Cucurbitaceae: Characters, Distribution and Types

In this article we will discuss about:- 1. Characters of Cucurbitaceae 2. Distribution of Cucurbitaceae 3. Economic Importance 4. Affinities 5. Important Types.

Characters of Cucurbitaceae:

Prostrate herb bearing tendrils; leaves palmately lobed, surface hispid; flowers pentamerous, unisexual, monoecious or less commonly dioecious; stamens five, usually less, anthers free or connate, ovary inferior, trilocular, parietal placentation, fruit fleshy, pepo. Vascular bundles bicollateral and in two alternating rows.

A. Vegetative characters:

Habit:

Mostly annual or perennial herbs, rarely shrubs (Acanthosicyos) or small trees (Dendrosicyos), usually trailing, climbing by means of tendrils.

Root:

Tap root, branched may be thickened due to storage of food and water.

Stem:

Herbaceous, climbing, angular, fistular, branched.

Leaves:

Alternate, petiolate- petiole long and hollow; simple, lobed, exstipulate, palmately veined; tendrils present in the axil of leaf or opposite to the leaf. In Acanthosicyos the leaves are absent but thorns are present.

Morphological nature of the tendril:

Morphological nature of tendril has been a subject of great controversy. Tendrils have been considered by various authors as roots, stems, leaves, stipules, shoots, flower stalks or organs sui generis.

According to Braun (1876) it is a modified bracteole. Engler considered it is modified stipule. Muller (1887) regarded the upper portion of the tendril as a modified leaf and lower stiff portion as the axis. This view was supported by Hagerup (1930).

Probably the tendrils originate as stipules as shown by their lateral position to leaf-base and being rarely paired. By the work of Sensarma (1955) it appears that the tendrils is partly vascularised in the manner of a stipule in some cases.

B. Floral characters:

Inflorescence:

There is great variation in the inflorescence. Flowers are solitary, or racemose or cymose panicles (Actinostemma).

Flower:

Regular, mostly unisexual rarely bisexual (Schizopepon), incomplete, epigynous, small or large, mostly white or yellow, pentamerous.

Male flower:

Produced in large numbers.

Calyx:

Sepals 5, gamosepalous, sepals pointed, rarely petaloid, campanulate, aestivation imbricate.

Corolla:

Petals 5, gamopetalous united at the base (Momordica) or through out (Cucurbita, Coccinea), polypetalous (Luffa, Lagenaria), may be campanulate, rotate, imbricate or valvate aestivation.

Androecium:

Stamens 5, sometimes free or combined to form a central column, anthers dithecous extrorse, dehiscence longitudinal or in curves; androecium may be modified in one of the following ways:

1. In Thaldiantha two pairs of stamens are closely approximated in the lower part of their filaments and the fifth stands apart.

2. In Sincydium the pairs of stamens are united below; in Momordica, Citrullus, the union of pairs of stamens is complete and apparently only three stamens are present.

3. In Sicyos and Sechium the filaments unite to form a central column and the anthers are very much curved.

4. In Cyclantliera the stamens are united into a central column with two ring like pollen chambers running round the top. (Compare with the condition found in Phyllanthus cyclanthera of the Euphorbiaceae).

5. In Fevillea a polyandrous condition is found with all the five stamens free and alternating to the five free petals. This is a primitive genus.

Genoecium:

Reduced or rudimentary or absent.

Female flower:

They are fewer in number than the male flowers.

Calyx:

Sepals 5, gamosepalous, calyx tube adnate to the ovary wall; imbricate aestivation, superior.

Corolla:

Petals 5, gamopetalous, inserted on calyx tube; imbricate aestivation, superior.

Androecium:

Staminodes 0, 3, 5.

Gynoecium:

Tricarpellary, syncarpous, ovary inferior, unilocular with parietal placentation, the intruding placentae make the ovary to appear trilocular.

In Luffa the ovary is narrow and ultimately 3-4 celled and apparently of the axile type. In Sechium the ovary is unilocular with only a single ovule; ovule bitegmic. Style stout and columnar and bears a forked stigma for each carpel.

The stigmas are commissural i.e. stand above the dividing lines between the carpels. This is explained by assuming that each is a joint structure and composed of a branch of the stigmas of two adjacent carpels.

Fruit:

Soft, fleshy, indehiscent and either a berry or pepo. Fruits sometimes very large in size (Citrullus sp. Benincasa sp., Cucurbita sp.). In Ecballium the fruit is highly turgid when ripe and dispersal is by explosion.

Seed:

Exalbuminous, flattened, numerous, embryo straight, cotyledons large and oily.

Pollination:

Entomophilous.

Floral formulae:

Distribution of Cucurbitaceae:

It is commonly called gourd family. The family has 110 genera and 850 species out of which 86 species are found in India. The members are chiefly inhabitants of tropical regions; a few in temperate regions. The members are wanting in the colder regions.

