Animal Feed Science and Technology, 21 (1988) 1-9 1 Elsevier Science Publishers B.V., Amsterdem - - Printed in The Netherlands

Composit ion of Kermes Oak Browse as Affected by Shade and Stage of Maturity

ZOI KOUKOURA

Laboratory of Range Science (236), University of Thessaloniki, 54006 Thessaloniki (Greece)

(Received 19 March 1987; accepted for publication 23 December 1987)

ABSTRACT

Koukoura, Z., 1988. Composition of kermes oak browse as affected by shade and stage of maturity. Anirn. Feed Sci. Technol., 21: 1-9.

Kermes oak (Quercus coccifera L.) is a sclerophyUous evergreen shrub of the Mediterranean region. In Greece, it grows either alone or in a mixture with other sclerophyllous species in shrub- lands or as the understory in Pinus brutia forest.

The nutritive value and digestibility of kermes oak browse were investigated under 2 light con- ditions: as an understory species in a P. brutia forest and in adjacent open shrublands. The com- parison was made at 3 phenological stages: during the season of rapid growth (in April), after rapid growth was terminated (in May) and when growth had ceased and stems had hardened (in June).

Crude protein content of the leaves and twigs was higher in the shaded than in the unshaded plants during the growing season, while the concentrations of total non-structural carbohydrate, cell contents and soluble protein were higher in the unshaded than in the shaded plants. Tannins and lignin content were higher in shaded than in unshaded plants. Similarly, dry matter digesti- bility was higher in unshaded plants, but declined more drastically in the shaded plants during the growing season. Production was also higher in unshaded than in shaded plants at the end of the growing season.

INTRODUCTION

K e r m e s oak (Quercus cocci[era L. ) is a sc lerophyl lous evergreen shrub of the M e d i t e r r a n e a n region t h a t c o v e r s ~ l . 8 mil l ion ha (le Houerou , 1973). In Greece, this sh rubs grows e i ther a lone or in a mix tu re wi th o the r sc lerophyl lous species in sh rub lands or as the u n d e r s t o r y in Pinus brutia an d P. halepensis forests. P r o d u c t i o n and nu t r i t ive value of ke rmes oak are a f fec ted by cl imat ic condi t ions wi th in the fores t s tand. In th is e n v i r o n m e n t , l ight i n t ens i ty is the l imi t ing fac tor of p l an t growth (Larcher , 1980).

U n d e r s t o r y p roduc t i on and nu t r i t ive value have been s tudied by m a n y in- vest igators , bu t t he i r resul ts have var ied greatly. M u r p h y an d B e r r y (1973)

0377-8401/88/$03.50 © 1988 Elsevier Science Publishers B.V.

reported that Quercus douglasii forest reduces the quality and quantity of for- age growing beneath the tress. In contrast, Holland (1979) reported that for- age production under Quercus douglasii forest was significantly higher than in the adjacent open grassland, while understory nutrient content was also higher under the forest canopy (Holland and Morton, 1979). Mayland and Grunes (1974) reported that shade decreased the total non-structural carbohydrate and total N content in grasses. Burns et al. ( 1972 ) found that high quantities of tannins reduced forage quality when measured as dry matter digestibility in vitro.

The purpose of this study was to investigate the effects of light intensity on production and digestibility, and on crude protein, total non-structural car- bohydrate tannin and lignin contents of kermes oak leaves and twigs.

MATERIALS AND METHODS

The study was carried out in Macedonia, Greece, in an oak shrubland par- tially forested with P. brutia. The experimental area has an elevation of 650 m and a sub-humid Mediterranean climate with 630 mm annual rainfall and 13 °C mean annual air temperature. The climatic conditions during the study period are shown in Table 1.

Nine kermes oak shrubs of the same age and morphological appearance were selected in both the understory of the forest (shaded plants) and the adjacent open areas (unshaded plants). The shaded shrubs were exposed to variable light intensities, depending on the interception of solar radiation by the tree canopy, while the unshaded shrubs were fully exposed to sunlight.

The mean daily solar radiation reaching the shrub crowns at each cardinal compass point was measured over the entire growing season (Table 1 ). Three measurements were made with a selenic photocell on sunny days. Measure- ments were taken when the sun was at zenith and at 3 h before and after zenith.

Leaf and twig samples were hand clipped at 3 phenological stages: during the season of rapid growth (in April), after rapid growth was terminated (in May) and when growth had ceased and stems had hardened (in June). Sam- ples were obtained by cutting all new twigs in a 35 X 35-cm quadrat from each side of every shrub. Leaves and twigs together were dried at 40 ° C, weighed and ground through a 40-mesh sieve. Total dry matter production was determined by sampling in the same way at the end of the growing season and drying at 100°C.

