- Email: [email protected]
Plant growth-regulating factor in the salivary gland of several heteropterous insects
Comp. Biochem. Physiol., 1976, Vol. 53B, pp. 435 to 438. Pergamon Press.
Printed in Great Britain
P L A N T GROWTH-REGULATING FACTOR IN THE SALIVARY G L A N D OF SEVERAL HETEROPTEROUS INSECTS* K. HORI
Division of Entomology and Plant Physiology, Obihiro Zootechnical University, Obihiro, Hokkaido, 080 Japan (Received 14 February 1975) Plant growth-regulating factor in the salivary gland was compared among several phytophagous bugs. 2. In the absence of IAA, the growth of Avena coleoptiles was significantly accelerated by the salivary gland solution of Adelphocoris suturalis. 3. In the presence of IAA, the growth of Arena coleoptiles was strongly promoted by the salivary gland solutions of Stenotus binotatus, Palomena angulosa, Carpocoris purpureipennis and Coreus marginatus orientalis with a significance at 5% level. 4. The extract from the fraction III of the salivary gland solutions of Lygus saundersi, Orthocephalus funestus and P. angulosa significantly accelerated the growth of Arena coleoptiles, exceeding that of the IAA control. 5. Almost all the bugs used seem to have auxin and/or factor indirectly promoting plant growth (IGPF) in their salivary gland. 6. The relationship between the presence of plant growth-promoting factor in the salivary gland and the phytopathogenicity of heteropterous insects is discussed. Abstract--l.
INTRODUCTION IT HAS been known that various plant-sucking invertebrates disturb the hormonal balance in their host plants by the feeding (increase or decrease of auxin and growth-inhibitors) (Nysterakis, 1948a; Avery & Lacey, 1968; Ishaaya & Sternlicht, 1969; Markkula & Laurema, 1971; Storms, 1971; Viglierchio, 1971; Brueske & Bergeson, 1972; Hussain et al., 1973). Schfiller (1968a) and Miles (1968a,b, 1972) ascribed the plant galls and malformations caused by the feeding of hemipterous insects partly to the 3-indoleacetic acid (IAA) that is either secreted in the saliva or may be formed from tryptophan by oxidative deamination brought about by salivary oxidases. Strong (1970) and Varis (1972) concluded that the lesions caused by the feeding of certain mirid bugs on their host plants were due to the mechanical destruction of the growing tissue by the stylets and to the chemical action of the salivary pectinase. In addition to these factors, Hori (1973, 1974) ascribed the malformations of sugar beet leaf caused by Lygus disponsi (Hori, 1967) to the toxic action of quinones produced in the injured tissue and to the plant growth-promoting substances in the saliva spreading to the surrounding tissues. Therefore, the plant growth-regulating factor in the salivary gland of hernipterous insects is of great importance in relation to their phytopathogenicity, but there have been only few works on this problem (Nysterakis, 1948b; Nuorteva, 1956; Cutler & Stimmann 1971; Markkula & Laurema, 1971). The present author reports the results of the bioassay of growth-regulating factor, especially plant growthpromoting factor, in the salivary gland of several phytophagous bugs with different degrees of phytopathogenicity. The results might clarify the relationship between the presence of the regulating * Contribution No. 62 from the Laboratory of Entomology, Obihiro Zootechnical University.
factor in the salivary gland and the toxicity of the bug to its host plant as well as the taxonomic position of the bug. MATERIALS AND METHODS
Insects used Plant growth-regulating factor in salivary gland was compared among the following nine species collected from the field: Lygus saundersi, Adelphocoris suturalis, Orthocephalus funestus and Stenotus binotatus (Miridae), Palomena angulosa, Eurydema rugosum and Carpocoris purpureipennis (Pentatomidae), and Coreus marginatus orientalis and Rhopalus maculatus (Coreidae). Preparation of salivary gland solution (test solution). The test solutions were prepared following the procedure previously employed by Hori 0974). The number of the bugs used for bioassay is shown in Table 1. Table 1. Arena bioassay of plant growth-regulating factor in the salivary gland of several bugs in the absence of IAA Species
No. of Insects used
Length of Aven~ e o l e o p t l l e (ms)
control
Salivary gland solution
CA)
(B)
Water
Dlffefence
CB - A)
L. saundersi
42
10.89
A. suturalis
50
10.39
i0.65"
103
0.26
O. funestua
50
10.77
10.89
101
0.12
S. blnot aZus
50
10.45
10.62
102
0.17
P. exuzu.1o~
40
10.39
10.63
102
0.24
E. ruA,o sum
50
10.45
10.59
i01
0.i0
C. ~urDur~i~en~is
19
10.77
10.83
I01
0.06
C. mar~ina%us ori~ntalis
22
10.89
11.02
i01
0.13
R. maev/a%ue
21
10.85
10.89
1(30
0.04
*
435
Slgnif:kcant a t 5 per cent l e v e l .
