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The Journal of Indian Botany/Volume 1/December 1919/Abnormal number of needles in the spurs of Pinus Longifolia

ABNORMAL NUMBER OF NEEDLES IN THE

SPURS OF PINUS LONGIFOLIA

BY

S. R. Kashyap

Professor of Botany, Government College, Lahore.


Pinus Longifolia is a common connifer of the outer hills of the Punjab Himalayas and is often cultivated in the plains. The number of leaves in the dwarf shoots in this species is described in the Indian Floras 1 as three. So constant is this number in the adult plant that the writer has not come across a single example of a different number during many years for which the plant has been a subject of study in the Botany classes at the Lahore Government College and in spite of a careful examination of several trees recently. It came as a surprise therefore when, last year, while examining a seedling he came across an abnormality in this respect quite by chance. On examining the seedling further and later on examining more seedlings many such instances were found. On looking up the literature 2 of the subject it was found that the abnormal number of needles in the spurs of many species both in the seedling and the adult plant is by no means rare though no mention of Pinus longifolia has been met with anywhere. Among a pretty large number of species mentioned by Thomson (Botanical Gazette, May, 1914) in this connection, Pinus excelsa is the only Indian species. Again although a number of observations are recorded in the papers mentioned yet the writer has not come across any quantitive study of this subject. This paper records a short study of this kind.

In order to find out the relative frequency of plants with abnor- mal spurs as regards the number of needles and the relative number of different kinds of such spurs on the same plant one hundred and one seedlings were taken from the nursery of the Lawrence Gardens, Lahore, through the courtesy of the Superintendent, and carefully

1 Hooker: Flora of British India; Brandis : Indian Trees, also his Forest Flora ; Parker : Forest Flora of the Punjab, etc. Among other standard books on this subject may be mentioned Elwes and Henry : The Trees of Great Britain and Ireland.

2 Thomson, R. B.: The Spur Shoots of the Pines. Bot. Gazette, May, 1914. Dufrenoy, J. : Pine Needles, Their significance and History. Bot. Gaz., November, 1918. Reference to other literature bearing on this point is given in these papers. examined as regards their general condition, height, branching, dwarf-shoots, etc., by L. Earn Lai Sethi, M.Sc, Demonstrator of Botany at the Government College. As he had to leave for Europe immediately after the completion of these observations the writer looked up the literature and prepared the analysis. The seedlings were about four years of age and varied in height from 11 inches to 22 inches. All the plants had been kept under the same conditions along with many others.

As is well known young seedlings bear only scattered green leaves and scale-leaves and dwarf-shoots are developed only gradually. Of the 101 seedlings one did not possess any dwarf-shoots at all and was unbranched. Otherwise the plant was erect and healthy so far as could be seen. No further notice will be taken of this plant. All the remaining one hundred possessed dwarf-shoots and a great many possessed long shoots in addition. No plants were found with abnormal shoots only, but normal and abnormal shoots were mixed in more than one half, 57 per cent, to be exact. The abnormal num- ber of needles was 2, 4 or 5. No spur was found with 1 or more than 5 needles. The analysis is given below : —

Plants examined : 100. All with dwarf-shoots.
Plants with 3-leaved shoots only 43
Plants with abnormal shoots in addition to 3-leaved shoots 57
Plants with 2-leaved abnormal shoots only 2
Do. 4-leaved abnormal shoots only 40
Do. 5-leaved abnormal shoots only 2
Do. 2-and 4-leaved abnormal shoots 6 V 57
Do. 2-and 5-leaved abnormal shoots
Do. 4-and 5-leaved abnormal shoots 3
Do. 2 — 4-and 5-leaved abnormal shoots 4 i

It will bo seen from the above that plants with 4-leaved abnormal shoots only are by far the most common. If we add to these the plants that bear 4-leaved shoots in addition to other abnormal shoots the number becomes still larger, i.e., 53. The relative number of shoots is given below : —

Plants examined : 100 as above, of which 57 possessed abnormal shoots.
2-Ieaved shoots in all the plants 17
4-leaved shoots in all the plants 145
5-leaved shoots in all the plants 11

It is clear that the 4-leaved shoots are by far the most common of all the abnormal shoots. It may be mentioned here that the number of 3-leaved shoots on these plants was very variable. It ranged from a few to about 300 on each plant. The co-relation of the presence of the long shoots to the number of abnormal dwarf shoots is shown below : —

Plants with long shoots (branched) ... ... 90
Plants without long shoots (unbranched)... ... 10
Plants with normal shoots only ... ... 5 1
Plants with abnormal shoots also ... ... 5 )

It will be seen from this that 50 % unbranched plants show the presence of abnormal shoots in addition to the normal shoots, while 52 out of 90, i.e., nearly 58 %, of branched plants possess the same peculiarity. This small difference has probably no significance. A very interesting point, however, is that that all the abnormal shoots on these 5 plants were 4-leaved. The details are as follows : —

