V. Distribution of Dry Matter and Some Nutrient Elements

GROWTH AND PHASIC DEVELOPMENT

OF WHEAT

V. Distribution of Dry Matter and Some Nutrient Elements Between Stem and Leaf

BY K. K. NANDA,1 J. J. CHINOY2 AND K. L. SAWHNEY3 Department of Botany, University of Delhi, Delhi-8

IN a previous communication of this series it was shown that there is a considerable reduction in the number of tillers and leaves of wheat when the time of flowering is accelerated by long photoperiods and vernalization treatment (Nanda et al., 1959). This suppression in the vegetative growth takes place in spite of the fact that the photosynthetic activity of the plants under LD treatmerts is maintained at a high level as can be seeu from the values of net assimihtion rates (Sawhney et al., 1959, Table I). It is, therefore, clear that this reduction i:l growth under long-day and vernalization treatments is not due to any deficiency of carbohydrates. The total N, P and K contents as well as the rates of uptake of these nutrients which have also been considered previously are also at a high level ia these plants (Sawhney eta!., 1959). Evidently, therefore, lesser tiller and leaf production under long-day and vernaliza-tion treatments can not be ascribed to the deficiencies of these inorganic nutrients as well. Chinoy and Nanda (1952) have also shown that in the case of one variety of wheat-Triticum aestivum var. N.P. 52-the level of carbohydrates as well as mineral nutrients was adequate for growth of plants under long-day treatments. Clearly, therefore, the reduction in growth under these treatments is due to some other causes. The results presented in those papers indicated that the rates of uptake of mineral nutrients as well as the rates of dry matter production were governed mainly by the developmental process of the plant. It was, therefore, considered of interest to study the distribution of dry matter as well as N, P and K between stem and leaves of this plant under the influence of a change in the developmental process with a view to elucidat-ing the cause of the differences in the magnitude of growth in different varieties of wheat under different photoperiodic and vernc.lization treatments. The results of these investigations constitute the subject-matter of the present communication.

_1 Present Address: Senior Research Officer (Plant Physiology), Fcrut Rt:sec.rcl. Institute and Colleges, P.O. New Forest (Dehra Dun).

1 _{Present Address: Professor of Botany, Gujerat University, Ahmedabad-9 .}

• 3 Permanent Address: Professor of Biology, Jat Heroes College, Rd.tak

EXPERIMENTAL PROCEDURE

Graded seeds of three pure line varieties of wheat- Triticum

aestivum vars. C-13 and Lutescens and Triticum durum var. Kubanka-were placed on thin layer of sand in enamelled dishes and Kubanka-were genni-nated at room temperature. These were, then, placed in the refrigerator and were vernalized at 3-5° C for 32 days. In order to obtain control seedlings of the same stage of growth at the time of transplanting another set of seeds was sown in dishes 4-5 days before the vernalization treat-ment was completed. After vernalization treattreat-ment the seedlings of both the vernalized (V) and unvernalized (C) sets were transplanted in pots and were subjected to the following light treatments: (1) Short Day (SO) of 8 hours ligl:tt alternating with 16 hours of darkness; (2) Normal Day (ND) with periods of light and darkness of the normal day at Rohtak from October to May (mean period of 11 hours of light alternating with 13 hours of darkness); and (3) Long Day (LD) of 19 hours of illumination alternating with 5 hours of darkness.

Observations were made for growth characters and flowering behaviour of plants under different vernalization and photoperiodic treat-ments. The periodic growth and sampling data of this experiment have been reported in previous communications (Chinoy et a/., 1959; Nanda et al., 1959; Sirohi et a!., 1959). The net assimilation rates were calculated out from the data of dry matter production of the whole plant and leaf and have also been reported in the last communication of this series (Sawhney et a!., 1959). After dry weight determinations samples were powdered and were then chemically analysed for nitrogen by a modified micro-Kjeldahl method; phosphorus by a micro-titri-metric phosphomolybdate method and potassium by a micromicro-titri-metric K-cobaltinitrite method (Sawhney, 1955). The total N, P and K contents of the plant parts were obtained by multiplying the percentage concen-trations of N, P and K with their dry weights on a given sampling dat~.

These results have also been reported in the previous paper (Sawhney

et a/., 1959). From the data of dry matter production and total N, P and K contents of different plant parts determinations were made of the ratios of dry matter and N, P and K contents of•stem over leaf at differ-ent stages of growth in all the three varieties of wheat under varying vernalization and photope~iodic treatments.

