Agronomy Journal 92:428-435 (2000)
© 2000 American Society of Agronomy
CORN
Effect of Soil Phosphorus on Leaf Development and Senescence Dynamics of Field-Grown Maize
Bruno Colomba,
Jim R. Kiniryb and
Philippe Debaekea
a INRA, BP 27, 31326 Castanet Tolosan, France
b USDA-ARS, 808 E. Blackland Rd., Temple, TX 76502 USA
colomb{at}toulouse.inra.fr
 |
ABSTRACT
|
|---|
Phosphorus deficiency generally decreases plant biomass accumulation by limiting interception of photosynthetically active radiation (PAR) rather than reducing efficiency of conversion of PAR into dry matter. To document the role of P availability in leaf growth and senescence dynamics in maize (Zea mays L.), a 3-yr field experiment was conducted in southern France with very low, moderate, high, or very high soil test P levels. Leaf appearance rate, individual leaf area, and green fraction changes were recorded at weekly intervals. Rates and duration of expansion and senescence processes were derived independently from fitted logistic functions. Phosphorus deficiency slowed the rate of leaf appearance and reduced the final area of leaves located below the main ear by 18 to 27%, depending on year. The reduction in leaf expansion rates accounted for most of the area reduction over leaf position and years. Senescence rates of the lower leaves were reduced by 29%. The expansion and senescence dynamics of upper leaves were little affected by soil P level. The whole plant peak green leaf area was lower under P-stressed conditions (16%), and its date of occurrence was significantly delayed (6%). Plant senescence rate was reduced by 15 to 33% during most of the grain filling period. Leaf area duration from emergence to complete senescence was reduced by 13.5%. The early effects of P deficiency on leaf dynamics accounted for most of the 7 to 10% reduction in the amount of absorbed PAR, observed as soon as canopy development allowed maximum light interception.
Abbreviations: DD, degree-days • GLA, whole plant green leaf area • LAD, leaf area duration • LAI, leaf area index • LED, leaf expansion duration • LER, leaf expansion rate • LLO, leaf longevity • LSD, leaf senescence duration • LSR, leaf senescence rate • MLA, maximum leaf area • n, leaf node number • PAR, photosynthetically active radiation • RSR, whole plant relative senescence rate
|
INTRODUCTION
|
|---|
PHOSPHORUS-INDUCED REDUCTION in plant biomass accumulation may result from perturbation of several interacting physiological processes (Halsted and Lynch, 1996). However, at the canopy level, this reduction may be ascribed to either a limited amount of absorbed PAR or a less efficient conversion of the intercepted radiation into dry matter. Several reports (McCollum, 1978; Lynch et al., 1991; Kemp and Blair, 1994; Colomb et al., 1995; Plénet et al., 1998; Rodriguez et al., 1998a and 1998b) have shown that light interception by crops is generally the most sensitive component of biomass accumulation under varying P supply levels. These authors reported that plants grown under low soil P concentrations develop a smaller leaf area index (LAI), and that peak green leaf area is delayed. How LAI is reduced is not well understood. In a glasshouse experiment, Usuda and Shimogawara (1991) observed that the detrimental effect of low P supply on maize leaf area resulted primarily from a diminished rate of expansion and secondarily from a reduced duration of expansion. The magnitude of the responses as a function of the node position of leaves were not considered.
Existing knowledge is not sufficient for modeling leaf expansion and decline in crops grown under varying P conditions. Our objective was to study the effect of soil P supply level, ranging from very low to very high, on maize leaf area development and senescence component parameters. Leaf analysis has proved useful in understanding differences between maize cultivars in response to water stress (Dwyer and Stewart, 1986), temperature (Hesketh and Warrington, 1989; Zur et al., 1989; Reid et al., 1990), and both factors combined (Stewart and Dwyer, 1994a). These studies led Stewart and Dwyer (1994b) to model expansion and senescence of maize leaves using temperature and water stress functions. By using such a level of analysis, this work aims to provide modelers with relevant information to simulate the evolution of LAI either with a leaf-to-leaf or a whole canopy approach, in varying P conditions.
|
Materials and methods
|
|---|
Field Context
The study was conducted in 1995, 1996, and 1998 at the INRA Research Center of Toulouse (43.5° N, 1.43° E), on a long-term P experiment initiated in 1968. The treatments were P0 (no P since 1968), P1 (17.5 or 11 kg P ha-1 yr-1, depending on year), P2 (35 or 22 kg P ha-1 yr-1) and P4 (70, 33, or 22 kg P ha-1 yr-1, Table 1)
. The 16 selected plots from the 48 in the field experiment formed a randomized block design with four replications. Each plot measured 72 m2. Soil test P concentrations, determined by the Olsen et al. (1954) procedure from topsoil (0–0.3 m) samples taken in January 1995 and 1997, ranged from very low to very high (Table 1). Due to the substantial reduction of annual P fertilizer applications initiated in 1992, a significant decrease in soil test P concentrations was observed in the P2 and P4 treatments between the two sampling dates.
