RELATIONS BETWEEN GRAIN YIELD AND PHOTOSYNTHETIC PARTS
ABOVE THE FLAG LEAF NODE IN BARLEY
T. C. YAP' and B. L. HARVEY
Crop Science Department,
University of Saskatchewan,
Saskatoon,
Sask.
Received Feb. 18, 1971, accepted Dec. 3, 1971.
ABSTRACT
All possible crosses, including reciprocals,
among seven Hordeum vulgare L. cultivars of
diverse origin were evaluated in the field in
1969 and 1970. The results of graphical and
multiple regression analyses show that esti­
mated areas of head surface, peduncle surface,
flag leaf area, and erectophile portion of the
flag leaf were highly associated with grain
yield. Thus these areas above the flag leaf
node might be good indicators of potential
grain yield. The developmental patterns from
anthesis to maturity for each of these traits
were similar in the homozygotes and the
heterozygotes. There were, however, substan­
tial differences in magnitude for these traits
between genotypes. Possible ways to establish
a high yielding plant type are discussed.
RESUME
Tous les croisements possibles, y compris !es
croisements reciproques, entre sept cultivars
de Hordeum vulgare L. de diverses origines
ont ete evalues en cultures de plein champ en
1969 et 1970. Les resultats decoulant des
analyses graphiques et des regressions multi­
ples font voir que les aires estimatives occu­
pees par l'epi, le pedoncule et la gaine foliaire
etaient etroitement liees au rendement en grain.
Ainsi, trois organes au-dessus du no�ud de
la gaine foliaire pourraient servir d'indices
valables du rendement potentiel en grain. Les
processus de developpement, depuis l'anthese
iusqu'a la maturite, de chacun de ces organes,
etaient analogues chez les homozygotes et les
neterozygotes. Mais les genotypes ont pre­
sente des differences notables quant a l'ordre
de grandeur des organes etudies. Suit !'examen
des possibilites d'etablir un type de plant a
grand rendement.
INTRODUCTION
Results of shading experiments by many workers have shown that carbohydrates
contributed by assimilating green parts above the flag leaf node amount to more
than 85% of the total accumulation in the grain (Archbold 1942; Asana and Mani
1950; Thorne 1961; Watson et al. 1958). The importance of green parts above
the flag leaf node was further confirmed by autoradiographical studies (Quinlan and
Sagar 1962; Rawson and Hofstra 1969; Stoy 1963). High correlations between
grain yield and areas of green parts above the flag node have been reported (Simpson
1968; Voldeng and Simpson 1967). However, to reduce error, most of the
physiological experiments were conducted in controlled environments. Thus, the
findings may not apply to field conditions. In addition, their objective has been to
look for the morpho-physiological characters that control grain yield and thus the
materials used were not hybrid populations. Therefore, their studies provide no
information on the inheritance of the morpho-physiological traits that they proposed
to be highly related with grain yield.
In this paper observations on the developmental patterns of flag leaf area,
erectophile flag area, peduncle area, and head area from anthesis to maturity and
their importance in relation to grain yield in barley under field conditions are
reported. The genetics of these morpho-physiological characters will be reported
in a separate paper.
MATERIALS AND METHODS
All possible crosses, including reciprocals, among seven Hordeum vulgare L.
cultivars (Table 1) were evaluated in the field in 1969 and 1970. The plant
characteristics and the origin of the parental cultivars are presented in Table 1.
1Present address: Facuhy of Agriculture, University of Malaya, Malaysia.
Can.
J. Plant Sci.
52: 241-246 (Mar. 1972)
241
242
CANADIAN JOURNAL OF PLANT SCIENCE
Table 1.