10.99
Relative value
i01
0.i0
K. HOR]
436
Bioassay for plant-regulating factor Bioassay was carried out by means of the straight elongation test of Arena coleoptile as previously reported by Hori (1974). For bioassay of the crude test solution, which was performed both in the presence and absence of IAA, 5 ml demineralized water (in the case where IAA was absent) or 5 ml 0.1 ppm 1AA solution (in the case where IAA was present), 0.5 ml test solution, and 15 Arena segments were put in a Petri dish of 4.5cm diameter. For the control (water and IAA controls), the 0.5 ml test solution was replaced by the same volume of demineralized water. For bioassay of the Rt fractions of the test solution, each of six equal R~ zones (I-VI fractions) fractionated by paperchromatography was placed in a Petri dish of 4-5 cm dia, to which 5 ml 0.1 ppm IAA solution and 15 Arena segmants were added. Controls with IAA solution alone and with demineralized water alone were included in the experiment. The experiment was repeated twice and the results were expressed as the average. RESULTS AND DISCUSSION
Bioassay for crude test solution in the absence of IAA The results are shown in Table 1. The growth of
Arena coleoptiles was significantly p r o m o t e d by the salivary gland solution of A. suturalis and, through not significantly, by those of L. saundersi, O. funestus, S. binotatus, P. angulosa, E. rugosum and C. marginatus orientalis. The results indicate that the salivary gland of A. suturalis obviously contains, and those of the latter bugs seem to contain, a factor directly p r o m o t i n g plant growth, auxin.
Bioassay for crude test solution in the presence of IAA The growth of Arena coleoptiles was strongly accelerated by the salivary gland solutions of S. binotatus, P angulosa, C. purpureipennis and C. marginatus orientalis with a significance at 5% level, and by those of L. saundersi, A. suturalis, O. funestus and E. rugosum with no significance (Table 2). It may safely be said that L. saundersi, S. binotatus, P. angulosa, C. purpureipennis and C.
marginatus orientalis have a factor indirectly promoting plant growth (IGPF), a factor promoting the activity of I A A or a factor inhibiting the activity of I A A - o x i d a s e , in the salivary gland, because these salivary gland solutions did not significantly p r o m o t e the plant growth in the absence of I A A (Table l), whereas they did significantly p r o m o t e it in the p r e s e n c e of I A A (Table 2) or because the difference b e t w e e n the elongation length of Arena coleoptile under the f o r m e r condition and that under the latter condition was relatively great (Tables l and 2). Bioassay for the Rf fraction of the test solution The results are shown in Figs. 1 and 2. The extract from fraction III of the salivary gland solutions of L. saundersi, O. funestus and P. angulosa significantly accelerated the growth of Arena coleoptiles, e x c e e d i n g that of the IAA control. In the case of L. saundersi, the fraction IV also significantly accelerated the plant growth. Though not significantly, the fraction III of the salivary gland solutions of all other bugs with the e x c e p t i o n of R. maculatus accelerated the plant growth more strongly than the other fractions and the I A A control. Hori (1974) also found the strongest plant growth-promoting activity in the fraction III of the salivary gland solution of Lygus disponsi. Since the figures in the cases of O. funestus and P. angulosa, and of A. suturalis, S. binotatus, E. rugosum, and C. purpureipennis were relatively similar to those of L. saundersi and of C. marginatu~ orientalis, respectively, they were not illustrated. F r o m the a b o v e three experiments, one may well draw the following conclusions: L. saundersi; The
~u
m
~ ,3 !~
Table 2. Arena bioassay of plant growth-regulating factor in the salivary gland of several bugs in the presence of 1AA
Water control
IAA control
q
v
vl
CONTROL A N D FRACTION
Length of Arena coleoptile (mm)
Species
IAA
control
(A)
Salivary gland solution
Relative value
(B)
Difference
(~ - A)
L. saundersi
13,23
13.45
102
0.22
A, suturalis
11.98
12.22
102
0.24
0. fttnestus
12.42
12.b0
101
0.18
Fig. 1. Plant growth-regulating factor in each fraction of the salivary gland solution of L. saundersi. Black area represents promoting activity differing significantly from IAA control at 5% level. ~ 14
13 W S. binotatus
11.99
12.45"
104
0.46
F. an~ulosa
11.98
12.45"
104
0.45
11.99
12.18
102
0.19
C ~ our~ureiDer,nia
12.42
12.81"
103
0.59
C. marglnatus 9rientalis
13.23
13.70*
104
0.47
R, maculatu8
13.01
13,O7
ILK)
0.~o
:;.
