Manthriratna, M.A.P.

Sambasivam, S.

Coconut Research Institute Repository

Ceylon Cocon. Q. (1974) 25, 105-108 Printed in Sri Lanka. STOMATAL DENSITY IN VARIETIES AND FORMS OF THE COCONUT COCOS NUCIFERA L. M. A. P. P. M A N T H R I R A T N A and S. S A M B A S I V A M Coconut Research Institute, Lunuwila, Sri Lanka. S U M M A R Y An assessment of stomatal densities of varieties and forms of the coconut palm (Coca nucifera L . ) , indicates that this may be a varietal characteristic. Variations due to the environ ment are negligible. Al l three colour forms of the self-pollinating nana variety have more stomat i per unit area of leaf surface than the varieties typica and aurantiaca. Stomatal density may b? of use in identifying typica x pumila F t hybrids. I N T R O D U C T I O N Studies on leaf anatomy of several plant species have revealed that the number of stomata per unit area of the leaf surface is, within certain limits, a characteristic of the particular specie.; or variety under consideration. Observations have also been made that the environment can influence stomatal size and frequency. ' The estimation of stomatal size and frequency is a useful tool in plant breeding, parti­cularly, in screening diploids from tetraploids (Speckmann et. al. 1965). I n tree crops, stomatal density has also been used to identify different races and clones of forest trees (Muhle Larsen, 1957), as well as apple cultivars, (Lihonas &Bolasova 1964).Studies carried out on Hevea species (Senanayake & Samaranayaka 1970), revealed differences in the density of stomata per unit area among twenty-five cultivars and breeders clones. They further report that there is no detectable relationship between stomatal density and yield. According to Menon & Pandalai (1958), nearly 200 stomata occur in each square millimetre of leaf surface of the coconut palm each stoma being approximately 38/t x. 40/t including the subsidiary cells. The object of the present investigation is to determine whether the stomatal density of varieties and forms of the coconut is a varietal character and also to study the relationships (if any) between stomatal density and the environment. M A T E R I A L S A N D M E T H O D (a) S t o m a t a l densities in var iet ies and f o r m s of the coconut The coconut varieties block at Bandirippuwa Estate provided the material for this investigation. Five palms from each of the twelve forms belonging to the three varieties (Table 1) were sampled. A single leaflet was taken from the mid-region of the most mature green leaf from each of the selected palms. 105 106 STOMATAL DENSITY IN VARIETIES AND FORMS OF THE COCONUT ( b ) Stomatal densities in- the typica and nana varieties from different agro-climatic . regions . From each location, five palms from each of the two varieties were taken at random. Five leaflets from the middle of the most mature green leaf were sampled from each of the five palms representing a variety. (c) Stomatal densities in typica x pumila (Fi) hybrids 15 palms from the Demonstration Block, Bandirippuwa Estate were sampled using the same sampling procedure as in (b) above. (d) Procedure Epidermal peels were taken from the abaxial surface of each leaflet, and these were immersed in absolute alcohol. Five epidermal peels taken at random were mounted in Heath's Reagent on a microscope slide. Stomatal density was scored within the field of view of the microscope, keeping the eye-piece, objective and tube length constant. RESULTS AND DISCUSSION The stomatal densities of the varieties and forms of the coconut growing in Ceylon are given in Table 1. I t will be observed that all three colour forms of the nana variety have more stomata per unit area of leaf surface than the variety typica. Differences between forms with regard to stomatal density are significant (P < O.OOi., Table 2). TABLE 1 Avorage stomatal density per unit area of leaf of varieties and forms of coconut Variety Form No. of stomata Typica typica 24.3 navasi 25.3 rantkembUi 28.5 gon thembili 26.2 boiiri 26.3 kamandalu 25.7 pora pol 21.2 Nana • punttia 30.7 eburnea . 