For further details of the experimental procedure reference may be made to a previous communication (Chinoy et a/., 1959).

EXPERIMENTAL FINDINGS

114 K. K. NANDA AND OTHERS

ratio of stem dry weight/leaf ary weight on a p::..rticular date was ob-tained by adding all the values of stew dry weight/leaf dry weight ratios under this treatment on that date irrespective of the vernalization treat-ment and variety and dividing the sum by 6 (2 vernaliZdtion treattreat-ments

X 3 varieties). The single factor effects obtained by compiling the data in this manner are shown graphically in Figs. 1-12.

Ratio of stem/leaf dry weight.-Figures 1-3 exhibit the effect of photoperiodic treatments, veraalization and varieties respectively of the ratio of stem dry weight/leaf dry weight at successive stages of growth. Each point in Fig. 1 is a mean of 30 readings (2 vernalization treatments X 3 varieties X 5 replicates), in Fig. 2 of 45 readings (3 photo-periodic treatme.1ts x 3 varieties x 5 replicates) and in Fig. 3 of 30 readings (3 photoperiodic treatments x 2 vernalization treatments

x 5 replicates). It can be seen from figure 1 that the ratio of stem/leaf dry matter increases very rapidly in ,Jlants under LD treatment, less so in those subjected to ND treatment and very slowly in those exposed to SD treatment. Tnus the ratio is the highest in LD !)lants at all stages of growth and the least in SD plants. It may also be noted that as a result of this faster increase the ratio reaches unity earliest of all in plants exposed to LD treatment, then in ND ones and last of all in SD plants. Thus in LD plants the ratio reaches a value more than 1 in about 63 days after sowing as compared with about 95 days in ND plants and about 120 days in plants subjected to SD treatment. This clearly indicates that the increase in the dry weight of the stem starts earliest of all in LD plants and is progressively delayed with a decrease in the length of the daily photoperiod to which plants are exposed.

Considering the effect of vernalization on the ratio of stem dry weight/ leaf dry weight (Fig. 2) it can be seen that the vernalized plants show a consistently higher ratio than the unvernalized plants. Agd.in the ratio reaches a value higher than 1 earlier in vernalized plants as compared with the controls. Thus in vernalized plants the ratio reaches a unit value after about 74 days as against about 80 days in unvernalized ones.

It may, however, be noted that the effect of the photoperiodic treatments is much more marked than that of the vernalization treatment. This point will be discussed further a little later in the light of some more data to be presented.

The varietal differences in the ratio of stem dry weight/leaf dry weight can be seen from Fig. 3. It is seen that while the ratios of stem dry weight/leaf dry weight of C-13 and Lutescens do not show significant differences between themselves these are definitely higher than the ratio of stem dry weight/leaf dry weight of variety Kubanka at all stages of growth. The unit value is also reached later in this variety as com-pared with the other two varieties. This is probably because Kubanka is a later flowering variety as compared with C-13 and Lutescens. It

0.4

48

4.4

4.0

36

3·2

... 1·6

;:;

~1.2

_... ... "'OB

0.4

VENNALI.Z A TtON Tflt:ATMt:NT

20 40 10

PHOTOPERIODIC TREATMENT

20 40

DAYS FROM

~ 1,6

'"

~1.2

~

1/) 0.1

0.4

40 /00 1.10 140

DArS f"/1/0M SOWING

r

NfJ

120 140

SOWING

VARIETICS

LU'Z

if·

f'IG. J

i!O 80 100 120 140

DAYS F If OM SOWING

Fms. 1-3. Efl'ect of photoperiodic treatment (Fig. 1), vernalizaticn (Fig. 2) and varieties (Fig. 3) on the ratio of stem dry weight/leaf dry weigl-.t at successive stages of growth. For legends see Figs. 5, 8 and 10 respectively.

22

1.e

I~

1-2

1-0

z

...

.. 0.8

'"

... ...

zo.ti

::i

...

~0.4

In order to compare the effect of photop~riodic treatments the graphs for the three nutrients are shown side by side in Figs.· 4-6 respectively. Simlilarly the graphs showing the effect of vernalization treatment are shown in Figs. 7-9 and for varieties in Figs. 10-12. As in the case of stern dry weight/leaf dry weight ratios each point in Figs. 4-6 is a mean of 30 readings, in Figs. 7-9 of 45 readings and in Figs. 10-12 of 30 readings.