View this table:
[in this window]
[in a new window]
|
Table 1 Annual P dressings (kg P ha-1) applied in the four treatments of the Toulouse experiment and Soil Test Phosphorus concentrations of P, determined by the Olsen et al. (1954) procedure on topsoil (0–0.3 m) samples taken in January 1995 and 1997
|
|
The soil of the experimental site was a fine mixed mesic Udic Haplustalf with 23 to 31% clay; 7.1 to 8.2 pH in water with soil–solution ratio 1/10; 0 to 8.4% total CaCO3; 14 to 16.5 cmol kg-1 soil cationic exchange capacity and 0.80 to 0.95% total C. Crop residues were incorporated into the soil from the beginning of the experiment. Maize was sown on 20 Apr. 1995, 11 Apr. 1996, and 22 Apr. 1998, at a rate of 80000, 83000, and 87000 seeds ha-1, respectively. The hybrid `VOLGA' required 1950 degree-days (DD, base 6°C) from sowing to maturity. Each year, residues of the previous crop were disked into the top 8 cm of the soil in late summer or early autumn. Land preparation consisted of moldboard plowing (0.3 m depth) performed in late autumn, and disking (6 cm) before planting. Nitrogen was applied as urea at a rate of 180 kg N ha-1 in 1995 and 1996, and at 200 kg N ha-1 in 1998, 1 or 2 wk before planting. Phosphorus was broadcast as superphosphate (17.5% P) about two months before sowing. Irrigation was applied according to water balance to avoid severe water deficit before anthesis and during grain filling (100, 140, and 190 mm water in 1995, 1996, and 1998, respectively). Rainfall, solar radiation, and minimum and maximum temperatures were recorded daily from sowing to complete senescence of the canopy at a standard weather station located at the research center.
Procedures
Visible leaf numbers were recorded from emergence to silking for 160 plants per P treatment in 1995, 120 in 1996, and 280 in 1998. Phyllochron refers to the interval between appearance of two successive leaf tips outside the whorl (Kiniry et al., 1990). The observed visible leaf numbers vs. thermal time (accumulated degree-days) were smoothed with a cubic spline function (Hamming, 1973; Hastie and Tibshirani, 1990). Thermal time relationships with integer values of leaf number were inferred by fitting smoothed splines, estimating phyllochron values for leaves 5 to 15.
After seedling emergence, 12 plants per P treatment (i.e., 3 per plot) were randomly selected and tagged within the two innermost rows of the plots. Length and width of each expanding leaf were measured (±1 mm) at 5- to 7-d intervals until maximum values were reached. Leaf area was calculated by multiplying the product of length and width by 0.75 (McKee, 1964). A logistic function (Stewart and Dwyer, 1994b) was fitted to the graph of the area of each leaf against node position (n), the latter ranging from 4 to 18, using the nls procedure available in Splus for solving the minimization problem of nonlinear least squares (Bates and Chambers, 1986). There can be difficulties with this method in evaluating expansion characteristics of leaves from field data (Stewart and Dwyer, 1994a). In particular, the parameters of the logistic function appeared highly sensitive to the early observed data with low leaf area values. This caused inconsistent predictions with changing leaf number or P treatment. In order to overcome this limitation, an extra point was added when leaf area value was 0 at the estimated time of initiation of the leaf. This time was estimated using a relationship between initiation time and tip appearance time for maize leaves obtained by Zur et al. (1989). Few data for leaves with node position less than 4 or greater than 18 were obtained because of the short expansion duration compared with the time interval between field observations. These leaves were discarded from the analysis because they did not contribute much to the total leaf area. For leaves in positions 4 to 18 on the plant axis, there were at least eight points (including the extra one) in each of the 60 (15 leaves x 4 P nutritional conditions) sets of data per year of experimentation, so that parameters were fitted with a minimum of five degrees of freedom. The curve of the logistic function was asymptotic, so it was not possible to determine a leaf maturity time. Nevertheless, to compare the effects of P treatments on leaf events, leaf maturity time was defined as the thermal time required to reach 97.5% of the maximum leaf area (MLA). Similarly, the onset of leaf expansion was defined as the thermal time required to reach 2.5% of a leaf's maximum area. Both criteria were calculated from fitted logistic equations. Leaf expansion duration for leaf n (LEDn) was the difference in accumulated degree-days between the onset time and end of leaf expansion. The time-averaged leaf expansion rate for leaf n (LERn, cm2 DD-1) was calculated by taking the ratio of the maximum area to the duration of expansion LEDn.
