KENAF
Hibiscus cannabinus L., family MalvaceaeKenaf has been grown for centuries throughout the world as a fiber crop. A few thousand acres are grown in Florida for bean poles (Killinger 1969). Recently, it has been tested as a silage crop and for paper pulp (Killinger 1965,1967). In general, kenaf is grown between 45deg N and 30deg S latitudes (Purseglove 1968*).
Plant:
Kenaf is an erect herbaceous annual, 4 to 22 feet tall (Pate et al. 1954, Killinger 1965), with straight and slender green, red, or purple prickly stems. It is photoperiodic, flowering on shortening days of 12.5 hours or less. When grown for seed, 700 to 800 lb/acre have been harvested. The fruit is a capsule of several carpers, each producing several seeds.
When grown for bean poles or forage, the plant, itself, is harvested (Killinger 1967). About 200,000 poles per acre are harvested when the plant is about 10 feet tall and before it blooms. Only when seed production is desired is the plant allowed to remain through flowering and until the pods are ripe and harvested. Killinger (1969) stated that some cultivars are ready for harvest in early July to early September from seeds planted March 27 to April 5 (120 to 160 days), whereas other cultivars are ready within 60 days, and still other cultivars produce seed and are dead within 100 days after planting.
Inflorescence:
The flowers, similar to those of cotton, okra, or the common hollyhock (Althea rosea (L.) Cav.), are large (7.5 to 10 cm) with five yellow or red petals with crimson-centers. They usually open just before daybreak, begin to close about midday, and are closed by mid-afternoon never to open again. Within the corolla, the staminal column, with its short stamens, surrounds the style. The anthers release pollen about the time the flower opens, and the style emerges shortly thereafter. Then, the five-part stigma expands; the lobes become turgid but do not touch the anthers. The corolla closes spirally so that the anthers are pressed into contact with the stigma, and, if cross-pollination has not occurred, self- pollination may result. However, Ochse et al. (1961 *) stated that pollen of the same flower is seldom found on the stigma. Nectar is secreted at the base of the corolla. Nesmeyanova (1968) stated that only the nectaries on the outside of the calyx were well visited by bees, but Jones and Tamargo (1954) and Tamargo and Jones (1954) stated that honey bees visited within the blossom sufficiently to be considered efficient pollinators.
Pollination Requirements The pollination requirement of kenaf is not too well worked out. Pate and Joyner (1958) stated that kenaf has been classified on several occasions as a self-pollinated crop, but that more recently it has been classified as an often cross-pollinated crop. In a hand-pollination experiment, Dubey and Singh (1968) observed that some setting began by 11 p.m. and extended to the next 2 p.m., but only between 5 and 9 a.m. did more than 50 percent set. This would indicate that the spiraling action of the closing corolla would likely contribute to perpetuation of the species if previous pollination had failed but would not result in maximum fruit set. Crane (1947) (citing Ustinova 1938) stated that cv. 'Viridis' is entirely self-pollinated while cv. 'Vulgaris' is cross-pollinated 2.6 to 2.9 percent of the time.
As early as 1911, Howard and Howard (1911) concluded that the opportunities for cross-pollination are very great; however, studies on pollination of kenaf have dealt mainly with the effects of cross- pollination between strains, with little attention given to the effect of pollination on total production of seed.
Pollinators:
Jones and Tamargo (1954) concluded that wind is not a factor in kenaf pollen dispersal. A wasp (Campsomeris trifasciata (F.) was observed in the field (in Cuba) throughout the flowering period; however, it visited only the extrafloral nectaries on the seed capsule during most of the flowering season. A wild bee (Examalopsis similis Cresson) and a carpenter bee (Xylocopa cubaecola Lucas) were seen occasionally in kenaf flowers, but their numbers were too small to be of significance. Jones and Tamargo (1954) concluded that the honey bee was by far the most important insect involved in the pollination of kenaf flowers. It visited an average of 1.36 flowers per minute, 20 per foraging trip, and individual flowers were visited by an average of 16.7 (plus or minus)1.8 bees per day. The peak of honey bee visitation was between 11:30 am. and 2 p.m. No indication was given as to the honey bee colony concentration in the area. Jones et al. (1956) recorded a decreasing amount of crossing with increased distance from the plot of marker plants, when five colonies of honey bees were 1 mile away.