It is evident from Figs. 4-6 that the photoperiod has a marked effect on the ratios of the contents of all these three nutrients in stem

NITROGEN

LD

0..

...

..

"'

...

~

I

::i

..

....

31

"'

PHOTOPERIODIC TREATMENT

STE"'/lEAF LD - - - . . NO

~so

PHOSPHOIWS LD

"

..,.

..

"

...

so ...

::i

"'

,..

"'

FIGs. 4-6. Effect of photoperiodic treatmer.t on stem/leaf ratio of nitrogen (Fig. 4), phosph0rus (Fig. 5) and potassium (Fig. 6) at successive stages of growth.

to leaf. Thus the ratio in all the three C:lses increases very rauidly under LD treatment and very slowly under SO treatment as compared with that utider NO condition. As a result of this the values of the ratio in LO plants are higher than those ofND ones at all stages of growth. On the other hand these are much lower than those of NO plants in plants exposed to SO treatment (Figs. 4-6). As in the case of ratio of stem dry weightjleai dry weight, the ratio or N, P and K contents of stem to leaf also reaches a high level (above unity) earliest of all in LD plants, then in NO ones and last of all in those under SO treatment. Thus this value is reached after about 85, 70 and 56 days for the ratios of N, P and K contents respectively under LO treatment. In pla11ts under ND and SD treatments the unit value is not reached even when the experi-ment is terminated. The values under NO conditions are, however, higher than those under SD condition at the corresponding sampling

12

•

~oe

..

~

...._

06

•

~ ~0.-4 " 0·2 0 1·2 ~ 1·0 ... ~ ::o~ "-..

• o.

~

..

~0.4

02

0

The effect of vernalization treatment on the ratio of N, P and K contents of stern to leaf can be seen from figures 7-9 respectively. In all cases the ratio is consistently higher in vernalized plants as compared with unvernalized ones, although the differences are not as marked as in the case of photoperiodic treatments.

VERNA LIZ AT ION TREATMENT ~·

STEM/ LEAF

~

PHOSPHORUS POTASSIUM

NITROGEN

"

_{... c~}

..

I

/

~ ...

I

~ ~

~

"'

~

~

..

~ ~

~ ~

" "

VARlET IES

r

ST<EM I LEAF

eo""'""

~

NITROGEN PHOSPHORUS

...

Cl3 ~ _I A

LUTESCENS .~

..

? ' / I

I

. .

"

v

'

I I ~ '

~\

~

..

~

~ ~

" .._ ~

~ ~

~-P

60 so 100 120 20 40 60 (' 100

ll A Y S FR OU S 0 WI N G·

FIGS. 7-12. Figs. 7-9. Effect of vernali1ation on stem/leaf ratio of nitrogen (Fig. 7), phosphorus (Fig. 8) and potassium at successive stages of g1cwth. Figs.

10-12. Varietal effects on stem/leaf ratio of nitrogen (Fig. 10), phosphorus

(Fig. 11) and potassium (Fig. 12) at successive stages of growth.

Varietd..l differences in the ratios of N, P and K contents of stem to leaf are shown in Figs 10, 11 and 12 respectively. As in the case of ratios of stem dry weight over leaf dry weight here also varieties C-13 ·and Lutescens do not show significant differences between them-selves. The values of the ratio of all these three inorganic metabolites, however, are consistently lower in variety Kubanka than in the other two. The differences in the rdtios of these elements in the three varieties are, however, not as pronounced as in the case of photoperiodic treat-ments. This is probably because the three varieties do not differ very markedly in the length of their vegetative periods. ·

