Pollination as a Factor Limiting the Yield of Field Beans (Vicia faba L.) - Self-pollination vs cross-pollination effects

Q: Why can field bean yield be limited by pollination?

Hybrid plants can set seed via autopollination, while inbred plants have mechanical barriers and require insect visitation for reliable seed set. When insects are scarce, seed set and yield decrease.

Q: How were pollination treatments applied in the study?

In 1970 and 1971, plants were labeled near field centres and edges, then flowers were self-pollinated by hand, cross-pollinated by hand, or left to be naturally pollinated. After harvest, pods and seeds were counted and seeds were weighed.

Q: What did the results show about edge versus centre yield?

Seed yield was often greater near field edges than near the centre in large fields. The effect was stronger in fields larger than about 12 ha, with inconsistent differences elsewhere.

Aug 20, 2026

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Field bean commercial crops contain both hybrid and inbred plants, and inbred flowers rely on insect visits to overcome mechanical barriers to self-pollination. Experiments used caged and hand-pollinated flowers to test whether insufficient pollination limits yield. Results show insect (and hand) pollination increases seed set and overall yield, with seed production generally higher near field edges than in centres. Hand treatments increased seeds per pod and seed weight, and cross-pollination offered limited advantage over self-pollination.

LanguageEnglish

CategoryResearch & Report

FormatPDF

Pages5

Reading Time13 min

AccessFree to download

Introduction

Summary

Method

Results

# INTRODUCTION A commercial crop of field beans consists of aboutone-third hybrid plants and two-thirds inbredplants(e.g.Sirks,1923;Hua,1943;Fyfe &Bailey,1951;Fyfe,1954;Rowlands,1958).The flowers ofhybrid plants are able to set seed from autopollina-tion and their progeny is produced predominantlyby self-fertilization.However,flowers of inbredplants have some mechanical barrier to auto-pollination that is absent in hybrid flowers andalthough self-fertile do not set seed unless visitedby insects.As a result of this about half theirprogeny are from cross-fertilization (Drayner,1959). It might be expected,therefore,that althoughthe autofertility of the hybrid plants would ensurea fair crop under conditions of poor pollination,insect pollination could improve the yield bypollinating the inbred plants.Furthermore,seedproduced under conditions of poor pollinationwould produce a crop still more in need of insectpollination. Experiments in which plots of field beans havebeen caged to exclude or contain pollinating insectshave demonstrated that insect pollination increasesyield by about a third (e.g.Riedel &Wort,1960;Scriven,Cooper &Allen,1961;Watts &Marshall,1961;Cooper,1964;Free,1966),the amount de-pending,of course,on the proportion of plants thathave grown from self-fertilized and cross-fertilizedseed. We have now attempted to discover to whatextent yield of commercial crops is limited byinsufficient pollination. Pollination as a factor limiting the yield of field beans(Vicia faba L.) BY J.B.FREE AND INGRID H.WILLIAMS Rothamsted Experimental Station,Harpenden,Hertfordshire (Received 29 January 1976) # SUMMARY Self-pollinating and cross-pollinating by hand samples of flowers in field bean cropsusually gave an increased set of seed compared with control flowers left to be pollinatednaturally.Hence,insect pollination of field bean crops is often inadequate.In largefields of more than 12 ha the seed yield was greater by plants near the edge than nearthe centre.Fewer pods were produced from nodes at the upper than the lower parts of8 stem,and they contained fewer seeds which were of a smaller size. # METHOD Observations were made in 1970 and 1971 on 30and 7 crops,respectively,of spring-sown fieldbeans.Field size varied from 2 to 40 ha in 1970(mean 11 ha)and from 4 to 16 ha in 1971 (mean9 ha) During flowering in 1970,30 plants near thecentre of each field and 30plants 10m from the edgeof the field were labelled and metal plant rings putbelow the lowest node and above the highest nodethat had two or more flowers open.The plantswere allocated in order into three treatments inwhich all the open flowers(about 12)between theplant rings were either(a)self-pollinated by de-pressing the keel to push the pollen plug on to thestigma,or(b)cross-pollinated by depressing thekeel and brushing the exposed stigma with pollenfrom three or more flowers of other plants,or(c)not pollinated by hand and left to be pollinatednaturally.Just before the crop was harvested theentire plants were removed.From the treatedsection of each plant,the lower part that floweredbefore the treated section(pre-treatment section)and the upper part that flowered after thetreated section(post-treatment section)the podsand seeds were counted and the seeds wereweighed. The method used in 1971 was similar except thateach of the 30 plants used in the centres and edgesof the fields received all three treatments.The openflowers on three adjacent flowering nodes on eachplant were (a)self-pollinated by hand,(b)cross-pollinated by hand,or (c)not pollinated by hand,respectively,equal numbers of each treatment Edge of fieldCentre of feldEdge and centre of fieldMean of edge and centre of field*P<0·05;**P<0·01;***P<0001, being allocated to nodes in each of the relativepositions. # RESULTS The average yield of plants at the centres andedges of the fields were similar(Table 1)and suchdifferences as occurred were not consistent.Thusplants near the edges of 15 of 3

FAQs

Why can field bean yield be limited by pollination?

Hybrid plants can set seed via autopollination, while inbred plants have mechanical barriers and require insect visitation for reliable seed set. When insects are scarce, seed set and yield decrease.

How were pollination treatments applied in the study?

In 1970 and 1971, plants were labeled near field centres and edges, then flowers were self-pollinated by hand, cross-pollinated by hand, or left to be naturally pollinated. After harvest, pods and seeds were counted and seeds were weighed.

What did the results show about edge versus centre yield?

Seed yield was often greater near field edges than near the centre in large fields. The effect was stronger in fields larger than about 12 ha, with inconsistent differences elsewhere.

Aug 20, 2026

Upload by Melati