Is leaf age a predictor for cold tolerance in winter oilseed rape plants?

Abstract

In the present study, low temperature-dependent physiological changes were investigated through photosynthetic activity and some endogenous mechanisms in two winter oilseed rape cultivars (Brassica napus L. ssp. oleifera cvv. Eurol and Hansen) on the basis of leaf age. Chlorophyll fluorescence measurements demonstrated that low temperature caused decreased photosynthetic activity in both cultivars. However, photosynthetic apparatus in the young leaves of Hansen is more tolerant to low temperature as demonstrated by lower F0 (minimum fluorescence yield) and 1–qp (excitation pressure of photosystem II), higher Fm (maximum fluorescence yield), Fv/Fm and non-photochemical quenching (NPQ) compared with Eurol. In addition, young leaves of Hansen represented marked increase in some antioxidant enzyme activities (superoxide dismutase (SOD), ascorbate peroxidase (APX) and glutathione reductase (GR)) during cold exposure. In the young leaves of Eurol, however, APX and GR activity was decreased by low temperature, indicating lower efficiency of ascorbate-glutathione cycle. Lower antioxidant activity in the young leaves of Eurol may be responsible for increased malondialdehyde (MDA), H2O2 and membrane damage and decreased chlorophyll content as a result of oxidative damage during cold exposure. In the cold-stressed mature leaves, both cultivars represented similar antioxidant capacities and photosynthetic efficiency. As a consequence, coordinated increase in SOD, APX and GR activities, increased capacity to keep quinone A (QA) in an oxidised state (as indicated by lower 1–qp) and accumulation of soluble sugar and proline could be mainly attributed to higher level of tolerance of the young leaves of Hansen to low temperature when compared with Eurol.

Effects of salt stress on physiological and biochemical responses of three maize genotypes at the early seedling stage

“…In other words, H 2 O 2 accumulation in the salt-stressed leaves of the maize genotypes are prevented by the direct action of the reduced ascorbate instead of APOD activity. The elevated SOD activity in maize genotypes under salt stress may be an indicator of the accelerated rate of superoxide formation and detoxification (Doğru and Çakırlar, 2020a). GR activity increased in the salt-stressed leaves of the 'P3167' and 'Bora' while it did not change in '32K61' .…”

Ekzojen Salisilik Asit Uygulamalarının Tuz Stresi Altındaki Hıyar Bitkilerinde Fotosistem II Aktivitesi Üzerindeki Etkileri

“…Bu sonuç hıyar bitkisinde tuz stresinin etkisiyle FSII birimlerindeki elektron taşınım reaksiyonlarının belli oranda inhibe edildiğini göstermektedir [44]. F v /F m 'e göre performans indeksi (PI ABS ) multiparametrik olduğundan (primer fotokimyasal olaylar, elektron transportu gibi) daha duyarlı bir JIP parametresidir ve fotosentetik etkinliğin değerlendirilmesinde daha doğru sonuçlara ulaşmayı sağlar [58].…”

“…Bu sebeple fotosentetik aktivitede meydana gelen değişimler gelişmiş bitkilerde bir stres sensörü olarak kabul edilmektedir [33]. Günümüzde fotosentetik aktivitenin ölçülmesi için en modern ve güvenilir tekniğin klorofil a fluoresansı olduğu bildirilmiştir [32,43,44,45].…”

An Insight into the Responses of Early-Maturing Brassica napus to Different Low-Temperature Stresses

“…To date, many studies have investigated the morphological and physiological changes of low-temperature stressed rapeseeds. Leaves are the main organ to perceive low temperature stress and transmit stress signal in plants [24]. The morphological changes (dehydrated and wilting) of leaves became increasingly evident with the decrease of temperature, due to the total water content in leaves of rapeseed decreased [25,26].…”