118

DISCUSSION

The results presented in this paper clearly demonstrate that the distribution of dry matter as well as of N, P and K between stem and leaf in the three v;;.rieties of wheat is very much affected by vernalization and photoperiodic treatments. The ralio of dry matter as well as those of the three nutrient elements in stem to leaf are higher and reach unit values earlier in plants under long day than those under normal day. It remcins consistently lower in plants unde; short day so that the value reaches unity much later in these plants as compared with those under ND condition. It has already been shown that the flowering of wheat is hastened both by low temperature during ger.nination and longer photoperiod subsequently (Chinoy eta!., 1959). It would thus appear that the effect of these treatments-vernalization and photoperiod-on the ratio of organic and inorga >ic metabolites in stem to kaf is brought about as a result of their effect on flowering. This is supported by the fact that the treatment that affects the flowering response markedly is also the treatment that has a pronounced effect oil the ratio of these nutrients in stem over leaf and vice versa. Thus photoperiodic treat-ment which causes a pronounced effect on flowering also ha~ a marked effect on the ratios. On the other hand verna~ization treatment which

doe~ not show a very pronounced effect on the vegetative period also does not cause such a pronounced difference in the ratios of these metabolites in stem to leaf. This is <1lso substantiated by the varietal effects. Thus C-13 and Lutescens which do not show significant differences between themselves in their vegeLctive periods flower earlier than the variety Kubanka (Chinoy et a!., 1959). The ratio of these nutrients and dry matter in stem to leaf also show similar trends. Thus while the values of the ratios in C-13 and Lutescens are consiste11tly higher than those of Kubanka they do not show significant differences between themselves.

In order to further substantiate this point the correlation coefficients of the vegetative period and the period taken for the ratio of dry matter to reach unity and the ratio of N, P and K to reach a value or· 0 · 3 (as in some of these cases the value did not reach unity even when the experi-ment was terminated) were worked out separately and were found to be r₁₁~a

=

+ 0·96, + 0·95, + 0·85, and+ 0·77 respectively. These show highly significant positive correlations and lend support to the above-mentioned conclusion that the ratios of dry matter and N, P and Kin stem to leaf are determined by the developmental process. Earlier the flowering earlier is the rise of the ratio to unity and more. It is worthy of note that this relationship holds good whether earliness in flowering is caused by subjecting the plants to vernalization and photo-periodic treatments or by taking early and late flowering varieties.

on the one hand and the ratios of dry matter and nutrient elements in stem over leaf on the other suggests that the reduction in vegetative growth under long day and its enhancement under short day in these experiments is probably due to the mode of partitioning of these organic and inorganic metabolites between stem and leaf. It has already been shown that the dry matter and N, P and K contents increase at a much faster rate in the leaves than in stem at the i1.itial stages. Gradually. however, the contents ot' the leaves reach their maxima but those of the stem continue to increase rapidly till about the end of the experiment (Sirohi et al., 1959; Sawhney eta!., 1959). The maxima in dry weights and N, P and K contents of leaf are reached earliest of all in LD plants and last of all in SD ones. The subsequent increase of these metabolites in stem also starts earlier and takes place at a faster rate in LD plants than in ND ones. As d result of these there occurs an earlier termination in the production of tillers and leaves and at the same time an earlier shooting up of the stem under long days. Under short days where the increase in dry weight and N, P and K contents of stem is much delayed, the stem elongation is also delayed and the production of tillers and leaves continues for a longer period of time. Petrie (1937), Petrie eta!. (1939), Williams (1936, 1938, 1948), Wagner (1932) and Watson eta!.

120 K. K. NANDA ANb OTHERS

earlier in these plants than in those under ND or SD conditions. As a result of this there is a 1 e:ulier increase in the dry weight and inorganic

nutrient contents in the gro·.ving spike in LD plants than in plants exposed to ND or SD treatments. Tl>is is clearly seen from the results of dry weignt and N, P and K contents of different parts OI the plant presented

in previous papers of this series (Sirohi et a!., 1959; Sawhney et a!., 1959).

It would, thus, appear that the distribution of these organic and inorganic nutrients in different parts of the plant which determines their growtn is a function of the same regulatory mechanism which controls its flowering.

SUMMARY

This paper deals with the study of the effect of vernalization and photoperiodic treatments on the distribution of dry matter and some nutrient elements between stem and leaves of three varieties of wheat-Triticum aestivum vars. C-13 and Lutescens and wheat-Triticum durum var. Kubanka.

The ratios of dry weights and N, P and K contents of stem over leaf at different stages of growth were determined separately for photo-periodic and vernalization treatments as well as for varieties.

The ratios of ste1n/leaf dry matter as well as of their N, P and K contents increase very rapidly in the long day (LD), less so in normal day (ND) and very slowly in the short day (SD). The ratios of all these nutrients are highest in LD plants and the least in SD ones. The unit value of the ratios is also reached earlier in LD plants, then in ND ones and last of all in SD plants.

