Photosynthesis Research 11:61-69 (1987) © Martinus Nijhoff Publishers, Dor&echt - Printed in the Netherlands

61

Regular paper Diurnal patterns of canopy photosynthesis,

evapotranspiration

and

w a t e r u s e e f f i c i e n c y i n c h i c k p e a (Cicer a r i e t i n u m L. ) u n d e r f i e l d conditions

D.P. SINGH, D.B. PETERS, P. SINGH and M. SINGH UNDP Centre of Sell and Water Managment, Haryana Agricultural University, Hissax125004, India, and Agricultural Research, US Dept. of Agficultuxe, University of Illinois, 1102 S. Goodwin Avenue, Urbana, IL 61801, USA

(Received: 1 March 1985; in revised form: 30 December 1985; accepted: 29 January 1986) Key words: canopy photosynthesis, .evapotranspi~ation, water use efficiency Abstract. Diuxnal changes in net photosynthetic rate (PN), evapotranspixation rate (ET) and water use efficiency (WIFE= PN]ET) of field g~own chickpea (Cicer arietinum) L. cv. H-355) were studied from the vegetative phase through matutirty at Haryana Agricultural University Farm, Hissa~, India, The maximum photosynthetic rate (PN max) increased, from the initial vegetative phase to pod formation and declined at a rapid rate from pod filling to maturity. The response of PN to photosynthetic photon flux density (PPFD) (400-700 nm) was temperature-dependent during the day, i.e. on cool days the PN rates were lower for certain quanta of PPFD during the f'~st half than during the second half of day, and vice versa on warm days. ET was affected both by crop cover and evaporative demand up to flowering, but thereafter it was independent of crop cover and followed the course of evaporative demand. ET was related to al~ temperature during the day while PN was related to PPFD. There was a lag of two to three hours between PNmax (around noon) and ETma x (around 2 p.m.). WUE increased from the vegetative stage through flowering but decreased thereafter to maturity. Abbreviations. DAS, days after planting; ET, evapotxanspitation; LAI, leaf area index; PAR, photosynthetically active radiation (in figures) is equivalent to PPFD (see below); Phi, net photosynthetic rate; PPFD, photosynthetic photon flux density; WUE, water use efficiency ( -- PN/ET).

Introduction During the last three decades there has been a three-fold increase in the production o f cereals, while grain legume production has remained constant. The lack o f yield improvement in the latter has precipitated a need for a careful analysis o f the various constraints limiting the productivity o f grain legumes in India. A m o n g winter season grain legumes chickpea is one o f the most popular crops grown extensively in N o r t h India. It is a long duration 1 6 0 - 1 8 0 days) and indeterminate type o f grain legume which is planted during warm months. It grows through the mild winter and spring seasons and matures at the onset o f the summer season. Thus, the crop experiences a wide range o f atmospheric conditions from planting to maturity. Limited studies carried o u t under controlled conditions have shown that the photosynthetic

62 rate is sensitive to both sub-optimal temperature and radiation regimes in chickpea [11]. Also, the overcast weather at flowering stage has an adverse effect on grain yield of chickpea [12], because the setting of flowers and productive pods depend on the supply of photosynthates in grain legumes [4, 6, 9, 1 I, 12]. However, the authors are not aware of any report on daily patterns of photosynthesis and evapotranspiration of chickpea canopies. In this investigation, gas analysis techniques and field assimilation chambers were employed to study diurnal changes in net photosynthetic rate (PN), evapotranspiration rate (ET), and water use efficiency (PN/ET( at different growth stages of chickpea under field conditions. Materials and methods The study was conducted on chickpea (6~cerarietinum L., cv. H-355)during the crop season of 1979-80 at Haryana Agricultural University Farm, Hissar, India (29 ° 10'N latitude, 75 ° 45'E longitude). The soft of the experimental plot was sandy loam, medium in fertility and slightly alkaline. The field was irrigated with good quality canal water before seeding and was fertilized with 25 kg N + 2.7 kg P ha -i at the time of seed bed preparation. The chickpea was planted on October 19, 1979 in a 16m x 12m plot in rows 30cm apart. The plants were thinned to 5 cm intra-row spacing after germination. The field was subsequently irrigated on December 21, 1980. Net PN and ET were measured on ten clear days beginning in the vegetative stage (36 days after sowing) and subsequently to maturity (174 days after sowing). The measurement technique was a closed system analysis in which the rate of CO2 decline and the rate of H20 increase were determined simultaneously. The measurement period was a set CO2 decline (e.g. 20 ppm) and consequent time elapse between beginning and ending concentration. Beginning concentration was always near ambient outside air concentration. The small concentration gradient across the chamber barrier and the short time elapsed made errors in diffusion across the chamber walls less than could be measured. The portable chambers were covered with clear polyethylene (6m i1). Dimensions of the chamber were 2 m x 1.5 m with adjustable heights. Four fans were attached to the chamber to insure complete mixing of CO2 and Hs O during the transient period of measurement. The ground area was not covered since in the very low organic matter soils of the arid region COs exchange was found to be negligible. The chambers were temporarily placed over the plot for a period not exceeding 60 seconds. Air samples drawn continuously from the chamber were passed through the CO2 and water analyzers with return to the chamber. COs was measured with a differential analyzer (Analytical Development Co.,

