Factors Affecting the Phyllochron: The Scientific Bases for SRI

Ma. Lourdes S. EdañoUniversity of the Philippines, Los Baños

SRI is a promising way to increase rice yield and to realize its yield potential (Yuan et al., 2002).

In the Philippines, the Consortium for the Development of Southern Mindanao (CDSMC) in its initial evaluation in 1999 reported an average yield of 4.95t ha-1

compared to the usual yield of 1.5-2.5 t ha-1 in that area (Gasparillo, 2002).

INTRODUCTION

BIND (Broad Initiatives for Negros Development) working on SRI for three years reported a maximum yield of 7.5t ha-1 and an average of 6.9 t ha-1 with the new methods (Gasparillo, 2002).

The practices of SRI include: early transplanting (seedlings 8-12 days old) wide spacing (25 x 25, 30 x 30, even up to 50 x 50) planting one plant per hill with application of compost frequent weeding (mechanical weeding) less use of irrigation water (Uphoff, 2001).

The reported success of SRI is based on the synergetic development of both the tillers and roots.

What is a phyllochron?

Time interval between the appearance of two successive leaves (Klepper, 1982; and Nemoto et al., 1995), commonly observable in graminae species

The duration of a phyllochron is influenced by temperature, day length, light intensity, humidity, and soil nutrient availability (Nemato et al., 1995).

Its duration in rice is usually 5-7 days, still depending on temperature and climate.

Table 1. Phyllochron table of KATAYAMA indicating the number and location of tillers initiated during each stage of development in rice when tillers are appearing in an accelerating manner

PHYLLOCHRON

(sequence)

1st 4th 5th 6th 7th 8th 9th 10th 11th 12th 13th total

Days 18-26

23-33

28-40

33-47

38-54

43-61

48-68

53-75

58-82

63-89

Main stalk 1 1

Primary tillers 1 1 1 1 1 1 6

2nd row tillers 1 2 3 4 5 6 5 4 30

3rd row tillers 1 3 6 10 15 21 56

4th row tillers 1 4 10 20 35

5th row tillers 1 5 6

sum 1 2 3 5 8 13 21 33 53 84 134 134

Figure 1. Tillering dynamics of rice shoots based on Katayama’s analysis of rice growth (after Laulanié)

With SRI’s early and careful planting: Plants have time to re-establish themselves

quickly in the field Primary tillers are in the best condition to give rise

to possible succeeding tillers Less damage to roots when planted early

compared to transplanting older seedlings Dobech’s study (2004) shows that older seedlings

have longer phyllochron than younger seedlings for both wet and dry season.

Age of Seedling (in days)

LEAF NUMBER ON THE MAIN STEM

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 Total Leaves

  Elon-Elon

8 - - 4 3 3 3 3 3 4 6 7 8 9 9 7 13

15 - - 3 3 3 3 3 3 4 5 7 8 9 8 7 13

20 - - - 7 6 4 4 5 7 8 9 9 8 - - 10

25 - - - - 8 6 4 4 6 8 8 9 7 - - 9PSBRc-82

8 - - 3 3 3 3 3 3 4 5 7 8 8 7 - 12

15 - - 3 3 3 3 3 3 4 6 7 7 7 7 - 12

20 - - - 7 4 3 3 4 4 5 7 7 7 - - 10

25 - - - - 8 6 4 3 4 7 8 8 7 - - 9

Table 2. Phyllochron length (days/leaf) for each leaf of rice as affected by variety and by age of seedlings in the dry season, 2003 (Dobech, 2004).

Age of Seedlings (in days)

 LEAF NUMBERS ON THE MAIN STEM

1 2 3 4 5 6 7 8 9 10

11 12 13 14 15

16 17 18 T.Leaves

  Elon-Elon

8 - - 4 3 3 3 4 3 3 3 4 6 7 7 8 10 7 - 15

15 - - 4 3 3 3 4 3 3 3 4 5 6 7 8 10 7 - 15

20 - - - 6 4 4 4 4 5 6 7 7 8 10 7 - - - 12

25 - - - - 7 6 5 5 4 5 6 7 8 10 8 - - - 11

PSBRc-82

8 - - 3 3 3 3 3 3 3 3 4 6 6 7 7 8 - - 14

15 - - 3 3 3 3 3 3 3 3 4 5 6 7 6 7 - - 14

20 - - - 6 5 3 3 4 4 5 6 7 6 7 7 - - - 12

25 - - - - 6 5 4 4 4 5 5 6 6 8 7 - - - 11

Table 3. Phyllochron length (days/leaf) for each leaf of rice as affected by variety and by age of seedlings in the wet season, 2003 (Dobech, 2004).