Cultivar
The origin and the plant characteristics of the parental cultivars
Origin
Flag leaf
Peduncle
Head
Culm
Atlas 46
California
Narrow, short,
and mid-erect
Mid-long
Short
Thin
Brant
Ontario
Narrow and
horizontal
Long
Long
Thick
Conquest
:VIanitoba
Intermediate type,
moderate
erectness
Very long
Long
Thick
Galt
Alberta
Larger than C and
moderate
erectness
:VI id-long
Long
Thick
Gateway 63
Alberta
Long and wide,
similar to C
in erectness
Mid-long
Short
Thick
Jaybelle
Maryland
Wide but short,
and erect
Short
Long but
lax
Very thin
Minnesota 5
:'vlinnesota
Wide and long,
mid-erect
Mid-long
Long but
shorter
than C
Thick
These cultivars are six-rowed awned types and only Conquest, Galt, and Gate­
way 63 are currently grown in the Canadian prairie region.
The 42 Fi's and the seven parental cultivars were sown in the field in a 7 x 7
partially balanced lattice design with three replications. Each plot consisted of four
4.9-m rows, each containing 16 seeds. The spacing between rows was 30 cm.
The plots were given a light irrigation after seeding to ensure uniform germination.
Eight plants were randomly chosen and tagged. Measurements were taken on
the main tiller of the tagged plant every week starting at anthesis and continuing
until the flag leaf was no longer green. This allowed each set of measurements to
be taken four times.
The green area parts above the flag leaf node were estimated as follows:
Flag leaf area (cm2): Flag leaf lamina length X flag leaf lamina width X 0.67
(Fowler and Rasmusson 1969). Green portions only were measured. Erecto­
phile fiag leaf area (cm2): The area was determined from the length of the flag leaf
lamina measured from the auricles to the point where the flag leaf lamina started to
bend X flag leaf lamina width. Peduncle area (cm2): The peduncle length X
diameter of the peduncle plus flag leaf sheath X Jt. Preliminary observations
showed that inclusion of the flag leaf sheath did not give rise to any differential error.
Head area (cm2): The head length X head width X Jt.
Awns were not included
since all varieties were full-awned types and did not differ significantly in awn length.
These methods should not lead to serious differential errors since the cultivars
used were all six-rowed awned types. Furthermore, the shape of flag leaves in this
barley population varied little from one genotype to another.
A standardized multiple regression analysis was used to estimate the relative
importance of these traits in relation to grain yield by assuming that grain yield is
YAP AND HARVEY-BARLEY GRAIN YIELD RE GREEN PARTS
243
the dependent variable and the photosynthetic parts above the flag leaf node are
independent variables.
RESULTS
The area of the green flag leaf and of the erectophile flag leaf, both in the hybrids
and the parents, remained relatively constant for the first 2 weeks after anthesis
and then declined rapidly (Fig. 1A, B). Peduncle areas increased sharply for the
first 2 weeks and then showed no significant increase after the 3rd week of anthesis
(Fig. IC). Head areas increased sharply until the 3rd week (Fig. ID), and then
levelled off.
There was no significant difference between the heterozygotes and homozygotes
in the patterns of senescence of the flag leaf lamina or the development of the
peduncle and head areas; however, there were significant differences between geno­
types in the actual values. Differences among genotypes for yield and all the area
measurements were significant at the 1% level of probability as indicated by the F
test (Yap 1970). The results also show that the flag leaf area and the erectophile
flag leaf area had reached maximal size by the time anthesis occurred. The
increase in peduncle area was mainly due to elongation of the peduncle, whereas
the increase of head area was mainly due to expansion of the kernels, since the
peduncle diameter and head length were relatively constant over 4 weeks of
measurement (Yap 1970).
The grain yield of the hybrids was higher, on the average, than the mean value
of the parents. Similarly, the mean values for the green parts above the flag leaf
node of the hybrids were also higher than the mean values of the parents in both
years. These results suggest that the better yield performance of the hybrids was
associated with their greater photosynthetic area. To evaluate this assumption,
data for areas of the flag leaf, erectophile flag, peduncle, and head for the five highest
and the five lowest yielders, regardless of the genotypes, were plotted against time
(Fig. lA-D). The five highest yielders had high values whereas the five lowest
had low values for all the traits observed. The marked difference for these two
groups was particularly evident in peduncle and head areas.
