Study On The Differences Of Stomatal Behaviors Between The Tissue-cultured Plantlets And The Normal Plantlets Of Strawberry (Fragaria Ananassa Duch)

This paper studied the stomatal behaviors differences between the tissue-cultured plantlets (TCP) and the normal plantlets (NP) of strawberry (Fragaria ananassa Duch) on morphological, structural and physiological aspects. It also analyzed the mechanism making these differences.Stomata of the TCP were conspicuously bigger and present a rounder appearance than NP. The daily variation from 7:00 to19:00 of stomatal size of TCP and NP was 680μm2 to 900μm2 and 420μm2 to 530μm2, and that of the stomatal aperture of TCP and NP was 70μm2 to 105μm2 and 0μm2 to 21μm2 respectively. The stomatal aperture of TCP increased with a little fluctuation and reached the maximum at 15:00, then decreased. It increased again after 17:00 and got to another peak at 19:00. That of NP was nearly 0μm2 at 7:00 and increased continuously to 21μm2 at 13:00, then decreased to 0μm2 at 19:00 again.The structure of guard cell wall (GCW) was different between the two type plantlets. The cellulose content of TCP was less than NP. A network of cellulose bundles was presented in the GCW of NP, while in GCW of TCP the disposition of cellulose was homogeneous. The inner wall of the guard cell of NP was strongly lignified, while that of TCP was only slightly lignified.The K+ content of TCP's guard cells was higher than NP. The variation of K+ content from 7:00 to 15:00 of TCP was slightly and with the lowest level of 47, while that of NP was somewhat strongly and with the highest level of 44.The variations of Ca2+content from 7:00 to 15:00 of TCP and NP guard cells were contrary. For TCP, Ca2+content was lower in a.m. and higher in p.m.; and for NP, it was higher in a.m. and lower in p.m. When K+ content was high, Ca2+content was low, and vice versa.The structure of the GCW is important to maintain stomatal shape and function. For TCP, the variation such as stomatal shape or stomatal function is related to the structure of their GCW and K+ content of their guard cell. The rigidity of GCW impacts on the change of the water potential and pressure of the cell. The lignified degree of inner GCW and thecellulose content of GCW of TCP are lower, which make the rigidity of GCW weakly and insensitive to the pressure change of the guard cells. The cellulose distribution of GCW may also impacts on the rigidity of GCW and makes a non-functional state of the TCP stomata. High K+ content is another unfavorable factor for stomata close. Moreover, TCP have grown under high humidity condition. It may make guard cell always be in swell state and form a special shape. Even if TCP stomata lose much water and the turgor is very low, the stomata still couldn't close.