3.5. Effects of scant light on plant growth in greenhouse
The „red strawberry‟ growth observations in 2015 were as follows: (1) there was almost no effect on
the growth of „red strawberry‟ within 7 days scant light. (2) The effect was slight on the growth
between 7 and 10 days scant light, with the symptom of yellow leaves and less ripe fruit. (3) When
the low light spanned 11 to 13 days, the phenomenon of leaves turning yellow was serious, the flower
and fruit number was little, stems, leaves and fruits began to mildew. (4) The scant light spanning 14
to 16 days made it so worse that stems and leaves turned yellow and dried seriously, no flower, no
fruit. These injuries could not be recovered.
The strawberry „sweet Charlie‟ growth observations in 2016 were as follows: (1) there was almost
no effect on the growth of „sweet Charlie‟ within 10 days shading condition. (2) The effect was slight
on the growth between 10 and 19 days scant light. (3) The scant light spanning 20 to 26 days didn‟t
seem make a significant influence on the growth, but through careful observation, we found that most
of the stem base had got black and rotten.
Two years experimental observations allowed us to conclude that (1) 7 days scant light made no
significant effect on the two strawberry varieties growth. (2) More than 14 days scant light made „red
strawberry‟ injured that could not be recovered, but it made a great effect on the „sweet Charlie‟
strawberry until 20 days scant light, this indicated that „sweet Charlie‟ has the stronger resistant
ability than „red strawberry‟.
4. Conclusions and discussion
Based on two sets of experiment, it is revealed that the scant light condition significantly influenced
the strawberry on the Pn, ChlC, fruit number, sugar content and the growth. Two varieties had the
different resistant ability: the anti-disaster capacity of „sweet Charlie‟ was stronger than that of „red
strawberry‟.
By analyzing the influence of scant light on the Pn, ChlC, fruit number, sugar content and the
growth of strawberry, we identified the scant light disaster grade index of strawberry in the
greenhouse. The grade index of „red strawberry‟ was mild disaster (1-6 days), moderate disaster
(7-10 days), and severe disaster (more than 10 days). The sunless disaster indicator of strawberry
cultivar „sweet Charlie‟ was light disaster (1-9 days), medium disaster (10-19 days),and heavy
disaster (more than 19 days).
In production, based on the weather forecast, sunless forewarning can be made to help the farmers
to manage the scant light disaster in greenhouse.
In this study, the ChlC rose first and then fell, which may be the adaptive response of plant to low
light stress [16]. The ChlC increased when the light intensity decreased, which was beneficial to
improve the plant leaves‟ ability of absorption and utilization of low light and scattered light [17-18].
But after a long period of shading, the photosynthetic products decreased, the
respiratory consumption was still at a high level, which caused the cell damaged,
physiological metabolism was blocked, so the ChlC began to decrease [19].
Ferree and Stang [20]reported that shading reduced the strawberry production during the flower
formation, Demirsoy et al [21] also reported that the strawberry yield was significantly reduced by
shading during the flower initiation period. These were in agreement with our observations.
The recovery experiment after shading haven‟t been carried out yet. In future study, different
recovery treatments can be designed to observe and measure correlation indexes of the strawberry
after shading.
Acknowledgements
This study has been financially supported by Henan Key Laboratory of Agrometeorological Ensuring
and Applied Technique, CMA (Grant AMF201709,AMF201509), and the scientific research projects
of Henan Meteorological Bureau (Z201518).We would also like to thank the experts from Henan
Scant Light Disaster Index Determination of Strawberry in Greenhouse
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