Each sample was analyzed for crude protein (CP) by the micro-Kjeldahl procedure (Association of Official Analytical Chemists, 1975), cell contents (CC) (van Soest, 1967), lignin (L) (van Soest, 1963 ), dry matter digestibility in vitro (DMDIV) (Tilley and Terry, 1963), soluble protein (SP) (Howarth et al., 1977) and total non-structural carbohydrates (TNC) (Dale-Smith et al., 1964). Total tannins (TT), as total phenols (Burns, 1963) and condensed

TABLE 1

Clim

atic

factors of

the experimental area during the st

udy period

Clim

atic

factors

Apr

il

May

Ju

ne

Max

. M

ed.

Min

. M

ax.

Med

. M

in.

Max

.

July

Augu

st

Med.

Mi

n.

Max.

Me

d.

Min.

Ma

x.

Med.

Mi

n.

1982

T

emp

erat

ure

(°C

) 13

.0

9.9

5.8

20.5

17

.6

11.8

26

.2

Rel

ativ

e h

um

idit

y

(%)

72

59

Rai

nfal

l (m

m)

62.5

81

.1

Potential

evapotranspiration

(ram

day

-1 )

3.1

7.2

Lig

ht i

nten

sity

(l

dux)

63

.1

44.8

28

.1

61.7

43

.5

20.5

97

.3

1983

T

emp

erat

ure

(°C

) 18

.6

14.7

9.

3 21

.9

18.3

13

.7

22.4

Rel

ativ

e hu

mid

ity

(%)

57

58

Rai

nfal

l (r

am)

21.4

52

.6

Pot

enti

al

evap

otr

ansp

irat

ion

(r

am d

ay -

' )

5.6

7.38

Lig

ht i

nten

sity

(k

lux)

65

.8

47.5

30

.4

62.4

44

.9

27.5

95

.7

22.5

16

.1

26.3

22

.1

15.4

57

56

29.0

81

.5

9.4

10.3

65.3

35

.3

- -

18.6

14

.1

26.2

22

.8

64

59

114.

6 16

7.2

6.54

8.

8

64.1

34

.0

26.7

22

.3

16.4

62

51.4

17.7

7.3

25.2

21.2

16.9

59

76.5

7.8

e~

tannins (CT) (Bate-Smith, 1973, 1974) were also determined. This method measures the protein-precipitating ability of a tannin, which is the colorimet- tic estimation of hemoglobin remaining after the reaction between tannin and the protein of hemolysed blood. Results are expressed in terms of relative as- tringency, the ratio of the concentration of a tannic acid standard to that of the tannin which produces that amount of precipitate.

The means of CP, CC, L, DMDIV, TT and CT in the shaded and unshaded plants were compared by the t-test (Steel and Torrie, 1960) at P < 0.05.

RESULTS AND DISCUSSION

Production

Total dry matter production at the end of the growing season was 47% higher in the unshaded than in the shaded plants (Table 2). This difference may be

TABLE 2

Composition of kermes oak forage at 3 phenological stages in unshaded (U) and shaded (S) plants

Parameters 1st 2 2nd 2 3rd 2

U S U S U S

Crude protein content (CP, % ) 11.6a' 14.5b 7.35a 8.49b 6.70a 7.42a

Total non-structural carbohydrates (TNC, % ) 14.0a 12.1b 12.7a l l .2b 12.1a 10.99b

Cell contents (CC, % ) 74.0a 56.1b 52.5a 42.2b 43.3a 40.1b

Total tannins (CT, %) 17.2a 21.3b 14.2a 12.3a 13.7a l l .7a

Condensed tannins (CT, % ) 0.024a O.031b O.030a 0.026a O.031a 0.026a

Lignin (L, % ) 6.30a lO.6b ll.2a 16.2b 17.1a 20.6b Dry matter digestibility

in vitro (DMDIV, %) 52.2a 46.5b 35.7a 31.6b 32.9a 28.3b

Soluble protein (SP, % ) 9.42a 7.91b 6.22a 5.93a 5.96a 5.12a

Total dry matter production

- 3018.7a 1576.61b ( k g h a - ' )

'Means in the same line at the same phenological stage followed by the same letter are not signif-

icantly different at the 0.05 level. 21st, 2nd, 3rd, phenological stages. 1st, season of rapid growth (in April); 2nd, after rapid growth was terminated (in May); 3rd, when growth ceased and stems were hardened (in June).

explained by the higher photosynthetic efficiency of unshaded kermes oak shrubs relative to shaded ones (Koukoura, 1984). Similar results for unshaded plants were reported by Tsiouvaras (1984).

