LIFE CYCLE OF WEEDS, WEED MIGRATION, WEED SEED DISTRIBUTION IN DIFFERENT ECO SYSTEMS.pptx

LIFE CYCLE OF WEEDS, WEED MIGRATION, WEED SEED DISTRIBUTION IN DIFFERENT ECO SYSTEMS.

1. LIFE CYCLE OF WEEDS, WEED MIGRATION, WEED SEED DISTRIBUTION IN DIFFERENT ECO SYSTEMS LECTURE - 5

2. Based on life span (Ontogeny), weeds are classified as Annual weeds Biennial weeds Perennial weeds LIFE CYCLE OF WEEDS

3. Weeds that live only for a season or a year and complete their life cycle in that season or year are called as annual weeds. These are small herbs with shallow roots and weak stem. Mode of propagation is commonly through seeds. Examples are A) Monsoon annual - Commelina benghalensis , Boerhavia erecta B) Winter annual - Chenopodium album I. ANNUAL WEEDS

4. EXAMPLES OF ANNUAL WEEDS Commelina benghalensis Boerhavia erecta Chenopodium album

5. It completes the vegetative growth in the first season, flower and set seeds in the succeeding season and then dies. These are found mainly in non-cropped areas. Examples are Alternanthera echinata, Daucus carota……. BIENNIAL WEEDS Alternanthera echinata

6. Perennials live for more than two years and may live almost indefinitely. They adapted to withstand adverse conditions. They propagate not only through seeds but also by underground stem, root, rhizomes, tubers etc.….. There are further classified as i. Simple perennials, ii. Bulbous perennials, iii. Corm perennials, iv. Creeping perennials. PERENNIAL WEEDS

7. i. Simple perennials : Plants propagated only by seeds. Example: Sonchus arvensis ii. Bulbous perennials: Plants which possess a modified stem with scales and reproduce mainly from bulbs and seeds. Example: Allium sp. iii. Corm perennials: Plants that possess a modified shoot and fleshy stem and reproduce through corm and seeds. Example: Timothy (Phleum pratense) iv. Creeping perennials: Reproduced through seeds as well as with one of the following. (A) Rhizome: Plants having underground stem – Sorghum halapense (B) Stolon: Plants having horizontal creeping stem above the ground – Cynodon dactylon (C) Roots: Plants having enlarged root system with numerous buds – Convolvulus arvensis (D) Tubers: Plants having modified rhizomes adapted for storage of food – Cyperus rotundus TYPES OF PERENNIALS WEEDS

8. EXAMPLE OF PERENNIALS WEEDS Sonchus arvensis Phleum pratense Sorghum halapense

9. EXAMPLE OF PERENNIALS WEEDS Cynodon dactylon Convolvulus arvensis Cyperus rotundus

10. Seeds and vegetative propagules disperse freely to avoid competition among themselves. Dispersal - scattering or dissemination. Immigration Dispersal ----> + Emigration WEED MIGRATION

11. I. WEED SEED DISPERSAL Weed seed dispersal depends on Wind Water Animal Machinery Human being

12. 1) WIND Many seeds are well adapted to wind travel. Cottony coverings and parachute-like structures allow seeds to float with the wind. Weed seeds that disseminate through wind possess special organs to keep them float. Such organs are 1) Pappus 2) C omose 3) Feathery, persistent styles 4) Baloon 5) Wings

13. ORGANS RESPONSE FOR WIND SEED DISPERSAL Pappus – It is a parachute like modification of persistent calyx into hairs. E.g. Asteraceae family weeds - Tridax procumbens Comose - Some weed seeds are covered with hairs, partially or fully E.g. Calotropis sp

14. ORGANS RESPONSE FOR WIND SEED DISPERSAL 3) Feathery, persistent styles - Styles are persistent and feathery E.g. Anemone sp. 4) Baloon - Modified papery calyx that encloses the fruits loosely along with entrapped air. E.g. Physalis minima 5) Wings - One or more appendages that act as wings. E.g. Acer macrophyllum

15. FACTORS THAT INFLUENCE WIND SEED DISPERSAL

16. 2) WATER Aquatic weeds disperse largely through water. They may drift either as whole plants, plant fragments or as seeds with the water currents. Weed seed often remains viable in water for several years, creating a "floating seedbank" and allowing weeds to disperse over large areas in moving water.