63 2000

80II '0 E E

1600

r

t0

T t0 ,!,1 X

60-

I ~200

E

40-

I-I

?

BOO

20-

400

I1. @

J. O 0

I al (-

Q -

~° ~

E 0 Z

°~

Q

II !

~

4o

t0

z

2o

x

0

X IlU tJ

46

86

TSme

86

(Oeye

tON

After

t26

t,,46

t66

&SN

Sowing)

Figure 1. Variation in net photosynthesis (PN), evapotranspiration (ET), water use efficiency OVUE: PN/ET), leaf area index (LAI), photosynthetically active radiation (PAR: 4 0 0 - 7 0 0 nm) and pan evaporation (Pc) during the growing season of chickpea. The crip was planted October 19, 1979. The mid-day values of PN (on ground area basis) and ET have been plotted in the figure. U on this and other f~gures stand for greek tz.

225 Mark 111) and water with a hygrometer (American Instrument Co). The photosynthetic photon flux density (PPFD) ( 4 0 0 - 7 0 0 n m wave length) above the crop canopy was measured with a quantum sensor (Lambda) and air temperature by a Tele-thermometer (Thomas Scientific). The PPFD decreased by 8 to 10% inside the chamber. The air temperature after one minute of crop coverage did not rise more than 1 °C in any case. Canopy temperature was measured by an infrared thermometer (Barnes), and the leaf area by an portable area meter (Lambda Model 3000). Ten plants were sampled outside the chamber for leaf area meaurement. Both PN and ET have been expressed on ground area basis as single value in time for five stages of crop development.

1 Mention of a trademark, proprietary product, or vendor does not constitute a guarantee or warranty of the product by the U.S. Dept. of Agriculture and does not imply its approval to the exclusion of other products or vendors that may also be suitable.

rl

64 70

1800

"1 , 2 / 4 / 8 0

1/5/80

1 50

-,I

30

4

1400

1000

.1

I S

600

10

!

200

0

-4

-r •

,

,

,

,

,

,

,

,

,

°

E UJ v

,

,

,

,

,

,

,

,

,

,

i

I

0

r.l,-

70

3/J~/80

3/26/80

£600

i-0

I

J400

50

£000 30

E

0

600 :tO

200

X Z Q,.

' ~ ' 1'0 " ~'2 " ~5 " ~ ' ~'B '

20

' 1'o ' 1"~ ' 1"4 ' 1"6 " ~'B " 2 o

Time (hours)

Figure 2. Daily trends of net photosynthesis (PN-on gxound area basis)i evapotranspiration (ET), photosynChetically active radiation (PPFD; 400-700 nm) and air temperature (AT) at floral bud initiation (Figure 2a, LAI = 1.7), full bloom (Figure 2b, LAI = 3.6), 70-80% pod formation (Figure 2c, LAI = 3.3), and 60-70% pod filling (Figure 2d, LAI = 1.6) in chickpea. Remits and discussion

Photosynthesis On clear days PNm~ increased from the vegetative phase, 36 days after planting (DAS), to the active pod formation state (145 DAS) (Figure 1). A decline in leaf area index (LAI) from 4.1 at pod initiation stage (120 DAS) to 3.3 at 70 to 80% pod formation (145 DAS) did not result in any reduction in the daily peaks o f PN. Green pods might have contributed towards canopy photosynthesis in chickpea [3,7]. In general, the PN rates peaked during the period from full bloom to pod formation ( 1 0 9 - 1 4 5 DAS). It indicates that the photosynthesis duration in chickpea is controlled by the requirement of assimilates in the growing organs, the developing pods being a particular demanding sink as in other species [5]. A sharp decline in PN after pod formation might be due to decline in LAI and increase in air temperatures (Figures 1;) [ 111. The PN followed the course o f PPFD diurnally during the entire crop

¢.1

65 40o

2/4/80

~1518o

30"

f

20

"• I= CU 0 (.9 .~.