Table 4. Phyllochron length in rice as affected by seedling age in the dry and wet seasons, 2003 (Dobech, 2004).

PHYLLOCHRON (day/leaf)

Seedling Age Dry Season Wet Season

8 5.3c 4.7b

15 4.9d 4.5c

20 6.0b 5.6a

25 6.5a 6.2a

cv 4.9% 4.8%

The longer phyllochron in the older seedlings was because older seedlings had longer roots during transplanting as compared to younger seedlings, presumably with more trauma in the process.

When these seedlings were uprooted, more roots were cut off from their primary roots. This increased the stress of seedlings during the re-establishment period and diminished the subsequent growth and development of rice plants.

Table 4. Length of rice phyllochron as affected by variety in the dry and wet season, 2003 (Dobech, 2004).

PHYLLOCHRON (day/leaf)

Variety Dry Season Wet Season

Elon-elon 5.7a 5.5a

PSBRc-82 5.1b 5.1b

cv 4.9% 4.8%

The longer phyllochron in Elon-elon is attributed to its long culm that the developing leaves must pass through.

Table 5. Number of productive tillers per hill of rice as affected by seedling age in the dry and wet season, 2003 (Dobech, 2004).

NO. OF PRODUCTIVE TILLERS PER HILL

Seedling Age Dry Season Wet Season

8 26.2a 60.8a

15 26.2a 59.1a

20 25.7a 45.9b

25 17.4b 36.9c

CV 4.1 8.6%

Results show that the tillering capacity of rice is reduced when seedlings remain longer in the seedbed.

Enyi (1963) reported that the first or primary tillers contributed more than 30% of the total tillers of rice.

PHYLLOCHRON (Day/Leaf)

SPACING Dry Season Wet Season

20 x 20 cm 6.1a 5.6a

30 x 30 cm 5.5b 4.9b

45 x 45 cm 5.4b 4.8c

CV 1.5% 2.1%

Table 6. Length of phyllochron of rice as affected by spacing in dry and wet seasons, 2003 (Dobech, 2004)

Phyllochron length was longer at closer spacing compared to wider spacing, because at closer spacing, there is more competition among plants for nutrients, space, and solar radiation and other growth factors. This can drastically hinder the subsequent growth and development rate of the rice plants.

Phyllochron length increases with planting density (Nemoto et al., 1995).

NUMBER OF PRODUCTIVE TILLERS PER HILL 

VARIETY Spacing

20 x 20 cm 30 x 30 cm 45 x 45 cm

Elon–Elon 16.2c 28.6a 29.7a

PSBRc-82 16.00c 21.8b 23.3b

Table 7. Number of productive tillers per hill of rice as affected by the interaction of spacing and variety in the dry season, 2003 (Dobech, 2004)

NUMBER OF PRODUCTIVE TILLERS PER HILL

  VARIETY

SPACING

20 x 20 cm 30 x 30 cm 45 x 45 cm

Elon–Elon 20.4d 37.9c 63.9a

PSBRc-82 25.1d 37.7c 54.8b

Table 8. Number of productive tillers per hill of rice as affected by the interaction of spacing and variety in the wet season, 2003 (Dobech, 2004)

The number of productive tillers per hill was significantly influenced by spacing in both seasons.

Higher number of productive tillers at wider spacing was due to reduced competition in light, nutrients and water.

Conclusion

SRI methods can promote more vigorous growth of rice plants, especially the development of its tillers.

Early and gentle transplanting of seedlings can bring out the potential of the first three primary tillers that contributes to 80% of the possible production.