The total leaf area produced at any time by a plant was calculated as the summation of areas of expanding leaves and of fully expanded ones. The green fraction of each leaf was visually rated from 1 to 0 by steps of 0.1, from appearance to full senescence at weekly intervals. Because of the lack of previous work, the ability of Gompertz, logistic, and Weibull functions to fit the senescence curve (represented by green fraction vs. thermal time) were compared (data not shown). The logistic function gave the best fit over the 180 (15 leaves x 4 treatments x 3 yr) data sets, and was selected to investigate the effects of P on senescence dynamics. The onset time for senescence of leaf n was defined as the thermal time at which the mean green fraction equals 0.975. Similarly, full senescence time for leaf n was defined as the thermal time needed to reach a mean green fraction of 0.025. Leaf senescence duration for leaf n (LSDn) was given by the difference between full senescence time and the onset of senescence. The time-averaged leaf senescence rate (LSRn, cm2 DD-1) for leaf n was calculated as
.
There is no general definition of leaf longevity. Wolfe et al. (1988b) used the number of days from full expansion to 50% senescence. In this paper, leaf longevity (LLO) refers to the number of accumulated degree-days from 50% expansion to 50% senescence. This allowed better integration of the effects of P on both the growing and the declining phase of green leaf area development. At any time, the green area of each leaf was calculated as the product of leaf area and green fraction. The green leaf area (GLA) per plant was the summation of green areas of all visible leaves. The peak green leaf area produced per plant was given by max(GLA). Leaf n area duration (LADn) was calculated by integrating its green area over thermal time from appearance to full senescence. Within a P treatment, leaf area duration for the whole plant was provided by summation of LADn over node positions.
The whole plant relative senescence rates (RSR, cm2 cm-2 DD-1) were estimated between two successive measurements performed at t1 and t2 and were given by
These criteria allowed comparison of whole canopy senescence rates on a relative basis, with the effects of treatments on maximum green leaf area having been eliminated.
Absorbed photosynthetic radiation (MJ m-2) was assessed daily at the canopy level as
, where RG and LAI represent the incident total radiation (MJ m-2) and leaf area index values of the day, respectively (Goss et al., 1986; Russel et al., 1989).
Statistical Analyses
Paired t-tests were used to determine if differences existed between P treatments for individual leaf growth and senescence parameters (MLA, LER, LED, LSR, LSD, LLO, and LAD) within years and groups of leaves. The lower group of leaves refers to leaves located below the main ear, the upper one to leaves located above the main ear. The paired t-test, also used for the analysis of phyllochron responses, allowed the effect of node position on leaf appearance, development, and decline parameters to be taken into account. At the whole plant level, the effects of P treatments within years on the number of visible leaves, green leaf area, and senesced fraction over time were analyzed with repeated one-way analysis of variance, followed by the Bonferroni's test with P = 0.05 for separation of means. The final leaf number distributions recorded for P treatments within years were analyzed using a two-sample Kolmogorov–Smirnov test.
|
Results and discussion
|
|---|
Final Leaf Number, Leaf Appearance Rate, and Phyllochron
Field nutritional conditions are known to have little influence on final leaf number. Muchow (1988) reported that the average final leaf number of maize was not affected by the absence of N fertilizer. In our experiment, the final leaf number per plant ranged from 15 to 21. Frequency distributions of leaf number tended to narrow with increasing P inputs, as illustrated in the 1998 experiment (Fig. 1)
. Final leaf number distributions did not differ significantly at the P = 0.05 level among P treatments, except for P0 vs. P4 in 1998. Mean final leaf number in the P0 treatment was significantly lower (-0.2 to -1.2, depending on year) than those observed in the other treatments.