Economic Importance of Cucurbitaceae:

This family is particularly important economically because its fruits are edible.

I. Vegetables and fruits:

1. Cucumis melo (Hindi – Kharbuza):

The fruits are edible and a number of varieties are known. C. melo var. momordica is Phut and C. melo var. utilissimus is Kakri. Cucumis sativus is Khira.

2. Citrullus vulgaris (Hindi – Tarbuz):

The fruits are large and ripen during summers; it is cultivated on the sandy beds of rivers. C. vulgaris var. fistulosus is Tinda which is used as vegetable.

3. Cucurbita maxima is Kaddu:

Cucurbita maxima is Kaddu while C. pepo is Safed Kaddu; both are used as vegetable.

4. Benincasa heipida is Petha:

Benincasa heipida is Petha. It is used as vegetable; PETHE-KI-MITHAI is also prepared from the fruits.

5. Lagenaria vulgaris is Lauki:

Lagenaria vulgaris is Lauki; the fruit is commonly used as a vegetable. From ripe fruit-shells sitar is made.

6. Trichosanthes dioca is Parwal:

Trichosanthes dioca is Parwal whose fruits are also used in vegetable preparations. T. anguina is Chachinga which is also used as vegetable.

7. Luffa acutangula is Torai:

Luffa acutangula is Torai. This is also a popular vegetable.

8. Momordica charantia is Karela:

Momordica charantia is Karela. The fruits are bitter but used in vegetable preparations. It is said to be useful in gout and rheumatism.

II. Medicine:

There are a few plants also important medicinally.

9. Citrullus colocynthis – produces the alkaloid colocynthin from its fruits. The fruits and roots are used against snake bite. The alkaloid is also used in other diseases.

10. Ecballium elatarium fruits produce elaterium of medicine which has narcotic effect and useful in hydrophobia.

III. Ornamental:

Some plants viz., Ecballium, Sechium, Sicyos are grown in gardens.

Primitive characters:

1. Leaves simple and alternate.

2. Flowers actinomorphic.

3. Petals and stamens are free in some genera.

4. Ovules bitegmic.

Advanced characters:

1. Plants herbaceous and climbers.

2. Leaves exstipulate and palmately lobed.

3. Flowers unisexual and epigynous.

4. Calyx gamosepalous.

5. Stamens 3 to 5 in number.

6. Stamens show tendency towards fusion.

7. Anther lobes curved and controlled.

8. Gynoecium syncarpous.

9. Ovules campylotropuous.

10. Fruit simple.

11. Seeds non-endospermic.

Affinities of Cucurbitaceae:

The relationships of this family have been much disputed. Different authors have given different systematic position to this family. According to Robert Brown, De Candolle, and Bentham and Hooker this family is allied to Passifloraceae and placed with perigynous polypetalae under Calyciflorae.

Eichler, Engler and Wettstein on the other hand have considered it to be very advanced family of the sympetalae due to the gamopetalous corolla, epigynous and synandrous condition of the stamens.

These authors have placed this family under the Cucurbitales just after the Rubiales and before the Campanulales. Cucurbitaceae shows affinities with Campanulaceae in synandrous condition of stamens, similar structure of calyx and corolla and also in the presence of bicollateral bundles.

Regarding the nature of placentation there are differences of opinion. Willis, Eichler, Engler and Wettstein consider that the placentation is axile whereas Hooker, Warming and Rendle etc. support parietal nature of placentation.

The advanced nature of the Cucurbitaceae can be supported on the following points:

1. Plants herbaceous with climbing habit.

2. Corolla is gamopetalous in most of the genera.

3. Complex structure of stamens i.e., loss of one anther lobe, synandrium formation and curved anther lobes.

4. Flowers are epigynous and unisexual. That unisexuality is a derived condition as supported by the presence of bisexual flowers in Schizopepon.

5. Occurrence of bicollateral bundles and large wood vessels.

Chakravarty (1964) was of the opinion that the cucurbitaceae is a highly evolutionary group which has progressed tremendously onward with the consequent metamorphosis of structures, associated with reduction, amalgamation, connation, adnation and sterilization of sex organs.

It finds a close connection with the Passifloraceae amongst the following points in having placenta retained on the wall, single-chambered ovary, fleshy fruit, tendril structure and extra-floral nectaries. Though the Cucurbitaceae compares well with the Passifloraceceae on the one hand and Bigoniaceae on the other.

Common plant of the family:

1. Cucurbita:

Cultivated for vegetables.

2. Trichosanthes:

Scandent herb cultivated for delicious vegetable.

3. Lagenaria (H. Lauki):

Cultivated for common man vegetable.

4. Luffa aegyptcia (H. Tori):

Cultivated for vegetable.

5. Momordica charantia (H. Karela):

Fruits are slightly bitter in taste.