~0 o

40 3/26/80

30 Z (2.

2O ~0

460

860

s.2bO

~.sbo

460

86o

~.2bo

16bo

PAR (uE/m~2-s) Figure 3. Diurnal relationship between net photosyn.thesis (PN) and photosynthetically active radiation (PPFD: 400-700nm) at fottr growth stages in chickpea. Data f~om Figure 2 have been used.in the figure.

season (Figure 2). However, the chickpea canopy was never saturated with the incident PPFD because it always remained below 1500/aE m -2 s~1 during active growth of chickpea. Under controlled conditions, Singh et al. [11] ) found light saturation of leaves at 1800#Em-2s "1 at flowering stage in chickpea. The response of PN to light was temperature-dependent. During the cooler months (December to the middle of February), the PN rates were lower for a certain value of PPFD during the first half than the second half of the day (Figure 3a-b), but a reverse trend was observed on warm days in March (Figure 3c-d). On days with 25 °C maximum temperatures during the second half of February, the PN was linearly related to photon flux density (Y = 0.727 + 0.052X, R 2 -' 0.95), The peak rates of photosynthesis of leaves have been recorded at around 22°C air temperatures under controlled conditions in chickpea [11]. Thus, the suboptimal temperatures during morning hours in cooler months (December to the middle of February), and above optimum temperatures during afternoon hours in warmer months (March-April), were responsible for varied dirunal response of PN to PPFD (Figure 5a-d). The canopy air remained 2 - 3 °C cooler than ambient air during most of the clear days of measurements. From the data it seems that

66 only 2 to 3 hours of mid-day are optimal for PN during active reproductive growth of chickpea under North Indian conditions.

Evapotranspiration The ETmax, as defined, was affected both by crop cover and evaporative demand in chickpea (Figure 1). ET was lower at the initial vegetative stage (to 56 DAS), when chickpea had an incomplete crop cover but a higher evaporative demand than at mid-season (74-79 DAS). It showed that a greater plant cover at the latter stage compensated for higher evaporative demand at the beginning of the crop season. However, ET was markedly higher at pod filling and maturity (145-174 DAS) even with a sudden decline in LAI. This was due to very high evaporative demand (Figure 1) and loss of water from foliage other than leaves. As the crop developed pods, a substantial proportion of evaporative surfaces were represented by stem and green pods. Water lost from stems and pods could have helped maintain a high ET at relatively low LAI [3, 7]. Diurnally, ET followed the course of evaporative demand at different stages of crop development (Figure 2a-d). There was a lag of 2 to 3 hours between the ETmax and PNraax during the course of day. Peak rates of PN were recorded at around 12 noon, the period of maximum photon flux density of the day. However, the ET peaks were recorded at around 2 p.m., the time coinciding with maximum vapour pressure deficit of the day. In general, ET was related to ambient air temperature diurnally, indicating markedly lower values for certain PPFD during the first half than the second half of the day (Figures 4, 5). The dependence of water loss on vapour pressure deficit and temperature under non-moisture stress conditions have also been reported for several plant species [7, 8, 11 ]. In arid regions, where water is frequently in short supply, it is necessary to design cropping practices which make maximum utilization of the water resource. The term water use efficiency (expressed as PN/ET) is frequently cited as an index for maximum yield while maintaining the lowest possible water usage. Being a ratio, the index PN/ET is subject to a number of variables which make the index of doubtful value. Degrees of canopy cover, temperature, atmospheric humidity, and stage of growth all interact to produce a given PN/ET ratio. WUE for chickpea increased from the initial vegetative stage to full bloom and declined thereafter to maturity (Figure 1). The large period of slow growth after sowing tended to produce a low WUE primarily due to low photosynthetic rates. Efficiency is highest during the period of highest photosynthetic activity, thereafter declining with the onset of high evaporative demands during the latter stages of growth. Thus, a relatively higher ET than PN during the second half of the day was a liability in terms of water economy in chickpeas. In conclusion, the chickpea develops crop cover at a very slow rate from seeding to about 80 DAS and has a low rate of PN and poor WUE during that

67 ~6 2/4/80

~/5/'80

10 I ~"

4

o

(M I ~-0

16

3/26/8O

X [-Iii 4

4(~0

800

12'00

:16"00

460

860

:t2"00

16'00

PAR (uE/m1'2-s) Figure 4. Diurnal relationship between evapotranspiration (ET) and photosynthetically active radiation (PPFD: 400-700nm) at four growth stages in chickpea. Data from Figure 2 have been used in the figure.