Muchow (1988) found that leaf tip appearance rate of maize and sorghum responded negatively to decreasing N supply. In this study, the appearance of leaves was markedly delayed under very low soil P conditions in all three years, as illustrated for 1998 in Fig. 2
. The difference in emerged leaf number between P0 and P4 reached 2.7 at 550 to 600 accumulated degree-days. This agrees with previous findings in indeterminate species such as common beans (Lynch et al., 1991) or determinate species such as wheat (Rodriguez et al., 1998a) grown under P-deficient conditions. Mean phyllochron value for leaves 5 to 15 in the P0 treatment was significantly increased (Fig. 3)
in all three years of the study. The effect of P on phyllochron value was greater on the lower leaf group than on the upper one (Fig. 4) . Significantly longer phyllochrons have been observed in wheat (Rodriguez et al., 1998a) and sunflower (Rodriguez et al., 1998b) grown under low P conditions.
View larger version (22K):
[in this window]
[in a new window]
|
Fig. 2 Number of visible leaves as a function of accumulated degree-days from plant emergence in maize grown in various soil P conditions (1998). Upper line of error bars indicates SD for P1, P2, and P4 treatments. Lower line of error bars indicates SD for the P0 treatment
|
|
View larger version (28K):
[in this window]
[in a new window]
|
Fig. 3 Mean phyllochron value for leaves 5 to 15 in maize averaged over years as a function of soil P conditions (1995, 1996, and 1998). Within years, letters indicate significant differences between P treatments at the P  0.05 level by paired t-test. DD, degree-days
|
|
View larger version (21K):
[in this window]
[in a new window]
|
Fig. 4 Phyllochron in maize as a function of node number and soil P conditions (1998). Error bars indicate SD. DD, degree-days
|
|
Because leaf initiation rate and early leaf elongation inside the whorl were not considered, the effect of P on the rate of appearance and phyllochron values remained unclear. Etchebest et al. (1998) found that P deprivation reduced early elongation of maize leaves in a controlled environment. It is highly possible that changes in rate of appearance and phyllochron observed in our experiment may be partly ascribed to this effect, because we observed a reduced elongation rate for recently emerged leaves in the P0 treatment (data not shown).
Leaf Area Expansion
Leaf Expansion Rate
The LER as a function of increasing leaf node number displayed an overall bell-shaped response curve in all three years, as illustrated for 1996 in Fig. 5a
. This pattern is consistent with results obtained in previous work (Reid et al., 1990). Expansion rates of the lower leaves were strongly affected by soil P status (Table 2)
. For the P0 treatment, LER was reduced by 15 to 32% compared with the other treatments. For all years, the largest difference was observed for the 10th leaf. In 1995, for example, the minimal LER value of the 10th leaf in the P0 treatment was 2.4 cm2 DD-1, and the maximum value was 3.4 cm2 DD-1 for the P4 treatment. Leaf expansion rates for P1 compared with P2 and P4 treatments were 4 and 10% lower, respectively, when averaged over years. Expansion rates of the upper leaves were sensitive to P deficiency for P0 vs. P2 and P0 vs. P4 in 1996, the decrease being 10%.
View larger version (30K):
[in this window]
[in a new window]
|
Fig. 5 (a) Leaf expansion rate (LER), (b) leaf expansion duration (LED), and (c, d) maximum leaf area (MLA) in maize as a function of node number and soil P conditions. Statistics are presented in Table 2. DD, degree-days
|
|
View this table:
[in this window]
[in a new window]
|
Table 2 Expansion duration, expansion rate, and maximum area for lower leaves (node number 4 to 12) and upper leaves (node number 13 to 18) of maize plant as influenced by P treatment
|
|
Leaf Expansion Duration
The LED tended to follow a quadratic function of node position as mentioned by Zur et al. (1989) in 1996 (Fig. 5b) and 1998 (data not shown), but not in 1995 (data not shown). Leaf expansion duration was little influenced by P supply level (Table 2). Treatments P4 in 1995 and 1996 and P2 in 1998 resulted in an 8 to 11% reduction in expansion duration of the lower leaves compared with treatment P1 (n 12). There was no significant effect on LED for leaves at node position higher than 12.