31.0 regia 317 Aurantiaca - thembili 25.0 nawasi thembili 27.9 TABLE 2 Analysis of variance— -stomatal density of varieties and forms of coconut Source d.f. S.S. M.S. V.R. Bn. forms 11 2473 • Bn. trees 52 2647 Bn. sampfes 264 3079 -Bn. forms 11 2473 224.82 53.02*** Bn. trees wn. forms 41 174 4.24 2.08*** Bn. samples wn. trees 212 432 2.04 S T O M A T A L DENSITY IN VARIETIES A N D FORMS O F T H E C O C O N U T 107 For breeding purposes, interest is mainly focussed on the form typica of the variety typica and form pumila of the variety nana, and some features of botanical interest in these two have been reported (Liyanage, 1958). Table 3 gives the stomatal densities per unit area of leaf surface of typica and pumila palms grown in different agro-climatic regions. The pumila palms have a higher stomatal density than the typica palms at all four locations, and this value is remarkably constant. An analysis of variance for this character (Table 4) indicates that differences between the two varieties are highly significant, ( P < 0.05). There are no significant differences between palms within a variety. Furthermore, differences in the environment do not alter stomatal density to any appreciable extent. In this regard, the existence of "ecolines'' for stomatal frequency with respect to annual rainfall gradients has been reported for Indian cotton (Gadkari, 1964). TABLE 3 Average stomatal density per unit area of leaf of typica and pumila palms Location typica pumila Bandirippuwa 24.2 30.3 Ambakelle 26.5 30.5 Ratmalagara 26.8 30.4 Pothukulama 24.4 30.4 TABLE 4 Analysis of variance. stomatal density in different environments Source d.f. S.S. M.S. V.R. Bn. places 3 369 123.00 1.11 Bn. varieties 1 6037 6037.00 54.30** Error 3 333 111.00 Total 7 6739 Bn. palms wn. varieties 32 100 3.12 1.14 Bn.-leaflet wn. Palms 160 438 2.74 1.68* Bn. samples wn. leaflets 800 1307 1.63 The different locations described in this experiment are within the same coconut growing district, and although there are differences in temperature and rainfall, these are probably not of sufficient magnitude to appreciably alter the stomatal densities. Wood (1934) considered the variations in stomatal frequency to be genetically determined, and attributed a lesser role to the environment. The dwarf (nana) variety is self-pollinating, and the population of 'dwarfs' in Ceylon is probably the result of several generations of in-breeding. I t will be observed that stomatal densities of the self-pollinated form pumila palms oi the nana variety are remarkably constant in the different environments indicating the degree of genetic control for this character. The observed differences between, leaflets within palms may be attributed to the fact that the number of stomata per unit area varies not only with different leaves of the same plant but on different parts of the same leaf as well (Salisbury 1927). In general, stomatal density in most plants increases from the base of the leaf to the apex and from the midrib to the margin. I t is reasonable to suppose that the situation is the same with the coconut palm although this aspect was not studied in very great detail. 108 STOMATAL. DENSITY IN VARIETIES AND FORMS OF THE COCONUT The typica X pumila F, hybrids have on an a average 27 stomata (range 25-29).pet unit area of leaf surface, which is therefore the mid-parental value for this character. This may be a useful index in identifying these palms when in doubt. This aspect will be studied further together wi th any possible relationships of stomatal density and yield of palms. Our thanks are due to Mr. V. Abeywardena. Biometrician, Coconut Research Institute for statistical analysis of data. REFERENCES Gadkari, P. D . (1964). Cotton Growers Rev. 18: 222-247. Lihonas, F. D . and Bolasova. E. V . (1964). PI. Breed. Abstr. 37 Abstr. 4878. Liyanage, D . V . (1958). Ceylon Cocon. Q. 9:1-10. Menon, K. P. V . and Pandalai, K. M. (1958). The Coconut Palm. A Monograph 384 pp. Ernakulam. Indian Central Coconut Committe. Muhle Larsen, C. (1957). PI. Breed. Abstr. 27 Abstr. 2289. Salisbury, E. J . (1927). Phil Trans. R. Soc. B. 216 .1 -65 . Senanayake. Y . D . A. and Samaranayake, P. (1970). Q. J. Rnbb. Res. Inst. (Ceylon) 46 : 61-68. Speckmann, G. J . Post, J . , and Dijkstra, H . (1965). Euphytica 14:225-230. Wood, J . G. (1934) J. Ecol. 22 : 69-87. • 

Stomatal density in varieties and forms of the coconut, Cocos nucifera L.

Manthriratna, M.A.P.P.