•
rugosum
Significant at 5 per cent level.
]2 # z 11
18
Water control
IAA control
I
II
III
CON]ROt. AND FRACIIQN
IV
tl v
vl
Fig. 2. Plant growth-regulating factor in each fraction of the salivary gland solution of C. mur~inatus orientalis.
Plant growth-regulating factor in the salivary gland of several heteropterous insects salivary gland contains I G P F in addition to a small amount of auxin. A. suturalis; The salivary gland contains only auxin but no IGPF. O. [unestus; The salivary gland has a weak auxin- and a relatively strong IGPF-activity, since the fraction III of the salivary gland solution significantly promoted the plant growth, although the crude solution itself did not significantly promote it in the presence of I A A (Table 2). This seems to be due to the plant growth-inhibiting factor contained in the crude salivary gland solution. S. binotatus; The salivary gland includes a strong IGPF-activity as well as a weak auxin-activity. The reason why all the fraction showed no significant plant growthpromoting activity in spite of the presence of a significant activity in the crude solution (Table 2) may be that the activity was divided into various fractions. P. angulosa; The salivary gland contains a small amount of auxin and a large amount of IGPF. The plant growth-promoting activity of the crude salivary gland solution in the presence of I A A was lower than that of the fraction III of the salivary gland solution (Table 2). This result seems to be attributable to the plant growth-inhibiting factor present in the crude salivary gland solution. E. rugosum; The salivary gland seems to include a weak auxin- and a weak IGPF-activity. C. purpureipennis; The salivary gland has a very weak auxin- and a strong IGPF-activity. The plant growth-promoting aqtivity of the crude salivary gland solution in the presence of I A A was significantly higher than that of the I A A control (Table 2), whereas none of the fractions in the salivary gland solution was significantly higher in sensitivity than the I A A control. This result seems to be due to the same reason as in the case of S. binotatus. C. marginatus orientalis; The salivary gland has a weak auxin- and a strong IGPF-activity. The fact that the crude salivary gland solution in the presence of I A A showed itself a significant plant growth-promoting activity, whereas each fraction of the salivary gland solution did exhibit no significant activity (Fig. 2) may be due to the same reason as in the cases of S. binotatus and C. purpureipennis. R. maculatus; N o plant growthpromoting factor was detected in the salivary gland, possibly because of small number of the salivary glands used for the bioassay. Many aphid species have I A A in their saliva (Sch~iller, 1968a) and a certain cercopid has a plant-growth promotor in its salivary gland (Cutler & Stimmann, 1971), while several mirid bugs in natural tested so far have neither I A A nor other auxins in their saliva (Nuorteva, 1959; Strong, 1970; Hori, 1974). In the present study, it was found that most of bugs used included a small amount of auxin, although it was not always significant, and a factor indirectly promoting plant growth (IGPF) in their salivary gland as well as in that of L. disponsi (Hori, 1974). There seems to be no specific relationship between their presence and the kind of family to which the bug belongs. However, further investigations are needed, since there is a possibility that the distribution pattern of plant growthpromoting factor in the fractions of the salivary gland solution differs among the families or genera. Sch~iller (1968a,b) and Miles (1968a, b, 1972)
437
