the n u m b e r o f male and female plants was

Hemp

Spinach

Male plants

Female plants

Male plants

Female plants

No. %

No. %

No. %

No. %

l) With adven- 15 titious roots and with leaves

17.6

70

82.4

16

15.3

89

84.7

2) With roots, 18 without leaves

20.0

72

80.0

14

13.9

87

86.1

3) With roots, 68 without leaves. + GA3

80.9

16

19.1

76

76.7

23

23.3

Table 2. The influence of leaves and of GA3 on sex expression in hemp plants Treatment

Male plants

Female plants

No.

%

No.

%

1) With adventitious roots and leaves

14

13,8

88

86.2

2) With roots, leaves removed immediately after the plants were cut off the primary root

50

52.6

45

47.4

3) As 2) but +GA3

94

89.5

11

10.5

approximately the same (52.6 and 47.4%, respectively). This result m a y be explained by the fact that the roots o f the plants appeared after flowers had began to be formed, and thus could not affect sex expression. On the basis of our results we suggest that the influence o f leaves on sex expression in h e m p and spinach plants is based u p o n the synthesis and export o f gibberellins by the leaves. C o m p a r i n g the results of these and earlier experiments (Chailakhyan and Khryanin, 1978 a, b, c) we conclude that leaves, as organs synthesizing gibberellins and enhancing male sex expression (production of staminate flowers) and roots as organs synthesizing cytokinins and enhancing female sex expression (production of pistillate flowers) play an essential role in sex expression of dioecious plants and that this role is quite similar in short- and long-day plants. The role o f gibberellins and cytoki-

M.Kh. Chailakhyan and V.N. Khryanin: Leaves in Sex Expression in Hemp and Spinach

nins does not rule out the participation of other phytohormones and growth regulators (auxins, synthetic growth substances, ethrel, and growth inhibitors) in sex expression in dioecious plants (see reviews in Frankel and Galun, 1977, pp. 135-161; Sidorsky, 1978).

References Chailakhyan, M.Kh.,: Hormonale Faktoren des Pflanzenblilhens. Biol. Zbl. 77, 641-662 (1958) Chailakhyan, M.Kh.: Internal factors of plant flowering. Ann. Rev. Plant Physiol. 19, 1 36 (1968)

207

Chailakhyan, M.Kh., Khryanin, V.N.: The influence of growth regulators absorbed by the root on sex expression in hemp plants. Planta 138, 181 184 (1978a) Chailakhyan, M.Kh., Khryanin, V.N.: The role of roots in sex expression in hemp plants. Planta 138, 185 187 (1978b) Chailakhyan, M.Kh., Khryanin, V.N. : Effect of growth regulators and role of roots in sex expression in spinach plants. Planta 142, 207 210 (1978c) Frankel, R., Galun, E. : Pollination mechanisms, reproduction and plant breeding. Berlin, Heidelberg, New York: Springer 1977 Sidorsky, A.G.: Changes of direction of sexual differentiation in plants under the influence of physiological active substances. (In Russ.) Uspekhi Sovrem. Biol. 85 (l), 111-124 (1978)

Received 10 July; accepted 6 September 1978

The role of leaves in sex expression in hemp and spinach.

When shoots of young plants of hemp (Cannabis sativa L.) and spinach (Spinacea oleracea L.) were cultured as cuttings and allowed to regenerate adveni...
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