Crude protein (CP)

Crude protein content of the leaves and twigs was higher in the shaded than in the unshaded plants during the growing season (Table 2). The difference was significant (P~< 0.5) during the first and second phenological stages, but not during the third stage. Similar results are reported by Cook and Harris (1968), Burton et al. (1959), Deinum (1966), Myhr and Saebo (1969) and Blair et al. (1983). According to Delvin (1966), chlorophyll is discoloured at high light intensities when the enzymes participating in protein formation are inactivated. Photo-oxidation may be the reason for the lower CP content in the unshaded plants. In contrast, Halls and Epps (1969) reported lower pro- tein content in shaded shrubs than in those grown in the open. The magnitude of the seasonal protein decline that accompanied tissue maturation was less under shade than in full sunlight. Similar results are reported by other inves- tigators (Nastis, 1982). Kramer and Kozlowski (1960) reported that prior to the advent of cold weather and leaf senescence from deciduous species, a con- siderable portion of the nitrogen in leaves is translocated back into the shoots. This translocation of nitrogen probably explains the observed decrease in tis- sue protein.

Total non-structural carbohydrates (TNC)

The content of TNC was 13.9, 11.5 and 9.5% higher in unshaded than in shaded plants, respectively, at the 3 phenological stages (Table 2). Similar results are reported by Blair (1981). These differences may be attributed to the higher photosynthetic efficiency of unshaded kermes oak plants (Kou- koura, 1984).

A decrease of TNC content was observed during the growing season of 9.3 and 4.6% in unshaded plants and 6.8 and 2.4% in shaded plants from the first to the third phenological stages. The decrease is probably linked to tissue starch content which changes with translocation to the roots and other plant parts (Kramer and Kozlowski, 1960). Tsiouvaras (1984) found that unshaded kermes oak in the same region began accumulating TNC in the roots in April and continued until the end of the growing season.

Cell contents (CC)

CC were significantly higher in unshaded than in shaded plants (Table 2) by 24.1, 19.6 and 7%, respectively, for the phenological stages. The SP content

iii

Q

Fig. 1. Cross-section of a kermes oak leaf grown in the sun.

ii ̧~̧ ~̧ i iiiii!iiii~! •

• . •

Fig. 2. Cross-section of a kermes oak leaf grown in the shade.

was also significantly higher in the unshaded than in the shaded plants. This difference disappeared by the third phenological stage. The unshaded plants had both more and larger palisade cells than did the shaded plants (Figs. 1 and 2). The decrease of cell contents in unshaded and shaded plants over the grow- ing season (Table 2 ) parallels the decrease in TNC and SP.

Tannins and lignins

The TT content in the first phenological stage was higher in the shaded plants by 19.1%, while CT content differed by>24% (Table 2). Butler and Bailey (1973) found that the phenolic composition is influenced by far-red radiation (700-800 nm). Latchet (1980) reported that the composition of so- lar radiation under a forest canopy is in the red, far-red and green regions and that the amount of far-red can be 5-10 times that of red. The higher tannin content of shaded plants is probably due to the level of phytochrome activation and subsequent production of the enzyme phenylalanine ammonia lyase (PAL) that controls the biosynthesis of condensed tannins and lignin (Walker, 1975; Swain, 1979). This mechanism is supported by the significant difference in lignin content between the shaded and unshaded plants in the first phenolog- ical stage (Table 2).

In the second and third phenological stages, the contents of TT and CT tended to be higher in unshaded plants than in shaded ones, but were not significantly different. Differences in the lignin content were maintained, how- ever (Table 2). Hillis and Swain (1959) reported that plant lignification is related to the appearance of leucoanthocyanidins in leaves. Feeny (1970) ob- served that high light intensities increase the leucoanthocyanidin content of leaves. Haslam (1966) reported that condensed tannins are mainly derived from leucoanthocyanidins (flavan-3,4 diols), therefore, the higher content of tannins in unshaded plants was apparently due to PAL activity which pro- duced more tannins, while in the shaded plants the activity produced more lignin.

Digestibility

Digestibility was higher in the unshaded than in the shaded plants in all phenological stages (Table 2 ). Similar results are reported by Blair et al. ( 1983 ).

Tannin compounds are associated with cellular constituents and are dis- solved by neutral detergents (van Soest and Robertson, 1980). They appar- ently affect digestibility in a number of ways: through the formation of stable tannin-protein complexes, through enzyme inhibition or through microbial inhibition (McLeod, 1974).

Lignin probably plays a major role in the decreased digestion of the cell wall fraction (Wilson, 1981).

At the first phenological stage, the higher digestibility of the unshaded plant

tissue was perhaps due to its higher cell contents with lower tannins content. In the second and third stages, higher digestibility was due more to a signifi- cantly lower lignin content of cell walls.

During the growing season, the digestibility decreased in both unshaded and shaded plants (Table 2). This general decrease probably resulted from the decrease of cell contents in protein (Kramer and Kozlowski, 1979) and the increase in lignin of cell walls (Short et al., 1972; Wilson, 1981) as the plant matures.

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