Maximum Leaf Area
As reported by Dwyer and Stewart (1986), the MLA curves displayed a skewed bell shape over leaf position on the plant axis (Fig. 5c). In 1995 and 1996, leaf number 12 was the largest leaf grown under P1, P2, and P4 conditions, but leaf number 13 was largest for P0 plants. In 1998, the largest leaf shifted down to node 11 and 12 for the fertilized and unfertilized treatments, respectively (data not shown). In all three years, MLAs were greatly affected by soil P supply, as a consequence of the combined effects on both rate and duration of leaf expansion. For the lower leaves (node position 12), observed MLA reductions in the P0 treatment ranged from 18 to 27% when compared with the P-fertilized treatments (Table 2). In the P1 treatment, rate of expansion was reduced by 4 to 10% when compared with P2 and P4 treatments. Despite the lack of a significant effect on both duration and rate of expansion, with the exception of LER values for the P0 upper leaf group in 1996, the MLA of the upper leaves in the P0 treatment compared with the other P treatments was reduced by 13% in 1996 (Fig. 5c) and to 22% in 1998 (data not shown). In 1995, however, P treatments did not affect the MLA of the upper leaves (Fig. 5d).
Leaf Senescence and Leaf Longevity
Leaf Senescence Rate
Phosphorus deficiency decreased the LSR of the lower leaves significantly, with the degree of decrease depending on year (Fig. 6a and 6b)
. Senescence rates of the lower group of leaves did not vary among the three P fertilizer treatments (P1, P2, and P4). The decrease of LSR for P0 vs. the other treatments averaged 29% over years. Senescence rates of the upper leaves were not affected by P in 1995 and 1996 (Table 3)
. In 1998, senescence rates in the P1 treatment were low, as indicated by the close to 30% difference when compared with the three other P treatments (Table 3).
View larger version (32K):
[in this window]
[in a new window]
|
Fig. 6 (a, b) Leaf senescence rate (LSR) and (c, d) leaf senescence duration (LSD) in maize as a function of node number and soil P conditions (1995 and 1996). Statistics are presented in Table 3. DD, degree-days
|
|
View this table:
[in this window]
[in a new window]
|
Table 3 Senescence duration and senescence rate for lower leaves (node number 4 to 12) and upper leaves (node number 13 to 18) of maize plant as influenced by P treatment
|
|
Leaf Senescence Duration
A significant increase (21.5% on average) in the LSD of the lower leaves occurred for P0 vs. P1 in 1995 and P0 vs. all the other treatments in 1996 (Fig. 6c and 6d). In 1998, the senescence duration within the lower leaves fluctuated greatly from one leaf to the next, so that no clear trend of change was observed among P treatments (Table 3). Also, there was no effect of P level across years on the LSD of upper leaves. In 1998 (data not shown), P2 and P4 treatments produced a significant (27 and 31%, respectively) decrease in LSD for the upper leaves, when compared with the P1 treatment. Senescence rates of upper leaves averaged a 13.5% reduction for P0 compared with P2 and P4 in 1995. A greater reduction (28%) occurred in 1998 for P0 vs. P1 (P 0.001). There was no change at all for LSD values of upper leaves among P treatments in 1996.
In P-deficient conditions, the reduced senescence rates observed in all three years were not entirely compensated for by longer senescence durations, the deficit in compensation being greater for the lower leaves than for the upper ones. The inconsistent response to P levels across years provided evidence that environmental factors other than soil P concentrations triggered senescence and controlled its progress.
Leaf Longevity and Leaf Area Duration
The P0 treatment affected LLO, with opposite responses for the lower and the upper groups of leaves (Fig. 7a and 7b)
. The largest effects were observed in 1998, with a 9% increase in the mean value of LLO for the lower leaves, associated with a 10% decrease for the upper group (Table 4)
. The reduction of LAD in the P0 treatment compared with the other treatments averaged 20% over years for the lower group of leaves, as a result of the combined effects of P on the expansion and senescence processes (Fig. 7c and 7d). By contrast, a small LAD increase (5%) occurred for the upper leaves for P0 vs. P4 in 1995. Despite the large influence of P on LAD in 1996 and 1998, the contribution of each leaf to the whole plant leaf area duration remained unchanged. In 1995, this contribution was reduced by 15% in the P0 treatment for the lower leaves and increased by about 14% for the upper leaves (data not shown).