No determinations have been made on the effect of pollination on production of kenaf seed. Like its near relative, the cotton plant, kenaf may produce a crop of self-pollinated seed, but possibly at least some cultivars may produce significantly more seed if the flowers are cross- pollinated. This phase in the economics of seed-production should be investigated.
Pollination Recommendations and Practices:
Tamargo and Jones (1954) concluded that the percentage of natural crossing might be greatly increased if compatible cultivars of similar maturity dates were grown where large populations of honey bees were present. Jones and Tamargo (1954) dealing with the same subject, stated that "If the bee population were increased by placing hives of bees around the kenaf field at flowering time, obviously the number of visits per flower could be increased. Likewise the amount of natural crossing could probably be greatly increased."
Other than these rather vague recommendations for placement of colonies of bees in kenaf fields, there are no recommendations for the use of pollinating agents on kenaf.
LITERATURE CITED:
CRANE, J. C.
1947. KENAF - FIBER PLANT RIVAL OF JUTE. Econ. Bot. 1: 334-350.DUBEY, R. S., and SINGH, S. P.
1968. NOTE ON STIGMA RECEPTIVITY IN KENAF. Indian Jour. Agr. Sci. 38(1): 195 - 197.HOWARD, A., and HOWARD, G. L. C.
1911. STUDIES IN SOME INDIAN FIBRE PLANTS. II. ON SOME NEW VARIETIES IN HIBISCUS CANNABINUS L. AND HIBISCUS SABDARIFFA L. Indian Dept. Agr. Mem. Bot. Ser. 4: 1 - 36.JONES, D., PUENTES, C., and SUAREZ, R.
1955. ISOLATION OF KENAF FOR SEED INCREASE. Agron. Jour. 47: 256.JONES, M. D., and TAMARGO, M. A.
1954. AGENTS CONCERNED WITH NATURAL CROSSING OF KENAF IN CUBA. Agron. Jour. 46: 459 - 462.KILLINGER, G. B.
1965. KENAF - POTENTIAL PAPER-PULP CROP FOR FLORIDA. Fla. Agr. Expt. Sta. Agr. Res. RPt. 10(2): 4-5.KILLINGER, G. B.
1967. POTENTIAL USES OF KENAF (HIBISCUS CANNABINUS L.). Soil and Crop Sci. Soc. Fla. Proc. 27: 4-11.______ 1969. KENAF (HIBISCUS CANNABINUS L. ) A MULTI-USE CROP. Agron. Jour. 61: 734-736.
NESMEYANOVA, A. D.
1968. [SOME DATA ON THE NECTARIES OF THE AMBARY HIBISCUS CANNABINUS (KENAF).] Uzbek. Biol. Zhur. 12(1): 38 - 40. [In Russian, English summary.]PATE, J. B., SEALE, C. C., and GANGSTAD, E. O.
1954. VARIETAL STUDIES OF KENAF, HIBISCUS CANNABINUS L. IN SOUTH FLORIDA. Agron. Jour. 46 75.______and JOYNER, J, F.
1958. THE INHERITANCE OF A MALE STERILITY FACTOR IN KENAF, HIBISCUS CANNABINUS L. Agron. Jour. 50: 402.TAMARGO M. A., and JONES, M. D.
1951. NATURAL CROSS-FERTILIZATION IN KENAF. Agron. Jour. 46: 456 - 459.USTINOVA E. I.
1938. [CROSS-POLLINATION IN HIBTSCUS CANNABINUS.] Selek. i Semen. 6: 32-33. [In Russian.]