Vernaliz,ed plants show a consistently higher value of the ratios of these nutrients and dry matter in stem to leaf than the unvernalized plams. The vernalization effect, however, is less marked than the effect of the photoperiodic treatment.

C-13 and Lutescens do not show significant differences between themselves in the ratios of dry weights and N, P and K contents of stem to leaf. The values in all cases are, however, consistently lower in the late flowering variety Kubanka.

The results have been discussed in relation to the alteration that is caused by these treatments in the length of the vegetative period.

It is considered that it is the mode of partitioning of these organic and inorganic metabolites between different parts of the plant which deter-mines the growth of these plant parts and which in itself appears to he a function of the same regulatory mechanism which controls flowering in a plant.

REFERENCES

CHINOY, J. J., &NDA, K. K., SIROHI, G. S. AND SAWHNEY, K. L. (1959). Growth

~nd phasicaevelopment of wheat. I. Vegetative period and protothermic

requirement. Indian J. Plant Physiol., 2, 29.

- - AND-- (1952). Effect of vernalization and photoperiodic treatments on growth and development of crop plants. IV. Uptake of nitrogen, phosphorus anp· potassium by wheat plant under varying photoinductive and

post-photoin-ductive treatments. Physiol. Plantarum, 5, 11.

NANDA, K. K., SIROHI, G. S., SAWHNEY, K. L. AND CHINOY, J. J. (1959). Growth

and phasic development of wheat. II. Stem elongation, tillering and leaf

pro-duction. Indian J. Plant Physiol., 2, 52.

PETRIE, A. H. K. (1937). Australian J. Exptl. Bioi. Med. Sci., 15, 385 (seen in

Williams, 1955).

- - , WATSON, R. AND WARD, E. D. (1939). Physiological ontogeny in the tobacco plant. I. The drifts in dry weight and leaf area in relation to phosphorus

supply and topping. Ibid., 17, 93.

SAWHNEY, K. L. (1955). Interrelation between growth, nutrition and develormtnt of some crop plants as influenced by their varietal, photoperiodic and

vernaliza-tion responses (Thesis submitted to the University of Punjab for the degree of

Doctor of Philosophy).

- - , CHINOY, J. J., NANDA, K. K. AND SIROHI, G. S. (1959). Growth and phasic

development of wheat. IV. Net assimilation rate and uptake of mineral

nutrients. Indian J. Plant Physiol., 2, 116.

SnteHI, G. S. (1956). Physiological studies of growth and yield in crop plants (Thesis submitted to the University of Delhi for the degree of Doctor of Philosophy).

- - , SAWHNEY, K. L. ,CHINOY, J. J. AND NANOA, K. K. (1959). Growth and phasic

development of wheat. III. Dry matter production and water content. Indian

J. Plant Physiol., 2, 83.

TIVER, N. S. (1942). Studies of the flax plant. I. Physiology of growth, stem

anatomy and fiber development in fiber flax. Australian J. Exptl. Bioi. Med.

Sci., 20, 149.

--AND WILLIAMS, R. F. (1943). Studies of the flax plant. II. The effect of

arti-ficial drought on growth and oil production in a linseed variety. Ibid., 21, 201.

WAGNER, H. Z. (1932).

z.

pflanzenernahr. Dung e Bodenk, 25 (A). 48 (seen in

Williams, 1955).

WATSON, R. AND PETRIE, A. H. K. (1940). Physiological ontogeny in the tobacco

plant. IV. The drift of nitrogen content of the parts in relation to phosphorus

supply and topping. Australian J. Exptl. Bioi. Med. Sci., 18, 313.

WILLIAMS, R. F. (1936). Physiological ontogeny in plants and its relation to nutri-tion. II. The effect of phosphorus supply on the growth of the plant and its

parts. Ibid., 14, 165.

- - - . (1938). Physiological ontogeny .in plants and its relation to nutrition. IV. The effect of phosphorus supply on the total-, proteir:· and soluble-nitrogen

contents and water content of the leaves and other plant parts. Ibid., 16, 65.

- - - . (1948). The effects of phosphorus supply on the rates of intake cf

pJ-.os-phorus and nitrogen and upon certain aspects of phospJ-.os-phorus metal:olism in

gramineous plants. Australian J. Sci. Res., 1, (B), 333.

- - - . (1955). Redistribution of mineral elements during development. Annual