View larger version (31K):
[in this window]
[in a new window]
|
Fig. 7 (a, b) Leaf longevity (LLO) and (c, d) leaf area duration (LAD) in maize as a function of node number and soil P conditions (1995 and 1998). Statistics are presented in Table 4. DD, degree-days
|
|
View this table:
[in this window]
[in a new window]
|
Table 4 Leaf longevity and leaf area duration for lower leaves (node number 4 to 12) and upper leaves (node number 13 to 18) of maize plant as influenced by P treatment
|
|
Whole Plant Green Leaf Area Expansion and Relative Senescence Rate
The GLA at low soil P status diverged early compared with that at high P status, as shown for 1995 and 1998 (Fig. 8a and 8b)
. The divergence resulted in a 16% mean decrease in the peak GLA for P0 vs. P1 across years. Within a given year, the GLA for P1, P2, and P4 plants had significant differences until 550 to 600 degree-days had accumulated, as shown for 1995 (Table 5) . After 600 degree-days had accumulated, differences no longer existed among P1, P2, and P4 in 1995 and 1996. In 1998, differences between P1 and P2 remained significant until the end of the plateau-like phase of the green area curve (up to 11% at peak levels, data not shown). In the P0 treatment, the growing period of leaf area up to the peak point was extended by 6%, averaged over years, compared with the other treatments.
View larger version (34K):
[in this window]
[in a new window]
|
Fig. 8 (a, b) Whole plant green leaf area (GLA) and (c, d) relative senescence rate (RSR) in maize as influenced by soil P conditions (1995 and 1998). Statistics for GLA are given in Table 5. Upper line of vertical bars in Fig. 8c and 8d indicates SD for P1 and P4 treatments. Lower line of vertical bars indicates SD for the P0 treatment. DD, degree-days
|
|
In 1995, the 10% senesced fraction was reached at approximately the same time in all P treatments (data not shown). Later, during the grain filling period, the green area declined more slowly in P0 compared with the other treatments (Fig. 8a and 8b). In 1996 and 1998 the onset of the whole plant GLA decline was delayed in the P0 treatment, with the 10% senesced fraction reached later in both years. In 1996, the GLA decline in P0 paralleled that observed in the other treatments (data not shown). Plants in the P0 treatment had the slowest RSR from the onset of canopy senescence to the pre-maturity stage, at approximately 1800 degree-days (Fig. 8c and 8d). The differences for P0 vs. P1 for this period were -33, -15 and -23% in 1995, 1996, and 1998, respectively. The effects of P on LSR at the whole plant level were in contrast to the effect of N restriction found by Muchow (1988) for maize in a semiarid tropical environment, and by Wolfe et al. (1988a and 1988b) for N-deficient and water-stressed maize plants.
Because senescence proceeded more slowly, P-stressed maize plants partially compensated for reduced peak leaf area so that the magnitude of the mean decrease LAD at the whole plant level, from emergence to full senescence, was less than the peak area reduction. The LAD for a whole maize plant was reduced by about 13.5% across years in the P0 treatment compared with P1.
Light Interception
The calculated amount of PAR absorbed by the canopy at 1800 accumulated degree-days, when averaged across the three years, were 706 ± 40, 758 ± 41, 781 ± 52, and 782 ± 49 MJ m-2 for the P0, P1, P2, and P4 treatments respectively (Fig. 9a)
. Absorbed PAR averaged significantly less in the P0 treatment vs. P1 (-7%) and vs. P2 or P4 (-10%). The ratio of absorbed PAR for the P0 or P4 treatments to the amount absorbed in the P1 treatment deviated most from 1.0 at nearly 400 accumulated degree-days (Fig. 9b). During the remainder of the growing season, there was no difference in absorbed PAR among P treatments. For example, the amounts of PAR absorbed by the canopy at silking averaged 320 ± 18, 330 ± 11, 340 ± 5, and 335 ± 7 MJ m2 for the P0, P1, P2, and P4 treatments respectively (Fig. 9a). These results indicated that the deficit in light interception may be ascribed mainly to the early delay in leaf area expansion processes.
View larger version (22K):
[in this window]
[in a new window]
|
Fig. 9 Light interception by maize as a function of soil P conditions (1998). (a) Absorbed photosynthetically active radiation (PAR) vs. accumulated degree-days from plant emergence through maturity. Upper line of vertical bars indicates SD for the P1 and P4 treatments at LAI = 3, silking and grain maturity. Lower line of vertical bars indicates SD for the P0 treatment. (b) Relative absorbed PAR in P0 and P4 treatments, with values of absorbed PAR in the P1 treatment taken as the reference
|
|
|
Summary and conclusions
|
|---|
The main results of this work document the role of soil P status in leaf growth and decline dynamics at both individual leaf and whole plant levels in maize. Phosphorus limitation slowed the rate of leaf appearance and strongly increased phyllochron values for leaves located below the main ear. The final size of leaves was reduced by P restriction, with the lower leaves being most affected. The reduction in LER accounted for most of the size variation across leaf position and years. Some small significant changes may have also affected the LED of the lower leaves. Although LER increased for leaves below the main ear on maize grown at very high soil P concentrations, this effect was mostly or totally offset by a decrease in the LED. The LSRs of the lower leaves were strongly reduced in low P conditions. The senescence dynamics of the upper leaves was little affected by changes in P conditions. As a result of the effect of P limitation on appearance, LER, and LSR, longevity of lower leaves was increased in two of the three years. Nevertheless, this response did not compensate for the reduced final leaf area under P-stressed conditions, and individual LAD decreased.