17. 3) ANIMALS Several weed species produce seeds with barbs, hooks, spines, and rasps that cling to the fur of animals or to clothing and then can be dispersed long distances. This is aided by special appendages such as Hooks ( Xanthium strumarIium ), Stiff hairs ( Cenchrus sp), Sharp spines ( Tribulus terrestris ) and Scarious bracts ( Achyranthus aspera ).

18. 4) MACHINERY Weed seeds often are dispersed by tillage and harvesting equipment. Seeds move from field to field on the soil that sticks to tractor tires, and vegetative structures often travel on tillage and cultivation equipment and latter dropping them in other fields to start new infestation.

19. 5) HUMAN BEING Man disperses numerous weed seeds and fruits with raw agricultural produce. Weeds mature at the same time and height along with crop, due to their similar size and shape as that of crop seed man unknowingly harvest the weeds also, and aids in dispersal of weed seeds. Such weeds are called “Satellite weeds” E.g. Avena fatua , Phalaris minor.

20. 6) MANURES AND SILAGE Improper decomposition without optimum temperature and acidity make the weed seeds viable in FYM. e.g. Convolvulus arvensis 4 % viability in 1 month decomposition. Trianthema sp 40% viability after a month treatment. Convolvulus arvensis Trianthema sp

21. II. VEGETATIVE PROPAGULES DISPERSAL Careless cultivation of land is the foremost factor in dispersal of vegetative propagates of weeds. Cultivation detaches underground organs of weeds such as rhizomes, rootstocks, tubers and drags them to uninfested spots. Transplants also carry weeds. e.g. Echinochloa sp. in rice. Solanum elagaenifoilum , Cynodon and Cyperus rotundus.

22. WEED SEED DISTRIBUTION IN DIFFERENT ECOSYSTEMS Based on ecology, weed seeds are distributed as 1) Wetland weeds, 2) Dryland weeds, 3) Gardenland weeds.

23. WETLAND WEEDS Annual weeds are predominant under cropped system. Perennial weeds are predominant in field bunds. WEEDS EXAMPLES Grasses Echinocloa colona, Echinocloa crusgalli, Panicum repens Sedges Cyperus deformis, Cyperus iria, Fimbris stylis sp. Broad Leaf Weeds Marshilia quadrifoliata , Eclipta alba, Ammannia braccifera , Centrala asiatica, Commelina benghalensis

24. GARDENLAND WEEDS WEEDS EXAMPLES Grasses Dactylactinium egyptium, Cynodon dactylon, Chloris barbata , Panicum sp. , Cenchrus ciliaris Broad Leaf Weeds Amaranthus viridis, Cleome viscosa, Euphorbia hirta, Acalypha indica, Trianthema protulacastrum Sedges Cyperus rotandus , Cyperus esculentus Neither require high moisture nor dry conditions for the survival and growth.

25. DRYLAND WEEDS Weeds coming under this ecosystem have certain adaptations to thrive. ADAPTATIONS OF WEEDS : Reduced number of leaves. Deep root system. Reduced Leaf Area. Thick and hairy leaf. Waxy coatings on leaf.

26. DRY LAND WEEDS EXAMPLES Grasses Dactyloctenium aegyptium, Cynodon dactylon, Chloris barbata , Andropogon sp. Sedges Cyperus rotundus Broad Leaf Weeds Abutilon indicum, Phyllanthus maderaspatensis , Tridax procumbens, Lucas aspera EXAMPLES OF DRYLAND WEEDS

27. REFERANCES Dr.T.K.Das.,2021.weed science (Basics and applications) www.iaritoppers.com

28. THANK YOU