period. Efforts should be made to develop short duration chickpea genotypes with a rapid phenological development suitable for early planting in September, as Brassica campestris var. Toria [10]. This will make proper use of the initial long unproductive period and characteristic of chickpea, which is grown on conserved soil moisture from monsoon rains in India [12]. In irrigated areas, chickpea sewings are generally delayed as it is planted after harvest of monsoon season crops. Low air temperature and irradiance, which are most common constraints to attain a high rate of PN during cool winter months in North India, warrant selection of genotypes with a rapid growth and development under such sub-optimal atmospheric conditions as has been achieved in sorghum by Downes [2] and in Brassica napus by Campbell et al. [1]. Low temperatures also result in an ineffective flowering (pseudo and aborted flowers) during the cool winter months, and pod setting begins as temperatures rise in February (ICRISAT, Hyderabad-India, Annual Report 1978/79, pp 125-126). A sharp decrease in PN and increase in ET during pod filling stage, because of high evaporative demand, are apparent barriers to increase gain yields of chickpea, particularly under unirrigated conditions [ 14]. Developing genotypes better adapted to high temperatures, or selection of those that mature before the onset of high late spring temperatures are the possibilities.

68 40

1/5/80

2/4/8o

3/2/8o

3/26/80

30 20

10

D

o

(D r-4

C3

I---

40

30 20 l0

46o

86o

46o

~2bo

isbo

PAR

(uE/m1'2-s}

88o

~2bo

~sbo

Figure 5. Diurnal relationship between evapottanspiration (ET) Temperature, and photosynthetically active radiation (PPFD: 400-700nm) at four growth stages in chickpea. Data from Figure 2 have been used in the figuxe. Acknowledgments We thank UNESCO and the Indian Council o f Agricultural Research for supporting the consultancy visits of Dr D.B. Peters of Haryana Agricultural University, Hissar, India.

References 1. Campbell D, Degenhardt D and Kondra Z (1978) Breeding for early maturity in summer type Brassica napus. Proc V Intl Rapeseed Conf, Maline, Sweden. Vol 1, pp 52-55 2. Downes RW (1972) Physiological aspects of sorghum adaptation. In Rao NGP and House LR, eds., Sorghum in seventies, pp 265-74. New Delhi: Oxford & I.B.H 3. Johnson RC, Witters RE and Ciha AJ (1981) Apparent photosynthesis, evapotranspiration and light penetration in two contrasting hard red winter wheat canopies. Agron J 73:419-22 4. gsamer PJ (1980) The role of physiology in crop improvement. In: Staples RC and Kuhx R.I (eds) Linking research to crop production, pp 51-62. New York: Plenum Press 5. Lush WM and Rawson HM (1979) Effects of deomestication and region of origin on leaf gas exchange in cowpea (V/gna unguiculata (L)WalpJ. Photosynthetica 13:419-29

69 6. Pate JS (1978) Pea. In: Evans ET (ed) Crop physiology, pp 191-224. Cambridge: Cambridge Univ Press 7. Rawson HM and Constable GA (1980) Carbon production of sunflower cultivars in field and controlled environment. I. Photosynthesis and transpiration of leaves, stems and heads. Austral J of Plant Physiol 7:555-73 8. Rawson HM, Begg JE, and Woodward RG (1977) The effect of atmospheric humidity on photosynthesis, transpiration and water use efficiency of leaves of several plant species. Planta 1 3 4 : 5 - I 0 9. Sheldrake AR and Saxena NP (1979) Growth and development of chickpeas under progressive moisture stress. In: Mussel H and Staples RC (eds) Stress physiology in crop plants, pp 465-83. New York: Wfley-interscience i0. Singh H and Yadav CK (1980) Gene action and combining ability for seed yield, flowering and maturity in rape seed. Indian J of Agric Sci 50:655-58 11. Singh DP, Rawson HM, and Turner MC (I 982) Effect of radiation, temperature and humidity on photosynthesis, transpiration and water use efficiency of chickpea (Cicer arietinum L.). Indian J Plant Physiol, 25:32-39 12. Singh DP, Singh P., Singh P, Sharma HC and Singh M (1982) Effect of crop geometry and irrigation management on growth, evapotranspiration and water use efficiency of chickpea. Proc IV Afro-Asian Conf of ICID, Vol 1, pp 489-504. Lagos, Nigeria 13. Threshow M (1970) Environment and plant response, pp 51-62. New York: McGraw-Hill 14. Turner NC (1982) The role of shoot characteristics in drought resistance of crop plants. In: Drought Resistance in Crops with emphasis on rice, pp 115-124. Philippines: IRRI