At the whole plant level, the peak GLA was 16% less under P-stressed conditions and the date of occurrence of peak GLA was delayed by 6%. Rate of senescence of the whole plant green leaf area was delayed during most of the grain filling period. Consequently, LAD at the whole plant level, from emergence to entire senescence, was less affected by P deficiency (-13.5%) than peak green area was. Despite the wide range of soil P concentrations tested in our experiment, leaf growth and decline of field-grown maize plant appeared much less responsive to P than to N deficiencies (Girardin et al., 1985; Muchow, 1988; Wolfe et al., 1988a; Sinclair and Muchow, 1995). Nevertheless, because leaf area responded to P stress during vegetative growth, maize absorbed less PAR (7–10%) in low P conditions when canopy development allowed maximum light interception. The early sensitivity of maize growth to P limitation was previously reported by Barry and Miller (1989), El-Hamdi and Woodward (1995), Etchebest et al. (1998), and Gavito and Miller (1998). These works and our findings suggest that P plays a key role in the morphogenetic and leaf expansion processes, which take place early in maize development.
|
ACKNOWLEDGMENTS
|
|---|
We thank J. Laurent and D. Vialan for field technical assistance, A. Moisan and M. Messine for assistance with the statistical analysis, and P. Loisel, who kindly provided consultation on selection and fitting procedures for growth functions.
Received for publication January 25, 1999.
|
REFERENCES
|
|---|
- Barry D.A.J., Miller M.H. Phosphorus nutritional requirement of maize seedlings for maximum yield. Agron. J. 1989;81:95-99.[Abstract/Free Full Text]
- Bates D.M., Chambers J.M. Nonlinear models. In: Chambers J.M., Hastie T.J., eds. Statistical models in S. Pacific Grove, CA: Wadsworth & Brooks/Cole Advanced Book and Software, 1986:422-454.
- Colomb B., Bouniols A., Delpech C. Effect of various phosphorus availabilities on radiation use efficiency in sunflower biomass until anthesis. J. Plant Nutr. 1995;18:1649-1658.
- Dwyer L.M., Stewart D.W. Leaf area development in field-grown maize. Agron. J. 1986;78:334-343.[Abstract/Free Full Text]
- El-Hamdi K.H., Woodward K.H. Response of early corn growth to fertilizer phosphorus rates and placement method. J. Plant Nutr. 1995;18:1103-1120.
- Etchebest, S., D. Plénet, and S. Pellerin. 1998. Expansion rates of maize leaves and spatial distribution of growth within the elongation zone as affected by P deprivation. p. 316–317. In M. Zima and M.L. Bartosova (ed.) ESA 5th Congr. Short Communications, Vol. II, Nitra, Slovak Republic. 28 June–2 July 1998. Slovak Agric. Univ., Nitra, Slovak Republic.
- Gavito M.E., Miller M.H. Early phosphorus nutrition, mycorrhizae development, dry matter partitioning and yield of maize. Plant Soil 1998;199:177-186.
- Girardin P., Tollenaar M., Deltour A., Muldoon J. Effect of temporary N starvation on leaf photosynthetic rate and chlorophyll content of maize. Can. J. Plant Sci. 1985;65:491-500.
- Goss G., Varlet-Granchet C., Bonhomme R., Chartier M., Allirand J.M., Lemaire G. Production maximale de la matière sèche et rayonnement intercepté par un couvert végétal. Agronomie (Paris) 1986;6:47-56.
- Halsted M., Lynch J. Phosphorus responses of C3 and C4 species. J. Exp. Bot. 1996;47:497-505.
- Hamming R.W. Numerical methods for scientists and engineers, 2nd ed New York: McGraw-Hill, 1973.
- Hastie T.J., Tibshirani R.J. Generalized additive models. London: Chapman and Hall, 1990.