Two plants possessed only one such shoot each ; one possessed 5 such shoots ; one possessed 8 such shoots, and one possessed 13 such shoots. This last plant was growing in a larger pot than the others,

This relation between the absence of long shoots and the presence of 4-leaved abnormal dwarf shoots only (of course in addition to nor- mal shoots) can hardly be accidental. Of course some branched plants also had 4-leaved shoots, either alone or along with other abnormal shoots, but no unbranched plants were found with any but 4-leaved abnormal shoots. The large size of the pot in one case may explain the large number of the 4-leaved shoots in that plant, but hardly the fact that all shoots were 4-leaved and not even one 5- leaved. Another fact which was noticed in this connection was that plants with few and small branches showed a greater tendency on the whole to form abnormal shoots than plants with long and many shoots but no exact numbers were obtained.

Below is given an analysis of the plants which possessed five or more abnormal shoots. The total number of such plants was 12. Nine plants had purely 4-leaved shoots as follows : —

4 with 5 such shoots.
1 with 7 such shoots.
2 with 8 such shoots.
1 with 10 such shoots.
1 with 13 such shoots.

A combination of 2-and 4-leaved shoots with more than five shoots occurred in one plant : — 2-leaved shoots, 2 ; 4-leaved shoots, 5.

A combination of 4-and 5-leaved shoots with more than five shoots occurred in one plant : — 4-leaved shoots, 8 ; 5-leaved shoots, 3.

A combination of 2-, 4-and 5-leaved shoots with more than five shoots occurred in one plant : — 2-leaved shoots, 1 ; 4-leaved shoots, 7 ; 5-leaved shoots, 1. As regards the position of the abnormal shoots on the plant no special relationship could be found. They occurred scattered on the plant. This point is also referred to take on in the paper.

The length of the needles of the abnormal shoots was also measured but no special relationship with the length of the needles of the normal shoots could be made out.

It will be seen from what has been described before that 4-leaved spurs are by far the most common of abnormal shoots in the seedlings of Pinus longifolia forming as they do 83'8 % of the whole lot of abnormal shoots. The actual numbers observed in one hundred plants were 145 out of 173. The numbers of 2-leaved and 5-leaved shoots were 17 and 11 respectively. (The normal number of leaves in the dwarf shoot is three and according to the observations of the writer variations in the adult plants is extremely rare.) The seedlings show therefore that a very great majority of abnormal shoots possess a larger number of leaves than the normal shoots. This is contrary to the observations of Thomson who says (Bot. Gaz., May, 1914) : — " It is more usual to find the spurs poorly developed when they first appear on the seedling .... This feature shows itself especially in species which have normally more than two leaves in the mature condition." Out of the 57 plants with abnormal shoots only two possessed 2-leaved abnormal shoots only, and ten more which possessed 2-leaved shoots in addition to other forms of abnormal shoots did not show that the 2-leaved shoots were in 6very case the first formed abnormal shoots. In one the only 2-leaved shoots present was near the top above some other abnormal shoots, but in the other nine the shoots were near the base.

The writer is however in perfect agreement with the conclusion arrived at by Thomson when he says :" The lack of definiteness in the number of leaves in a fascicle, and the occurrence of supernumerary needles in the recognised primitive region and after wounding, are evidence of the branch character of the spur of the pines." He points out also that the normal proliferation of the spur in the seed- ling and young plant into an ordinary branch with both primordial and fascicled leaves, and the traumatic revival of this condition in the mature tree place this conclusion beyond reasonable doubt, strength- ened as it is by the normal occurrence of the spirally arranged leaves in the seedling and other facts.

According to this view it would also appear that species of pine possessing a smaller number of leaves in their spurs are more specia- lised than the others and the tendency has been towards forming spurs with fewer and fewer leaves. This conclusion is also supported by the facts reported by Boodle (New Phytologist, 1915) : — " In Pinus monophylla the spur shoots as a rule bear each a single needle, but two are occasionally present. Masters found by studying early stages that two leaf-rudiments are always produced, but that one of them generally becomes arrested at an early stage. "

A paper on the comparative anatomy of the needles of the seed- lings and mature plants is in preparation.

The main conclusions of the paper may be stated as folllows : —

1. Spurs with more or less than three needles in the adult

plants of Pinus longifolia as seen in Lahore are extremely rare.

2. Spurs with more or less than three leaves are very common

in seedlings. Eifty-seven per cent, seedlings possesses such abnormal spurs.

3. Spurs with 4-leaves are the commonest of all, being 83'8 % of

all abnormal shoots.

4. The conclusion is drawn from these facts that a 3-leaved spur

has been derived from a spur with more leaves, that the spur is equi- valent to an ordinary shoot and that pines with a small number of needles in their spurs are more highly specialised than species with a larger number of needles.