It was noteworthy that the flag leaf area and erectophile flag leaf area exhibited
a very high association. The correlation coefficients between these two characters
were +0.92 to +0.98 and +0.97 to +0.98, respectively, in 1969 and 1970 over four
sampling times. Since flag leaf area and erectophile flag leaf area were highly
associated, further attention was paid only to the flag leaf, peduncle, and head areas.
The relative degree of association of these three areas was demonstrated by the
magnitude of the standardized partial regression coefficients. However, only data
in the 2nd week for flag leaf and peduncle areas and 4th week for head area were
subjected to the analysis. These data were chosen partly because these traits had
reached a maximal stage of development at these times and partly because the
variation within each genotype was the smallest at these stages.
The regression mean squares were highly significant for both years, indicating
the significance of the regression coefficients (Table 2). These three traits also
showed a positive association with grain yield when they were considered at the
same time. The order of the magnitude of the coefficients for the three traits was
consistent in both years, suggesting that the relative importance of these traits was
quite stable. Among the three characters, head area showed the most association,
peduncle, second, and flag leaf area the least association with grain yield variation.
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YAP AND HARVEY-BARLEY GRAIN YIELD RE GREEN PARTS
245
Table 2. Standardized partial regression and multiple cor­
relation coefficients (R) between grain yield and the photo­
synthetic area above the flag leaf node
Standardized partial
regression coefficient
Trait
1969
1970
Leaf area
Peduncle area
Head area
Regression mean square
R
0.148
0.250
0.530
212 .56**
0.68**
0.107
0 .198
0.674
1122.52**
0.91**
**Indicates significance at the I% level of probability.
The multiple correlation coefficients in the 1969 and 1970 trials for the three
traits were 0.68 and 0.91, respectively, suggesting that these three traits were
associated with 46-83% of the total grain yield variation in this population
(Table 2).
DISCUSSION
Areas of flag leaf, peduncle, and head can be assumed to be the photosynthetic area
above the flag leaf node (Simpson 1968; Thorne 1966). The results of the
multiple regression analysis, showing the association of these plant parts with yield,
agree with the findings of other workers (Frey-Wyssling and Buttrose 1969; Porter
et al. 1950; Thorne 1965).
On the basis of our results it seems that selection for larger photosynthetic
areas above the flag leaf node would be a promising approach to obtaining higher­
yielding barley plants. Peduncle area can be increased by selecting for greater
length and diameter. Selection for too great a length may result in stem weakness
and would thus be undesirable. Selection for greater diameter, on the other hand,
should result in a stronger stem and may also give a greater vascular capacity
allowing greater water and nutrient movement. The latter may or may not be
beneficial.
Flag leaf area duration has been shown to be highly associated with yield
(Welbank et al. 1966; Yap 1970). There are two ways to increase this: ( 1) in­
crease the size of the flag leaf; and (2) increase the length of time that the flag leaf
remains green. In regard to the former, several authors have suggested that
drooping leaves are not a desirable feature in a high-yielding plant (Gardener 1966;
Jennings 1964; Matsushima et al. 1964; Pendleton et al. 1968). Our results
indicate that selection for a larger flag leaf lamina should not necessarily result in a
drooping leaf, since flag leaf lamina area was highly associated with the erectophile
portion, indicating that a larger flag leaf would have a larger erectophile portion.
Delaying senescence of the flag leaf also seems feasible, although there is a limit to
the amount that one can increase the length of the growing period in areas where
the crop season is short.
A larger head could have two benefits. It will have a larger photosynthetic
area and more florets potentially capable of producing seeds, providing the larger
head was not obtained by selecting for laxness.
Our results were obtained from plants grown under widely spaced conditions.
Therefore, the conclusions may not apply to plants grown in dense seedings. How-
246
CANADIAN JOURNAL OF PLANT SCIENCE
ever, the parents and F2's of the materials used in this study were grown in yield
trials with heavier seeding rates and the results were highly correlated to those
reported here (Yap 1970).
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