6. Ecballium elaterium:

It has a special method for the dispersal of seeds.

Division of the family and chief genera:

Muller and Pax divided the family Cucurbitaceae into 5 tribes viz., Fevilleae, Melothrieae, Cucurbiteae, Sicyocae and Cyclanthereae.

Jeffrey (1962) divided the family into two sub-families and 9 tribes.

A. Cucurbitoideae:

Tendrils proximally 2-7 fid or simple; seed winged.

(a) Receptacle tube usually relatively short; if long in male flowers than short in female flowers.

1. Jolifeieae:

Petals fringed or with ventral scales. Momordica, Telfairia.

(b) Petals without fringe or ventral scales.

2. Benincaseae:

Ovules many horizontal; pollen reticulate, tricolporate. Citrullus, Luffa, Bryonia, Lagenaria, Ecballium.

3. Schizopeponeae:

Ovules 1-2 pendulous, pollen reticuloid, tricolporate. Schizopepon.

4. Cyclanthereae:

Ovules 1 to many, ascending; pollen smooth, mostly polycolporate. Echinocystis, Cyclanthera.

5. Sicyocae:

Ovule solitary, pendulous; pollen spinulose, polycolporate. Sicyos, Sechium.

6. Cucurbiteae:

Ovules many, horizontal or 1 to few, ascending, pollen spinose: pentaporate. Cucurbita, Cayaponia, Sicana.

(c) Receptacle tube relatively long, alike in male and female flower.

7. Melothrieae:

Pollen usually reticulae, flower small, stamens usually free and with simple thecae. Melothria, Cucumis, Gurania.

8. Tichosantheae:

Pollen striate, smooth verrucose; flower large, stamens united, with triplicate thecae. Trichosanthes, Peponium.

B. Zanonioideae:

Tendrils distally bifid; seed mostly winged.

9. Zanonieae:

One tribe. Zanonia, Fevillea.

Important Types of Cucurbitaceae:

1. Cucurbita maxima (Fig. 64.2):

Habit:

A cultivated climber.

Root:

Tap, branched.

Stem:

Herbaceous, prostrate, weak, hairy, angular, fistular, juicy, green.

Leaf:

Alternate, petiolate, exstipulate, simple, palmate, hairy, toothed margin, multicostate reticulate venation.

Inflorescence:

Female flowers solitary axillary but male flowers in cymose clustors.

Flower:

Unisexual.

Male flower:

Bracteate, pedicellate, actinomorphic, incomplete, staminate, yellow.

Calyx:

Sepals 5, gamosepalous, green, hairy, lobes linear or leafy, imbricate aestivation.

Corolla:

Petals 5, gamopetalous, campanulate, yellow, imbricate aestivation.

Androecium:

Stamens 5, two united in two pairs and one free, anthers twisted spirally mono and dithecous, extrorse.

Gynoecium:

Absent but pistillode present.

Floral formula:

Female flower:

Bracteate, pedicellate, pistillate, actinomorphic, incomplete, epiygnous.

Calyx:

Sepals 5, gamosepalous, green, hairy, lobes linear, imbricate aestivation, superior.

Corolla:

Petals 5, gamopetalous, campanulate, yellow, imbricate aestivation, superior.

Androecium:

Absent but staminodes present in three bundles 2 + 2 + 1.

Gynoecium:

Tricarpellary, syncarpous, ovary inferior, unilocular, parietal placentation. ovules many on each placentum, style one stigma 3 forked.

Floral formula:

2. Coccinea grandis (syn. Coccinea indica) (Fig. 64.3):

Habit:

An annual climbing herb.

Root:

Tap, branched and annual.

Stem:

Herbaceous, weak, green, cylindrical, solid, branched, hairy, tendril-climber.

Leaf:

Alternate, exstipulate, simple, petiolate, palmate, dentate margin, mucronate apex, multicostate reticulate venation.

Inflorescence:

Solitary axillary.

Flower:

Unisexual.

Male flower:

Flower:

Bracteate, pedicellate, incomplete, staminate, actinomorphic, pentamerous.

Calyx:

Sepals 5, gamosepalous, green, campanulate, hairy, imbricate aestivation.

Corolla:

Petals 5, gamopetalous, campanulate, imbricate aestivation.

Androecium:

Stamens 5, syandrous, seemingly 3; 4 stamens fused in two groups of 2 each, one free; anthers basifixed, extrorse, coiled.

Gynoecium:

Absent.

Female flower:

Flower:

Bracteate, pedicellate, incomplete, pistillate, actinomorphic, pentamerous, epigynous.

Calyx:

Same as in the male flower.

Corolla:

Same as in the male flower.

Androecium:

Absent, staminodes are present.

Gynoecium:

Tricarpellary, syncarpous, ovary inferior, trilocular, parietal placentation, style long and slender, stigma 3 and each is bilobed.

Floral formulae: