Red means go for plants

Warwick Daily News - South West Queensland Rural Weekly - - Livestock - James Wagstaff news@ru­ral­

RUN­NING a red light has taken on a whole new mean­ing dur­ing a study into plant growth at one of the world’s lead­ing agri­cul­ture in­sti­tutes.

A re­search pro­gram is un­der way at the Wa­genin­gen Univer­sity and Re­search Cen­tre at Wa­genin­gen, about 80km south­east of Am­s­ter­dam in The Nether­lands, to de­ter­mine the per­fect “light recipe” for plants in green­house and ver­ti­cal farm en­vi­ron­ments. And re­sults show that red – and po­ten­tially far red with a mix of blue – are cer­tainly the new, well, black when it comes to tomato pro­duc­tion.

The QS World Univer­sity Rank­ing last year named Wa­genin­gen – which has more than 12,000 stu­dents from more than 100 coun­tries – the world’s best univer­sity for agri­cul­ture and en­vi­ron­men­tal science.

Its pro­fes­sor of hor­ti­cul­ture and plant phys­i­ol­ogy, Leo Marcelis, has been a plant sci­en­tist for 31 years and dur­ing his time at the univer­sity has worked in a range of dif­fer­ent depart­ments.

His re­search has fo­cused on plant phys­i­ol­ogy in green­houses and, more re­cently as the world at­tempts to be­come more en­ergy ef­fi­cient, the more-in­ten­sive ver­ti­cal farms where plants are grown in­doors with­out so­lar light.

Light is a ma­jor is­sue for green­house hor­ti­cul­ture pro­duc­tion through­out Europe with the amount of sun­light dur­ing win­ter in­suf­fi­cient when it comes to the growth and pro­duc­tion of crops.


PROF Marcelis said while green­houses of­fered a huge pro­duc­tion level of up to 70kg of toma­toes per square me­tre, and were sus­tain­able “in a num­ber of as­pects”, their reliance on as­sim­i­la­tion light­ing meant they con­sumed sig­nif­i­cant amounts of en­ergy.

“A large part of the en­ergy is used for lights, es­pe­cially now we are head­ing to­wards the win­ter pe­riod (in Europe),” he said.

He said tra­di­tion­ally the green­houses used high-pres­sure sodium lamps – “like lamps you see on the street” – but now more grow­ers were con­vert­ing to the more en­ergy ef­fi­cient LED light­ing. Coloured lights in par­tic­u­lar have been proven to stim­u­late plant de­vel­op­ment and growth re­sult­ing in the pro­duc­tion of more en­ergy ef­fi­cient pro­duce.

Prof Marcelis said the aim of the re­search at Wa­genin­gen was to de­ter­mine which coloured LED light­ing pro­duced the most toma­toes with “taste, shelf life and all the nu­tri­tional val­ues”.

As part of the ex­per­i­ment, plants are grown un­der dif­fer­ent colours of light – red, blue, green – and are mon­i­tored for plant length, photosynthesis, plant tem­per­a­ture, stom­atal open­ing and leaf an­gles.

Af­ter three to four weeks, the plants are har­vested and di­vided into leaves and stems.

The num­ber of leaves are counted, the leaf area is mea­sured and weighed, so too the stems.

Prof Marcelis said red was prov­ing the most ef­fi­cient light from a pro­duc­tion stand­point with blue and, to a lesser, ex­tent green (“we don’t need that much but it has spe­cific ef­fects”) throw­ing up in­ter­est­ing re­sults.


THE study has also found that plants are sen­si­tive to the ra­tio be­tween red and far red light “in par­tic­u­lar at the end of the day” which Prof Marcelis said was not un­sur­pris­ing as it “is what also hap­pens in na­ture”.

He pre­dicts a lot of work on the role of far red light to be car­ried out, with op­por­tu­ni­ties to in­crease pro­duc­tion by at least five per cent.

Prof Marcelis said although the more light the plant was ex­posed to, the more flavour the fruit had, he was not in a po­si­tion to de­ter­mine which colour pro­duced the best-tast­ing prod­uct.

“It is too early to say now be­cause it seems that it also af­fects a whole level of anti-ox­i­dants or in gen­eral se­condary me­tab­o­lites,” he said.

Prof Marcelis said in The Nether­lands, red and blue were the most com­mon lights used, with a mix­ture of 90 per cent red and 10 per cent blue the most com­mon.

When it came to dif­fer­ent tomato va­ri­eties he said some fared bet­ter un­der the red-blue and some un­der white lights prov­ing a “huge ge­netic dif­fer­ence”.

“I would think in five years from now that you’d prob­a­bly add a lit­tle bit of far red light and maybe a bit of green light,” he said.

Adding more than a splash of colour to the tomato source.


LIGHT EF­FI­CIENCY: Coloured lights have been proven to stim­u­late plant de­vel­op­ment and growth, with red light prov­ing to have a pos­i­tive ef­fect on the growth of toma­toes.

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