ascribed the phytopathogenicity of some hemipterous insects to the I A A which was secreted in the saliva or which might be formed from tryptophan by oxidative deamination brought about by the salivary phenoloxidases. Hori (1974) inferred that the malformations of sugar beet leaf caused by the feeding of L. disponsi was attributable partly to the toxic action of quinones produced in the injured tissue and the growth-promoting activity in the saliva spreading to the surrounding tissues. Thus the plant growth-promoting factor in the salivary gland comes out to be an important problem in relation to the phytopathogenicity of hemipterous insects. The present study indicated that almost all the bugs used had auxin or other plant growthpromoting factor in their salivary gland and so a potential toxicity to their host plants. However, the injury pattern caused by the feeding differs among the kinds of bug or host plant. It is possible, therefore, that the malformations induced on host plant depend not only the plant growthpromoting factor in the salivary gland but also the feeding habit of the bug, the physiological condition of the host plant and so on. The synthetic study including the studies on the salivary physiology and the feeding habit of hemipterous insects, the change of composition in the injured plants and the reaction of host plants to the insect attack is essential for the study on the physiology of plant injury caused by hemipterous insects. Acknowledgement--The author wishes to express his sincere thanks to Professor Y. Nishijima of the Obihiro Zootechnical University for valuable discussion and criticism throughout this work. REFERENCES AVERY D. J. & LACEY H. J. (1968) Changes in growth regulator content of plum infested with fruit tree red spider mite Panonychus ulmi (Koch). J. exp. Bot. 19, 760-769. BRUESKEC. H. & BERGESONG. B. (1972) Investigation of growth hormones in xylem exudate and root tissue of tomato infested with root-knot nematode. J. exp. Bot. 23, 14-22. CULTERH. G. & STIMMANNM. W. (1971) The presence of plant growth promotor in isolated salivary glands of Prosapia bicincta (Homoptera: Cercopidae). J. Georgia Entomol. Soc. 6, 69-72. HORI K. (1967) Studies on the salivary gland, feeding habits and injury of Lygus disponsi Linnavuori (Hemiptera, Miridae)--I. Morphology of the salivary gland and the symptoms of host plant. Res. Bull. Obihiro Univ. 5, 55-74. HORI K. (1973) Studies on the feeding habits of Lygus disponsi Linnavuori (Hemiptera: Miridae) and the injury to its host plant--III. Phenolic compounds, acid phosphatase and oxidative enzymes in the injured tissue of sugar beet leaf. Appl. Ent. Zool. 8, 103-112. HORX K. (1974) Plant growth-promoting factor in the salivary gland of the bug, Lygus disponsi. J. Insect Physiol. 20, 1623-1627. HUSSAIN A., FORRESTJ. M. S. & DIXON A. F. G. (1973) Changes in growth regulator content of radish seedlings, Raphanus sativus, infested with the aphid Myzus persicae. Ann. appl. Biol. 75, 275-284. ISHAAYAI. & STERNLICHTM. (1969) Growth accelerators and inhibitors in lemon buds infested by Aceria sheldoni (Ewing) (Acrina: Eriophyda) J. exp. Bot. 20, 796.804.
438
K. HORI
MARKKULA M. & LAUREMA S. (1971) Phytotoxaemia caused by Trioza apicalis F6rst. (Hom., Triozidae) on carrot. Ann. agric. Fenn. 10, 181-184. M~LES P. W. (1968a) Studies on the salivary physiology of plant-bugs: experimental induction of galls. J. Insect Physiol. 14, 97-106. M~LES P. W. (1968b) Insect secretions in plants. Rev. Phytopath. 6, 137-164. MILES P. W. (1972) The saliva of Hemiptera. Adv. Insect Physiol. 9, 183-256. NUORTEVA P. (1956) Studies on the effect of the salivary secretions of some Heteroptera and Homoptera on plant growth. Suom. Hybnt. Aikak. 22, 108-117. NYSTERAKIS F. (1948a) Phytohormones et inhibition de la croissance des oranges vegetaux attaques par des aphides. C.r. hebd. seanc. Acad. Sci. Paris 226,746-747. NYSTERAKIS F. (1948b) Autres preuves sur la secretion d'aukines par certains insectes. Un nouveau test, tres
sensible pour le dossage des substances de croissance. C.r. hebd. seanc. Acad. Sci., Paris 226, 1917-1919. SCHALLER G. (1968a) Biochemische Analyse des Aphidenspeichels und seine Bedeutung fiir die Gallenbildung. Zool. Jb. Physiol. 74, 57-87. SCHALLER G. (1968b) Untersuchung zur Erzeugung kiinstlicher Pflanzengallen. Marcellia 35, 131-153. STORMS J. J. H. (1971) Some physiological effects of spider mite infestation on bean plants. Neth. J. Plant Path. 77, 154--!67. STRONG F. E. (1970) Physiology of injury caused by Lygus hesperus. J. econ. Ent. 63, 808-814. VARIS A.-L. (1972) The biology of Lygus rugulipennis popp. (Het., Miridae) and the damage caused by this species to sugar beet. Ann. agric. Fenn. 11, 1-56. V~GLIERCmO D. R. (1971) Nematodes and other pathogens in auxin-related plant-growth disorders. Bot. Rev. 37, 1-21.