- Hesketh J.D., Warrington I.J. Corn response to temperature: Rate and duration of leaf emergence. Agron. J. 1989;81:696-701.[Abstract/Free Full Text]
- Kemp P.D., Blair G.J. Phosphorus efficiency in pasture species: VIII. Ontogeny, expansion, P acquisition and P utilization of Italian Ryegrass and Phalaris under P deficient and P sufficient conditions. Aust. J. Agric. Res. 1994;45:669-688.
- Kiniry J.R., Rosenthal W.D., Jackson B.S., Hoogenboom G. Predicting leaf development of crop plants. In: Hodges T., ed. Predicting crop phenology. Boca Raton, FL: CRC Press, INC, 1990:29-42.
- Lynch J., Läuchli A., Epstein E. Vegetative growth of the common bean in response to phosphorus nutrition. Crop Sci. 1991;31:380-387.[Abstract/Free Full Text]
- McCollum R.E. Analysis of potato growth under differing P regimes: II. Time by P-status interactions for growth and leaf efficiency. Agron. J. 1978;70:58-67.[Abstract/Free Full Text]
- McKee G.W. A coefficient for computing leaf area in hybrid corn. Agron. J. 1964;56:240-241.[Free Full Text]
- Muchow R.C. Effect of nitrogen supply on the comparative productivity of maize and sorghum in a semi arid tropical environment: I. Leaf expansion and leaf nitrogen. Field Crops Res. 1988;18:1-16.
- Olsen S.R., Cole C.V., Watanabe F.S., Dean L.A. Estimation of available phosphorus in soils by extraction with sodium bicarbonate. Washington, DC: USDA Circ. 939. U.S. Gov. Print. Office, 1954.
- Plénet D., Mollier A., Etchebest S., Pellerin S. Leaf area index, PAR absorption and radiation use efficiency of a maize crop under phosphorus deficiency. In: Zima M., Bartosova M.L., eds. ESA 5th Congr. Short Communications, Vol. II, Nitra, Slovak Republic. 28 June–2 July 1998. Nitra, Slovak Republic: Slovak Agric. Univ, 1998:296-297.
- Reid J.F., Zur B., Hesketh J.D. The dynamics of a maize canopy development: 2. Leaf area expansion. Biotronics 1990;19:99-107.
- Rodriguez D., Keltjens W.G., Goudriaan J. Leaf area expansion and assimilate production in wheat (Triticum aestivum L.) growing under low phosphorus conditions. Plant Soil 1998;200:227-240 a.
- Rodriguez D., Zubillaga M.M., Ploschuk E.L., Keltjens W.G., Goudriaan J., Lavado R.S. Leaf area expansion and assimilate production in sunflower (Helianthus annuus L.) growing under low phosphorus conditions. Plant Soil 1998;202:133-147 b.
- Russel G., Jarvis P.G., Monteith J.L. Radiation absorption by canopies and stand growth. In: Russel G., et al. , ed. Plant canopies: Their growth, form and function. Cambridge, UK: Cambridge Univ. Press, 1989:21-39.
- Sinclair T.R., Muchow R.C. Effect of nitrogen supply on maize yield: I. Modeling physiological responses. Agron. J. 1995;87:632-641.[Abstract/Free Full Text]
- Stewart D.W., Dwyer L.M. Appearance time, expansion rate and expansion duration for leaves of field-grown maize (Zea mays L.). Can. J. Plant Sci. 1994;74:31-36 a.
- Stewart D.W., Dwyer L.M. A model of expansion and senescence of individual leaves of field-grown maize (Zea mays L.). Can. J. Plant Sci. 1994;74:37-42 b.
- Usuda H., Shimogawara K. Phosphate deficiency in maize: I. Leaf phosphate status, expansion, photosynthesis and carbon partitioning. Plant Cell Physiol. 1991;32:497-504.[Abstract/Free Full Text]
- Wolfe D.W., Henderson D.W., Hsio T.C., Alvino A. Interactive water and nitrogen effects on senescence of maize. I. Leaf area duration, nitrogen distribution, and yield. Agron. J. 1988;80:859-864 a.[Abstract/Free Full Text]
- Wolfe D.W., Henderson D.W., Hsio T.C., Alvino A. Interactive water and nitrogen effects on senescence of maize. II. Photosynthetic decline and longevity of individual leaves. Agron. J. 1988;80:865-870 b.[Abstract/Free Full Text]
- Zur B., Reid J.F., Hesketh J.D. The dynamics of a maize canopy development: 1. Leaf ontogeny. Biotronics 1989;18:55-66.
TOP
ABSTRACT
INTRODUCTION
