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Effects of Water Stress on the Development of the Inflorescence in two Spring Wheat

A. Bakhshandeh

Department of Agronomy, Shahid Chamran University, Ahwaz, Iran.

Abstract

The investigation was concerned with the effects of water stress on the growth and development of the inflorescence of two Iranian spring wheat cultivars namely 4820 (T. aestivum L.) and Coleh (T. durum L.), during different stages of development from the early vegetative phase up to the green anther stage. The results revealed that the severity of the effects and the type of damage caused in the two cultivars by water stress depend on the developmental stage of the shoot apex and the water stress treatments that were imposed. The patterns of shoot apex development in the two cultivars were considerably different and this played an important role in response to water stress. A long duration of primordial initiation (Leaf + Spikelet phases) in cv. Coleh (T. durum) assisted this cv. to have a better ability to resist water stress. The contribution of different developmental stages to final grain yield was considered.

Key words

Wheat, water stress, shoot apex, developmental stage, spikelet.

Materials and Methods

The green house experiment was conducted with 16 hours photoperiod and day and night temperature were controlled at and respectively. Plants were grown in 240 plastic pots and water stress imposed by withholding water until the pots reached 20 percent of field capacity. A completely randomised design was employed with six treatments (T0 - T5) and five replications. The treatments were:

T0: Control plants T1: stress during vegetative phase T2: stress during spikelet initiation phase T3: stress immediately after formation of Terminal spikelet primordial T4: stress during early stem elongation
T5
: stress during internode elongation (green anther stage). Measurements were only made on the main shoots. Apical development was described using the stage illustrated by Waddington (1).

Introduction

There have been many studies of the effects of drought on the growth and other aspects of the physiology of wheat. However, studies of drought effects on development, particularly of the inflorescence, have been less common despite the fact that development of this organ has a direct effect on grain number, which is a principal component of grain yield. In light of the above points, the present study was undertaken to study the effects of water stress, Imposed at different developmental stages on subsequent extent and rate of development of the inflorescence of two Iranian. Spring wheat cvs. Which are grown in the south of Iran.

Results and discussion

The mean scores of development according to the Waddington et al., (1983) scale was markedly affected by water stress in all treatments but the trend was not similar for all treatments and all stage of development (Table 1). For both cvs. in T1 and T2 water stress had no significant effect on the developmental score compared to control, but only until day 28 and 42 after sowing which coincided with lemma and pistil primordial stage in 4820 and Coleh respectively. At the ear emergence stage the effect lasted up and there were no significant differences in these treatments compared to control plants.

At the time of antithesis in both cvs. T3 and T4 had the lowest developmental score number compared to the rest of treatments. Treatment T5 in both cvs. had no significant effect on developmental score.

Table 1. Mean developmental score of the most advanced spikelet at different sampling dates and after imposition of five treatments (T1 – T5). Value in the same row for each cv. which have different superscripts were significantly different (P<0.05).

Developmental stage in control

Control

T1

T2

T3

T4

T5

4820

Coleh

4820

Coleh

4820

Coleh

4820

Coleh

4820

Coleh

4820

Coleh

Doublidges stage

2.5a

2.7a

2a

2.5a

               

Terminal spikelet

3.8a

3.8a

3.5b

3.6a

3.5b

3.7a

           

Style primordium

6.1a

6a

5.4b

6.1a

5b

5.5b

4.9b

5.2b

       

Green anther

7.2a

7.5a

6.5a

7.3a

6.5a

6.3b

5.6b

5.7b

       

Ear emergence

9.2a

9a

8.7a

8.7a

8.6a

8.5a

8.5a

8.1b

7.9b

7.3c

8.9a

9.2a

Statistical analysis revealed significant reduction of spikelet number due to water stress in treatments T1 and T2 compared to well watered plants (Table 2). The reduction in the number of spikelets corresponded to days to reach terminal spikelet and the reduction in the length of the spikelet initiation phase for T1 and T2 treatments.

Table 2: Rate of spikelet initiation and duration of spikelet initiation phase on the main shoot of both cvs. under two different water stress treatments (T1 and T2). In each column the left and right-hand side numbers are belong to cv. 4820 and Coleh respectively.

Treatment

Days to double ridges

Days to Terminal spikelet

Duration of
SP. IN*
(days)

Rate of
SP. IN
(day-1)

No of spikelets
at TS* stage

Control
T1
T2

23
22.5
23

30
29.5
30

33.5
31.25
31

42.5
40
39.5

10.5
8.25
8

12.5
10.5
9.5

1.2
1.38
1.13

.99
1.2
1.1

19.25
17.25
16.20

17
16.2
15.2

LSD(0.05)

NS

NS

0.7

0.77

0.7

0.77

0.09

0.1

1.33

1.25

*TS = Terminal spikelet *SP.IN = Spikelet initiation phase

*NS = Not significant. Each value is a mean of 5 plants

Different aspects of final yield were followed in order to see how changes in growth and development of inflorescence organ all alter magnitudes of yield components. In general the durum cultivar Coleh was significantly higher yielding than the aestivum cultivar 4820 when water stress was applied at any stage of development. In both cvs. reduction in grain yield was higher when water stress was applied during later stage of development (ie. T4 and T5) with more pronounced effects in cv. 4820 compared to cv. Coleh.

The work described in this paper has relevance to Iranian agriculture and may assist subsequent research in the development of new wheat varieties that are more resistant to drought conditions and thus help to improve crop yield in arid areas such as south of Iran.

References

1. Waddington, S.R., Cartwright, P.M. and Wall, P.C. (1983). A quantitative scale of spike initial and pistil development in barley and wheat. Annals of Botany. 51:119–130.

2. Moustafa, M.A., Boersma, L. and Kronstad, W.E. (1996). Response of four spring wheat cultivars to drought stress. Crop Sci. 39: 982-986.

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