Printed in Great Britain
P L A N T GROWTH-REGULATING FACTOR IN THE SALIVARY G L A N D OF SEVERAL HETEROPTEROUS INSECTS* K. HORI
Division of Entomology and Plant Physiology, Obihiro Zootechnical University, Obihiro, Hokkaido, 080 Japan (Received 14 February 1975) Plant growth-regulating factor in the salivary gland was compared among several phytophagous bugs. 2. In the absence of IAA, the growth of Avena coleoptiles was significantly accelerated by the salivary gland solution of Adelphocoris suturalis. 3. In the presence of IAA, the growth of Arena coleoptiles was strongly promoted by the salivary gland solutions of Stenotus binotatus, Palomena angulosa, Carpocoris purpureipennis and Coreus marginatus orientalis with a significance at 5% level. 4. The extract from the fraction III of the salivary gland solutions of Lygus saundersi, Orthocephalus funestus and P. angulosa significantly accelerated the growth of Arena coleoptiles, exceeding that of the IAA control. 5. Almost all the bugs used seem to have auxin and/or factor indirectly promoting plant growth (IGPF) in their salivary gland. 6. The relationship between the presence of plant growth-promoting factor in the salivary gland and the phytopathogenicity of heteropterous insects is discussed. Abstract--l.
INTRODUCTION IT HAS been known that various plant-sucking invertebrates disturb the hormonal balance in their host plants by the feeding (increase or decrease of auxin and growth-inhibitors) (Nysterakis, 1948a; Avery & Lacey, 1968; Ishaaya & Sternlicht, 1969; Markkula & Laurema, 1971; Storms, 1971; Viglierchio, 1971; Brueske & Bergeson, 1972; Hussain et al., 1973). Schfiller (1968a) and Miles (1968a,b, 1972) ascribed the plant galls and malformations caused by the feeding of hemipterous insects partly to the 3-indoleacetic acid (IAA) that is either secreted in the saliva or may be formed from tryptophan by oxidative deamination brought about by salivary oxidases. Strong (1970) and Varis (1972) concluded that the lesions caused by the feeding of certain mirid bugs on their host plants were due to the mechanical destruction of the growing tissue by the stylets and to the chemical action of the salivary pectinase. In addition to these factors, Hori (1973, 1974) ascribed the malformations of sugar beet leaf caused by Lygus disponsi (Hori, 1967) to the toxic action of quinones produced in the injured tissue and to the plant growth-promoting substances in the saliva spreading to the surrounding tissues. Therefore, the plant growth-regulating factor in the salivary gland of hernipterous insects is of great importance in relation to their phytopathogenicity, but there have been only few works on this problem (Nysterakis, 1948b; Nuorteva, 1956; Cutler & Stimmann 1971; Markkula & Laurema, 1971). The present author reports the results of the bioassay of growth-regulating factor, especially plant growthpromoting factor, in the salivary gland of several phytophagous bugs with different degrees of phytopathogenicity. The results might clarify the relationship between the presence of the regulating * Contribution No. 62 from the Laboratory of Entomology, Obihiro Zootechnical University.
factor in the salivary gland and the toxicity of the bug to its host plant as well as the taxonomic position of the bug. MATERIALS AND METHODS
Insects used Plant growth-regulating factor in salivary gland was compared among the following nine species collected from the field: Lygus saundersi, Adelphocoris suturalis, Orthocephalus funestus and Stenotus binotatus (Miridae), Palomena angulosa, Eurydema rugosum and Carpocoris purpureipennis (Pentatomidae), and Coreus marginatus orientalis and Rhopalus maculatus (Coreidae). Preparation of salivary gland solution (test solution). The test solutions were prepared following the procedure previously employed by Hori 0974). The number of the bugs used for bioassay is shown in Table 1. Table 1. Arena bioassay of plant growth-regulating factor in the salivary gland of several bugs in the absence of IAA Species
No. of Insects used
Length of Aven~ e o l e o p t l l e (ms)
control
Salivary gland solution
CA)
(B)
Water
Dlffefence
CB - A)
L. saundersi
42
10.89
A. suturalis
50
10.39
i0.65"
103
0.26
O. funestua
50
10.77
10.89
101
0.12
S. blnot aZus
50
10.45
10.62
102
0.17
P. exuzu.1o~
40
10.39
10.63
102
0.24
E. ruA,o sum
50
10.45
10.59
i01
0.i0
C. ~urDur~i~en~is
19
10.77
10.83
I01
0.06
C. mar~ina%us ori~ntalis
22
10.89
11.02
i01
0.13
R. maev/a%ue
21
10.85
10.89
1(30
0.04
*
435
Slgnif:kcant a t 5 per cent l e v e l .
10.99
Relative value
i01
0.i0
K. HOR]
436
Bioassay for plant-regulating factor Bioassay was carried out by means of the straight elongation test of Arena coleoptile as previously reported by Hori (1974). For bioassay of the crude test solution, which was performed both in the presence and absence of IAA, 5 ml demineralized water (in the case where IAA was absent) or 5 ml 0.1 ppm 1AA solution (in the case where IAA was present), 0.5 ml test solution, and 15 Arena segments were put in a Petri dish of 4.5cm diameter. For the control (water and IAA controls), the 0.5 ml test solution was replaced by the same volume of demineralized water. For bioassay of the Rt fractions of the test solution, each of six equal R~ zones (I-VI fractions) fractionated by paperchromatography was placed in a Petri dish of 4-5 cm dia, to which 5 ml 0.1 ppm IAA solution and 15 Arena segmants were added. Controls with IAA solution alone and with demineralized water alone were included in the experiment. The experiment was repeated twice and the results were expressed as the average. RESULTS AND DISCUSSION
Bioassay for crude test solution in the absence of IAA The results are shown in Table 1. The growth of
Arena coleoptiles was significantly p r o m o t e d by the salivary gland solution of A. suturalis and, through not significantly, by those of L. saundersi, O. funestus, S. binotatus, P. angulosa, E. rugosum and C. marginatus orientalis. The results indicate that the salivary gland of A. suturalis obviously contains, and those of the latter bugs seem to contain, a factor directly p r o m o t i n g plant growth, auxin.
Bioassay for crude test solution in the presence of IAA The growth of Arena coleoptiles was strongly accelerated by the salivary gland solutions of S. binotatus, P angulosa, C. purpureipennis and C. marginatus orientalis with a significance at 5% level, and by those of L. saundersi, A. suturalis, O. funestus and E. rugosum with no significance (Table 2). It may safely be said that L. saundersi, S. binotatus, P. angulosa, C. purpureipennis and C.
marginatus orientalis have a factor indirectly promoting plant growth (IGPF), a factor promoting the activity of I A A or a factor inhibiting the activity of I A A - o x i d a s e , in the salivary gland, because these salivary gland solutions did not significantly p r o m o t e the plant growth in the absence of I A A (Table l), whereas they did significantly p r o m o t e it in the p r e s e n c e of I A A (Table 2) or because the difference b e t w e e n the elongation length of Arena coleoptile under the f o r m e r condition and that under the latter condition was relatively great (Tables l and 2). Bioassay for the Rf fraction of the test solution The results are shown in Figs. 1 and 2. The extract from fraction III of the salivary gland solutions of L. saundersi, O. funestus and P. angulosa significantly accelerated the growth of Arena coleoptiles, e x c e e d i n g that of the IAA control. In the case of L. saundersi, the fraction IV also significantly accelerated the plant growth. Though not significantly, the fraction III of the salivary gland solutions of all other bugs with the e x c e p t i o n of R. maculatus accelerated the plant growth more strongly than the other fractions and the I A A control. Hori (1974) also found the strongest plant growth-promoting activity in the fraction III of the salivary gland solution of Lygus disponsi. Since the figures in the cases of O. funestus and P. angulosa, and of A. suturalis, S. binotatus, E. rugosum, and C. purpureipennis were relatively similar to those of L. saundersi and of C. marginatu~ orientalis, respectively, they were not illustrated. F r o m the a b o v e three experiments, one may well draw the following conclusions: L. saundersi; The
~u
m
~ ,3 !~
Table 2. Arena bioassay of plant growth-regulating factor in the salivary gland of several bugs in the presence of 1AA
Water control
IAA control
q
v
vl
CONTROL A N D FRACTION
Length of Arena coleoptile (mm)
Species
IAA
control
(A)
Salivary gland solution
Relative value
(B)
Difference
(~ - A)
L. saundersi
13,23
13.45
102
0.22
A, suturalis
11.98
12.22
102
0.24
0. fttnestus
12.42
12.b0
101
0.18
Fig. 1. Plant growth-regulating factor in each fraction of the salivary gland solution of L. saundersi. Black area represents promoting activity differing significantly from IAA control at 5% level. ~ 14
13 W S. binotatus
11.99
12.45"
104
0.46
F. an~ulosa
11.98
12.45"
104
0.45
11.99
12.18
102
0.19
C ~ our~ureiDer,nia
12.42
12.81"
103
0.59
C. marglnatus 9rientalis
13.23
13.70*
104
0.47
R, maculatu8
13.01
13,O7
ILK)
0.~o
:;.
•
rugosum
Significant at 5 per cent level.
]2 # z 11
18
Water control
IAA control
I
II
III
CON]ROt. AND FRACIIQN
IV
tl v
vl
Fig. 2. Plant growth-regulating factor in each fraction of the salivary gland solution of C. mur~inatus orientalis.
Plant growth-regulating factor in the salivary gland of several heteropterous insects salivary gland contains I G P F in addition to a small amount of auxin. A. suturalis; The salivary gland contains only auxin but no IGPF. O. [unestus; The salivary gland has a weak auxin- and a relatively strong IGPF-activity, since the fraction III of the salivary gland solution significantly promoted the plant growth, although the crude solution itself did not significantly promote it in the presence of I A A (Table 2). This seems to be due to the plant growth-inhibiting factor contained in the crude salivary gland solution. S. binotatus; The salivary gland includes a strong IGPF-activity as well as a weak auxin-activity. The reason why all the fraction showed no significant plant growthpromoting activity in spite of the presence of a significant activity in the crude solution (Table 2) may be that the activity was divided into various fractions. P. angulosa; The salivary gland contains a small amount of auxin and a large amount of IGPF. The plant growth-promoting activity of the crude salivary gland solution in the presence of I A A was lower than that of the fraction III of the salivary gland solution (Table 2). This result seems to be attributable to the plant growth-inhibiting factor present in the crude salivary gland solution. E. rugosum; The salivary gland seems to include a weak auxin- and a weak IGPF-activity. C. purpureipennis; The salivary gland has a very weak auxin- and a strong IGPF-activity. The plant growth-promoting aqtivity of the crude salivary gland solution in the presence of I A A was significantly higher than that of the I A A control (Table 2), whereas none of the fractions in the salivary gland solution was significantly higher in sensitivity than the I A A control. This result seems to be due to the same reason as in the case of S. binotatus. C. marginatus orientalis; The salivary gland has a weak auxin- and a strong IGPF-activity. The fact that the crude salivary gland solution in the presence of I A A showed itself a significant plant growth-promoting activity, whereas each fraction of the salivary gland solution did exhibit no significant activity (Fig. 2) may be due to the same reason as in the cases of S. binotatus and C. purpureipennis. R. maculatus; N o plant growthpromoting factor was detected in the salivary gland, possibly because of small number of the salivary glands used for the bioassay. Many aphid species have I A A in their saliva (Sch~iller, 1968a) and a certain cercopid has a plant-growth promotor in its salivary gland (Cutler & Stimmann, 1971), while several mirid bugs in natural tested so far have neither I A A nor other auxins in their saliva (Nuorteva, 1959; Strong, 1970; Hori, 1974). In the present study, it was found that most of bugs used included a small amount of auxin, although it was not always significant, and a factor indirectly promoting plant growth (IGPF) in their salivary gland as well as in that of L. disponsi (Hori, 1974). There seems to be no specific relationship between their presence and the kind of family to which the bug belongs. However, further investigations are needed, since there is a possibility that the distribution pattern of plant growthpromoting factor in the fractions of the salivary gland solution differs among the families or genera. Sch~iller (1968a,b) and Miles (1968a, b, 1972)
437
ascribed the phytopathogenicity of some hemipterous insects to the I A A which was secreted in the saliva or which might be formed from tryptophan by oxidative deamination brought about by the salivary phenoloxidases. Hori (1974) inferred that the malformations of sugar beet leaf caused by the feeding of L. disponsi was attributable partly to the toxic action of quinones produced in the injured tissue and the growth-promoting activity in the saliva spreading to the surrounding tissues. Thus the plant growth-promoting factor in the salivary gland comes out to be an important problem in relation to the phytopathogenicity of hemipterous insects. The present study indicated that almost all the bugs used had auxin or other plant growthpromoting factor in their salivary gland and so a potential toxicity to their host plants. However, the injury pattern caused by the feeding differs among the kinds of bug or host plant. It is possible, therefore, that the malformations induced on host plant depend not only the plant growthpromoting factor in the salivary gland but also the feeding habit of the bug, the physiological condition of the host plant and so on. The synthetic study including the studies on the salivary physiology and the feeding habit of hemipterous insects, the change of composition in the injured plants and the reaction of host plants to the insect attack is essential for the study on the physiology of plant injury caused by hemipterous insects. Acknowledgement--The author wishes to express his sincere thanks to Professor Y. Nishijima of the Obihiro Zootechnical University for valuable discussion and criticism throughout this work. REFERENCES AVERY D. J. & LACEY H. J. (1968) Changes in growth regulator content of plum infested with fruit tree red spider mite Panonychus ulmi (Koch). J. exp. Bot. 19, 760-769. BRUESKEC. H. & BERGESONG. B. (1972) Investigation of growth hormones in xylem exudate and root tissue of tomato infested with root-knot nematode. J. exp. Bot. 23, 14-22. CULTERH. G. & STIMMANNM. W. (1971) The presence of plant growth promotor in isolated salivary glands of Prosapia bicincta (Homoptera: Cercopidae). J. Georgia Entomol. Soc. 6, 69-72. HORI K. (1967) Studies on the salivary gland, feeding habits and injury of Lygus disponsi Linnavuori (Hemiptera, Miridae)--I. Morphology of the salivary gland and the symptoms of host plant. Res. Bull. Obihiro Univ. 5, 55-74. HORI K. (1973) Studies on the feeding habits of Lygus disponsi Linnavuori (Hemiptera: Miridae) and the injury to its host plant--III. Phenolic compounds, acid phosphatase and oxidative enzymes in the injured tissue of sugar beet leaf. Appl. Ent. Zool. 8, 103-112. HORX K. (1974) Plant growth-promoting factor in the salivary gland of the bug, Lygus disponsi. J. Insect Physiol. 20, 1623-1627. HUSSAIN A., FORRESTJ. M. S. & DIXON A. F. G. (1973) Changes in growth regulator content of radish seedlings, Raphanus sativus, infested with the aphid Myzus persicae. Ann. appl. Biol. 75, 275-284. ISHAAYAI. & STERNLICHTM. (1969) Growth accelerators and inhibitors in lemon buds infested by Aceria sheldoni (Ewing) (Acrina: Eriophyda) J. exp. Bot. 20, 796.804.
438
K. HORI
MARKKULA M. & LAUREMA S. (1971) Phytotoxaemia caused by Trioza apicalis F6rst. (Hom., Triozidae) on carrot. Ann. agric. Fenn. 10, 181-184. M~LES P. W. (1968a) Studies on the salivary physiology of plant-bugs: experimental induction of galls. J. Insect Physiol. 14, 97-106. M~LES P. W. (1968b) Insect secretions in plants. Rev. Phytopath. 6, 137-164. MILES P. W. (1972) The saliva of Hemiptera. Adv. Insect Physiol. 9, 183-256. NUORTEVA P. (1956) Studies on the effect of the salivary secretions of some Heteroptera and Homoptera on plant growth. Suom. Hybnt. Aikak. 22, 108-117. NYSTERAKIS F. (1948a) Phytohormones et inhibition de la croissance des oranges vegetaux attaques par des aphides. C.r. hebd. seanc. Acad. Sci. Paris 226,746-747. NYSTERAKIS F. (1948b) Autres preuves sur la secretion d'aukines par certains insectes. Un nouveau test, tres
sensible pour le dossage des substances de croissance. C.r. hebd. seanc. Acad. Sci., Paris 226, 1917-1919. SCHALLER G. (1968a) Biochemische Analyse des Aphidenspeichels und seine Bedeutung fiir die Gallenbildung. Zool. Jb. Physiol. 74, 57-87. SCHALLER G. (1968b) Untersuchung zur Erzeugung kiinstlicher Pflanzengallen. Marcellia 35, 131-153. STORMS J. J. H. (1971) Some physiological effects of spider mite infestation on bean plants. Neth. J. Plant Path. 77, 154--!67. STRONG F. E. (1970) Physiology of injury caused by Lygus hesperus. J. econ. Ent. 63, 808-814. VARIS A.-L. (1972) The biology of Lygus rugulipennis popp. (Het., Miridae) and the damage caused by this species to sugar beet. Ann. agric. Fenn. 11, 1-56. V~GLIERCmO D. R. (1971) Nematodes and other pathogens in auxin-related plant-growth disorders. Bot. Rev. 37, 1-21.